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Glossary of Terms

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Sclerotised mouth lining of a pentastomid.

Plural of caecum, the blind gut of the alimentary tract. In poultry there are two caeca opposite each other and opening into the intestine at the junction of the ileum and large intestine.

Caeco-colic junction
The junction in the alimentary tract of the caecum or blind-gut and the colon, ie. the first part of the large intestine.

An aecium that is surrounded by fungal filaments but that has no peridium.

Calabar swelling
Transient subcutaneous nodule, provoked by the filarial nematode Loa loa.

A plant growing in or confined to soil containing free calcium carbonate.

A plant not normally found on soil containing free calcium carbonate.

To determine the amount of pesticide that will be applied to the target area.

The process of changing model parameters to obtain an improved fit of model output variables to data time traces.

A virgin female moth releasing sex pheromones to attract males for the purpose of mating.

An amphorous, hardened, mucilaginous constituent of plant cells to block pores in cell walls, e.g. sieve plates and to inhibit invasion by some pathogens.

Tissue overgrowth around a wound or canker. A hard protuberance; the new tissue produced at the base of a cutting or when a part is severed or injured. Superficial unspecialised tissue produced by plants in response to wounding. Parenchymatous tissue of cambial origin that forms in response to wounding. A mass of thin-walled cells, usually developed as the result of wounding or infection.

Callus culture
A mass of undifferentiated cells originating from any type of explant. In a callus, usually developed on nutrient agar, the cells are generated in an unorganised clump, analogous to a pile of loose bricks. In a plant the cells are differentiated and organised systematically to form shoots, roots and other organs.

A unit of heat or energy; that amount of heat required to raise the temperature of one gram of water by 1 degree C.

'Head' end of a dicyemid mesozoan.

Calvin cycle
A series of reactions used by autotrophs to fix carbon dioxide into organic compounds.

Calving interval
The period between births of two successive calves from one cow.

Squama or lobe in the anal angle of a dipteran wing.

A layer of actively dividing cells in plants producing new tissues eg. fasicular producing new vascular tissue, cork cambium producing cork tissue.

Ventral grove in the propodosoma of soft ticks wherein lies the capitulum.

A type of disease in which normal cells lose contact inhibition, and grow profusely to form a malignant tumour, which invades surrounding tissue and sometimes spreads to other locations; there are many different causes, including carcinogenic chemicals, certain forms of radiation and some viruses.

A necrotic, sometimes sunken or cracked area surrounded by living tissue on a stem. A necrotic symptom of disease in woody plant parts: the necrosis is restricted to a definite area that is surrounded by callus.

Canonical distribution
Particular configuration of the log-normal distribution of species abundances.

Aerial parts of the pasture, especially the leaves. The tree foliage in a forest stand.

Capacity ratio
Used in standard costing to express the actual hours worked as a percentage of the budgeted standard hours.

Goods which have not been used up, includes land, equipment, livestock and cash.

Capital asset pricing model
A model which attempts to measure the return which investors will require from a security, as a function of risk.

Capital budget
The plan for expenditure of money for the purchase of major equipment, facilities and real property.

Capital budgeting
A criterion for project selection, particularly technique in the private sector. This approach is based on calculation of rates-of-return on investment in R&D.

Capital employed
All sources of finance excluding current liabilities. Sometimes called net capital employed.

Capital expenditure
Expenditure on fixed assets with a life expectancy of more than one accounting period.

Capital gains
Increase in the value of capital items due to a rise in their market price.

Capital gearing
The relationship of borrowed capital to either shareholders' funds or total capital employed.

Capital investment
Money spent on equipment, stock or on improvements which have a life of more than 1 year and which add to the productive capacity.

Capital outlay
One-time expenditure of a fairly significant sum of money.

Capital rationing
Investment conditions that are subject to financial constraint. Single period rationing is where the constraint is set for one accounting period and multi-period rationing where the constraint covers several periods.

The protein coat or shell of a virus particle; the capsid is a 'surface crystal', built of structure units. The protein coat of viruses forming the closed shell or tube that contains the nucleic acid and consisting of protein subunits or capsomeres.

A small protein molecule that is the structural and chemical unit of the protein coat (capsid) of a virus.

Capsular ligaments
The ligament in the form of a tough fibrous sac which surrounds every joint. The inner surface is lined with a membrane which secretes mucous (or synovia), the fluid which lubricates the joint.

A thick slime layer of mucopolysaccharides surrounding a bacterium and the protein material surrounding the granulosis-virus rod. Gummy materials secreted in a compact layer outside the cell wall. A compact layer of polysaccharide exterior to the cell wall in some bacteria.

Capsule suspension
A stable suspension of pesticide capsules in a fluid (normally intended for dilution with water before use).

Structure formed by posterior and lateral extension of dorsal sclerites of the head in many Crustacea, usually covering and/or fusing with one or more thoracic somites; considered as arising from a fold of head exo-skeleton. Also, a dorsal sclerotised plate often covering the idiosoma of acarines.

Carbamate insecticide
One of a class of insecticides derived from carbamic acid having anti-cholinesterase activity.

Starches, sugar, cellulose, fibres and woody materials. They are composed of carbon, hydrogen, and oxygen in the ratio of 2 molecules of hydrogen to 1 of oxygen. They are a major source of energy for the animal.

Carbon dioxide
A disease of adult fruit flies (Drosophlia), sensitivity caused by Sigma virus; a very brief contact with pure carbon dioxide gas is lethal to infected (sensitive) flies; the virus is transmitted to the off-spring by the gametes of one or both parents.

Carbon-nitrogen ratio
The relative proportion of weight by organic carbon to nitrogen in a soil.

A substance the causes the initiation of tumour formation (cancer). Frequently, a mutagen, that is said to be carcinogenic.

A malignant, epithelial tumour. A malignant, often metastasising tumour.

Carna-5 RNA
Cucumber-mosaic virus RNA 5 A satellite RNA of CMV which is dependent upon the remainder of the CMV genome for its own replication, but which is not essential for the replication of the CMV particle.

An animal (or, rarely, a plant) which feeds on animals. Flesh eating; organism that eats other animals; contrasted with herbivore. An animal which lives entirely or predominantly on animal matter, as distinct from a herbivore, which lives on vegetable matter, or an omnivore which lives on both animal and vegetable matter.

A yellow pigment in green leaves and other plant parts. It is the predecessor of Vitamin A.

Carpal joint
The joint of the 'wrist' or its equivalent in animals. The joint connecting the phalanges (or 'fingers') with the radius and ulna.

(i) an inert material serving as diluent and vehicle for active ingredients of pesticides, usually in dusts
(ii) organism harbouring a parasite without itself showing disease. The liquid or solid material added to a chemical compound to facilitate its application. (iii) an organism that bears an infectious agent internally but that shows no marked symptoms of the disease caused by that agent.

Carrier state
One type of attenuated infection characterised by the presence of a pathogenic microorganism within or upon host tissues.

Carrion's disease
Bacterial tissue transmitted by sand flies. See also Oroya fever and verruga peruana.

Carrying Capacity (k)
The size of a population when it is at equilibrium as determined by available food, space, or other resources or levels of predation/parasitism. The number of hectares that will carry one Mature Stock Unit.

Fusion of two haploid nuclei.

The seed (grain) or fruit of grasses, including that of cereals.

