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Glossary of Terms

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Number of hosts surviving parasitism.

S1, S2, etc.
Symbols denoting the first selfed generation, second selfed generation (progeny of the S1), etc.

Soil moisture content.

A lethal disease of larvae of the honey bee, caused by a virus.

Sacro-sciatic (ligament)
The large ligament in the form of a sheet which stretches over the area on either side of the sacrum, from the near edge of the hip bone to the bone of the buttocks. It covers the area generally referred to as the 'rump', and acts as a wall between the muscles of the rump and the pelvic cavity.

Saefftigen's pouch
Internal, muscular sac near the posterior end of a male acantheocephalan; it contains fluid that aids in manipulating the copulatory bursa.

A chemical that reduces the phytotoxicity or harmfulness of another chemical. A material added to a pesticide to eliminate or reduce phytotoxic effects to certain species. The term could also be applied to reducing adverse effects on livestock.

Safety (toxological)
Can be defined as the high probability that injury will not result from use of a substance under specific conditions of quantity and manner of use.

Safety factor
A factor applied to the no-observed-effect level to derive an acceptable daily intake (the no-observed adverse-effect level is divided by the safety factor to calculate the ADI). The value of the safety factor depends on the nature of the toxic effect, and the quality of the toxicological information available.

Sales price variance
The total gain or loss caused by selling the actual level of sales at a non-standard price. It is calculated by multiplying the actual sales quantity by the difference between standard and actual selling prices.

Sales variance
There are two types; sales value variances and sales margin variances. Sales value variances represent the difference between the budgeted and actual sales. Sales margin variances represent the difference between the actual and standard selling price multiplied by the actual quantity sold.

Sales volume variance
The total value of the profit margins gained or lost on the difference in quantity between actual sales and budgeted sales.

Chamber in buccal cone of acarines into which salivary ducts open.

A discharge of saliva.

A discontinuous variation of unknown origin.

A mutation within a fungal isolate known to be a pure genotype; dissociation.

Salting out
Precipitation and crystallisation of a virus out of suspension by the addition of a salt such as ammonium sulphate.

Any subset of a population.

Sample size
The number of units to be sampled (n) for a given standard deviation (SD) and standard error (SE) as expressed by the formula n = SD²/SE²

Sampling accuracy
Nearness to true value.

Sampling design
A method for selecting a sample.

Sampling distribution
The distribution of a statistic based on all possible samples that can be drawn according to a specific sampling plan. The term almost always refers to random sampling, and the statistic is usually a function of the n sample observations.

Sampling efficiency
The ratio of the estimated number of harmful organisms (or of their effect) in/on a given area or sample to the number actually present.

Sampling, multi-stage
A method of sampling from repeatedly smaller, internally subdivided divisions (stages) of a population to make survey activities more efficient. Same as cluster or nested sampling.

Sampling precision
Nearness to a given standard.

Sampling, sequential
A survey method without fixed sample size, in which sampling is continued until a predetermined, approximate level of objects or events is found.

Sampling, single random
A survey method in which every sample point has an equal chance of being sampled.

Sampling, stratified random
See stratified random sample.

Sampling units
Non-overlapping collections of elements from the population.

Sand fly
Member of the dipteran sub-family Phlebotominae, family Phychodidae; sometimes also applied to Simuliidae (New Zealand) and Ceratopogonidae (Caribbean).

Sand fly fever
Virus disease transmitted by sand flies.

The removal and burning of infected plant parts, decontamination of tools, equipment, hands etc.

Same as saprophyte when the organism is not a plant.

The period in the life cycle of a pathogen when it is not associated with living tissues of its host i.e. it is sapophytic. This may include a period of dormancy.

Organisms (usually fungus) living on dead and decaying tissue.

Free-living; obtaining all nutrients from non-living sources.

Saprozoic nutrition
Nutrition of an animal by absorption of dissolved salts and simple organic nutrients from surrounding medium; also, refers to feeding on decaying organic matter.

Powerful toxin produced by zoitocysts of Sarcocystis.

A hyperplastic symptom in which swellings occur above and below portions of organs that are tightly encircled, as a stem might be 'choked' by a twining vine.

A malignant tumour of connective tissue.

Sarcoptic mange
Disease caused by mites of the genus Sarcoptes; also called scabies.

A term first used to describe a small virus (satellite virus) associated with tobacco necrosis virus (TNV), which is dependent upon the TNV genome for its own replication. Also used to describe certain nucleic acid molecules that are unable to multiply in the host cell without the aid of other nucleic acid molecules.

Satellite DNA
DNA in eucaryotes that is present in large numbers of repetitive copies.

A form of behaviour where individuals seek to achieve a satisfactory target with respect to their goals, but do not seek more once that level has been achieved, at least in the short run.

A tract of comparatively level grassland with low vegetation and dotted with trees. Open country.

A hyperplastic symptom characterised by rough, crusty lesions formed by excessive cork production. A disease in which such lesions form.

Disease caused by mites of the genus Sarcoptes.

A lesion that suggests to the eye the apparent consequences of scalding with hot water, usually bleached and sometimes translucent.

Rough cleaning of paddy; removes most foreign material prior to drying and storage.

Scaly leg
Disease of birds, caused by mites of the genus Knemidokoptes.

Scarabaeiform larva
A grub-like larva with a thickened cylindrical body, well-developed head and thoracic legs without abdominal prolegs, and sluggish in behaviour.

Scratching or changing the seed coat.

Scatter diagram
A plot of the pairs of values (x, y) on a rectangular grid co-ordinated system, used to assess the relationship between x and y.

An animal that feeds on dead plants and animals, on decaying matter, or on animal faeces.

Juvenile stage of a blood fluke, between a cercaria and an adult; a migrating form taking the place of a metacercaria in the life cycle.

System of waste elimination found in some mites with blindly ending midgut; lobe from ventriculus breaks free and is expelled through split in posterodorsal cuticle.

Form of asexual reproduction in protozoa in which multiple mitoses take place, followed by simultaneous cytokineses, resulting in many daughter cells at once.

Cell undergoing schizogony in which the cell nucleus and cytoplasm divide numerous times to produce daughter cells enclosed in an outer membrane, the whole being called a schizont. Each daughter cell is a merozoite.

Schüffner's dots
Stippling that appears on the membrane of an erthrocyte infected with Plasmdodium vivax.

Scientific name
Name (genus and species) of a plant or animal used throughout the international scientific community.

A detached shoot or bud used in vegetative propagation for grafting or budding.

A protective or supporting plant tissue made up of cells with thickened, lignified walls.

Any well-defined, sclerotised area of arthropod cuticle limited by suture lines or flexible, membranous portions of cuticle.


Knots of thick-walled vegetative hyphae produced as the resting stage of some fungi.

Highly resistant and insoluble protein occurring in the cuticle of arthropods; also thought to occur in structures secreted by various other animals, such as in the eggshells of some trematodes, in which stabilisation of the protein is achieved by orthoquinone cross-links between free imino or amino groups of the protein molecules.

Hardened dense condition of cuticular structures.

A long lived, hard compact mass of vegetatively produced fungal hyphae, usually black on the outside, serving as a resting stage from which frutifications may be formed.

'Head' or holdfast organ of a tapeworm.

Lateral curvature of the spine.

'Burning' of leaf margins as a result of infection or unfavourable environmental conditions.

Scoring and ranking techniques
Any of a number of approaches to comparing R & D proposals in a psuedo-quantitative basis, prior to project selection.

An organism (eg. Mycobacterium) forming pigment both in the presence and absence of light.

'Scramble' competition
Where the resource is shared equally amongst the competitors.

