Investigation on sceptibility of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) to 5 incesticies: Abamectin, cypermethrin, endosulfan, malothion and methomyl

In this study, susceptibility of 7 different Frankliniella occidentalis (Pergande) populations collected around Antalya province to insecticides from 5 different groups namely abamectin, cypermethrin, endosulfan, malathion and methomyl were evaluated. Resistance potential, multiple resistance, efficacy on thrips larvae at greenhouse and the effect of resistance levels on management success were also investigated. Leaf residue method was used in laboratory bioassays. A series of 4-6 insecticide concentrations were sprayed on bean leaf discs using a potter spray-tower. After 1 day, adult female F. occidentalis were put on to leaf discs placed on the test cells. Thrips were exposed insecticide residue for a period of 2 days. Lethal concentration values (LC50 and LC90) and resistance levels were determined from the number of dead-alive thrips using probit analysis program, hi laboratory selection study, 5 different F. occidentalis populations originated from the susceptible strain were selected against the insecticides. In laboratory studies all F. occidentalis populations were maintained on whole bean plant placed in plexiglass cages in a growth chamber at 26+1 °C and 16:8 (LD) h. To determine the field efficacy of the insecticides to thrips larvae, an experiment was conducted in eggplant grown greenhouse. The number of dead-alive thrips on sampled leaves were determined 1 day before and 1, 3, 7 day after insecticides applications. Resistance to all insecticides except cypermethrin were determined to be low in all 7 F. occidentalis populations. According to leaf residue assay resistance levels for all populations changed from 0.8 to 1.8 fold at LC50 and from 1.3 to 2.4 fold at LC90 for abamectin, from 1.6 to 12.2 fold at LC50 and from 2.9 to 9.6 fold at LC90 for cypermethrin, from 0.9 to 2. 1 fold at LC50 and from 0.9 to 2.4 fold at LC90 for endosulfan, from 1.0 to 2.5 fold at LC50 and from 1.0 to 2.7 fold at LQ» for malathion and from 0.8 to 1.9 fold at LC50 and from 1.4 to 3.1 fold at LC90 for methomyl. 3.8-12.2 fold resistance levels for cypermethrin indicated that a moderate level of resistance existed in F. occidentalis populations of Antalya The highest resistance ratio among the populations sampled to abamectin, endosulfan, malathion and methomyl was found at 3.1 fold. 111Cyperaıethrin resistance of susceptible F. occidentalis strain sprayed 27 times in about six months increased to 28.0 fold at LC50 and 39.9 fold at LCjio- The resistance levels shown by cypermethrin selected strain to abamectin, endosulfan, malathion and methomyl were 0.8 fold at LC50, 2.1 fold at LC50, 3.2 fold at LC50 and 2.6 fold at LC90, respectively. Resistance ratio increased up to 139 fold at LC50 and 110 fold at LC90 when an additional 17 cycles of selection was applied on this strain. These results indicated thatF. occidentalis had significant resistance potential to cypermethrin. In other selection experiments susceptible strain was sprayed 6, 7, 12 and 9 times with abamectin, endosulfan, malathion and methomyl, respectively. However, in none of the selection experiments enough number of thrips were reared for the bioassays. In a greenhouse trial, the maximum efficacy of methomyl, endosulfan and malathion on thrips larvae were found 99%, 87% and 86%, respectively. Efficacy of abamectin increased gradually up to 72% at 7th day. Cypermethrin with a 52% efficacy was the least effective insecticide. Resistance levels of F. occidentalis population collected from the greenhouse varied from 0.9 to 4.8 fold for all insecticides. This suggest that these resistance levels do not significantly effect the management success. Results from the study indicated that the use of cypermethrin should be avoided in chemical control of F. occidentalis, and the other insecticides in different chemical classes; abamectin, endosulfan, malathion and methomyl can successfully be used as tools of resistance management tactics in IPM programs. KEY WORDS: Frankliniella occidentalis, insecticide resistance, resistance potential abamectin, cypermethrin, endosulfan, malathion, methomyl, efficacy in greenhouse