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Glossary of Terms

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R & D
Research and Development is a phrase which encompasses the wide range of technical activities required to derive special knowledge and process which will help resolve applied problems particularly as they relate to commercial opportunities and products.

R & D management
(see research management).

The intrinsic rate of natural increase.

Race or strain
Organisms (usually pathogens) of the same species and variety that differ in their ability to parasitise varieties of a given host or that differ in their reaction to pesticides. A genetically and often geographically distinct mating group within a species.

Race non-specific resistance
Resistance to all races of a pathogen.

Race-specific resistance
Resistance to some races of a pathogen, but not to others.

An inflorescence usually conical in form, consisting of an elongated axis bearing flowers on short stems.

A small rachis; the axis of a spikelet.

The axis of a spike or raceme. Central, longitudinal, supporting structure in the ovary of some nematodes.

Radial diffusion
An immuno-diffusion serology test in which liquid antigen (or antibody) is placed in a well cut in gel containing the other reactant and allowed to diffuse out into the gel.

Radiation frost
Frost caused by the ground radiating or losing heat at night.

Radiation night
A night characterised by the absence of cloud and wind, on which there is a major radiation cooling of the ground and, by conduction of heat from air to ground, of the surface layers of air.

The principal root or a seedling.

Radioactive tracers
Radioactive elements incorporated into insecticides or other chemicals to aid in tracing the metabolism of the compound in the living, moribund, or dead organisms.

An immunological assay employing radioactive antibody for the detection of certain antigens in serum.

A radioactive form of a chemical element. Often used to label or trace an element through an ecosystem or individual plant or animal.

One of a broad class of elements capable of becoming radioactive and giving off atomic energy. Some radioisotopes occur naturally, others are produced artificially. The word is synonymous with radioactive elements and includes tracer elements.

Randomised blocks design
The design used in experimental work in which the treatments are arranged in random order within the replicates blocks to eliminate bias.

Randomised response sampling
A survey sampling procedure for dealing with potentially sensitive or embarrassing material that requires a question on the sensitive topic be paired with an innocuous question. The respondent answers only one of the two questions, which he or she has selected at random.

Random numbers
Numbers generated according to some probability distribution.

Random sampling
The most commonly used method of sampling for pests in which samples are taken at random (each unit/point in the sample space is equally likely to be included) to determine pest numbers or damage levels. Sampling procedures in which each point in the sample space is equally likely to be included in the sample.

Random variable
A numerical quantity whose value is determined by the outcome of a random experiment.

Random walk
A probability model for movement direction and angle often simulated using Monte Carlo methods.

A large area of natural pasture land, or in statistics the range of a set of n measurements x1, x2, x3, ..., xn is the difference between the largest and smallest measurement. Of a pest, the geographical region or regions in which it is known to occur.

Rank correlation coefficient
A number between -1 and 1 that measures the correspondence between two sets of rankings rather than the data values themselves.

Term commonly used to denote the amount of active ingredient or formulation applied per unit area, per plant etc. (application rate) regardless of percentage of chemical in the carrier (dilution) or the volume of spray applied per unit area, per plant etc. (volume rate).

Rate and dosage
These terms are synonymous. Rate is the preferred term. Rate refers to the amount of active ingredient material (such as 2,4-D acid equivalent) applied to a unit area.

Rate of completion
Literally how fast a R & D project is complete; quantitatively the slope of a line which represents the total proportion of technical work done (or planned to be done) for each control point (e.g. monthly, quarterly, annually etc.).

Rate of expenditure
Literally how fast money is spent over the life of a R & D project; quantitatively it is represented by the slope of a line which represents the total proportion of available funds spent (or planned to be spent) for each control period (e.g. monthly).

Two figures usually extracted from the profit and loss account and/or balance sheet and related together as a percentage, ratio or function.

Ratio estimation
An estimation procedure based on the relationship between two variables y and x that have been measured on the same set of sampled elements.

