Definition of terms

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H

Name Description Related terms
HACCP program

The Hazard Analysis and Critical Control Points program, which is commonly a part of an industry quality assurance program.

half-life

Also expressed as T/50 or T1/2. The time taken for a substance to decrease by half.

hand sprayer

A small, portable pesticide sprayer that can be carried and operated manually.

handling

From s. 3 of the Agvet Code:

Includes transportation, storage, processing, use or disposal.

hard water

Water that contains certain minerals, usually calcium and magnesium sulfate, chlorides or carbonates in solution, to the extent that a curd or precipitate, rather than a lather, forms when soap is added. Very hard water may cause objectionable precipitates in some herbicidal sprays.

harvest aid

A chemical applied to a plant before harvest to make it easier to machine harvest the crop, often by reducing the amount of foliage.

harvest date

The day a crop is removed from its site of growth, as from a tree, bush or vine or cut (as in the case of forage).

harvest interval

The period between the last application of a pesticide to a crop and the harvest, usually defined by law.

haulm

The above-ground parts (stems and stalks) of potatoes, peas, beans, etc. (without the pods in the case of legumes).

haulm killer

A chemical that kills off the potato plant tops to facilitate harvest.

hazard

The inherent property of an agent (eg pesticide) or situation that has the potential to cause adverse effects when an organism, system, or (sub)population is exposed to that agent or situation.

hazard characterisation

The qualitative and/or quantitative description and evaluation of a hazard. An evaluation of the dose—response relationship for each of the adverse effects caused by a substance.

hazard identification

The identification—through animal and human studies, in vitro studies and structure—activity relationships—of adverse health effects associated with an exposure to an agent.

The determination whether a substance (at any dose) can cause an increase in the incidence of adverse effects, and the qualitative evaluation of these induced adverse effects.

head stage

When the seed head of a plant begins to emerge from the sheath.

health claim

A claim on a label that relates the nutrient(s) in a product to risk reduction of a disease condition (eg milk is a good source of calcium; a calcium-rich diet can reduce the risk of developing osteoporosis).

health surveillance

The monitoring of individuals for the purpose of identifying changes in their health status due to occupational exposure to a hazardous substance.

heavy metals

A term loosely applied to those metallic elements readily precipitated from solution as the sulphide; but, in particular, referring to antimony, arsenic, cadmium, copper, lead, mercury and selenium, which, at relatively low concentrations, are highly toxic to many forms of life.

helminths

Internal parasites of animals that take the form of roundworms (nematodes), flatworms, flukes (trematodes) or tapeworms (cestodes).

herbaceous

Plants that are perennial, but not woody shrubs.

Plants that have soft stems, such as annuals, biennials, and perennials that normally die back to the ground during winter.

herbaceous plants

Vascular plants that do not develop persistent woody tissue above ground.

herbage

Herbaceous plants grown especially for grazing. This excludes crops such as cereals, oilseeds, and vegetable and cole crops.

Herbal remedies
herbicide

Any substance or mixture of substances intended for preventing, destroying or controlling any unwanted plant, including algae or aquatic weeds.

herbicide modifier

A chemical substance used with herbicides to change their herbicidal properties by a physiological mechanism. This includes safeners, synergists, extenders, etc., but not compounds that may modify herbicidal activity by chemical or physical mechanisms, such as surfactants.

herbicide resistance

The ability of a plant to complete its life cycle and grow normally despite exposure to high rates of a herbicide that is lethal to susceptible plants (ie the plant is not injured by exposure to above normal rates of herbicide).

Herbicide tolerant
herpeticide

A chemical used against amphibians and reptiles to kill or cause other adverse effects when administered in small doses.

heteroploidy

Any abnormal number of chromosomes in a cell or organism. This is a general term that covers polyploidy, aneuploidy, hyperploidy, etc.

high-pressure sprayer
high-volume spray

A spray applied to leaves and stems of plants until they are thoroughly wet. The actual volume used depends on the size, nature and density of the weeds and varies from 1000 litres per hectare (L/ha) for low growing weeds to volumes as high as 5500 L/ha for dense shrubs.

highly flammable liquid

A liquid of flash point less than 21°C, as determined by the closed cup method.