Scrambling legumes
Legumes with a climbing or trailing habit.

Scrap bait
Special form of bait.

Screening or sieving
Separation of different size particles by using a wire mesh or perforated sheet in a moving pattern allowing the smaller size particles to fall through the openings and the larger size particles to remain on top.

Screening test
A test to observe the response of a range of plant cultivars or types to virus infection.

Parasitic maggot of the species Cochliomyia hominiovorax.

Scrub typhus
Rickettsial disease transmitted by certain chigger mites.

The single cotyledon of grass embryo.

Large, anteriodorsal sclerite on a tick or mite.

Surface layer of compacted or wetted soil intended to prevent escape of soil fumigant vapour.

Seasonal effect
The rises and falls in a time series, which always occur at a particular time of year because of changes in the seasons.

Seasonal index
An index measuring the seasonal effect of a particular month (when using monthly data) or quarter (when using quarterly data).

Secondary consumers
Animals that consume other animals (predators).

Secondary cycle
A cycle initiated by inoculum from a primary (or from another secondary) cycle without an interposed resting or dormant period for the pathogen.

Secondary growth
Growth resulting from the formation of new cells by the cambium.

Secondary host
In heteroecious aphids, plant on which only parthenogenetic reproduction takes place.

Secondary infection
Any infection caused by inoculum produced as a result of primary or a subsequent infection; an infection caused by secondary inoculum.

Secondary inoculum
Propagules produced as a result of infection by the primary inoculum.

Secondary metabolites
In addition to the primary products of metabolism, the building materials of which living cells are constructed, plants and animals produce a vast range of secondary metabolites, many of which find application in food, pharmaceutical and other industrial technologies.

Secondary migrants
Winged females migrating from a secondary host to other secondary hosts.

Secondary noxious weeds
Annual and biennial weeds that are difficult to control and which have been designated by the state as secondary noxious.

Secondary parasite
A parasitoid that develops in or on a primary parasite.

Secondary pests
Pests that do not normally occur in economically important numbers, but which can exceed the economic injury level as a result of changes in cropping and cultural practices or crop varieties, or the inappropriate use of insecticides applied for a key pest.

Secondary production
Production by herbivores, carnivores or detritus feeders; contrast with primary production.

Second-best optimum
The best allocation of resources available, given that a first-best optimum is not possible.

A well defined segment of an in vitro colony of a fungus differing visibly from the rest of the colony.

Staying in one place; stationary.

Sedimentation coefficient
The rate of sedimentation of a virus per unit centrifugal field measured in Svedberg units.

The reproductive unit formed from a fertilised ovule, consisting of embryo and seed-coat, and in some cases an endosperm. A starting integer for a random number generating algorithm.

Seed contamination
The intrusion of weeds, insects or pathogens in seeds having an adverse effect on germination or subsequent plant growth.

Seed dressing
A coating (either dry or wet) of protectant pesticide (fungicide, rodenticide or bird repellent) (with or without fertiliser) applied to seeds usually before planting. Dry seed dressings are often physically stuck to the testa of the seed by a sticker such as methyl cellulose.

Seed flow
Movement of seed through a machine.

Seedling resistance
Resistance detectable at the seedling stage.

Seedling stage
Usually refers to the early stages of growth of crop plants or weeds; technically a plant prior to the development of a root system other than the seed or seminal root.

Divided into distinct parts.

Segregating population
A population, generally the progeny of a cross, in which genetic differences are detectable, thus permitting identification of individuals having a desired trait and their selection for further breeding.

The separation of homologous chromosomes and genes from different parents at meiosis.

In breeding, any process, natural or artificial, which permits an increase in the proportion of genotypes of desired characteristics in succeeding generations.

Selection pressure
Exposure to stresses, such as pests or pesticides, that tend to induce natural selection in the exposed population. Negative selection pressure is used to denote the absence of or interference with selection pressure.

A term applied mainly to herbicides or insecticides, capable of killing some kind of plants or insects and not others.

Selective herbicide
Compounds that control weeds without adversely affecting the growth of a crop. Selectivity may be due to differences in retention, uptake, movement, metabolism or biochemical action of the herbicide in the crop and the weed.

Selective insecticide
One which kills selected insects, but spares most other organisms, including beneficial species. This is achieved either through differential toxic action or through the way in which insecticide is used.

Selective pesticide
Pesticide that, while killing the pest individuals, spares most of the other fauna or flora, including beneficial species, either through differential toxic action or through the manner in which the pesticide is used (formulation, dosage, timing, placement, etc.).

The choice exercised by an animal in what it feeds on.

To induce pollination with pollen from the same plant.

The process by which a number of protein molecules associate and form a specific structure; eg. virus protein coats and bacterial flagella.

Capable of fertilisation and setting seed after self-pollination.

The inability to produce seed by self-pollination.

Pollination with pollen from the same flower or from other flowers of the same plant.

Process of population regulation in which population increase is prevented by a deterioration in the quality of individuals that make up the population; population regulation by internal adjustments in behaviour and physiology within the population rather than by external forces such as predators.

System of animal production where part of the female progeny is retained each year to replace the older females sold.

The process of plants reducing light intensities with depth, thereby setting a limit on their own photosynthesis rates.

Failure to complete fertilisation and obtain seed after self-pollination.

Caterpillar from the sub-family Plusiinae (Noctudiae) with two or three pairs of prolegs, which locomotes in a somewhat looping manner.


Seminal vesicle
The portion of the male reproductive tract in which sperm is stored temporarily.

Semi persistent transmission
Virus transmission by an insect vector that is intermediate between non-persistent and persistent transmission.

Semi persistent virus
A virus which persists in its vector for between 10 and 100 hours.

Process or state of growing old.

Growing old.

Sensible heat
That heat energy able to be sensed (eg. with a thermometer). Used in contrast to latent heat.

Reacting with severe symptoms to the attack of a given pathogen of injurious factor.

Not capable of withstanding effects. Many broad-leaved plants are sensitive to 2,4-D.

Sensitivity analysis
A method used in modelling that identifies critical variables that significantly affect the system under study and then changing their values to determine the type and extent of their effect.

Sensitivity herbicide
Susceptibility of plants to effects of toxicant at low dosage; eg. many broad-leaf plants are sensitive to 2,4-D.

Dividing walls, eg. the walls dividing and supporting each of the lobules (ie. the respiratory tissue) of the lungs.

Of hyphae, divided into compartments ('cells') by crosswalls.

A morbid condition caused by the multiplication of micro-organisms in the blood.

A partition or cross-wall, as of a hypha or a spore. Hyphal septa are discoid with a central pore.

An after-effect of disease or injury; a morbid condition arising as a consequence of a previous disease.

Sequential application
Two or more pesticide treatments applied at different times to the same crop.

A means of identifying the order of nucleotides in DNA, RNA or amino acids in a polypeptide.

A piece of dead tissue which has become isolated from the surrounding living tissue.

Series of stages that follow one another in an ecological succession.

The keeping of silk moths and their larvae for the production of silk.

Referring to the properties of serum with reference to antigen/antibody reactions.

Serological typing
A technique based upon antibody-antigen reactions by which pathogenic bacteria are identified. It is particularly useful for strains of pathogens difficult to differentiate by morphological methods.

A method using the specificity of the antigen-antibody reaction for the detection and identification of anti-genic substances and the organisms that carry them (e.g. micro-organisms or viruses).

Serotinous cones
Cones of some pine trees which remain on the trees for several years without opening and require a fire to open and release the seeds.

A subgroup of a particular species unique because of the anti-genic properties of some cellular component; a given species may contain many different subgroups of different serotype.