Raw agricultural commodity
Any food in its raw and natural state, including fruits, vegetables, nuts, eggs, raw milk and meats.

Raw rice
Rice which has not been parboiled.

The degree of acidity or alkalinity of a soil.

An accounting concept which states that profit is earned when a sale takes place and not when cash from that sale is received.

The property of a model that it represents the best understanding of the composite processes available.

Money received by the farmer from either farm or non-farm sources.

Receptive hypha
A specialised hypha protruding out of a pycnium and functioning as a female gamete or gemetangium.

A heritable trait tending to be suppressed by a more active or dominant trait. Expressed only when present in an organism in the homozygous condition and which in a heterozygous condition is suppressed by the dominant allele of the pair.

Recipient controlled
A process whose rate of change depends on the compartment to which the process flows, the recipient compartment.

Reciprocal cross
A cross between the same two strains, but with the pollen and pistillate parents reversed.

Reciprocal crosses
Two crosses between two plants in which the male parent of one cross is the female parent of the second cross.

Reciprocal density- mortality dependence
Mortality inflicted on a population by a biotic factor whose own numbers are changed as a consequence.

Recirculating sprayer
A sprayer system with the nozzle aimed at a catchment device, which recovers and recirculates herbicide that does not hit plants or weeds.

An organism which has acquired DNA from another donor organism either naturally or by artificial gene transfer using genetic engineering.

Recombinant DNA (r-DNA)
A strand of DNA synthesised in the laboratory by splicing together selected parts of DNA strands from different organisms or by adding a selected part to an existing DNA strand.

Recombinant DNA technology
A series of enabling techniques for genetic engineering which allows the manipulation of the DNA.

Process by which genetic elements in two separate genomes are brought together in one unit. The occurrence of progeny with combinations of genes other than those that occurred in the parents, owing to independent assortment or crossing over (after King & Stansfield, 1990). Also, a new strain of a virus that occurs as a result of the breakage and renewal of co-valent links in a nucleic acid chain, so that the nucleic acids are rearranged in the chain.

Recommended limit
A maximum concentration of a potentially toxic substance which is suggested to be safe. Such limits often have no statutory implications and in which case a control or statutory limit should not be exceeded.

Animals (usually fish) reaching maturity.

The addition of new individuals to a population, usually either by birth or immigration.

The last part of the large intestine before the anus. In large animals approximately the last 30 cm.

Recurrent parent
Parent to which hybrid material is crossed in a back-cross.

Recurrent selection
Used in breeding to increase the frequency of favourable genes for yield and other characters by repeated cycles of selection.

An algorithm that operates by repeating itself.

A larval stage in the asexual development of trematodes between the sporocyst and the cercaria when multiplication occurs.

Movement of pesticide subsequent to initial application to other parts of plant, usually by rain.

Red mange
Disease caused by the dog follicle mite, Demodex canis.

Red muscardine
Denotes various mycoses of insects, caused by species characterised by the appearance of pink to brick-red colours on the body of the dying or dead hosts e.g. certain strains of Beauveria bassiana.

See oxidation-reduction system.

Reduced cultivation
A production system in which extent of soil disturbance is less than in conventional practice.

Reducing agent
A chemical which readily gives up the electrons and reduces more oxidised compounds; used to remove oxygen from anaerobic culture media.

Reducing power
Reduced chemicals which serve as electron donors in reduction reactions; often used to mean the source of electrons for reduction of carbon dioxide (CO2) during photosynthesis.

Any chemical reaction involving the removal of oxygen from or the addition of hydrogen to a substance; it occurs with concomitant expenditure of energy.

Reduction division
In which the chromosomes are reduced from the diploid to the haploid number in meiosis.

Reduction potential
The electrode potential for a formal reaction written as a reduction.

Re-entry intervals
That time-interval, required by law, between the application of certain hazardous pesticides to crops and the exposure of workers to treated crops.

