|Kariuki, C - KENYA AGRIC RES INST|
|Brenan, L - BASF|
|Dierks, P - BASF|
Submitted to: Biocontrol Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 21, 2002
Publication Date: June 21, 2002
Citation: MCINTOSH, A.H., GRASELA, J.J., KARIUKI, C.W., GOODMAN, C.L., BRENAN, L.A., DIERKS, P.M. EVALUATION OF A RECOMBINANT DIAMONDBACK MOTH BACULOVIRUS IN SELECTED LEPIDOPTERAN CELL LINES AND LARVAE. BIOCONTROL SYMPOSIUM PROCEEDINGS. 2002. Interpretive Summary: The diamondback moth is an insect pest of considerable importance leading to an estimated cost of one billion dollars (U.S.) for its management worldwide. It attacks many vegetable crops such as cabbage, broccoli, cauliflower and kale. Because of the wide use of large quantities of insecticides and a toxin (by-product) from a bacterium (Bt), the diamondback moth has developed resistance to these agents. In the present report, a modified insect virus called a baculovirus which carries a toxin specific for insects, was evaluated for its infectivity as well as its quickness of kill against the diamondback moth and several other insect pests. In the event that the insect developed resistance to this toxin, the baculovirus could still replicate in its host and kill it. The modified baculovirus was also evaluated for its ability to infect insect cells, grown in culture, that were derived from insect pests. The modified virus was infectious for and killed the diamondback moth larvae faster than the unmodified virus and was also infectious for other insect pests of economic importance. The modified virus can also be produced in cell culture which can serve as a cleaner microbiological system for the production of this biological control agent. Such a microbial could be useful to farmers, the scientific community and the general public as a biological control agent and for research investigations.
Technical Abstract: The diamondback moth (DBM), Plutella xylostella (L.) is one of the most important pests of the cabbage family, as well as other vegetable crops throughout the world. Its control by chemical insecticides as well as by the biopesticide Bacillus thuringiensis has become more difficult due to the development of resistance to these agents. The present study was initiated to evaluate the replication of a recombinant baculovirus of DBM (PxMNPV-AaIT) developed by BASF (formerly American Cyanamid Company) from the parental wild type baculovirus in insect cell lines, as well as to test its pathogenicity against several lepidopteran species. Cell lines evaluated in this study were derived from Helicoverpa zea (HZ-FB33), Heliothis virescens (HV-OV), Trichoplusia ni (TN-CL1), Spodoptera frugiperda (SF-TS) and S. exigua (SE-E4). Twenty-four hour old larvae of H. subflexa, H. virescens, H. zea, T. ni and P. xylostella were tested for their susceptibility to the recombinant virus employing the lethal concentration fifty( LC50) bioassay. The SE-E4 cell line produced the highest titer of 6.7 + or - 0.06 x 10**5 TCID50/ml, whereas the greatest number of occlusion bodies (OB) of 1.1 + or - 12.05 x 10**7/ml was produced by SF-TS. Of the five lepidopteran species of insects investigated, H. virescens was the most susceptible, with an LC50 of 0.452 OB/cm**2. The LT50 was 2.69 d for PxMNPV-AaIT as compared with 4.39 d for wild-type PxMNPV.