Pesticide Degradation in Stored Spray Mixtures

Question

Does pesticide breakdown occur after mixing or only after application? Roundup mixed in 5-gal batches loses effectiveness over weeks.

Scientific Explanation

Glyphosate is a polar molecule that binds to soil particles for microbial breakdown. In alkaline tap water (pH 8–10), glyphosate molecules break apart within days. Acidic water stabilizes it.

Practical Rule

Mix only what you need immediately; do not store diluted pesticide.