Re-introduction of mutualistic fauna in a host deprived of such fauna.

Reflecting boundary
The property of edge or end states in a model involving movement such that movement beyond the edge results in reflection of movement back to the same edge state.

Reflective mulch
A polythene or straw layer placed on the soil surface around the crop plant to control air-borne insect vectors.

A wound or disease that does not respond to treatment.

Prey may be completely free from predation within a spatial or temporal refuge. Spatial refuges can take a variety of forms between two extremes (i) where a constant proportion of the prey are protected and (ii) where a constant number are protected. Temporal refuges occur where prey and predators do not completely overlap in time thereby tending to protect a constant proportion of the prey.

Reproduction of a host part (this may be at the molecular, cellular, tissue or organ level) also the development of whole organisms from single cell cultures.

Chemicals that have been approved for use in agriculture by a Ministry of Agriculture.

Registered seed
Seed that is the progeny of foundation seed, traces directly to it, and is approved and certified to comply with specified standards of purity and quality.

Agricultural and veterinary chemicals registered for sale under appropriate statutes. Details of formulation, safety, efficacy, and environmental acceptability are considered before granting registration.

A statistical technique for fitting a function to a set of data having independent and dependent variables such as to optimise some criterion of fit between the function and the data points.

Regression analysis
The process of fitting a regression equation to a set of data by using the method of least squares. Also includes the various statistical tests and estimates associated with the use of the fitted equation.

Regulated population
One which tends to return to an equilibrium population density following any departure from this level.

As related to population dynamics, the control of population density. Also, a process that controls the rates of synthesis of proteins. Induction and repression are examples of regulation.

A second infection by the same micro-organism or virus, after recovery from or during the course of a primary infection.

Rejection region
In the theory of hypothesis testing the set of values such that if the test statistic assumes one of these values, the null hypothesis is rejected.

Relational diagram
A diagram normally used in modelling to show the inter-relationships of components and processes in a system.

Relative humidity
The ratio of the amount of water contained in a sample of air to that which could be contained in the same volume if it were saturated. The temperature at which the RH is measured is always important since warm air at 50% RH has a much greater drying capacity than cold air at 50% RH.

Release behaviour
Micro-encapsulated pesticides are released by (i) diffusion through the capsule wall and (ii) destruction of the capsule wall by either physical or chemical means. Most are released by diffusion.

Relevant costs
Costs which are affected by the decision under review and which therefore must be taken into account.

Relevant range
The range of activity level within which costs behave in a linear fashion.

Remote sensing
The process of obtaining information on disease/weed/pest intensity from a distance using specialised techniques and instrumentation.

Infected tissue (leaves, etc.) on which the pathogen has ceased to sporulate, hence, no longer infectious host tissue; transition from the infectious to the non-infectious state is also called removal.

Kidney shaped.

A chemical which has the property of inducing avoidance by a particular pest due to unpleasant odour, colour, taste or mechanical effect e.g. substances used to repel ticks, chiggers, gnats, flies, mosquitoes and fleas.

Replacement tissue
Thick-walled parenchymatous cells replacing the mesophyll of leaves injured by 2,4-D.

Repetitions of the same experiment. It is applied in statistics to represent observations that have the same experimental conditions.

The exact duplication of a DNA (or occasionally an RNA) nucleotide sequence.

Reportable disease
A disease which must or should be reported to public health authorities; notifiable disease.

Representational error
The error arising when plots differ from the fields they are meant to represent.

The process by which the synthesis of an enzyme is inhibited by the presence of an external substance, the repressor protein.

The multiplication of one cell into more than one offspring cell.

Reproductive capacity
The capacity of the individuals in a population to increase in number by the production of progeny.

Reproduction curve
The relationship between the numbers of a given stage in generation (n+1) plotted against the numbers of that stage in generation (n).

Reproductive toxicology
(Mammalian) The study of the effects of chemicals on the adult reproductive and nueroendocrine systems, the embryo, foetus, neonate and pre-pubertal mammal.

