Full explanation
An IRAC group is labelled by number + letter (e.g. 3A pyrethroids, 4A neonicotinoids, 5 spinosyns, 6 avermectins, 28 diamides). The number identifies the target site in the insect nervous or endocrine system; the letter identifies the chemical subclass. The core rule: do not apply two consecutive products from the same group against one pest generation — this selects resistant populations in 3–5 seasons. Practical example for Vinnytsia rapeseed: first cutworm spray Karate Zeon (3A) → second Coragen (28) → third Spintor (5). IRAC numbers are published in Ukraine's State Register of Pesticides and on every manufacturer's label.