The hemipteran whitefly Bemisia tabaci (Gennadius) is one of the most destructive pests damaging more than 600 agricultural crop species worldwide. The B and Q biotypes are most widely spread in Korea but they are not distinguishable based on morphological characters. Carboxylesterase 2 (Coe2) was determined to be 5.9 times more expressed in B biotype compared to Q biotype. Comparison of deduced amino acid sequences of Coe2 (595 a.a.) showed a total of 3.85% polymorphisms between B and Q types but no differences in major active sites. Quantitative real-time PCR revealed that both B and Q biotypes possess a single copy of coe2, suggesting that the overexpression of Coe2 in B biotype is likely due to overtranscription. To determine the putative role of Coe2 in insecticide tolerance, esterases were separated by native isoelectric focusing (IEF) and inhibited by various insecticides. The putative Coe2 band was apparently inhibited by pyrethroid and organophosphate insecticides, but not by imidacloprid. These findings suggest that overexpression of Coe2 confers chemical defense against pyrethroid and organophosphate insecticides, perhaps by sequestration.

Developmental time, mummification, pupal mortality, sex ratio of a South Korean strain of Aphelinus varipes Förster parasitizing the green peach aphid, Myzus persicae were studied at 20, 25 and 30℃ in controlled climate cabinets. Plastic container with sweet pepper(Capsicum annuum L.) were used as experimental units. Green peach aphid in different larval instars and as adults, reared at the three different temperatures, were presented to A. varipes in a 'no-choice' and 'choice' situation for 6h. These presentations were done at 25℃ in each experiment to avoid an influence of temperature on parasitization rate. In case of no-choice test, more 1st(24%), 2nd(22%) and 3rd(38%) instar aphids were parasitized than 4th(14%) instar and adult(10%) among the aphids reared at 25℃. In case of choice test, more 1st(41%), 2nd(42%) and 3rd(29%) instar aphids were parasitized than 4th(13%) instar and adult(0%) among the aphids reared at 25℃. Pupal mortality of the parasitoid was not influenced by temperatures. The sex ratio of A. varipes was male-biased, and varied between 49.4% females developed from aphids reared at 30℃ and 42.8% from aphids reared at 20℃. The sex ratio was not significantly influenced by host stages. The developmental time of A. varipes parasitizing the green peach aphid ranged from 26.1days at 20℃ to 11.1days at 30℃.

The molecular mechanisms and genetics of abamectin resistance mediated by target site insensitivity in the two-spotted spider mite, Tetranychus urticae, were investigated by comparing two isogenic AbaS and AbaR strains. Cloning and sequencing of full-length cDNA fragments of GABA-gated chloride channel genes revealed no polymorphisms between the two strains. However, sequence comparison of the full-length cDNA fragment of a T. urticae glutamate-gated chloride channel gene (TuGluCl) identified a G323D point mutation as being tentatively related with abamectin resistance. In individual F2 progenies obtained by backcrossing, the G323D genotype was confirmed to correlate with abamectin resistance. Bioassays using progeny from reciprocal crossings revealed that the abamectin resistance trait due to TuGluCl insensitivity is incompletely recessive.