The watery liquid which separates when animal blood coagulates. Also the blood serum containing antibodies from an animal previously inoculated with a pathogen or pathogenic toxin, used to immunise human or other animals.

Animal that is attached to an object or is fixed in place (eg. barnacles), or a leaf lacking a petiole or a flower or fruit lacking a pedicel.

A stiff hair; in fungi a bristle-like or hair-like structures occurring in certain fruiting bodies (eg. in acervuli) and on certain spores.

The opposite of rotational grazing - keeping the same animals in one area month in and month out.

A piece of tuber used as planting material.

Disease severity is a measure of the amount of disease in a plant eg. the percentage leaf area occupied by lesions of a pathogen.

Sex lure (sex pheromone lure)
A synthetic chemical which acts as the natural lure (pheromone) for one sex of an insect species.

Sex pilus
A specific pilus that is present in fertile cells, both Hfr and F+, and is involved in DNA transfer during conjugation.

Participating in or produced as a result of a union of nuclei in which meiosis took place.

Sexual morphs in insects, males and oviparae (female)

Sexual reproduction
Reproduction involving the union of gametes.

Parthogenetic females which produce one or both of the sexual morphs.

Shade tolerance
The degree to which a tree can grow or establish under a forest canopy.

Reducing sunlight received by a plant.

The strain produced in a substance as its layers are shifted laterally over each other. In a gas/liquid interface this will produce corrugations on the liquid surface which develop until stripped off as droplets.

A filamentous structure external to the wall.

Sheep bot
Oestrus ovis, a fly maggot parasitic in the head sinuses of sheep and related animals.

Shikimic acid
A crystalline acid C6H6 (OH)3COOH formed in plants as a precursor in the biosynthesis of aromatic amino acids and of lignin.

Shock symptoms
The severe, often necrotic symptoms produced on the first new growth following infection with some viruses; also called acute symptoms.

Short day (obligate)
Plants which will not flower if days are longer than a certain period.

Short-term exposure limit
The time weighted average (TWA) airborne concentration to which workers may be exposed for periods up to fifteen minutes, with no more than four such excursions per day and at least sixty minutes between them.

Short-term toxicity study
An animal study (sometimes called a subacute or sub-chronic study) in which the effects produced by the test material, when administered in repeated doses (or continuously in food or drinking-water) over a period of about 90 days, are studied.

Shot hole
A symptom of certain leaf-spotting pathogens in which small diseased fragments of leaves fall off and leave small holes in their place.

A woody plant with branches from the base and not reaching any great size.

Full brothers or sisters without regard to sex. Half-sibs - half-brothers or sisters.

Low molecular weight, virtually Fe(III)-specific ligands produced as scavenging agents in order to combat low iron stress (Neilands & Leong, 1986).

Sieve plate
Perforated wall area between two phloem cells through which their protoplasts are connected.

Sieve tube
Plant cells specialised for the transport of sugars, connected one to another by perforated sieve plates to form a cellular tube. Found in the vascular strands of leaves, stems and roots.

Sigma virus
The agent of carbon dioxide sensitivity in various species of fruit flies; the virion is cylindrical, with one hemispherical end.

Sigmoid curve
S-shaped curve (eg. the logistic curve).

Evidence of disease as indicated by the presence of the disease-producing organisms or of any of their parts or products e.g. bacterial ooze or fungus structures.

Signal sequence
A specific sequence of 15 to 20 amino acids that is involved in the movement of a sector protein through the plasma membrane.

Signal word
A required word that appears on every pesticide label to denote the relative toxicity of the product. The signal words are Danger-Poison for highly toxic compounds, Warning for moderately toxic, or Caution for slightly toxic.

Signed-rank test
A non-parametric statistical test of the difference between two treatments using paired observations. The differences are ranked according to their absolute magnitude, and each rank is given the sign of the original difference. The sum of the positive or negative ranks provides the test statistic developed by Wilcoxon.

Significance level
The probability of _ of making a type I error.

Sign test
A non-parametric statistical test of significance depending on the signs of differences between matched or unmatched pairs and not on the magnitudes of the differences.


Silk toxicity
A term used to describe a lethal hyperamino-acidemia in the silkworm, caused by silk retention; the inability to emit silk is related to structural and functional lesions in the silk glands, caused by endocrine disturbances, genetic factors, or infectious micro-organisms.

Herbicide used to control undesirable brush and trees, as in wooded areas.

Simple-interest disease
A disease which goes through only one cycle of infection during a growing season, analogous to a bank account giving simple interest.

Simple linear regression
A regression analysis in which the mean value of a dependent variable y is assumed to be related to a single independent variable x by the expression y = _ + ßx where _ = intercept and ß the slope of the regression.

Simple-stomached animal
Those without major adaptation to components of their diet (especially fibre) such as pigs and man.

Simplified programming
Technique which does not need access to a computer, to help plan mixed-cropping farms.

The use of a model, normally a series of equations, to mimic or imitate the behaviour of a system which changes through time.

Simulation experiment
A designed experiment to investigate some phenomenon of interest about the model, eg. effect of perturbations, parameter sensitivity.

Single-cell protein
Protein produced by microbes for use as food by humans or animals.

Single plant/single tiller comparisons
A method to estimate crop losses by comparing yields of individual plants or components differentially affected by yield constraints.

In modelling, a state variable outside the system boundary, ie. not quantified, to which outputs may go but do not return.

Of certain filamentous algae, a state in which the filaments are non-septate.

The paired protruding organs near the terminal end of the abdomen of the insects Aphidoidea, also called cornicles, through which a sugary secretion is extruded.


Sister chromatid exchange
A reciprocal exchange of DNA between the two DNA molecules of a replicating chromosome.

Skewed distribution
A frequency distribution that is not symmetrical about its mean.

Skin bot fly
Member of the family Cuterebridae.

Slack time
Period during the conduct of any research project during which no work can be done for reasons beyond the control of project managers.

Sleeping sickness
Name given to both African trypanosomiaisis and mosquito-borne, virus-induced encephalitis.

Slime ball
Mass of mucous-covered cercariae of decrocoeliid flukes, released from land snails.

Chemical used to prevent slimy growth, as in wood-pulping processes for manufacture of paper and paperboard.

Slime layer
A diffuse layer of polysaccharide exterior to the cell wall in some bacteria.

A thick suspension of a finely divided substance in a liquid producing a paste-like liquid. Agriculturally, usually refers to a mixture of faeces, urine and water, sometimes containing bedding materials (such as straw or sawdust). Also fungicides and some insecticides are applied to seeds as slurries to produce thick coating and reduce dustiness.

Small area comparison
A method to appraise crop losses based on comparative yield measurements in areas differentially affected by yield constraints. Smith period (Blight infection period) Two consecutive days (ending 0900 hours) when the temperature has not been less than 10°C and relative humidity above 90% for at least 11 hours of each day. Used in forecasting outbreaks of late blight of potatoes.

Aerial dispersion of minute solid particles. Smoke generator A combustible formulation, generally solid, which upon ignition releases the active pesticide ingredient(s) in the form of smoke. A smoke generator may take the form of a candle, pellet, rodlet, tablet or tin.

Smoothed statistic
In time series analysis an average of a set of process values, usually a moving average or an exponentially smoothed statistic. It is used to represent a time series after eliminating random fluctuations.

A group of Basidiomycete fungi (order Ustilaginales) with sooty spore masses.

Smut spore
A dark, thick-walled resting spore of a smut fungus; may germinate to produce a promycelium, the organ of meiosis; often improperly termed chlamydospore.

