Insecticides and Aging

[Ashby Chadburn]

I grow orchids in a greenhouse in Northern California. I have had some pretty bad infestations of mealy bugs and scale. I have treated the plants with several products, but I have found Orthene and Merit to be especially effective. I mix it in a five gallon container and use it for weeks at a time. My question is whether the insecticide mix remains potent and effective or is it getting weaker and weaker and ineffective? ( I use one product at a time, not mixed together). Your thoughts?

[Orchid Whisperer]

I don't have a specific answer, but I do have a couple suggestions.

Two possible places to get an answer to your question:
1. See if either product has a hotline for end-user questions. I suspect that others have asked before about the shelf life of these products after they have been mixed for use.
2. The closest university with an agriculture program will likely have faculty with pesticide expertise. They may also have a Cooperative Extension office (or "county agent") that can answer questions like this.

Would it be possible for you to mix and use the pesticides in smaller batches (is one gallon possible)? That way, you would know you are applying freshly-mixed chemicals.

Good luck!

[Ray]

In solution, they are likely stable for several weeks, but I would be careful to keep the container closed to avoid evaporation of the water diluent.

The primary reason pesticide manufacturers recommend against the retention and storage of unused product is because many people are idiots, don't label things, and end up poisoning themselves or someone else.

[dounoharm]

I agree fully with ray, but I would also keep any mixture in a cool dark place....please do make sure its labeled well! mixing chemicals is NOT a good idea as a rule, BUT, soaps are fine to mix with other chemicals and are beneficial in that they are termed a 'spreader-sticker' and keep the chemicals in place longer....I use either a dish soap (good old dawn) or any insecticidal soap that's handy....good luck!

[james mickelso]

And blame the pesticide/insecticide manufacturer and point of sale. Just like guns.