Caseating mass
A mass of structureless material which is cheese-like in consistency and which may follow tissue necrosis.

Case fatality rate
The number of deaths in every 100 cases of a particular disease.


Cash budget
A monthly plan of future cash receipts and payments showing the cumulative balance.

Cash cows
Businesses which have large market shares but slow growth.

Cash flow
The movement of money in and out of the hands of an enterprise or individual farmers.

Cash flow budget
A budget of the expected cash in (receipts) and cash out (payments) associated with a particular plan.

Cast for age (CFA)
A reject old animal that is past its economic life for particular conditions.

Castration, parasitic
Any process that interferes with or inhibits the production of mature ova or spermatozoa in the gonads of an organism.

An introduced plant which has not become established, although sometimes found in places where it is not cultivated.

Metabolic processes that liberate energy, eg. the breakdown of complex organic molecules by living organisms to liberate energy. The process of breakdown of sugars to produce energy. This is analogous to respiration.

The speeding up of a chemical reaction by lowering the activation energy, often through addition of a substance that accelerates the reaction but is not used up in the reaction.

A substance that causes cataracts in the eyes of animals.

Catarrhal rhinitis
Inflammation of the mucous membrane of the nose characterised by the presence of a free, fluid discharge.

Catarrhal stomatis
Inflammation of the mucous membrane of the mouth, characterised by the presence of a free, fluid discharge.

Catastrophic agents
Term used by Howard & Fiske to describe agents of destruction in which the percentage of destruction is not related to population density; synonymous with density-independent factors.

Catch crop
A crop planted on land where other crops have failed, usually a quick growing one.

Area which collects rainfall.

Larva of a moth, butterfly, or sawfly.

Chemical bearing a positive ionic charge; cations interact with anions in ionic bonding reactions.

Cation-exchange capacity
Often used to characterise the nature of the soil; the strength of the universally negative charge carried by the solid soil matrix. The charge is crucial when defining the behaviour of weakly basic or acid chemicals which are either repelled or attracted by the solid matrix depending on soil pH.

In which the hydrophobic portion of the molecule carries a residual positive charge.

Cationic surfactant
Material in which surface activity is determined by basic part of compound.

Cattle, European
Humpless cattle, although a distinct crest may occur on bulls, especially beef breeds; Bos taurus. (There are a few breeds of humpless cattle in eg. west Africa, that are not B. taurus).

Cattle, Zebu
Humped cattle probably originating in south-west Asia, now spread widely through the tropics and introduced to America and Australia; Bos indicus.

Causal agent of disease
That which is capable of causing disease.

Causal organism
The organism (pathogen) that produces a given disease.

Controlled droplet application; a spray technique which produces a narrower range of droplet sizes than conventional hydraulic machines.

Complementary DNA produced via a mRNA template using the enzyme reverse transcriptase.

Ceiling value
The airborne concentration of a potentially toxic substance which should never be exceeded in the breathing zone.

The living cell includes protoplasm, nucleus and cytoplasm within its walls. An individual biological unit, capable of independent function and able to divide to form two new identical cells.

Cell culture
The growing of cells in vitro. A group or colony of cells propagated from a single cell in a specifically formulated nutrient medium.

Cell fusion
The fusing together of two or more cells to become a single cell.

Cell-mediated immunity
An immune response generated by the activities of non-antibody-producing T cells. Compare with humoral immunity.

Cell membrane
A thin envelope surrounding the cell through which food materials pass in and waste materials and other metabolic products pass out.

Cell nucleus
A spheroid body within a cell distinguished from the rest of the cell by its denser structure. It is responsible for the functional activity and continued life of the cell.

Cellular immune response
Binding of antigen with receptor sites on sensitised T lymphocytes to cause release of lymphkines that affect macrophages, a direct response with no intervention of antibody; also, the entire process by which the body responds to an antigen, resulting in a condition of cell-mediated immunity.

An enzyme that breaks down cellulose.

A carbohydrate composed or repeating units of the sugar glucose linked in a specific way (ß-1,4 linkage); often a main component of plant and algal cell walls.

A recording of every element in a population.

Central Limit Theorem
If random samples of n observations are drawn from a population with finite mean µ and standard deviation _, then when n is large, the sample mean x will be approximately normally distributed with mean µ and standard deviation __n. The approximation will become more and more accurate as n becomes larger.

Centred moving average
An average of M terms in a time series, calculated for successive groups of M terms and plotted at the time periods associated with the middle of each particular group.

Centrifugal pump
See pump i.

Centrolecithal egg
Type of egg, found in many arthropods, in which the nucleus is located centrally in a small amount of non-yolky cytoplasm, surrounded by a large mass of yolk; after fertilisation and some nuclear divisions, the nuclei migrate to the periphery to proceed with superficial cleavage, the yolk remaining central.

Refractive areas of the cuticle that encircle the body in the head region.

Contractile organ in adult epicardean isopods that functions in sucking blood and perhaps in respiration.

Antibiotics produced by moulds of the genus Cephalosporium which inhibit the synthesis of the bacterial cell wall.

The fused head and thorax found in forms such as spiders.

The final free swimming stage in the life cycle of a trematode, produced by asexual reproduction within a sporocyst or redia.

Slender, paired and segmented sensory appendages arising from the tenth abdominal segment of some insects.

Posterior, knob-like attachment on a procercoid or cysticercoid. It usually bears the hooks of the oncosphere.

A grass grown for its edible seed or grain, such as maize, wheat and rice.

The posterior section of the brain concerned with the co-ordination of movement.

The risk-free return on capital which gives the same level of satisfaction as other combinations of risk and return.

Crop in which plants are true to type, and incidence of designated pests and diseases does not exceed specified tolerance levels.

Certified applicator
Commercial or private applicator qualified to apply restricted-use pesticides as defined by the appropriate government authority.

Certified seed
Seed produced from foundation, registered or certified seed authoritatively endorsed as being as represented, for use in commercial crop production.

The arrangement and nomenclature of the bristles on the insect exo-skeleton, both adults and larvae. Especially important in the order Diptera.

The glumes, lemmas, paleas and light plant-tissue fragments broken in threshing of grain.

Chagas' disease
Disease of humans and other mammals caused by Trypanosoma cruzi.

Reddish nodule that forms at the site of entrance of Trypanosoma cruzi into the skin.

Chain of command
The relative vertical depth in an organisation chart reflects the number of discrete levels of authority.

Specialised, parasitic copepodid found in copepod order Caligoida; attached to its host by an anterior 'frontal filament' that is secreted by the frontal gland.

Chalk brood
A disease of larval honey bees, caused by the fungus Ascosphaera apis.

Chalky grain
Kernels of grain which have some portion as opaque or milky white in colour.

The term used to indicate form, functions or features of individuals.

Characteristic species
Species that are rigidly limited to certain communities and thus can be used to identify a particular type of community.

The opening of the flowers at maturity for the purpose of pollination.

Condition of an arthropod appendage in which the sub-terminal podomere bears a distal process to form a pincer with the terminal podomere; sometimes (incorrectly) used to describe the sub-chelate condition.

Chelating agent
Organic chemical (e.g. ethylene-diaminetetraacetic acid) that combines with metal to form soluble chelates and prevent conversion to insoluble compounds.