Snipe fly
Fly of the family Rhagionidae.

Layer of basal stems.

Sod seeding
Sowing directly into a sward without previous cultivation.

Soft water
Water which does not contain those minerals that prevent free lathering when soap is added.

Soft rot
Rotting of tissue (usually parenchymatous) by action of the pathogen on the middle lamella of cell walls: cells are separated.

Soil application
Application of pesticide to soil surface rather than to vegetation (most commonly used for herbicides).

Soil incorporation
Mechanical mixing of herbicide with the soil.

Soil inhabitant
An organism that is a more or less permanent part of the soil flora.

Soil injection
Mechanical placement of a pesticide beneath the soil surface with a minimum of mixing or stirring. Special applicators are usually used. Common method of applying liquids that change into gases.

Soil invader
An organism that is not a permanent member of the soil micro-flora but persists in the soil as long as host debris is available.

Soil persistence
Refers to the length of time that an herbicide applied to or in the soil remains effective; to some degree phytotoxic to some species.

Soil solarisation
A hydrothermal process that occurs in moist soil which is covered by a transparent or black plastic film and exposed to sunlight during warm summer months. During solarisation, soil temperatures are increased to lethal level for many plant pathogens and pests but which can improve the growth and development of plants.

Soil sterilant
See soil application. A material which renders the soil incapable of supporting plant growth. Sterilisation may be temporary or relatively permanent.

Blood-feeding arthropod that introduces its mouthparts directly into a blood vessel to feed.

Solid cone
Jet with air cone reduced to give a cone of spray drops.

Solids not fat
The solids of milk excluding the butterfat, eg. lactose (or milk sugar), casein, albumen, globulin and minerals. The legal minimum of cow's milk in many countries is 8.5%.

Solitary parasite
A parasitoid whose food requirements are such that only a single individual can develop successfully in the body of the host.

Soils with strong differences in texture with increasing depth; acid surface layers and strongly alkaline deeper layers.

A highly saline soil type.

Solonised solonetz
Similar to a solodic soil but with soil columns developed in the lower horizons.

Soluble concentrate
A liquid homogeneous pesticide formulation to be applied as a true solution of the active ingredient after dilution in water.

Soluble powder
A finely ground, solid pesticide formulation that will dissolve in water or some other liquid carrier.

A measure of the amount of substance that will dissolve in a given amount of another substance.

This term applies to a homogenous mixture of two or more constituents in which the particles are of molecular magnitude. This type of mixture is characterised by the absence of separation or settling.

Solution for seed treatment
A solution for application to the seed either directly or after dilution.

Generally the medium within which a substance is dissolved, also a carrier solution in which the pesticide (active ingredient) is dissolved to form the concentrate.

Solvent abuse
The intentional inhalation of volatile organic chemicals, including anaesthetic gases.

Somaclonal variation
Somatic (vegetative non-sexual) plant cells can be propagated in vitro in an appropriate nutrient medium. According to the composition and conditions the cells may proliferate in an un-differentiated (disorganised) pattern to form a callus or in a differentiated (organised) manner to form a plant with a shoot and root. The cells which multiply by division of the parent somatic cells are called somaclones and, theoretically, should be genetically identical with the parent. In fact in vitro cell culture of somatic cells, whether from a leaf, a stem, a root, a shoot or a cotyledon, frequently generates cells significantly different, genetically, from the parent. During culture the DNA breaks up and is reassembled in different sequences which give rise to plants different in identifiable characters from the parent. Such progeny are called somaclonal variants and provide a useful source of genetic variation.

Plants produced by a genetic engineering technique by which single cells or protoplasts are cultured to produce individuals which are genetically variable from their genetically stable parent. The variation induced is called somaclonal.

Referring to the diploid body cells, normally having one set of chromosomes from the male parent and one from the female parent.

Somatic cell
Literally any cell from the 'soma' which includes all cells of an organism except the germ cells. In some instances the term is used to describe un-differentiated cells, such as those found in a cultured callus.

Somatic embryogenesis
The generation from somatic cell or tissue culture of bipolar embryos, similar to sexually derived embryos. Both sexual and somatic embryos possess a primordial root and shoot.

Somatic hybridisation
The formation of hybrids by fusion of somatic cells, as opposed to the fusion of gametes. The term is commonly applied to fusion of plant protoplasts.

Body segment or metamere, a term usually used in reference to arthropods.

Sooty mould
A sooty coating on foliage and fruit formed by the dark hyphae of fungi that live in the honeydew secreted by insects such as aphids, mealybugs, scales and whiteflies.

A compact cluster of spores produced in or on the host plant by fungi such as the rusts and smuts.

In modelling a state variable outside the system boundary, ie. not quantified, from which inputs are derived but does not return to it.

Sources and applications of funds statement
A financial statement for a period of time showing both internal and external sources of income and where that income has been applied.

Southern blotting
This is a method for transferring separated DNA fragments from an agarose gel to a solid support such as a nitrocellulose membrane.

Space spray
This term, used largely in house fly and mosquito control, implies filling the air with suspended droplets of insecticide so that flying insects will collect these droplets on their bodies as they fly through the treated space.

Spade leaf
The first true leaf of a seedling clover or lucerne plant. The leaf is simple in contrast to the subsequent trifoliate leaves.

Span of control
The relative extent of control exerted by a research manger as reflected in the number of individuals under their supervision.

Non-ionic surfactants, fatty acid esters of sorbitan.

Cestode plerocercoid of unknown identity.

Spatial heterogenity
Differences in density of some quantity over space.

Spatial homogeneity
The assumption that biota are distributed uniformly in space, such that their density can be represented by a spatial average.

One kind of plant of animal. Abbreviated as sp. singular and spp. plural. Spp. following genus name means that a number of species of that genus are indicated. The fundamental category used in the taxonomic classification of living organisms which ranks below genus. It is generally the final category and is composed of individuals having common characteristics which distinguish them from other categories, eg. two of the species of the genus Bos are Bos taurus (temperate-type cattle) and Bos indicus (zebu-type cattle).

Species specific
An insecticide that has a limited range of toxicity is said to be species specific. Synthetic organic insecticides sometimes show wide variations in toxicity to closely related groups. Some compounds have been developed as strict acaracides with high toxicity to mites, but with little or no action against insects.

Specification limits
The upper and lower specification limits are the largest and smallest values that a material product etc. can have and still be considered acceptable for use.

Specific dynamic action
The part of animal respiration that depends on the feeding rate.

Specific gravity
A ratio of weight of the volume of any substance to the weight of the volume of another substance which is used as a standard. For instance, water as the standard for all liquids.

Specific heat
The heat capacity of a system per unit mass.

Specific seasonal index
The ratio of the time series at time t to a corresponding centred moving average at time t. The ratio measures by how much the seasonal component affects the series at time period t.

Resting a pasture from grazing.

A male gamete or reproductive cell.

A flask-shaped, fruiting body of the rust fungi in which the gametes or gametangia are produced.

Organ that receives the sperm in the female cimicid but during copulation.

An enlarged portion of the female nematode reproductive system between the oviduct and uterus in which sperm is stored.

A gamete produced in a spermogonium, a uninucleate cell produced by certain fungi and functioning only in fertilisation.

Modification of chelicera in some Acari, which functions in transfer of sperm from male's gonopore to copulatory receptacles between third and fourth coxae of female.

The quality of causing a reduction in sperm.

Formed 'container' or packet of sperm, which is placed in or on the body of a female, in contrast to copulation in which the sperm are conducted directly from male reproductive structures into the female's body.

A fruiting body in which gametes (spermatia) are produced.