Scientists primarily responsible for the output of the research through (i) bringing specialised technology to bear on the resolution of specific problems (ii) proposing, conducting and reporting the results of research projects; and (iii) furthering the technical productivity and capability of the research organisations.

Research management
The efficient and effective marshalling, allocation and control of human, material and financial resources in a manner which perpetuates a creative environment in which research and development activities may be used to focus on priority problems.

Living or (rarely) non-living source of infection not always showing symptoms, in which a pest may pass a period free of economic hosts, and serving as a source of inoculum. For instance domestic cats are reservoirs of Toxoplasma gondii.

In statistics, the difference between the observed value of y and the value predicted by a model, (y - y), sometimes referred to as the error of prediction.

Residual herbicide
Herbicide that persists in the soil and injures or kills germinating weed seedlings over a relatively short period of time.

Residual insecticide
An insecticide with properties that make it suitable for application to surfaces which will later be visited by insects. Its efficacy depends upon remaining after application.

Residual pre-emergence
Application of a residual herbicide to the soil before the crop has emerged (see pre-emergent herbicides).

Trace of a pesticide and its metabolites remaining in or on any commodity, animal, plant or environmental component. The term may be applied to contaminants of natural, industrial or environmental origin, but particularly in relation to crops at harvest time.

Residue tolerance
The amount of chemical pesticide residue which may legally remain in or on a food crop.

Natural or genetic ability to avoid or repel attack by parasite or to withstand toxic effects of pesticide (microbial or chemical). Various types of inherited (or constitutive) resistance to pathogens are recognised in plants, but the terms used to describe them have a multiplicity of meanings to different workers. The following terms have been defined according to their most common and accepted usage: Resistance: a host plant can be considered resistant if it has the ability to suppress or retard virus activity. Resistant is the opposite of susceptible and may be quantitatively identified as high (extreme), moderate or low, depending on the effectiveness of the protective mechanism. Tolerance: a host response to virus infection that results in negligible or mild symptom expression, but relatively normal levels of virus concentration and movement within the host compared with a susceptible host. Immunity (immune): terms used to describe absolute exemption from infection by a specific pathogen. An immune plant is not attacked at all by the particular virus and is a non-host of the virus concerned. Field resistance: resistance shown by a host plant under natural field conditions, even though the same host may be susceptible to the virus under experimental conditions. Horizontal resistance: resistance that protects a host against all genetic variants of a pathogen to a greater or lesser degree. Vertical resistance: resistance that protects a host against only specific strains of a pathogen. Continuous resistance: a response involving a gradient from severe infection to extreme resistance in a segregating population. Discontinuous resistance: a response involving distinctive, clear-cut symptoms in a segregating population, which is often controlled by a single dominant gene.

Resistance factor
Resistance gene or genes in a host which have not necessarily been identified but can be used for practical purposes in gene-for-gene relationships.

Factor of production. Commonly classified under labour, land, capital, raw materials.

The oxidative breakdown and release of energy from fuel molecules by reaction with oxygen in aerobic cells. A series of chemical oxidation reactions within the cell controlled and catalysed by enzymes in which carbohydrate and fats are broken down, releasing energy to be used by the cell or organism in its various functions.

Respiratory poison
Material which kills the insect by clogging the respiratory system; may be fumigant or contact poison.

The change produced in an organism by a stimulus.

Response (production) function
Relationship between the amount of variable inputs applied to a fixed resource and the output which results from the inputs.

Resting spore
A fungal spore, usually thick-walled, that is resistant to extremes of temperature and moisture and can remain viable in a dormant condition for an extended period, e.g. chlamydospores, oospores, amphiospores, teliospores.

Restricted-use pesticide
One of several pesticides, designated by an appropriate Governmental Authority, that can be applied only by certified operators, because of their inherent toxicity or potential hazard to the environment.

