Pesticide Formulations and Compatibility
Formulation basics
The active ingredient is packaged with carriers and adjuvants to make handling practical. Know these: EC (emulsifiable concentrate - solvent-based, can injure sensitive foliage, needs agitation), WP (wettable powder - suspension, visible residue, abrasive to nozzles), WDG/DF (water-dispersible granule - low dust, good suspension), SC or flowable (liquid suspension), S (true solution), G (granule - never left suspended in a tank), and microencapsulated products (slow release; watch bee exposure). Adjuvants include surfactants, crop oil concentrate, methylated seed oil, drift control agents, defoamers, and water conditioners such as AMS.
Compatibility
Physical incompatibility shows as clumps, flakes, oil separation, or heat. Chemical incompatibility shows as antagonism with no visible sign - amine formulations in hard water are the classic case. Always jar-test a new mix: add the carrier water, then products in the labeled order at field ratios, and check at 15 to 30 minutes and again after standing.
Order of addition (rule of thumb)
- Water to one-half to three-quarters volume; 2) water conditioners and AMS; 3) dry products (WP, WDG); 4) liquid flowables; 5) emulsifiable concentrates; 6) surfactants and oils. Agitate continuously. Never add product to an empty tank.
Traps
- Boosting surfactant rate 'to make it work' - surfactants burn crops and are label-limited.
- Assuming a jar test that passes stays compatible for hours in a hot tank.
- Mixing more than can be sprayed that day.
- Assuming every product tolerates a liquid fertilizer carrier; the label must say so.