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Mode of Action

Three main groups of agrichemicals are used in horticulture: insecticides, fungicides, and herbicides. Agriculture primarily uses herbicides, animal remedies and, in the dairy sector, dairy detergents.

Agrichemicals in each group are further categorised according to their mode of action - how they kill or disrupt their target.


Mode of action How it works Examples
Systemic Moves within plant sap, eaten by sucking insects Attack, Counter 20G, Rogor E
Contact Picked up when insects are hit directly by spray droplets or move across treated plant surfaces Azinphos methly, Lannate L
Stomach poison Must be eaten by the insect Azinphos methyl, Foray, 48B
Nerve poison Affects the insect's nervous system Lorsban, Rogor E, Folidol M50, Tamaron
Fumigant Active in the vapour phase Attack, Thimet 20G, Pirimor 50


Mode of action How it works Examples
Protectant Contact acting chemicals that prevent new infections by killing fungal spores Combo, Baycor, Kocide, Rovral
Partially systemic or translaminar Usually exhibit protectant activity plus suppression or control of established disease within plant tissue Combo, Acrobat MZ 690, Twist
Fully systemic Move freely in plant vascular system, exhibit curative activity against established disease Bayleton, Speartek, Ridomil
Curative or eradicant Kill out established diseases Rizolex, Tilt EC, Topas


Mode of action How it works Examples
Desiccants or knockdowns (contact) Rapid response to burn off green parts of plants Reglone, Preeglone
Translocated or systemic Absorbed into the plant and moves to active area Amitrole, Answer, Glyphospate
Hormone-type (translocated) Mimic plant growth regulators, often translocated. Phenoxy-herbicides are the main group 2,4-D, MCPA, MCPB
Pre-emergent Applied to seed bed before planting or crop emergence Treflan NF

Animal Remedies

Animal remedies are usually categorised by the way in which they are applied to the animal.

Mode of action How it works Examples
Pour-on Drench applied to the skin of animal Cydectin, Bomectin, ProAbamec
Oral drench Drench given via the mouth using a drench gun Alliance, Converge, SCANDA Selenised
Injection Administered into the neck of the animal via a needle and syringe Cydectin, Closamectin, Noromectin
Intramammary Tube containing antibiotic that is inserted into one of the cow's teat canals Bovaclox Dry Cow, Cobactan lC, Penalone
Controlled release drug Capsule delivered down the animal's throat via an applicator Rumetrace,Magnesium Capsules, Rumensin

Dairy Detergents

Milking plant and vat cleaning routines involve the use of acid and alkaline solutions,

Mode of action How it works Examples
Acid detergent Removes mineral deposits
Acid sanitisers Chemicals such as chlorine, iodine or cationics kill bacteria Quantum, Optimum
Alklaine (base) detergents Remove fat and protein Rapid, Protosol, Quantum