The trapping of a multi-valent ionic species by ionic bonding to a larger water soluble molecule so as to render the ion inactive in the biological matrix and to aid excretion.

A compound that combines with a metal and keeps it in solution.

Anteriormost pair of appendages in the chelicerate arthropods, which include spiders, ticks and mites; generally the most important feeding appendages in these groups.

Chemical ecology
The chemistry and biochemistry of ecological situations involving interactions among organisms and between organisms and their environment.

Chemical feedstock
A source of chemicals used in the industrial synthesis of organic chemical polymers, e.g. petroleum or specific chemicals produced by micro-organisms.

Chemical name
Scientific name of the active ingredient(s) found in the formulated pesticide.

Chemically compatible
A mixture of formulations or chemicals that does not result in any mixture physical or chemical interactions which would lead to reduction in biological efficiency or increase in phytotoxicity of a pesticide.

The use of ion gradients across membranes, especially proton gradients, to generate ATP.

An autotrophic organism that utilises CO2 as it sole carbon source and an inorganic compound as its energy source.

The fate and transport of chemicals in the environment, including soil and water.

An organism that uses an inorganic compound as energy source.

The use of a drug or antibiotic to prevent future infections in people who are unusually susceptible.

A continuous culture device controlled by the concentration of limiting nutrient.

Chemical compounds that cause sterilisation or prevent effective reproduction.

Movement of a cell in response to a chemical; movement may be toward an attractant chemical or away from a repellent chemical.

Chemotherapeutic agent
A chemical agent which is harmful to micro-organisms.

The treatment of a plant or animal with chemicals to destroy or inactivate a pathogen or parasite without seriously affecting the host.

Black earth soils have a high clay content which changes little with depth; usually neutral or alkaline.

Mite of the family Trombiculidae; also, sometimes applied to Tunga penetrans, the chigoe flea.

An organism, tissue or recombinant DNA molecule which is composed of genes from more than one organism.

Chi-square statistic
A statistic having the distribution of a sum of independent squared standard normal variables. The number of independent squared normal variables is called the degrees of freedom.

Chisel plough
An implement, with points about 30 cm apart, used to till the soil some 30-45 cm deep.

The horny outer coating of an insect formed by cells that secrete a semi-liquid substance which solidifies on exposure to air. It is a high molecular weight polymer of N-acetyl glucosamine linked by 1,4-ß-glycosidic bonds.

Small bacteria which have an obligate dependence on host cells and thus are obligate intra-cellular parasites; cause of non-gonococcal urethritis (NGU) and trachoma.

A thick-walled asexual resting spore that develop from vegetative cells in the middle of hyphal strands.

A broad-spectrum antibiotic produced by streptomycete bacteria, which inhibits protein synthesis in bacteria.

The necrotic symptom of yellowing; a loss of chlorophyll.

Chlorinated hydrocarbons
A group of synthetic organic insecticides characterised by the presence of chlorine atoms as the halogen constituent in combination with carbon and hydrogen.

The practice of adding small amounts of chlorine to drinking water to ensure micro-biological safety.

The green coloured, photosynthetically active part of most plants.

The organelles inside plant leaf cells which contain chlorophyll and in which the reactions of photosynthesis are carried out.

Yellowing or mottling of normally green tissue as a result of lack of chlorophyll, through its failure to develop, or destruction by chemical effects, disease etc.

A chemical derivative of tetracycline, a broad-spectrum antibiotic produced by streptomycete bacteria, which inhibits bacterial protein synthesis.

Like a promastigote but with the flagellum emerging from a collar-like process, as in Crithidia spp.

Cholinesterase (ChE)
An enzyme that is necessary for proper nerve function that is inhibited or damaged by organophosphate or carbamate insecticides.

Cholinesterase and pseudocholinesterase inhibitor
A substance which inhibits the enzyme chlorinesterase and thus prevents transmission of nerve impulses from one nerve cell to another to a muscle.

Pertaining to chorea, a convulsive nervous state, characterised by involuntary and irregular jerking movements.

Chorioptic mange
Disease caused by mites of the genus Chorioptes.

The half chromosome appearing during certain phases of cell division.

Chromatid bae
Masses of RNA, visible with light microscopy, in young cysts of Entamoeba spp.

A method of separation and identification of closely related chemical substances by their differential movement on or through certain materials, such as paper and resins, and by their specific colour reactions with certain reagents.

Intra-cellular membranes of purple photosynthetic bacteria. Contain bacteriochlorophylls and carotenoids.

A subcutaneous fungal disease which causes cauliflower-like growths on the skin.

Producing colour; a chromogenic colony is a pigmented colony.

Chromosomal aberration
An abnormality of chromosome number or structure.

A thread-like body found in cell nuclei, comprised of genes arranged in linear order. In higher organisms chromosomes consist of DNA in association with protein. In bacteria they exist as naked DNA. While genes are the units of heredity, chromosomes are the units of transmission from one generation to the next. During cell division chromosomes may break, rejoin or cross over giving rise to new genetic combinations.

Not acute; of long duration e.g. 'chronic disease or infection'.

Chronic effect
Slow and continuous effect.

Chronic symptoms
Symptoms that appear over a long period of time.

Chronic toxicity
The effect of a chemical (or test substance) in a mammalian species (usually rodent) following prolonged and repeated exposure for the major part of the lifetime of the species used for the test. Chronic exposure studies over two years are often used to assess the carcinogenic potential of chemicals.

Lymph in the urine, characterised by a milky colour.

A healing process which leaves a scar (i.e. a cicatrix).

Cilia (sl. cilium)
Tiny hair-like processes growing on cell walls, especially in some Protozoa.

Ciliary organelles
Organelles of specialised function formed by the fusion of cilia.

A type of protozoa which moves by means of cilia.

Cinnamic acid
An acid C6H5CH: CHOOH found especially in cinnamon oil and sterax.

Term used by Kennedy et al. (1962) and by Harris (1977, 1978) to refer to disease agents that are persistent in the vector.

Circulative virus
A virus that is acquired by their vectors through their mouthparts, which then passes through the gut wall of the vector into the haemolymph and eventually contaminates the mouthparts via the saliva.

Fused tufts of cilia in some protozoa, which function like tiny legs. Also plural for cirrus.

A gelatinous mass of extruded spores. Penis or copulatory organ of a flatworm.

The sequence of nucleotides within a certain area of a nucleic acid (DNA or RNA).

Complex set of sclerotised bars, forming a 'pinching' organ on the opisthaptor of a monogenetic trematode.

Claparedé organs
See urstigmata.

Agents which cause chromosome breakage.

Mineral soil particles that are less than 0.002 mm in diameter.

Clay-based formulations
Pelleted or granular formulations based on clays were some of the first controlled- release formulations to be had with aquatic herbicides.

The process of removing foreign material or impurities from the crop product e.g. rice.

A forestry practice of removing all trees from a forest stand.

Adjective for a plant in which pollination and fertilisation may occur in an unopened flower bud e.g. sorghums with long papery glumes through which the anthers fail to extrude during anthesis.

A semi-spherical sexual fruiting body totally closed structure, containing ascospores with their asci.

A case of multiple parasitism in which a parasitoid preferentially attacks a host already parasitised by another species rather than an unparasitised host.

The total long-term characteristics of weather for any region It includes rainfall, temperature, humidity, wind direction and wind velocity.

