Insecticide Tolerance in the Bruchid Callosobruchus Maculatus
Date
2001-11-16
Authors
Bogamuwa, M. M. S
Karunaratne, S. H. P. P.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya, Peradeniya, Sri Lanka
Abstract
Bruchid Callosobruchus maculatus is a storage pest of legumes. Status and the mechanisms of insecticide resistance were investigated in adults. Insects were collected from a culture in Horticultural Research and Development Institute (HORDI) Gannoruwa and reared at the Department of Zoology, University of Peradeniya. Adults were subjected to insecticide bioassays by topical application using a microapplicator. Different dosages of four insecticides; carbamate carbosulfan, organophosphate dimethoate and pyrethroid permethrin were used. LD50 and LD90 values were obtained using log-probit mortality curves. Percentage mortality for fixed dosages of malathion (50 [ ]) and DDT (40 [ ]) were also obtained.
LD50 [ ] values for carbosulfan, dimethoate and permethrin were 6.23,2.17 and 5.21 respectively. LD90 [ ] values were 371.23, 48.85 and 3842.81 respectively. Resistance percentages (percentage survivals) to malathion and DDT were 11.25% and 10% respectively.
Activity of insecticide metabolizing enzymes such as glutathione S-transferases (GST), carboxylesterases and monooxygenases, in insect crude homogenates (n> 200) were investigated using a kinetic spectrophotometer. Mean' GST specific activity for the reduced glutathione/chlorodinitrobenzine was 0.55 ± 0.28 [ ]". Mean specific activity of carboxylesterases with the substrate para-nirtophenylacetate was 0.49 ± 0.36 [ ]". Native polyacrylamide gel electrophoresis resolved two elevated esterase isoenzymes in adult bruchids. Mean monooxygenase level was 0.14 ± 0.21 OD/mg. Sensitivity of the insecticide target-site, acetylcholinesterase (AChE), to insecticides was monitored by inhibiting AChE with the carbamate propoxur. Inhibition co-efficient (Ki) for the inhibition reaction was 0.10 x 105 M-1 min-1 indicating a high sensitivity of the target-site. Results show that the resistance to insecticides in C. maculatus is mainly due to increased activity of insecticide metabolizing enzymes.
Description
Keywords
Science , Bruchid , Callosobruchus , Maculatus
Citation
Proceedings & abstracts of the Annual Research Sessions 2001,University of Peradeniya, Peradeniya, Sri Lanka,pp.119