Tank Mix Conflicts, Alkaline Water, and Mixing Order

Not as proposed.

• The 4EC label prohibits tank mixing with any copper-containing product. That alone rules out CopperGard in the same tank.
• The CopperGard label prohibits mixing with alkaline materials or solutions above pH 8.0. Your well water is pH 8.6, so even a copper-alone load is off-label until the water is acidified and rechecked.
• Rule for conflicting labels: the most restrictive statement governs. A tank mix has to satisfy every label in the tank simultaneously. Where one label forbids the combination, mixing is a FIFRA misuse regardless of what the other label allows.
• No 2(ee) escape hatch. Section 2(ee) covers pests not on the label, rates below the label rate, and certain fertilizer combinations - it does not authorize a tank mix that a label specifically prohibits.

Sequence that works: buffer the water into the 6.5–7.0 range and verify with a pH meter, apply the copper in a separate pass (or separate load), apply the 4EC alone in buffered water, and treat the phosphite under its own label. Also consider that at pH 8.6 an EC insecticide can hydrolyze in the tank within hours, so even a physically compatible mix can lose efficacy overnight.

Jar test (do it with the actual well water):

• Use a clear quart jar, water at the same dilution ratio you will run in the field, and the same products.
• Add products in the intended order, cap, and shake.
• Check immediately, at 15–30 minutes, and again after an hour: look for clumps, flakes, oily film or separation, sediment, heat, and foam that will not break. Any of these means do not tank mix.

Order of addition (follow the label if it specifies one):

1. Fill the tank half to three-quarters full and start agitation.
2. Add buffers/water conditioners first - they must act on the water before the actives go in.
3. Add dry formulations (WP, WDG, DF) - pre-slurry powders in a bucket to avoid lumps.
4. Add flowables/suspension concentrates.
5. Add emulsifiable concentrates.
6. Add surfactants, oils, and other adjuvants last.

Keep agitation running throughout, clean the screens, and never let a slurry sit in the tank overnight.

On 2(ee): it does permit combining a pesticide with a fertilizer when the label does not prohibit it. But that provision does not override the 4EC's copper prohibition or the CopperGard pH ceiling - those are explicit label statements that still bind. And whether a phosphite nutrient counts as a fertilizer for this purpose doesn't matter, because the copper/insecticide conflict blocks the three-way mix either way.

On 'it looked fine last year': visible compatibility is not the whole story. Antagonism, reduced control, and sublethal phytotoxicity can appear days to weeks later, and an incompatible mix can plug screens and leave streaks. One season of observation is not a substitute for the label.

Liability: the applicator is responsible for an off-label tank mix. Advice from a county agent, a dealer, or the grower does not transfer that responsibility, and it is not a defense.

Document: the labels you read and the conflicting statements, the water test and pH reading, the jar-test result, what you advised the grower, and the final decision on the work order. If the grower insists, decline the three-way mix in writing and offer the split application.