Pesticide Products, Formulations, and Modes of Action
Formulations and what they imply
Candidates must match formulation letters to behaviour: EC (emulsifiable concentrate, solvent-based, can damage tender foliage and some plastics), SC or F (suspension concentrate/flowable), WP (wettable powder, requires good agitation, leaves visible residue), WDG or DF (water-dispersible granule), SL (soluble liquid), and formulations such as dusts, granules and baits used for specific sites. Understand that the active ingredient is only part of the product; carriers, surfactants and solvents affect phytotoxicity, rainfastness, mixing order and compatibility.
Learn the difference between contact, translaminar and systemic activity, and between residual and non-residual products. Know that protectant fungicides must be present before infection, whereas eradicant or systemic products act after. Traps: assuming a higher rate always works better (it can cause phytotoxicity and resistance selection); assuming two products with different trade names have different active ingredients; and ignoring that surfactants can injure some species.
Mode of action and grouping
Mode of action describes how a product kills; the site of action is more specific. Resistance management depends on rotating by mode-of-action group, not by product name or brand. Know that products in the same group share a site of action, so switching brands within a group is not rotation. Also understand selectivity: why a grass herbicide can be used in a broadleaf crop, and why that selectivity can fail under stress.
Rule of thumb: identify the group before you plan a rotation, and never apply the same group consecutively when the label restricts it.
Worked example: a grower has applied two different brand-name products from the same group in sequence and believes rotation was achieved. It was not; the correct action is to switch to a different group with a different site of action for the next application, subject to the label.
Always read the label for mixing order, adjuvant requirements and compatibility before tank mixing.