Efficacy of insecticides for control of stored-product psocids

A series of experiments were carried out between 2007 and 2009 to test the efficacy of selected insecticides against several stored-product psocids. Three series of experiments were conducted against Liposcelis spp. (Psocoptera: Liposcelididae) and Lepinotus reticulatus (Psocoptera: Trogiidae). In the first series of tests, contact insecticides were evaluated in the laboratory as grain protectants. Among these insecticides, diatomaceous earth (DE), natural pyrethrum, and the insect growth regulator methoprene were unable to control psocid populations on wheat, rice, and maize. For the same commodities, spinosad was effective against L. reticulatus, but was effective for Liposcelis entomophila only on maize; spinosad was not effective against Liposcelis bostrychophila and Liposcelis paeta. Chlorpyriphos-methyl + deltamethin and pirimiphos-methyl were very effective for all species tested. In the second series of tests, sulfuryl fluoride (SF) was tested against L. pata eggs, nymphs, and adults, and Liposcelis decolor eggs and adults. Nymphs and adults were very susceptible; for most species mortality was 100%, after 48 h of exposure to SF doses ranging between 4 and 8 g of SF/m3. In contrast, eggs were less susceptible to SF, and 100% mortality after 48 h of exposure was recorded only at doses ranging between 24 and 96 g of SF/m3. In the third series of experiments, several contact insecticides were evaluated as surface treatments on concrete. In these tests, pyriproxifen and esfenvalerate provided poor control of psocids. The results of the above tests indicate that Liposcelis spp. and L. reticulatuswere generally less susceptible than other major stored-product insect species to several insecticides, and susceptibility level is determined by the target species, the insecticide, and the commodity.Keywords: Psocoptera, Stored grains, Grain protectants, Sulfuryl fluorid