A polygonal diagram resulting from plotting temperature means against relative humidity.

Kind of community achieved in theory by an ecosystem left undisturbed over a long time.

An opening or cavity at the posterior of a vertebrate, usually a bird, into which the intestinal, urinary and reproductive ducts open. Also a chamber in male nematodes into which the digestive and reproductive systems enter and which empties through the anus.

A collection of genetically identical cells or organisms derived asexually from a common ancestor eg. a group of plants originating by vegetative propagation from a single plant

In this process one gene is isolated and inserted into a vector which has the capacity to transport genes into a host cell. Ideally the vector replicates itself and the gene which it is to carry inside the host.

Cloning vector
A DNA molecule that is able to bring about the replication of foreign DNA fragments.

Closed system
A system which does not exchange matter with the surroundings; it may, however, exchange energy with the surroundings.

Cluster analysis
A statistical technique for grouping together different entities according to their similarity with regard to specific attributes.

Cluster cup

Cluster sample
A cluster sample is obtained by first randomly selecting a set of m collections of sample elements, called clusters, from the population and then conducting a complete census within each cluster.

Coarctate pupa
An insect enclosed inside a hardened shell formed by the previous larval skin.

Coarse spray
See spray ii.

Cobb-Douglas production function
A mathematical function showing a particular form of relationship between inputs and outputs.


A spherical bacterium.

A small pile into which hay may sometimes be built in order to complete its curing or to protect it from rain and sun.

A protective sac, spun by the larvae of many insects, in which a pupa is formed.

The process by which the sequence of nucleotides within a certain area of RNA determines the sequence of amino acids in the synthesis of the particular protein.

Coding sequence
The region of a gene is expressed i.e. translated into protein.

A coding unit. A sequence of three purine and pyrimidine bases on DNA or messenger RNA that codes for a specific amino acid.

Coefficient of correlation
A number that measures the linear dependence between two random variables. Limiting values of -1 and +1 indicate perfect negative and perfect positive correlation, respectively; a correlation of zero suggests a complete lack of association between the two variables.

Coefficient of determination
A measure of the goodness of fit of a regression model that is equal to the square of the coefficient of correlation (simple or multiple).

Coefficient of selection
A measure of the relative change in gene frequency between generations as a result of differential selection.

Living in the lumen of a hollow organ, such as the intestine.

A number of united protoplasts, forming a single large cell containing several or many nuclei and continuous cytoplasm, surrounded by a common wall.

In pathology; a continuous mass of cytoplasm and nuclei unbroken by septa.

The larval stage of Multiceps, the tapeworm commonly found in the brain of sheep, goats and other ruminants in which several scolices bud from an internal germinative membrane, but none of which is enclosed in an internal secondary cyst.

A low-molecular-weight chemical activating or accelerating enzyme action.

Compound or element that is required for the efficient performance of enzyme activity.

A group of individuals all born at the same time and thus all of the same age. Used to denote a model where separate ages of each cohort are kept track of as opposed to a dynamic pool model.

A poisonous yellow crystalline alkaloid C22H25NO6 extracted from the meadow saffron (Colchicum autumnale) that induces polyploidy when applied to mitotic cells.

Cold dressed weight (CDW)
The weight of a carcass after being dressed, i.e. rejecting the entrails, head, feet etc., and allowing for 'shrinkage' or drying which occurs in the first 12-24 hours after it has been placed in a cold store.

Cold fogging concentrate
A pesticide formulation suitable for application by cold fogging equipment.

Cold frame
A plant bed on the ground enclosed by side walls and covered with transparent material but not heated artificially.

The sheath covering the first leaf of a grass seedling as it emerges from the soil.

Gram-negative, non-sporing, facultative rods that ferment lactose with gas formation within 48 hours at 35°C.

Coliform test
Prescribed methods for analysis of water for the presence of coliform bacteria. May use either the most-probable number of the membrane filtration procedure.

An enzyme which breaks down the protein collagen, a type of cell-cementing substance found in the body.

Colletrial glands
Female accessory glands in insects that produce a substance to cement eggs together or material for an ootheca.

Collodial formulation
Pesticide in which the particle size is less than 6 µm in diameter, and that stay indefinitely dispersed.

Collodial suspension
A term applied to chemicals dissolved in a suitable solvent then added to water throughout which the chemical is dispersed. This produces a condition of extreme subdivision (0.1 micron or less particle size) of the chemical which remains suspended in the water. Collodial suspensions do not diffuse readily through vegetable or animal membranes.

The section of the large intestine extending from the caecum to the rectum.

The introduction and establishment of a species (usually beneficial insects) in a new area or the spread of a pathogen in host tissue away from the initial site of infection and the dependence on the host for nutrients.

In bacteria and yeasts a mass of individuals, generally of one species, living together; in mycelial fungi a group of hyphae (frequently with spores) which, if from one spore or cell, may be individual.

An instrument used in analysing compounds that form a dye or colour when reacted with proper reagents.

The first milk suckled by a new-born animal. The milk contains immune bodies essential for the health of the new-born animal.

The number of combinations of n objects taken r at a time denoted by the symbol Cnr, where Cnr = n! / r!(N-r)!

Combined nitrogen
Nitrogen in a form in which it is bonded to other elements; e.g. ammonia (NH3), nitrate (NO3-), and nitrite (NO2-).

Combine harvester
A machine which harvests and threshes a crop in one operation.

The degradation of a compound only in the presence of other organic material which serves as the primary energy source.

A symbiotic relationship between two species where one benefits but without apparent effect to the other species.

The area where two opposite parts meet e.g. the joint of the upper and lower wings of the nostril; the angle of union of the upper and lower lips.

Commodity product
An expression used to distinguish a patent-free product from one where a company exercises exclusive rights.

Common fixed cost
A fixed cost which does not relate to any one cost unit but is incurred on behalf of multiple cost units.

Common pesticide name
A common chemical name given to a pesticide by a recognised committee on pesticide nomenclature. Many pesticides are known by a number of trade or brand names but have only one recognised common name e.g. the common name for Sevin (R) insecticide is carbaryl.

The relationship between two model compartments such that flows leaving either compartment can get to the other.

Collection of populations of plants and animals in a given habitat; the ecological unit used in a broad sense to include groups of various sizes and degrees of integration.

Companion crop
A regular crop in which a slow growing, later maturing crop is also sown e.g. oats and clover.

Compartment diagram
A diagram for a simulation model where state variables are in boxes (compartments) and flows are represented by arrows.

Two compounds are compatible when they can be mixed without undesirably affecting each other's properties. In plant pathology this term means that a pathogen is able to form a parasitic relationship with a host plant. Normally, this involves avoiding the resistance response of the host by various procedures. These may include delay or failure in triggering of the response or overcoming the response (e.g. phytoalexin degradation).

Capable of co-existing in harmony. When two or more chemical insecticides or diluents are mixed together they must not react in such a way that the chemical composition is changed (gelling or precipitation) so as to render the mixture harmful to plants, less toxic to pests, more corrosive to equipment or in some cases, completely useless.

Compatibility agent
A substance which improves compatibility of pesticides.

The ability of plants or plant parts to make up for the yield producing function of other plant or plant parts.

Compensation point
Depth in a body of water at which the light intensity is such that the amount of oxygen produced by a plant's photosynthesis equals the oxygen it absorbs in respiration; the point at which respiration equals photosynthesis so that net production is zero.