An instrument that analyses characteristics of organic compounds through transmittance of light waves through solutions. Ultra-violet, and infra-red wave lengths are commonly employed. Ordinary light can be used in certain types of instruments, and electromagnetic fields are employed in some instruments.

A disease of Lepidopteran and Coleopteran larvae, caused by an agent of the poxvirus group.

A spherical, osmotically sensitive cell derived from a bacterium by loss of some but not all of the rigid wall layer. If all the rigid wall layer had been completely lost, the structure is called a protoplast.

One of a pair of copulatory organs in male nematodes.

Spider mite
A tiny, plant-feeding, spider-like mite.

Spike stage
The early emergence stage of corn in which the leaves are still tightly rolled to form a 'spike', usually before the corn is more than 2 inches tall.

Small, localised swellings on leaves of certain plants infected with Ditylenchus dipsaci.

Organs found in certain insect larvae and in spiders, which are used in spinning silken threads.

Small openings in the abdominal segments of insects connected to a system of internal tubes (trachea) through which the insect 'breathes'. Openings into the respiratory system in various arthropods.

A micro-organism characterised by having a morphology, when viewed under the microscope, like a spiral.

A coiled bacterium.

Split application
The total amount of a herbicide divided between two or more applications made at different times to the same crop.

Degeneration of a vertebra.

The population of airborne particles of plant and microbial origin, as in air spora.

A mature trophozoite of a gregarine protozoan.

A specialised branch of fungal hyphae bearing sporangia.

A non-motile asexual fungal spore produced in a sporangium.

A container which produces asexual fungal spores applies to asexual spores of Zugomycetes and endospores of bacteria.

A general term for resistant resting structures formed by many bacteria and fungi.

Small spore produced on basidia. A small spore produced on a promycelium, as in the smuts and rusts.

Cell mass that will differentiate into a sporocyst within an oocyst.

A cyst or sac containing spores especially in connection with spores of protozoa; also, an asexual stage of development in some trematodes.

Sporocyst residuum
Cytoplasmic material 'left over' within a sporocyst after sporozoite formation; seen as an amorphous mass.

A closely woven mycelial stroma which condiophores develop over the surface of an erumpent, cushion-like fungal structure.

Multiple fission of a zygote; such a cell also is called a sporont.

Un-differentiated cell mass within an un-sporulated oocyst.

A fungus structure producing spores.

A phase of the life cycle during which the plant has diploid nuclei and in which spores are produced after meiosis.

Amoeba-like portion of a micro-sporan or myxosporan cyst that is infective to the next host.

A skin disease of horses caused by a fungus. An infection by Sporotricae producing indolent, subcutaneous abscesses.

A type of protozoan which is usually non-motile; many cause important intra-cellular infections, eg. malaria.

The individuals formed by multiple fission of the zygote, the reproductive process called sporogony.

The process of producing spores.

A symptom of disease characterised by a limited necrotic area, as on leaves, flowers and stems.

Solution for spot application on the skin of animals in a low volume (normally less than 100 ml per animal).

Spot treatment
An application of spray to a localised or restricted area as differentiated from an overall (broadcast) or complete coverage.

Dispersion of a liquid in the form of droplets suspended in air. i) air-carried. Spray propelled to target in airstream ii) coarse. Dispersion of drops of mass median diameter over 200 microns, and volume median diameter over 500 µm iii) concentrate. Undiluted commercial pesticide preparation iv) curative. Fungicide effective shortly after infection has occurred v) fine, dispersion of drops of 50-150 microns mass median diameter vi) floor. Spray applied to over-wintering dead leaves on ground surface vii) hormone. Spray material having growth-regulating action viii) mist. Dispersion of droplets 50-100 microns diameter

Spray angle
Angle between sides of spray jet leaving orifice

Spray drift
See drift. The movement of airborne spray particles outside the intended area of application.

Apparatus for applying pesticide sprays. i) air-blast. Machine employing air-blast nozzles ii) air-carrier. Machine employing air to propel spray iii) hydraulic. Machine depending on liquid energy both to form and to propel spray iv) logarithmic. Equipment for applying herbicide in concentrations decreasing exponentially with time or distance

Spray operator
Person operating a sprayer, and applying a spray.

Spray recovery
Usually expressed as a percentage of quantity of spray actually emitted per unit area treated and is the amount of actual deposit of the spray found impacted on the target crop. This gives a measure of the efficiency of the operation since the remainder will be made up of drift and run off which is lost.

Spray spectrum
A method of describing the nature of a spray droplet cloud in terms of the range of droplet diameters present.

Spray volumes
Term Bushes & trees Ground crops High volume spray More than 1,000 l/ha More than 700 l/ha Medium volume spray 500 to 1,000 l/ha 200 to 700 l/ha Low volume spray 200 to 500 l/ha 50 to 200 l/ha Very low volume spray 20 to 200 l/ha 5 to 50 l/ha Ultra low volume spray less than 20 l/ha less than 5 /ha

Uniformity and completeness with which pesticide spray deposit covers continuous surface, such as single leaf or seed.

A substance added to sprays to make the material more readily spread over the foliage and not deposited in spots.

Spreading agent
A substance used to improve the wetting, spreading or possibly the adhesive properties of an herbicide spray solution.

Spreading oil
Formulation designed to form a surface layer on application to water.

Spring disease
A disease of the cutworm Euxoa segetum caused by Pseudomonas septica.

Spring dwindling
Disease of honeybees caused by micro-sporan protozoan Nosema apis; also called nosema disease, bee dysentery, bee sickness and May sickness.

The signs shown by a cow indicating the approach of calving.

Sprout depressant
Material arresting growth of potato sprouts.

In insects, an articulated spine, often on a leg segment, usually the tibia. A serrulate tibial spur is characteristic of the Delphacidae. A short twig on which much of the fruit of many trees is produced.

Spur precipitation line
An antibody-antigen precipitation line formed when two anti-genically distinct strains of a virus are placed in adjacent wells in a gel double-diffusion test.

Prominent lobe in the anal angle of a dipteran wing.

An unopened cotton flower with its enclosing bracts

Absence of fluctuations in populations; ability to withstand perturbations without large changes in composition.

Stability (biological control)
It is generally accepted that characteristic of effective biological control that natural enemy/pest equilibria appear quite stable without periodic outbreaks. An important element in the understanding of biological control is therefore to identify the factors that may be responsible for this stability. The following are usually considered to play a role; density dependence, a type III functional response, mutual interference, host susceptibility, variable parasitoid sex ratios, synovigney and non-random search in a patchy environment.

Stability (of pesticide deposit)
The ability of a pesticide formulation to resist decomposition by chemical or environmental factors eg. light, heat.

Stabilising selection
Natural selection tending to maintain an established equilibrium between host and pest populations.

Stable age distribution
The steady state solution to a Leslie matrix model in which relative abundance of each age class remains constant.

A bullet-shaped structure used by Plasmodiophora brassicae to directly penetrate a host cell.

A well-built pile of grain, forage or straw, which usually has a square or circular base. A rick is rectangular.

Stage (of fungi)
One morphologically characterised phase in the life cycle of a plemorphic fungus, eg. the imperfect stage, characterised by asexual spores; the perfect stage, by sexual spores. Stain Area covered by residue of a pesticide droplet.

Stale seed-bed
A seed-bed which is prepared and left untouched to encourage weed germination and into which the crop is later sown with minimum soil disturbance, before or after the weeds are killed with a herbicide.

Decrease and eventual cessation of growth of a fungus due in whole or in part to the effects of the metabolic products of the fungus itself.

