The baseline suscepitbility of eggplant fruit and shott borer (Leucinodes orbonalis) populations in the Philippines to a Bacillus thuringiensis Cry1Ac protein was evaluated using a diet-overlay bioassay. Infested fruits with larvae were collected from none eggplant growing provinces in the Philippines during the 2012-2013 crop growing seasons. L. orbonalis larvae were reared to adults on semi-synthetic diet, allowed to mate in the laboratory and produce eggs. The neonate larvae, from eggs of the field collected parents, were3 exposed to eith concentrations of Cry1Ac along with an untreated control and then assessed for mortality. The results showed that all L. orbonalis populations tested were susceptible to the Cry1Ac protein obtained from a bio insecticide that was used in the assay. Probit analyses of 35 bioassays of EFSB larvae collected from nine provinces showed that the median lethal concentrations ranged from 0.45 to 2.07 ng/cm while LC values ranged from 65.10 to 1501.00 ng/cm. Interpopulation variation in susceptibility was 4.6-fold and 23-fold at the LC and LC values, respectively. Linear Mixed Model and pairwise mean comparison analysis allowed pooling of the 35 bioassays data into four (4) groups. Effects of season and province for lethel concentrations and the slope for each group were insignificant. The median lethal concentrations ranged from 0.88 to 1.54 ng/cm and the LC values ranged from 119/23-470.73 ng/cm which represented a <2-fold and 4-fold variation in suscepibility, respectively. The results obtained in this study will be continued to generate more reliable estimates of the LC values which can be considered for develolpment of diagnostic concentrations in resistance monitoring.
BASELINE SUSCEPTIBILITY OF EGGPLANT FRUIT AND SHOOT BORER, Leucinodes orbonalis Guenée IN THE PHILIPPINES TO A Bacillus thuringiensis CRY1Ac INSECTICIDAL PROTEIN
Submitted by jb755 on Wed, 2017-04-05 14:04
The Philippines Entomologist