Ability to take up DNA and become genetically transformed.

Occurs when two or more organisms, or populations, interfere with or inhibit one another through striving against each other to secure some resource that is in limited supply e.g. the active demand by weeds for nutrients, moisture, light and other essential growth factors adversely affecting crop yields. Occurs when two or more organisms, or populations utilise common resources that are in short supply ('exploitation'); or if the resources are not in short supply, competition occurs when the organisms seeking that resource harm one another in the process ('interference).

'Competition curve'
The relationship between percent parasitism and the area traversed by a parasite population Pa (Nicholson, 1933) The curve rises asymptotically towards 100% as parasite density increases.

Competitive exclusion
Two species competing for limited resources can only co-exist if they inhibit the growth of competing species less than their own growth (Ayala, 1970). Where one species eliminates the other is known as competitive exclusion or 'Gause's Principle'.

Collective name for a complex of proteins in blood serum that bind in a complex series of reactions to antibody (either IgM or IgG) when the antibody is itself bound to antigens on the cell surface.

Complement fixation
Removal of complement can be measured and is a sensitive indicator of occurrence of an antigen-antibody reaction.

Complement fixation test
Immunological method used to detect presence of antibodies that bind (or fix) complement; a standard diagnostic test for many infections.

Complement of an event
The complement of an event A is the collection of all sample points in the sample space that are not in A. The complement of A is denoted by the symbol A, and P(A) = 1-P(A).

The exact pairing of the nucleic acid base sequence of two single strands of DNA or RNA; based on the hydrogen bonding of adenine with thymine (or uracil) and guanine with cytosine.

Complementary products
Where the process of producing product X also leads to more of product Y.

Non-identical but related genetic structures that show precise pairing. Serving to complete or to balance a deficiency.

Resistance governed jointly by two or more genes, one of them alone resistance being ineffective.

Occurs when a virus is assisted by another virus (or a strain of the same virus) to replicate.

Complete factorial design
An experimental design in which parameters at fixed levels are included in all possible combinations.

Completely randomised design
A simple form of experimental design in which the treatments are randomly allocated to the experimental units.

Complicating disease
A disease supervening during the course of an already existing infection which is not an essential part of the infection itself, though it may result from it or from independent causes.

An identifiable unit within a system; it may be capable of independent physical existence or be an entirely conceptual entity.

A mixture of organic materials used as a soil conditioner and fertiliser; prepared by microbial degradation of plant materials.

A specific association of atoms held together by strong chemical bonds, e.g. oxygen gas (O2) and water (H2O).

Compound event
An event composed of two or more simple events.

Compound-interest disease
A disease which goes through more than one cycle of infection during a growing season, analogous to a bank account giving compound interest.

Compound interest rate
The rate of interest used in compounding or discounting.

Adding interest to a sum of money at a chosen rate, including interest on the interest accumulated each year i.e. calculation of the future value of a present sum.

Flattened from side to side.

A DNA molecule consisting of two or more separate molecules linked end-to-end to form a long linear structure.

Normally referring to commercial pesticide preparation before dilution for use.

Concentrate spraying
Application of concentrate (q.v.). Direct application of the pesticide concentrate without dilution.

Proportion of active ingredient in liquid or dust pesticide preparation, before or after dilution e.g. kilo/litre or percent by weight.

Forming one circle around another with a common centre.

A general idea of understanding, especially one derived from specific instances or occurrences.

The process of formation of a liquid from its vapour: in meteorology, the formation of liquid water from water vapour. Since the capacity of air to hold water in the form of vapour decreases with temperature, cooling air is the normal method by which first saturation, then condensation, is produced. Such cooling is effected by three main processes: (i) Adiabatic expansion of ascending air; (ii) Mixing with air at lower temperatures; (iii) Contact with earth's surface at lower temperature. The water vapour condenses as a cloud in (i), as fog or cloud in (ii), and as dew or hoar frost in (iii).

Conditional probability
The probability of occurrence of an event A given that another event B has occurred is called the conditional probability of A given B and is denoted as P(A\B). Computationally P(A\B) = P(A\B)/P(B).

To bring something to a certain condition by means of an appropriate treatment.

The part of a toxic molecule that functions to produce an effective concentration of the toxicant at the site of activity.

Bearing surfaces between arthropod joints, which provide the fulcra on which the joints move.

Cone (or Swirl) nozzle
See nozzle iii.

Confidence coefficient
A probability associated with a confidence interval that expresses the probability that the interval will include the parameter value under study.

Confidence interval
An interval computed from sample values. Intervals so constructed will straddle the estimated parameter 100(1-_)% of the time in repeated sampling. The quantity (1-_) is called the confidence coefficient.

Congeneric species
Species belonging to the same genus.

Congenital disease
One that is present in an animal at birth, it is not necessarily inherited. A disease which is determined by the genetic structure of the animal; a disease which is acquired during foetal life.

Congo floor maggot
Bloodsucking African maggot, Auchmeromyia luteola.

Congruential generator
An algorithm for generating pseudorandom numbers that involves starting with a seed and generating the numbers by a series of multiplications, additions, and divisions of numbers.

Asexual spores produced on conidiophores other than sporangiospores and chlamydospores spread by air currents.

Simple or branched hypha bearing one or more conidia.

Any asexual spore (other than a sporangiospore or intercalary chlamydospore).

Asexual fungal spore produced exogenously on a specialised hypha (conidiophore) by Zygomycete fungi or actinomycete bacteria.

A water soluble derivative of a chemical formed by its combination with glucuronic acid, gluthathione, sulphate, acetate, glycine etc.

In eucaryotes, the process of sexual reproduction by which haploid gametes fuse to form a diploid zygote; in procaryotes, transfer of genetic information from one cell to another by cell-to-cell contact.

The delicate mucous membrane that lines the eyelid and covers the eyeball.

Inflammation of the conjunctiva.

Truncated cone of spiral fibrils located within the polar rings of the suborder Eimeriina.

A two-membered bacterial culture (or natural assemblage) in which each organism benefits from the other.

Constant or proportionately
Proportional means corresponding in degree or amount; in y = a, y corresponds with x in a fixed proportion, a, which is the constant of proportionality.

Always synthesised; a type of enzyme whose synthesis is not regulated.

Constitutive enzyme
One synthesised continuously during growth, not subject to induction or repression.

Constitutive resistance
Genetically controlled, inherited resistance.

A quantitative limit imposed on variables or combinations of variables in an optimisation problem.

A hetertrophic organism or population, usually animal, fungus or virus that utilises dead or living organic matter as food.

Contact action
The act of clogging spiracles of joints, surface corrosion of the cuticle, or creation of physical and chemical changes in nervous systems in whole or part of pests exposed to this class of insecticides.

Contact herbicide
Herbicide that kills those plant parts with which it comes into contact (as opposed to translocated herbicide). Often acting on the membrane systems of leaf tissues and inhibiting photosynthetic and respiratory metabolism.

Contact inhibition
The ability of a cell to stop growing when it contacts adjacent cells.

Contact insecticide
Insecticide that kills insects by contact with and probably absorption through cuticle.

Contact pesticide
One which relies on actually hitting the target or which persists until a mobile pest comes into contact with it. Has little or no power of movement in the plant.