Staling effect
Slowing-down of growth of a fungus in pure culture as a result of accumulation of self-inhibiting metabolites, adverse pH, etc.

A stem, usually of large plants; also an elongate structure, either cellular or excreted, which anchors a cell to a surface.

The male part of a flower. It consists of an anther and a filament. Pollen is produced in the anther.

Possessing stamens but no pistils.

The density of a plant population.

Standard cost
A pre-determined cost which is compared with the actual cost to highlight any significant variances for investigation and analysis.

Standard (area) diagram
Set of drawings illustrating different pest or disease intensities, used to increase accuracy of appraisal.

Standard deviation
The standard deviation of a set of n measurements x1, x2, x3, ..., xn is equal to the positive square root of the variance of the measurements.

Standard error
The precision of an estimator is measured by its standard deviation; hence, the standard deviation of an estimator is called its standard error.

Standard hour
A measure of the volume of work achievable in one hour.

Standard normal probability distribution
A normal probability distribution having a mean equal to zero and a variance equal to one.

Standing feed
Pasture standing in a field.

Standing hay
Grass which has matured and dried out while still standing, ie. uncut. The value varies roughly in inverse ratio to rainfall but is never as good as properly made hay.

Stand over
Surplus pasture standing in the field.

A polysaccharide consisting of glucose units; the principal food storage substance of plants.

Staring coat
A symptom noted in sick animals in which the hairs of the coat, instead of lying flat and being smooth and shiny, are standing up with the ends clear of each other and are dull and lustre-less.

Starter culture
A pure culture, available commercially, for use as a direct inoculum in production of fermented milk and meat products.

State of nature
In a decision analysis the states of nature are the uncertain events over which the decision maker has no control.

State variables
Major elements of the model whose rates of change are given by differential equations.

Not changing over time, in contrast with dynamic.

In population ecology the study of the reasons of equilibrial conditions or average values; contrast with dynamics.

The property of a stochastic process of not changing in distribution over time or space.

Stationary phase
The period in the growth-cycle when rapid cell division has ceased; cells divide slowly or not at all.

Stationary state
The set of state probabilities of a Markov chain model that do not change over time.

A value computed from sample measurements, usually but not always as an estimator of some population parameter.

A non-equilibrium state of an open system in which all forces acting on the system are exactly counter-balanced by opposing forces, in such a manner that all its components are stationary in concentration although matter is flowing through the system.

Feeding a cow or heifer before calving so as to increase her subsequent lactation.

Steam sterilisation
Treatment of soil with steam to depress growth of harmful organisms.

Steam/air mixture
Steam suitably diluted with air for use in soil sterilisation.

Steckling bed
A sugar-beet seedling bed.

Liquid formulation of seed protectant or disinfectant in which grain is immersed.

Steepest ascent
An algorithm for solving non-linear optimisation problems with stepwise search proceeding in the direction of steepest increase in the objective function.

A castrated male being reared for meat, a bullock.

The central cylinder, inside the cortex, of roots and stems of vascular plants.

The part of the plant above ground which supports leaves, flowers and fruit.

Stem and leaf display
A tabular-graphical method whereby each observation is divided into a stem value and a leaf value. The stems define a set of classes, and the number of leaves within a stem defines the frequency with which the values in that class occur.

Stem mother
Synonym for fundatrix, the founder of a clone of aphids.

A symptom of some viral diseases characterised by depressions on the stem of the plant.

The restriction of an animal to the consumption of but a narrow range of closely related species of food organisms.

Having little or no modificational plasticity; steno- means narrow; opposite of euryplastic.

Growing over a narrow temperature range.

Extensive area of natural, dry grassland; usually used in reference to grasslands in south-western Asia and south-eastern Europe; equivalent to prairie in North American usage.

Stepped fixed costs
The increase in fixed costs that occurs in specific levels of output.

Stepwise regression
A method of selecting the 'best' set of independent variables for a regression equation. Variables are introduced one at a time, with the criterion for accepting a variable based on the correlation of that variable and y in the presence of the other variables already in the model.

A slender protuberance on a fungal basidium that supports the basidiospore.

Any agent or chemical that destroys all living organisms or renders it barren.

Incapable of sexaul reproduction; also taken by many to mean free from living micro-organisms.

Sterile fungi
A group of fungi that are not known to produce any kind of spores.

Sterile insect control
A pest control method that makes use of artificially sterilised populations of the pest to mate with and thereby interfere with the normal reproductive efforts of the target species.

To treat with a chemical or other agent to kill every living thing in a certain area.

The elimination of living organisms by means of heat or chemicals.

Main ventral sclerite of a somite of an arthropod.

The ventral body sclerite of an insect or the breast bone in higher animals.

Any of a group of solid, mostly unsaturated polycyclic alcohols, such as cholesterol or ergosterol, derived form plants and animals.

Column of large, rectangular cells called stichocytes, supporting and secreting into most of the oesophagus of nematodes of the family Trichuridae.

Material of high viscosity added to increase adherence or tenacity of pesticide to its target surface eg. stickers are used to stick powdered dressing to seeds or to increase retention on plant foliage.

Stieda body
Plug in the inner wall of one end of a coccidian oocyst.

The part of the female flower that which receives the pollen from the anthers and the operculum-like area of an eggshell through which the miracidium of a schostosome fluke hatches; also, the sclerite surrounding a spiracle on a maggot or tick.

An environmental change capable of inciting a change in the activities of an organism without itself providing energy for the new activities.

A stalk, as of mushrooms.

Affected by random variations; a stochastic variable can assume any one of a set of values, each value having a certain probability. Contrast deterministic where the state is known with certainly.

Stochastic model
Mathematical model based on probabilities; the prediction of the model is not a single fixed number but a range of possible numbers; opposite of deterministic model.

Stochastic process
A collection of random variables that have some common structure or relationship, usually over time or space.

A seedling or other plant, often referred to as rootstock, upon which the scion is budded or grafted; also the reproductive females of a population; may be expressed as numbers or biomass.

Stock culture
A culture maintained in a culture collection for future study or reference.

Stock equivalents
Units used in livestock feed budgeting whereby the energy needs of different categories of livestock are expressed in terms of one type of livestock, eg. livestock months, tropical livestock units.

Stock turnover rate
A ratio used to measure the time in weeks over which any kind of stock is used up.

The determination of weight relations in a chemical reaction.

Stoichiometric ratio
The average ratio for some biota of one element to another; eg. the nitrogen to phosphorous ratio for phytoplankton.

A modified, creeping, above-ground stem capable of rooting and sending up new shoots at its nodes, as in the strawberry plant.. Stolinferous; bearing stolons or runners or shoots that take root.

Small apertures (bounded by guard and accessory cells) in the surface of a leaf or a young stem, opening or closing in response to light intensity, time of day and other factors, adapted to control exchange of carbon dioxide, oxygen and water vapour between active internal leaf cells and the atmosphere for respiration and photosynthesis, pl. stomata.

Stomach poison
A pesticide that exhibits toxicity only after ingestion.

Inflammation of the membrane lining, the inside of the mouth.

Stone brood
A disease of larval and adult bees, caused by the fungi Aspergillus flavus.

A group of stems arising from a single plant eg. tillering.

Stooling out
New shoots appearing on the edge of the crown.

Grain stalks after removal of the ears, usually cured and used as feed.

Breakage of a few plant stems, especially cereals resulting in a few tillers falling down.

In plants a group of individuals of a common origin, usually a more narrowly defined group than a cultivar. For pathogens, the descendants of a single isolation in pure culture; an isolate. Also a group of similar isolates; a race. In plant viruses: a group of virus isolates having most of their antigens in common.

