Management of Helicoverpa armigera (Lepidoptera: Noctuidae) on chickpea in southern India: thresholds and the economics of host plant resistance and insecticide application

Wightman, J A and Anders, M M and Rameshwar Rao, V and Reddy, L M (1995) Management of Helicoverpa armigera (Lepidoptera: Noctuidae) on chickpea in southern India: thresholds and the economics of host plant resistance and insecticide application. Crop Protection, 14 (1). pp. 37-46. ISSN 0261-2194

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A study of the influence of the density of larval Helicoverpa armigera (instars 4-6) on the seed yield of chickpea plants growing in large cages indicated that one larva per plant was a critical density as far as economic injury levels are concerned. The results indicated that larval feeding activity during the first 2 weeks of flowering had no effect on yield. There was also no evidence of compensatory growth following insect attack during the flowering stage. These data were adopted to set action thresholds in a large (0.8 ha) field experiment that was designed to investigate the economics of insecticide application in the context of an on-farm chickpea enterprise. The field was managed with bullock-drawn implements and hand labour. Insecticides were applied to three varieties - Annigeri (an insect-susceptible landrace), ICCC 37 (a recently released variety) and ICC 506 (an insect-resistant landrace) - weekly, not at all (controls) and when the larval density exceeded 0.5 or 2.0 per plant. Economic parameters were assembled from village and local market records. Helicoverpa had a marked effect on the yield of the two pest-susceptible varieties, both of which would have made a loss in the context of a chickpea enterprise unless protected by insecticides. Helicoverpa-resistant ICC 506 did not achieve as high a yield as the other two varieties when treated with insecticides but did `make a profit' when no insecticide was applied. The relationship between yield and insect days was virtually identical for Annigeri and ICCC 37. The latter needed five insecticide applications to maximize yield and the former four. The relationships between insect day summations (integrals of population curves) for eggs, and small and large larvae, suggested that eggs were undersampled and were not suitable as an indicator for insecticide applications. The density of small larvae, although probably undersampled, was a suitable indication of the damage likely to be caused by the large larvae they would develop into. A set of insect day summations indicates when insecticides in the current price range (Rs300, 400 or 850 ha-1) need to be applied. The thresholds were verified in neighbouring fields. Three insecticide applications during the following season resulted in a greater than threefold increase in yield (from 0.65 to 2.2 t ha-1).

Item Type: Article
Subjects: Mandate crops > Chickpea
Depositing User: Mr Charan Sai Ch
Date Deposited: 28 Oct 2011 09:12
Last Modified: 28 Oct 2011 09:12
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Acknowledgement: UNSPECIFIED
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