Contact poison
Pesticide that kills when it contacts some external part of a pest - see contact herbicide and contact insecticide.

Contact pre-emergence herbicide
Application of a contact herbicide to weeds before the treatment crop has emerged.

Contagious disease
An infection transmitted through the air, by water, food, objects, direct contact or by insects or animals, synonymous with communicable disease.

A micro-organism, virus or substance accidentally introduced into a culture, substrate of medium.

To alter or render a material unfit for a specified use, as by the introduction of a chemical.

Material bearing or containing a foreign substance or organism but not infected by it.

Harbouring of or contact with micro-organisms (or other organisms such as insect parasites) in absence of a relationship which may be considered commensalistic, mutualistic or parasitic or the presence of an unwanted pesticide or other material in or on a plant, animal or their by-products.

Contaminative antigen
Antigen borne by the parasite that is common to both the host and the parasite, but which genetically is of host origin.

Contestable markets
Markets in which entry and exit is costless.

'Contest' competition
Where each successful competitor gets all it requires for survival or reproduction while the remainder gets none or insufficient.

Contingency allowance
Allowance to cover unexpected events e.g. a drought resulting in severe losses of cattle or crops.

Contingency planning
The process of developing secondary plans for R & D tasks, activities, administration etc. which will be implemented if the primary plans turn out to be unrealistic.

Contingency table
A two-way table for classifying the members of a group according to two or more identifying characteristics.

Continuous distribution
A distribution with an infinite number of states, with the states being contiguous.

Continuous random variable
A random variable defined over, and assuming the infinitely many values associated with, the points on a line interval.

Continuum index
Measure of the position of a community on a gradient defined by the species composition.

Contract costing
A type of job costing where all costs are accumulated on an individual contract, e.g. for a building construction.

The difference between sales and the variable cost of goods sold, before charging any fixed costs.

Contribution graph
A graph that plots the total cost, total revenue and variable costs for a specific product, thus highlighting a product's contribution.

Contribution margin
The difference between revenue per unit and variable cost per unit, in the framework of break-even analysis.

Contribution price variance
Used in standard marginal costing to evaluate any difference in actual sales price from the standard sales price for the actual quantity sold. Identical with the sales price variance in standard absorption costing.

Contribution ratio or profit/volume
Contribution expresses as a percentage of sales revenue.

Contribution volume variance
Used in standard marginal costing to evaluate the total contribution gained or lost through actual sales volume varying from the budgeted sales volume.

In experiments; untreated subjects that affords a standard of comparison with those given crop protection treatment.
(i) Legislative; the use of legislation to control the importation and to prevent any spread of a pest within a country.
(ii) Physical; the use of mechanical (hand picking) and physical (heat, cold, radiation) methods of controlling pests.
(iii) Cultural; regular farm operations designed to destroy pests.
(iv) Chemical; the use of chemical pesticides as smokes, gas, dusts and sprays to poison pests.
(v) Biological; the use of natural predators, parasites and disease organisms to reduce pest populations.
(vi) Integrated; the very carefully reasoned use of several different methods of pest control in conjunction with each other to control pests with a minimum disturbance to the natural situation.
Any of a number of factors that affect the rate of change of a state variable in a simulation model. These controls are usually exercised through functional relationships (equations) for process rates.

Control chart
Used in quality control to monitor product consistency it is a graph of a sample statistic over many successive samples from a production process.

Controllable cost
A cost which is the direct responsibility of, and influenced by, the manager concerned.

Controlled drop application
A term used loosely to describe spinning disc and other systems intended to produce spray droplets of uniform size.

Control limits
Values on a control chart that are three standard deviations (of the sample statistic used) on either side of the centreline. Also the limiting airborne concentration of potentially toxic substances which are judged to be 'reasonably practicable' for the whole spectrum of work activities and which must not normally be exceeded.

The process of making adjustments to correct for the deviations from a planned scheme.

Control loss
Cost increases attributable to management's inability to monitor and control the performance of subordinates.

Control points
Those points-in-time in the course of a project, when some technical or administrative deliverable may be used as an indicator of the overall technical cost and/or performance of the project.

Control system
Optimisation techniques for maximising some objective function over time by exercising continuous control over a system. The methods have been most successfully applied in physics and electrical engineering.

Convenience sampling
The selection of a sample that can be obtained simply and conveniently.

Conversion costs
The cost of converting raw materials into finished goods.

Conveying equipment
Equipment used to move grain from one place to another by mechanical means, belt or screw conveyors are used to move grain horizontally and up small inclines. Bucket elevators are used to move grain e.g. rice vertically.

Cool-season grass
Grass that grows most luxuriantly during the cool seasons of the year.

A crustacean zooplankton common in marine and, to a lesser extent, freshwater systems.

Juvenile stage(s) that succeed the naupliar stages in copepods, often quite similar in body form to the adult.

Copy number
The number of molecules expressed per genome of a plasmid or gene which are contained in a cell.

Larva with a ciliated epithelium, hatching from the egg of certain cestodes; a ciliated oncosphere.

An asexual fruiting body consisting of a cluster of erect intertwined hyphae bearing conidia at their apices.

A chemical which, when bound to a repressor protein, shuts off expression of a gene; usually the chemical produced by the enzymes coded for by that gene.

Coriolis acceleration
In meteorology, coriolis acceleration is described as an apparent acceleration which air possesses by virtue of the earth's rotation with respect to axis fixed in the earth. Sometimes termed 'geostrophic acceleration'.

Coriolis error
If an aircraft could hold an exact great circle heading and fly at a constant speed, its track would be slightly curved in space due to the rotation of the earth. In the northern hemisphere the aircraft curves to the right. This effect must be allowed for in aircraft instrumentation, liquid filled instruments, pendulums, accelerometers, etc.

An external, secondary tissue impermeable to water and gasses. It is often formed in response to wounding or infection.

A solid, short, swollen underground stem, usually erect and tunicated, of one year's duration, with that of the next year at the top or close to the old one.

Secondary corm produced from an old corm.

The transparent structure forming the anterior part of the eye.

A pair of tubes on the upper posterior end of the abdomens of some Hemiptera, which secrete a waxy liquid.

Coronary band
The band joining the skin of the pastern to the upper edge of the hoof.

The line where the pastern and hoof meet.

Correlation coefficient
A measure of the degree of the linear relationship between two variables.

A graph illustrating the auto-correlations between members of a time series (vertical axis) for different separations in time k (horizontal axis).

The process of checking whether a model agrees with available evidence about the ecosystem or processes it represents.

In plants the tissue region between the vascular system and the epidermis. In fungi the region inside the spore coat of an endospore, around the core.

A solvent having a very high solvency for a pesticide which is used in combination with a cheaper solvent processing lower solvency. The resultant effect is to increase the solvency of the lower priced solvent and enable the formulation to contain a higher content of active ingredient.

Cosmetic quality
Aesthetic characteristics of a fruit or vegetable which have no relation to nutritional quality e.g. no blemishes or discolouring.

Plasmid vectors designed for cloning large fragments of eukaryotic DNA. The vector contains cos site (= cohesive end sites) that enable it to be packaged in a phage coat in vitro (after King & Stansfield, 1990).

A species occurring very widely throughout the major regions of the world.