Holder

From s. 3 of the Agvet Code:

  1. in relation to an approval or registration, means:
    1. the person entered in the Record, Register or relevant APVMA file as the holder of the approval or registration, or
    2. if the holder was an individual who has died or is an individual whose affairs are being lawfully administered by another person—the legal personal representative of the individual or the person administering the individual’s affairs, or
    3. if the holder was a body corporate—a successor in law of the body corporate, or
  2. in relation to a permit or licence, means the person to whom the permit or licence was issued.

Generally speaking, the definition extracted above extends to the following 3 categories of person:

  • The person entered in the Record of Approved Active Constituents for Chemical Products or the Register of Agricultural and Veterinary Chemical Products or the relevant APVMA file as the holder of an active constituent approval or a chemical product registration.
  • The person to whom a permit has been issued under Part 7 of the Agvet Code.
  • The person to whom a license has been issued under Part 8 of the Agvet Code.
hollow cone

A spray jet for pesticide application, having a core of air breaking to give drops in an annular pattern.

home garden and domestic pest control products

Agricultural chemical products that are used in a domestic or home garden setting, where there is no economic risk from product failure.

hormesis

A demonstrated beneficial effect of an agent when used at low (but not homeopathic) doses (but with toxicity occurring at higher doses).

hormonal growth promotant (HGP)

From r. 3 of the Agvet Code Regulations (unless the contrary intention appears):

Means a veterinary chemical product containing a substance that is, or a mixture of substances that are, responsible for oestrogenic, androgenic or gestagenic activity to enhance growth or production in bovines or bubalines.

The promotants referred to in the definition extracted above are generally used to improve feed conversion in cattle and their supply is controlled by the APVMA through the National HGP Control and Monitoring System.

hormones

Chemicals that affect or regulate growth, reproductive activity and other physiological activities of plants or animals.

host

The living plant or animal that a pest depends on for survival.

An organism infected or infested by a parasite.

hot fogging concentrate

A formulation suitable for application by fogging equipment operating at high temperatures.

hue

The attribute of a colour by which it is recognised as a red, green, etc. The hue is dependent on the dominant wavelength of the light and is independent of intensity or lightness.

human pathogens

Microorganisms that cause disease in humans.

humectant

A compound that has the ability to absorb water from the air. Its swelling effect can slow down the penetration of spray oils into leaf cuticles, and delay evaporation of the water carrier.

humus

Organic matter in soil.

hybrid

The first generation progeny from a cross of different varieties, strains or inbred lines.

hydraulic agitator

A device that keeps a pesticide formulation in a tank from settling out (precipitating) by means of water flow under pressure.

hydraulic sprayer

A machine that delivers large volumes of pesticide spray at high pressures to a target, often used for fruit trees, shade trees and ornamental plants.

Compare with 'low-pressure boom sprayer'.

hydrocarbon

A chemical whose molecules contain only carbon and hydrogen atoms.

hydrogen ion concentration

A measure of acidity or alkalinity, expressed in terms of the pH of the solution.

hydrolysis

A chemical reaction involving the uptake of water. In herbicide science, often the decomposition of an ester in the presence of water to release the parent acid and alcohol.

hydrophilic

Water attracting.

hydrophobic

Water repelling.

hydroponics

Growing plants without soil, using mineral and nutrient solutions.

hygroscopic

Having a tendency to absorb water.

hyperplasia

An increase in the number of cells in an organ or tissue.

hyperploidy

An increase over the normal number of chromosomes in a cell or organism.

hypertrophy

The enlargement of an organ due to an increase of cell volume.

hypha (hyphae)

One (many) of the thread-like strands, or filaments, that constitute the body (mycelium) of a fungus.