STUDIES ON PREDATION OF HELIOTHIS ARMIGERA HUBNER AND SPODOPTERA LITURA FAB. BY INSECTIVOROUS BIRDS WITH SPECIAL REFERENCE TO ACRIDOTHERES TRISTIS L.
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Date
1988
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AAU, Anand
Abstract
Studies on identification of avian predators H. armigera and S. litura, assessment of their predation and the breeding biology of chief predatory species, Acridotheres tristis L. were carried out at Anand Campus of Gujarat Agricultural University, during 1986-1987. Studies on identification of avian predators of the pests revealed that Acridotheres tristis, Acridotheres ginginianus, Passer domesticus, Dicrurus adsimilis, Bubulcusibis, Merops orientalis and Sturnus roseus were observed preying on H. armigera in different crops. Whereas, Corvus macrorhynchos and B. ibis found preying on S. litura in tobacco nursery. The studies revealed that birds are highly attracted when host density was high. Their predation resulted as much as 47.74 per cent reduction in the larval population of S.podoptera litura in tobacco nursery. The average being 40.33 per cent. As a result of effective predation, there was only 0.26 and 0.55 per cent increase in the seedling damage by the pest as compared to 13.31 and 10.57 per cent increase in control plots. The avian predation of S. litura showed their maximum activity between 0630 and 0900 hours and 1600 and 1800 hours. Their activity was not found between 1000 and 1400 hours. Jungle crow, C. macrorhynchoa and house crow, C. splendens were most voracious feeders of S. litura larvae consuming on an average 3.00and 3.01 larvae per minute respectively. The feeding rate of common myna, A. tristis; bank myna, A. ginginianus; cattle egret, B, ibis and house sparrow, P, domesticus averaged 1.94. 2.07. 0.88 and 0.83 larvae per minute respectively. Among the different bird species found preying on S. litura« jungle crow appeared in great number (27) than house crow (5), common myna (7) and bank myna (6). The avian predation of H. armigera in gram exerted very effective check on the pest. On an average large sized (1.31) larvae per m2 were recorded in experimental area as against 7.2 larvae per m2 in control area. Similarly greater number of pupae (46.78/m2) wag recorded from netted area than that in experimental area (3.0/m2). There was 38.75 per cent more pod damage in control area than that in experimental area. The experimental area recorded 939 kg/ha more yield than control. The birds J however, fed indiscriminately on healthy and parasitised larvae.
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AGRICULTURAL ENTOMOLOGY, AGRICULTURE, A STUDY