A longitudinal wing vein on an insect, usually forming the anterior margin. Also a prominent striated rod in some flagellate protozoa that courses from one of the kinetosomes along the cell surface beneath the recurrent flagellum and undulating membrane.

Cost benefit analysis
An appraisal technique that attempts to place values on all benefits arising from a project and then compares the total value with the project's total cost.

Cost centres
A concept for financial management, which identifies the smallest particular organisational units or research activities to which costs may be held accountable in a institute.

Cost classification
The analysis of costs into homogeneous groups according to source, nature and ultimate destination in the costing system.

Cost code
A numbering system used to describe the type, source and purpose of all costs and income.

Cost direct or indirect
A direct cost is one which can be specifically allocated to a product, as in the case of materials used and labour expended. An indirect cost cannot be directly related to any particular product but is more general in nature. Indirect costs are alternatively called overheads and direct costs are sometimes referred to as prime costs.

Cost effectiveness analysis
An appraisal technique aimed at finding the cheapest way of achieving a detailed objective and of getting the best value from a specified expenditure level.

Cost element
The primary division of expenditure into materials, labour and expense where the latter represents any expenditure that is not for materials and labour.

Cost of uncertainty
The smallest expected opportunity loss in a decision-making problem involving uncertainty.

Cost leadership
A 'generic' form of corporate strategy which involves producing at lower cost than the competition.

Cost-plus pricing
Where a percentage mark-up is added to the total cost of a product to calculate the selling price.

Cost prediction formula
A quantitative technique for predicting the ultimate costs of a R & D project, or components of a project.

Cost standards
Uniform and relatively stable guide-lines for planning the costs of resources which are used frequently by the research institutes.

Cost unit
Any product or service to which costs can be charged.

Cost variable or fixed
A variable cost varies in total pro rata to the volume of production. A fixed cost stays the same total sum over a range of output levels.

Cost/volume/profit analysis
A study of the effect of changing levels of output on profit.

Cotton square
Fruiting bud of the cotton plant.

Seed leaf: leaf-like structures in the embryos of seeds. Grasses have one cotyledon in each seed (monocotyledon), while legumes have two (dicotyledon).

The first leaf, or pair of leaves - depending on whether the plant is monocotyledonous or dicotyledenous - developed by the embryo of seed plants.

A substance that deters feeding by certain insect pests Derived from glucosides in the plant, it is formed when tissues are disrupted by the feeding insect.

Covalent binding
The irreversible interaction of xenobiotics or their metabolites with macro-molecules such as lipids, proteins, nucleic acids.

Proportion of surface area of plant material on which a pesticide has been deposited.

Cover crop
A crop grown to maintain a plant cover on the land to prevent erosion and leaching. When turned under to improve the soil, it becomes a green-manure crop.

A bovine female which has had at least one calf.

Coxa (pl. coxae)
The basal segment of an arthropods limb.

Crude protein.

Crude protein equivalent.

Cracking clay
Clay which forms cracks upon drying.

The active first instar of a scale insect.

Any creamy layer that separates at the top or the bottom of a pesticide emulsion.

Creamed emulsion
A liquid mixture in which a fat is suspended in minute globules; any milky solution.

Any third party to whom money is owed. Trade creditors are purchases bought on credit and awaiting payment in due course.

The fisherman's sack. Creel censuses are a method of asking fishermen what they have caught and is used as a measure of catch and effort in recreational fisheries.

Creeping eruption
Skin condition caused by hookworm larvae not able to mature in a given host.

A hooked, or spine-like process at the posterior end of the insect pupa, often used for attachment.

A crackling sound which is heard, e.g. in some lung diseases when the ear is placed close to the thorax; or when the fingers are pressed into the skin covering a gaseous lesion such as occurs in black-quarter.

Animals that are active in the twilight, pre-dawn and at dusk.

Inner membrane in a mitochondrion, site of respiration.

Critical level
Maximum level or intensity of pests or other constraints at which crop damage has not yet occurred but it is expected to occur soon.

Critical path
That path along a network plan which requires the greatest time for completion.

Critical path analysis
A networking technique that breaks a project down into separate tasks and places them in sequence in an arrow chart.

Critical Path Method (CPM)
A quantitative technique which, when applied to network planning, is helpful in calculating the minimum time and sequence of tasks needed to complete a R & D project.

Critical period
The time span during which crops must be kept weed-free to maximise yield.

Critical point model
Equation providing estimates of crop losses for a given kind and level of constraint assessed at a particular point in time.

Critical value
In statistical tests it is the value of the test statistic that separates the rejection and acceptance regions.

Hooked spines at the tips of the prolegs of lepidopterous larvae.

Crook stage
The stage after bean seedlings have broken through the soil but before the stem has become erect.

Community of plants grown to provide feed, food, fibre or other useful commodities.

Crop diversification
Cropping system where a number of different crops are planted in the same general area and may be rotated from field to field, year after year.

Crop hygiene
(= Phytosanitation) The removal and destruction of heavily infested or diseased plants from a crop so that they do not form sources of re-infestation.

Crop injury (by pests)
The detrimental effects of the pests on the plant tissue.

Land used regularly for the production of crops, except forest crops.

Crop loss
A reduction in either quantity and/or quality of yield. The detriment caused by the pests expressed in the market as monetary values.

Crop loss data
Factual information on crop losses obtained through individual expert testimony, farmers, enquiries, literature reviews, field experiments, surveys or remote sensing.

Crop loss direct data
Estimate that assumes that crop loss is equal to the proportion of plants lost in a crop.

Crop loss distribution
The frequency of occurrence of different degrees of crop loss in space or time.

Crop loss (economic)
Direct loss per unit area (i.e. expected yield minus actual yield). The assessment of economic losses is the ultimate objective of work on crop loss.

Crop loss (indirect by pests)
A loss that is a consequence of a direct loss, e.g. the cost of treatment, or of using an unnecessary amount of land for a crop, etc.

Crop loss inquiries
A method of securing subjective crop loss information mainly from farmers or people otherwise connected with crop production, processing or marketing.

Crop loss profile
A set of data, often in quantitative graphical form, defining the relative importance of individual constraints on yield.

Crops loss programme
A programme designed to evaluate crop losses and structured on a number of essential stages; field experiments; surveys; integration of experimental and survey data; extrapolation to national (regional) figures.

Cropping intensity
The number of years of cropping multiplied by 100, and divided by the number of years of the rotation. It is expressed as 'R', e.g., 3 years crop, 7 years fallow = 10 year rotation. Thus R = (3x100)/10 = 30

Crop production constraint
Any factor which interferes with the maximisation or optimisation of yield e.g. pest damage.

Crop residue
The unused part of the crop that is not harvested in the grain system of farming and is usually returned to the land e.g. straw, cornstalks, clover and soybean hulls.

Crop yield (actual)
The commercially valuable harvested produce of the field, expressed in market (e.g. weight) or in monetary units.

Crop yield (direct effect of pesticides)
The effect of a pesticides on yield other than that resulting from its control of specific pests.

Crop yield (expected)
The actual yield plus assessed losses.

The exchange of corresponding segments between chromatids of homologous chromosomes.

Placing or deposition of the pollen from a flower to the stigma of a flower of another plant.

Cross protection
The phenomenon in which plant tissues infected with one strain of a virus are protected from infection by other strains of the same virus.