A filament. Also, the single or each of the two chains of nucleotides that make up RNA and DNA.

Strategic managers
Those research managers who are primarily responsible for directing the whole R & D activity through (i) ensuring that the R & D activity coincides with identified priorities; (ii) garnering the human, material and financial resources needed to carry out the work of the organisation; and (iii) establishing the fundamental rules and standards by which all activities will be managed.

Strategic planning
Focuses on institute goals, scope of R & D activities and institute resources; frequently serves as a basis for institute policy development.

The science of art of employing various available techniques to confuse or defeat an enemy; in comparison to tactics, strategy is a long-term activity.

(Of sheep breeds) Spatial distribution of the different breeding components involved in sheep production, including the crossing of breeds developed for different attributes and the exploitation of different environments.

Stratified lake
A lake having no mixing between layers.

Stratified random sample
A sample obtained by separating the population elements into non-overlapping groups, called strata, and then selecting a simple random sample within each stratum.

Stratified sampling
A sampling procedure in which the sample space is partitioned into groups or strata and each stratum is sampled randomly. This helps assure that the sample has values over the full range of the sample space, eg. Latin hypercube sampling.

The dried remains of fine-stemmed plants from which the seed has been removed in threshing.

Strength & weakness
Used with reference to vertical resistance, these terms do not describe the intrinsic effectiveness of the resistance trait but rather the relative rarity of the matching pest pathotype. A 'strong' vertical resistance will tend to last longer because of the scarcity of the pest pathotype.

A filamentous eubacterium which forms extensive myclium, aerial hyphae and conidiospores in a manner similar to moulds; many produce antibiotics.

A state manifested by a syndrome or bodily changes, caused by some force, condition or circumstance e.g. constraints upon plant growth or survival caused by a harsh environment.

Linear cuticular depressions.

Deposition of fly eggs or larvae on a living host.

Strip cropping
Growing crops on a contour in long narrow strips.

Strip cutting
A term used to denote the practice of harvesting alternate borders of a crop, so that some partially-grown crop is maintained in the field at all times.

Formation of a chain of zoids by budding, as in the strobila of a tapeworm.

Cysticeroid that undergoes some strobilation; found only in Schistotaenia.

A cushion-like mycelial mass often sclerotised, in which fruiting bodies are produced. Mycelium of the stroma may often be intermingled with host tissue.

Structural pests
Pests that attack and destroy buildings and other structures, clothing, stored food and manufactured and processed goods; eg. termites, cockroaches, clothes moths, rats and dry rot fungi.

The arrangement of soil particles.

Structure-activity relationship
The correlation between molecular structure and biological activity. It is usually applied to observing the effect that the systematic structural modification of a particular chemical entity has on a defined biological end-point.

The basal portions of plants that remain after cutting off the upper parts.

Stubble mulch
A means of conserving water and soil by leaving crop residue on the surface of the soil.

Student's t distribution
The distribution of t = (x - µ)/(s/_n) for samples drawn from a normally distributed population and used for making inferences about a population mean when the population variance _² is unknown and the sample size n is small.

Stupefacient or sporific
Drug used as a pesticide to cause birds to enter a state of stupor so they can be captured and removed, or to frighten other birds away from the area.

In plants, the portion of the pistil between the stigma and ovary. In maize it is known as the 'silk'. Also the terminal segment of the antenna of a brachyceran dipteran. It is drawn into a sharp point.

The slender, hollow, piercing and sucking organs of insects and nematodes that feed on plant sap.

A term proposed by Kennedy et al (1962) to refer to disease agents that are not persistent in the vector.

Common name for legume Stylosanthes.

Hardened, tube-like structure secreted by a feeding chigger mite.

An animal that has not reached sexual maturity, yet displays many other adult behaviours.

Condition of an arthropod appendage in which the terminal podomere can fold back like a pincer against the terminal podomere.

Sub-chronic toxicity
The adverse effects occurring as a result of the repeated daily (oral) dosing of a chemical to experimental animals for part (not exceeding 10%) of the life span. (Usually 1-3 months).

A condition in an animal in which it is diseased, but in which the symptoms are not sufficiently serious to be clinically manifest.

Under the skin.

Subcutaneous toxicity
The toxicity (usually of a pesticide) determined following its injection just below the skin of the test animal.

See economic level injury.

Under the surface of the inner wall of the heart.

Under the surface of the outer wall of the heart.

A mixture of fatty acid derivatives deposited in cell walls to make them impermeable to water, as in corky cells. Often produced in wound healing reaction and to prevent penetration by a pathogen.

The formation of cork by the action of a cork cambium, or the deposition of suberin in or on cell walls as in cork cells.

Refers to cell walls hardened by their conversion to cork (suberin).

A climate with enough moisture to support a moderate to dense growth of natural grasses but not enough to produce a dense hardwood forest; usually with an annual rainfall of 50 to 80 cms.

A dosage which injures but does not kill.

The transition of a substance directly from the solid to the vapour phase or vice versa.

Sub-maxillary (lymph node)
Lymph nodes situated one on each side, just inside the angle of the jaw, and lying between the jaw bone and the salivary gland. They drain the head, nose and mouth.

Sub-pleural (connective tissue)
Under the pleura. The connective tissue lying beneath the serious lining of the lungs and inner surface of the thorax.

One of a number of subunits comprising a process controlling material flow in an ecosystem model, eg. the effect of temperature on plant photosynthesis.

Soil below plough depth.

Tillage of the subsoil, usually to break up a hardpan.

A division of a species. Subspecies may differ from each other in certain minor details often because of geographical location.

Sub-stiedal body
Additional plug material underlying a Stieda body.

The material or substance on which a micro-organism feeds and develops, the word substraum is often used. Also, a substance acted upon by an enzyme.

Substrate-level phosphorylation
Synthesis of high-energy phosphate bonds through reaction of inorganic phosphate with an activated (usually) organic substrate.

Sub-surface tillage
Tillage, through use of sweep-like plough or blade, that does not invert its surface cover or incorporate it with the lower portion of the surface soil.

Often used to describe any part of a system eg. the vertical system could be referred to as a Sub-system of the pathosystem.

Lower division in the sea from a depth of 40 to 60 m to about 200 m; below the littoral zone.

Replacement of one kind of community by another; the progressive changes in vegetation and animal life that may culminate in the climax.

Successive percentage mortality (= apparent mortality)
The mortality in each developmental stage expressed as a percentage of the number alive at the beginning of that stage.

A plant having tender, juicy or watery tissues.

Tillers or shoots produced from a plant crown or rhizome.

Suggested no adverse response level
The maximum dose or concentration which on the basis of current knowledge is likely to be tolerated by an organism without producing any adverse effects.

Suicidal emergence
Refers to emergence of insects at a time when host plants are unavailable for reproduction and the emerging insects die without having reproduced.

Sulfhydryl radical
The -SH group found in many plant and animal enzymes.

Susceptible to phytotoxic injury by sulphur.

Summer annual
A plant that completes its life cycle during a summer period, such as soy-beans.

Summer spore
A fungal spore that germinates without resting and that is usually the inoculum for secondary infections during the growing season of the suscept.

Sunk costs
Costs which were previously incurred and are now irrelevant to the decision under review, other than any opportunity costs they may possess.

The situation in which more individuals of a parasitoid species occur in a host than can survive.

A pathogen race which contains virulence factors to match any resistance factors available in the host.

See adjuvant.

Supplementary products
Where producing more of product X does not reduce the output of product Y.

"Support" energy
All forms of energy other than direct solar radiation.

