Parasitic Potential of some Braconid Parasitoids against Okra Fruit Borers
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Author:G. Thanavendan and S. Jeyarani
p-ISSN:0024-9602, e-ISSN:2582-5321, Vol:99, Issue:oct-dec
DOI: https://doi.org/10.29321/MAJ.10.100211
Abstract
In surveys conducted in Coimbatore district during 2009-10, Okra fruit borers, Earias vittella
Fabricius, Earias insulana Boisdual and Helicoverpa armigera (Hübner) were the serious
pests causing 50 per cent loss. During the survey, three hymenopteran parasitiods viz.,
Bassus spp., Brachymeria lasus Walker, Goryphus spp., of the families Braconidae, Chalcididae
and Ichneumonidae against Earias spp. and the dipteran parasitoid, Carcelia illota (Tachinidae )
against H. armigera were recorded with 0.00 to 10.00 per cent parasitization. All the parasitoids
recorded were not amenable for mass culturing, and hence, other braconid parasitoids viz.,
Bracon brevicornis Wesmael, Bracon hebetor Say and Chelonus blackburni Cameron were
studied for their parasitic potential against fruit borer complex. Cent per cent parasitization
was observed with B. brevicornis against all instars of E. vittella and H. armigera, higher
parasitizaion of 100 and 97.50 per cent was observed by B. hebetor at a parasitoid-host ratio of
5:10 on second instar larvae of H. armigera and fourth instar larvae of E. vittella respectively.
The egg - larval parasitoid, C. blackburni recorded the highest parasitization of 70.54 per cent
and 64.58 per cent against E. vittella and H. armigera at a parasitoid host ratio of 5:100. For
B. brevicornis and B. hebetor, highest cocoon formation and parasitoid emergence was
recorded at 4:10 ratio against third and fourth instars. In C. blackburni, the parasitoid host
ratio of 3:100 yielded the highest number of adult parasitoids. B. brevicornis was found to be
more effective against fruit borers.
Key words : Okra fruit borers, parasitic potential, Bracon brevicornis, Bracon hebetor, Chelonus blackburni