Restriction enzyme
An enzyme that cuts and effectively excises a piece of DNA. Some restriction enzymes cut the DNA at specific points, others appear to cut at random. Restriction enzymes, of which many hundreds have been identified and isolated, are important tools in the excision and transfer of specific gene sequences from one organism's DNA to another's.

An increase of a pest population after a period of decline, to a level higher than its original one, especially when the decline is caused by a pest control measure.

Covered with net-like ridges.

Reticulo-endothelial system
Total complement of special cells in the spleen, lymph glands, liver and bone marrow which are directly concerned with blood formation, phagocytic destruction of cells, metabolism of iron and the establishment of antibodies.

Process of re-infection, whereby juvenile nematodes hatch on the skin and re-enter the body before moulting to third-stage larvae.

Retro-pharyngeal (lymph node)
The lymph nodes situated posterior to and either side of the pharynx and within the space between the angles of the jaw. They drain the tongue, pharynx and larynx.

A type of RNA virus which can make DNA from its RNA using the enzyme reverse transcriptase; the DNA can then integrate with the host cell DNA; cause of some cancers and AIDS.

Return on extra (marginal) capital
The 'extra' profit resulting from investing extra capital expressed as a percentage.

Return to total capital
The annual operating profit expressed as a percentage of total capital. This figure does not take account of interest, loan repayments, living costs, new capital and tax payments.

Reversible process
A process which proceeds with no change in entropy.

An organism which has regained a characteristic either through reversal of a mutation of because a new mutation cancels the effect of the original one.

Inflammation of the mucous membrane of the nose.

Of the legume root nodule bacteria which fix nitrogen from the atmosphere.

A short, thin hypha growing in a root-like fashion toward the substrate.

A horizontal, underground stem which is distinguished from a root by the presence of nodes, buds and leaves or scales.

An aggregation of hyphae resembling a root and having a well defined apical meristem capable of transporting nutrients and spreading infection over considerable distances; often differentiated into a rind of small dark cells surrounding a core of elongate colourless cells.

A region immediately around plant roots in which the microbial population is enhanced by root exudates.

The two-dimensional micro-environmental space at a root surface.

Stage in the life cycle of a dicyemid mesozoan.

Elongate, electron-dense bodies extending within the polar rings of an apicomplexan.

A five-carbon sugar (pentose) found primarily in ribonucleic acid.

A subcellular particle composed of RNA and protein, which is part of the protein-synthesising machinery of the cell.

Plant disease agents belonging to the Schizomycetes group of bacteria, which may cause virus-like symptoms.

Infection with rickettsiae.

Rigidity; stiffness.

A spot, usually on leaves, surrounded by a ring or rings of chlorotic, necrotic or abnormally dark green tissue, a symptom of many virus diseases.

The likelihood of suffering a harmful effect or effects resulting from exposure to a risk factor (usually some chemical or physical or biological agent). Risk is usually expressed as the probability of occurrence of an adverse effect, i.e. expected ration between the number of individuals that would experience an adverse effect in a given time and the total number of individuals exposed to the risk factor. The term absolute risk is sometimes expressed per unit dose (or exposure) or for a given dose (exposure).

Risk assessment
The outcome of risk identification and risk estimation (identification and quantification of the risk resulting from a specific use or occurrence of a chemical compound including the establishment of dose-response relationships and target populations). When quantitative data on dose-response relationships for different types of population, including sensitive groups, are unavailable, such considerations may have to be expressed in more qualitative terms.

Risk control
The type and level of control required for a specified level of risk.

Risk estimation
The quantification of dose effect and dose response for a substance and linking exposure to the probability and nature of an effect.

Risk evaluation
The complex process of determining the significance or value of the identified hazards and estimated risks to those concerned with or affected by the decision. It therefore includes the study of risk perception and the trade-off between perceived risks and perceived benefits.

Risk identification
The identification of the substance of concern, its adverse effects, target populations and conditions of exposure.