Support staff
Those research managers who are primarily responsible for supporting strategic and research activities by (i) collecting, combining, analysing and interpreting information on all institute operations; (ii) converting institute policies to management systems; and (iii) facilitating the relationship between institute policy makers and researchers.

A hypoplastic symptom characterised by the failure of plant organs or substances to develop.

Suppressive soil
Soil in which a pathogen may persist, but either causes little or no damage to crops grown or causes diseases for a short time only and then declines.

A mutation that restores wild-type phenotype without affecting the mutant gene, usually arising by mutation in another gene.

Having the property of secreting or inducing the formation of pus.

Supra mammary (lymph node)
Lymph nodes in the female, lying above and behind the upper posterior edge of the udder. There are one or two on each side, the larger ones on each side being in close apposition. They drain the udder and external genitals.

Suprapopulation of parasites
All individuals of a single parasite species at all stages in the life cycle in all hosts in an ecosystem.

Surface soil
The upper soil to a usual plough depth of 12 to 20 cm.

Surface tension
Surface property of a liquid causing it to act as an elastic enveloping membrane. This causes droplets to form spheres in flight. When the drop impacts it spreads, when that kinetic energy is expended the surface tension draws the droplet margins back. Materials which reduce surface tension thus increase spreading and because they decrease the cohesion between surface molecules compared with pure water smaller droplets are produced at the nozzle.

Abbreviated form of "surface-active agent", a material (eg. wetting agent, emulsifier spreader) affecting surface tension by reducing inter-facial tension. Used to enhance surface retention and penetration of pesticides. There are three classes of surfactants, cationic, anionic and non-ionic and compounds belonging to the last two groups are most commonly used as herbicide adjuvants.

Disease of large mammals caused by Trypanosoma evansi.

Survey, pilot
A preliminary survey conducted to check all aspects of a main survey to obtain realistic estimates of time and/or resources, and to test the effectiveness of methods.

Any plant or species of plant that is susceptible to disease; an abbreviated term denoting 'susceptible plant' or 'susceptible species'.

Capable of being easily infected of infested; not resistant, i.e. lacking the inherent ability to resist disease or attack by a given pathogen; non-immune.

The condition of being susceptible.

A system in which very fine solid particles are dispersed but not dissolved in a solid liquid or gas e.g. particles of a pesticide, dispersed and suspended in liquids such as water and oils (wettable powders).

Sustainable agriculture
Reducing inputs and developing strategies which do not result in the crop system being made increasingly vulnerable to the side effects of technology.

Svedberg unit
The units used to measure the rate of sedimentation of a virus to determine its sedimentation coefficient.

A turf.

Daughter trophozoites resulting from multiple fissions of Ichythophthirius multifiliis and a few other protozoa.

Spread of a motile organism over the surface of a semisolid medium due to movement of individual cells in groups.

Motile naked spores. Zoospore.

Width of a target area sprayed at one pass or a strip of cut herbage lying on the stubble.

Saturation vapour concentration.

Existing normally in the wild, not in the human environment.

Study of symbioses.

Any organism involved in a symbiotic relationship with another organism, the host.

The general term for two organisms (species) that live together in a partnership, sometimes beneficial; includes commensalism, inquilinism, mutualism and parasitism.

An organism living in symbiosis; usually the smaller member of a symbiotic pair of dissimilar size (also called the micro-symbiote); frequently, those micro-organisms associated in a regular mutualistic manner with insects and other invertebrates; usually preferred to 'symbiont'.

The accepted symbol for male is J and for female K. The symbol is often used for castrates, ie. steers.

Symmetrical distribution
A frequency distribution for which the values of the distribution that are equidistant from the mean occur with equal frequency.

Symmetrogenic fission
Mitotic fission between the rows of flagella of protozoa.

Having the same; occurring in the same geographical area without loss of identity through interbreeding.

The living matter of cells; the cytoplasm.

A visible abnormal change in a host (including behaviour) as a result of pest infestation or infection.

The study of symptoms of disease and signs of pathogen throughout the plant.

Symptomless carrier
A plant which although infected with a pathogen (usually a virus) produces no obvious symptoms.

The space between nerve fibre endings where biochemical reactions occur in nerve transmission.

Habit of an organism to live in or around human dwellings.

A multi-nucleate mass of protoplasm surrounded by a common cell wall.

The totality of effects produced in a host by one disease, whether simultaneously or successively and whether detectable to the unaided eye or not.

Study of groups of organisms in relation to their environment; includes population, community and ecosystem ecology.

An activity of two or more agents which is greater than would be expected from summation of their single actions eg. complementary action of two or more pesticide chemicals providing levels of control greater than the sum of their combined effects. Co-operative action of different agencies such that the total effect is greater than the sum of the two effects working independently. (i) The association of two organisms acting at one time and effecting a change which either one was not able to make alone; (ii) Increased fungicidal value of certain mixtures of fungicides or of fungicides and non-toxic materials; (iii) Greater than additive. Increased activity arising from the effect of one chemical on another; opposite of antagonism.

The union of gametes in fertilisation. Especially the process of union of the micro-gamete and macro-gamete in the sexual form of reproduction in protozoa.

Synovial bursa
A bursa or enclosed cavity filled with an oily substance which facilitates the movement of one ligament or tendon over another or over a bone.

Synxeic cultivation
The rearing of one or more individuals of a single species in association with one or more known species of organisms.

Referring to the use of meteorological data obtained simultaneously over a wide area for the purpose of presenting a comprehensive and nearly instantaneous picture of the state of the atmosphere.

Synoptic methods
Procedures used for quantitative analysis of survey data where many factors are monitored simultaneously, based on correlation and including principal component, correlation and regression analysis.

Compounded in the laboratory, as opposed to occurring naturally. A crop plant line or variety produced by combining genes unlikely to occur in nature; lines having a high general combining ability.

Synthetic cultivar (or variety)
Advanced generations of open-pollinated seed mixtures of a group of strains, clones or inbreds, or of hybrids among them.

To produce a compound by joining various elements or simpler compounds.

A complex of interrelated components linked together for some common purpose or function eg. agro-ecosystem, pathosystem. A system is defined by sets of variables, rules governing rates of change of variables, initial conditions and constraints.

System analysis
The study of system structure and behaviour.

Not localised. Term applied to pesticide applied to soil or foliage, absorbed by plant parts, translocated to other parts of an organism and imparting protection from insect or disease attacks; the action of a herbicide in affecting the entire plant resulting in death; action of plant disease in which a single infection results in spread of pathogen throughout the organism.

Systemic sampling
Sampling procedures in which the sample space is sampled at a priori determined points.

Systems approach
A scientific philosophy which proposes a holistic view of systems implying that systems will not be properly understood by studies limited to their components alone

The classification of animal and plant species into their higher taxa; sometimes regarded as synonymous with taxonomy.

Systematic sampling
A method of selecting a sample by a systematic method as opposed to random sampling eg. select each tenth name from a list or sample every third resident in every other block in an area sample.

System, eco
An ecological system with defined conceptual or geographical boundaries.

A compound that is absorbed and translocated throughout the plant or animal eg. a system herbicide, absorbed through the roots and then translocated by the plants vascular system to the shoots.

Systemic disease infection
One in which the pathogen spreads throughout the host.

Systemic herbicide
A compound which is translocated readily within the plant and has an effect throughout the entire plant system.

Systemic invasion
A type of invasion in which the greater part or whole of the plant is involved.

System, patho
A sub-system of an ecosystem involving parasitism.

System, patho-management
The deterministic control of a pathosystem in order to reduce crop loss due to parasites.

State during sexual reproduction of some gregarines in which two or more sporadins connect end to end.