This table summarizes the various ways nematicides dissipate following application.
Fumigants are designed to volatilize and thus may dissipate into the air where they can be decomposed by sunlight. Within soil, fumigants are also decomposed by hydrolysis. In soil, organophosphates and carbamates are typically decomposed by microbial activity. The zone of greatest microbial activity surrounds roots and decreases with increasing depths in soil. To be used successfully, nematicides must be able to dissolve in the water lining soil pores in order to contact nematodes. This same water solubility, though, can result in their leaching below the depth of microbial activity. Once past this zone, degradation proceeds very slowly, if at all, resulting in the potential for groundwater contamination.
There have been a number of reports of "loss of activity" of nematicides following repeated application. In some cases, it has been shown that the microbes which decompose organophosphates and carbamates can be selected for and increased over a period of time to the extent that products can be broken down too rapidly to provide effective control.