A phenomenon that occurs when the development of physiological resistance to a given chemical results in the simultaneous increase in dosage rates to other chemicals required to produce mortality in the resistant strain as compared to the dosage required to produce mortality in susceptible strains with the other chemicals.

Having a thin sheet of matter covering the surface of a tissue or organ when it is inflamed.

The point where stem and root join in a seed plant. Group of central basal stems.

Crown closure
The time in a forest's life when all the ground surface is covered with leaf area.

Crown roots
Roots arising directly from the crown.

Crozier formation
Process of ascus development from coiled tips of ascigerous hyphae.

Branches of intestine of a flatworm.


Cryptic error
The biological error arising when plots in an experiment differ from the fields they are meant to represent. Also called 'representational error'.

Intermediate, free-swimming larval stage of the isopod suborder Epicaridae, developing after microniscus; attaches to definitive host.

Pre-erythrocytic schizont of Plasmodium spp.

Producing or bearing crystals; the term is applied to a number of Bacillus species (bacteria) which, in addition to the endospore, produce a discrete, characteristic crystal or crystal-like inclusion in the sporulating cell.

Series of stout, peg-like spines on the head (genal ctenidium) and first thoracic tergite (pronotal ctenidium) of many fleas.

To remove unwanted animals (e.g. non-breeding cows or aged stock) for sale or slaughter.

Cull pile
A discarded pile of plant material, especially potato tubers.

Breeding animals removed from the breeding population, generally on account of some physical or performance deficiency.

A monocotyledonous stem which is usually hollow except at the nodes or joints.

An agricultural, horticultural or forestry variety, which, when reproduced (sexually or asexually) retains its distinguishing features, as distinct from a botanical variety. A cultivar name should always be written with a capital letter and given single quotation marks, e.g. banana 'Gros Michel'.

Cultural control
A pest control method in which normal agronomic practices, tilling planting, crop spacing, irrigating, harvesting, waste disposal, crop rotation are altered so that the environment is less favourable for the pest (Stirling, 1985) The application of agronomic, agricultural and silvicultural practices etc. to control pests e.g. ploughing under of crop residues, pruning and destruction of infected tree branches, crop rotation (van den Bosch, 1980).

A particular strain or kind of organism growing in a laboratory medium.

Culture medium
A preparation of nutrient material which is used for cultivation of micro-organisms or other living cells.

Cumulative distribution function
A function that gives the probability that a random variable takes on any value less than or equal to its argument. Usually denoted by F(x) and abbreviated c.d.f.

Cumulative pesticides
Those chemicals that tend to accumulate or build up in the tissues of animals or in the environment (soil, water).

Curative pesticide
A pesticide that can inhibit or eradicate a disease-causing organism after it has become established in the plant or animal.

Curative spray
See spray iv.

Curative treatment
Treatment that reduced disease when infection has already taken place.

Current assets
Stocks, work-in-progress, debtors and cash/bank balance.

Current cost accounting
A procedure for adjusting items in a company profit and loss account and balance sheet for the effects of inflation.

Current liabilities
Short-term sources of finance from trade creditors, bank overdraft, dividend and tax provisions awaiting payment within the next twelve months.

Current ratio
A measure of liquidity obtained by dividing current assets by current liabilities.

Curve expenses
A term often used to describe a curvilinear total cost function. The curved total cost line can be drawn on a graph to determine a budget cost allowance for different levels of activity.

Relating to the skin.

Cutaneous exanthema
An eruptive condition of the skin.

The outer protective envelope of any living organism. In the case of mammals or arthropods the alternative names skin or integument are often used but cuticle invariably in respect of green plants. Plant cuticle is a macro-molecular structure of predominantly paraffinic composition over-lying cellulose and pectin.

A waxy, fatty material that with the cuticle forms the cuticularised layers covering the shoot of a plant.

Larva of certain Noctuidae (Lepidoptera) that live in the soil, emerging at night to eat foliage and stems; serious pests of root crops of many other crops as seedlings.

Blue-green bacteria; photosynthetic procaryotes which contain chlorophyll and phycocyanin pigment.

A blueness of the skin or mucous membrane, due to insufficient oxygenation of the blood, often found in cardiac insufficiency or occlusion of main veins.

Cyclic effect
A periodic movement in a time series that occurs as a result of stimuli from the economy and is generally not predictable.

Cyclic photophosphorylation
Light-driven ATP synthesis in which no external electron donor or acceptor is involved.

Cyclodiene insecticides
Highly chlorinated cyclic hydrocarbons with characteristic endomethylene bridged structures.

An antibiotic synthesised by streptomycete bacteria which inhibits protein synthesis in eucaryotic cells.

Cyclone separator
Large, round, tank-like structure, usually metal, used to separate particles carried in an airstream in the post-harvest industry.

Post-naupliar larva of barnacles (crustacean subclass Cirripedia) in which the carapace largely envelopes the body; so called because of its resemblance to the ostracod genus Cypris.

An encysted zoospore (fungi); in nematodes, the carcass of dead adult females of the genus Heterodera which may contain eggs. In bacteria and protozoa a resting stage in which the whole cell is surrounded by protective layer.

Juvenile acanthocephalan that is infective to its definitive host.

Metacestode developing from the oncospher in most Cyclophyllidae. It usually has a 'tail' and a well-formed scolex.

Infection with one or more cysticerci.

Cysticercus bovis
The tapeworm with a life cycle from human faeces to cattle where it causes cysts typically in the muscles and near joints. These may be ingested by man eating raw or lightly cooked meat, who then becomes infected with the tapeworm.

Cystogenic cells
Secretory cells in a cercaria that produce a metacercarial cyst.

A respiratory pigment which occurs in three forms a, b, and c, and is found in most, if not all, aerobic cells. This hemochromagen especially in the c form has been studied in arthropods relative to the effects of toxins, and possible insecticide-resistance mechanisms.

Cytochrome P-450
A haemprotein involved, e.g. in the liver, with Phase 1 reactions of xenobiotics.

That which kills cells.

Proteins essential for oxidation-reduction processes in cells.

Cytogenetic breeding
Breeding techniques that involve the manipulation or alteration of genetic material in cells, e.g. exposure to radiation or application of chemicals such as colchicine.

Separation of cytoplasm into daughter cells following nuclear division.

Plant growth-regulating chemicals which promote cell division in cells of various plants; endogenous cytokninis are mostly N6-substituted adenine derivatives.

The science of the structure, function and life history of the cell.

Fibres radiating out from a zoitocyst into surrounding muscle; found in some species of Sarcocystidae.

The material enclosed by a cell wall in which are situated the nucleus, endoplasmic reticulum, mitochondria and other organelles.

Cytoplasmic incompatibility
'A kind of prefabricated sterility' in the directed matings between certain allopatric populations of the same species, resulting from the inability of the sperm from one strain to penetrate the cytoplasm and fertilise the egg of the other strain.

Cytoplasmic inheritance
Inheritance dependent upon hereditary units in the cytoplasm, e.g. cytoplasmic male sterility.

Cytoplasmic polyhedrosis
A viral disease of insects characterised by the formation of polyhedral inclusion bodies (polyhedra) in the cytoplasm of the midgut epithelial cells.

Causing disturbance to cellular structure or function often leading to cell death.

Cytotoxic T cell
A T lymphocyte which is able to recognise foreign antigens on other cells and then destroy the other cell; also called killer T cells.