Resistance of Aphis gossypii (Homoptera:Aphididae) to Insecticides
Feb 14, 2019
The cotton aphid Aphis gossypii is a serious cotton pest in some regions of Greece. Recently, reports from different regions suggest that it can no longer be controlled with applications of insecticides that were formerly effective, especially organophosphates and pyrethroids. Laboratory biossays were conducted from 1993 to 1997 to determine the susceptibility of cotton populations to the most commonly used insecticides. LC50s were determined using the dip test method (FAO, 1979), with assessment of mortality after 24 hours. The results show that resistance to insecticides has spread to many different regions. Of fifty tested populations 25%, were resistant to pirimicarb, showing up to 16-fold resistance and 13% were resistant to carbosulfan with up to 42-fold resistance. Some populations were very susceptible to fenvalerate and some very resistant. Cross-resistance between the pirimicarb and triazamate a carbamoyl-triazole has been observed. The newly introduced insecticide, imidacloprid, was effective enough in cotton except in a few cases where some tolerance was evident. Populations that were resistant to pirimicarb and carbosulfan were susceptible to imidacloprid and no cross-resistance was observed. LC50s for organophosphates, pyrethroids and carbamates were positively correlated with the previous use of these insecticides in the region where the aphids were collected. This study reports the incidence of insecticide resistance in Aphis gossypii to several insecticides over a three year period in Greece.