Shelf life of Imidan

Does anyone have practical experience with the shelf life of Imidan? Cornell has it at 2 to 3 years.




I expect the shelf life is a lot less if the factory bag has been opened compared with the original sealed bag

I plan to use some 3 year old stuff next year so I guess I’m going to find out.

I find some of those figures highly suspect. Stored in good conditions these compounds break down very slowly.

I recall one grower on the Apple-crop listserv had a 50 gal drum of oxytet for fireblight. As I recall the drum was 50 years old. He sent a sample to a lab and it tested nearly fully potent.

Like antibiotics, pesticides slowly lose potency. Some researchers may feel like the compound is compromised when it loses 5 or 10% potency, but in reality it’s still very efficacious.

Copied from somewhere else, here is the response from the manufacturer.

Thank you for your inquiry concerning the shelf life of Imidan. Your unopened bag of Imidan will be effective for many years. It is true that after 3 years, as with most pesticides, the percentage of phosmet (active ingredient in Imidan) begins to slowly decrease. Though measurable in a lab, it is unlikely that you will notice any difference in field usage for years.

What you may see is a deterioration of the WSB (water soluble bag) in which the Imidan is packed. You could see one or more of the following issues:

  • Cracking of the film

  • Solubility and/or dispersion of the film


Rod Kitterman