Stored Rice Insect Management Update

In general there are a limited number of products labeled for stored grain insect management.  For rice these products include Storicide II (deltamethrin plus chlorpyrifos-methyl, pyrethroid and organophosphate, respectively), Diacon IGR (methoprene, insect growth regulator), diatomaceous earth (Insecto, Protect-It, and other trade names), Suspend, Centynal, D-Fence, etc. (deltamethrin, pyrethroid), and Diacon IGR Plus (methoprene plus deltamethrin, IGR and pyrethroid, respectively).  In some areas Storicide II has been used extensively to manage insect pests of stored rice.

The labels for all chlorpyrifos products (Lorsban, Dursban, etc.) have been cancelled and these products are being removed from the market.  Because the chlorpyrifos-methyl component of Storicide II is very similar to chlorpyrifos (Lorsban), Storicide II will be discontinued also.  For growers that store rice through the winter into the spring and summer following harvest this could be problematic.  In our trials during 2020 and 2021, Diacon IGR (methoprene), Diacon IGR Plus (methoprene and deltamethrin), and Suspend (deltamethrin) did not reduce maize/rice weevil densities compared to the untreated during June and July of each year (Figures 1 and 2).  Weevil densities were much higher in those bins than ones treated with Storicide II.  However, insect response to insecticides can vary across locations, and the addition of the insecticide synergist PBO (piperonyl butoxide) may improve efficacy of deltamethrin.

Currently there is some Storicide II product in the supply chain.  However, production is scheduled to be discontinued soon.