Risk management
The managerial, decision-making and active hazard control process to deal with those environmental agents for which risk evaluation has indicated that the risk is too high.

Risk perception
An integral part of 'risk evaluation'. The subjective perception of the gravity or importance of the risk based on the subject's knowledge of different risks and the moral and political judgement of their importance.

Associated with a river and the area adjacent to it.

Ribonucleic acid, a polymer of the sugar ribose, phosphate, purine and pyrimidine bases which, as an adjunct to DNA, helps to transmit and implement the genetic instructions for protein synthesis carried on the DNA. Some viruses store their genetic information as RNA not as DNA.

Ribonuclease; an enzyme that breaks down RNA.

RNA virus
A virus which contains RNA as its genetic material.

Pesticide applied as a bait, dust or fumigant to destroy or repel rodents e.g. rats or mice and other animals, such as moles and rabbits.

In Gymnosporangium species it is an aecium with a strongly developed peridium extending beyond the chains of aeciospores.

Rogue (or rogueing)
To weed out or cull diseased or defective individuals from a crop field or from a stand of timber.

A sock-like structure facilitating host penetration by Plasmodiophora brassicae.

Roller vane pump
See pump vi.

Romana's sign
Symptoms of recent infection by Trypanosoma cruzi, consisting of edema of the orbit and swelling of the pre-auricular lymph node.

Romanovsky stain
Complex stain, based on methylene blue and eosin, used to stain blood cells and hemoparasites; Wright's and Giemsa's stains are two common examples.

A breeding colony of birds or animals.

Galls and swellings produced on roots as a result of nematode attack.

Root mean square error
A measure of forecast accuracy calculated by taking the square root of the mean square error.

Same as rhizome.

Ropewick applicator
A rope saturated with a foliage-applied translocated herbicide solution that is wiped across the surface of weed foliage. The rope utilises forces of capillary attraction and conducts the herbicide from a reservoir.

A short, circular cluster of leaves.

The beak or proboscis of insect order, Hemiptera. (Tectum) Dorsal part of capitulum projecting over chelicerae in acarines.

The softening, discoloration and often disintegration of a succulent plant tissue as a result of fungal or bacterial infection.

Applied to cropping, the practice of growing different crops on the same land in a regular, recurring sequence. Rotation is adopted to hinder the development or because of complement effects, or demands on the soil or for convenience of spreading the times of peak labour demand.

Rotational grazing
Moving cattle methodically from one paddock to another in a rotation of paddocks, resting each in turn (see set-stocking).

A power-driven agricultural machine having an axle on which are mounted L-shaped blades and which rotates faster than the supporting wheels, so that the blades chop and stir the surface of the soil.


Species of organism that uses a survival and reproductive 'strategy' characterised by high fecundity, high mortality, short longevity; populations controlled by density-independent factors.

Rubber roll husker
Machine used to remove the husk from the paddy grain by passing the grain between two rubber rolls operating at different peripheral speeds.

Slender projections of the exterior surface of a dicyemid mesozoan.

Rough; said of leaves roughened or crinkled by viral diseases, e.g. rugose mosaic of potatoes.

The state of being wrinkled or with ridges.

The first and largest of the four stomachs of ruminant animals in which initial digestion occurs by anaerobic fermentation by bacteria and protozoa.

In a series of observations of attributes the occurrence of an uninterrupted series of the same attribute is called a run. A run can be a length of 1.

A numerical approximation technique for differential equations.

Process of shedding spray from surface during and immediately after pesticide application, when droplets coalesce to form continuous film and surplus liquid drops from surface. Also, the water, derived from precipitation, that ultimately reaches stream channels.

With creeping stems or roots.

Running mean
A consecutive series of averages of two or more consecutive data.

A hyperplastic symptom of disease in which brownish, roughened areas form on the skin of fruit or tubers because of excessive cork-cell production caused by a rust fungus (order Uredinales).