ANTIBIOSIS MECHANISM OF RESISTANCE TO THE LEGUME POD BORER, MARUCA-TESTULALIS GEYER (LEPIDOPTERA, PYRALIDAE) IN COWPEA

The biology of Maruca testulalis Geyer was studied on different parts of 18 cowpea cultivars to determine the role of antibiosis in their levels of resistance. M. testulalis larvae were successfully reared from first instar to adult stage on floral buds, flowers and sliced pods, but not on stems, terminal shoots and intact (unsliced) pods, where there was complete larval mortality. The mean pupal weight ranged from 43.5-54.5 mg on floral buds, 38.5-58.6 mg on flowers and 42.7-58.6 mg on sliced pods, with highly significant differences between (P < 0.01) resistant and susceptible cultivars on each part. Growth indices showed that sliced pods were the most suitable for larval growth and development, followed by flowers and floral buds. The levels of resistance round were inadequate for solving the M. testulalis problem in cowpea. Selection and breeding for cowpea ideotypes (architypes), to combine such resistance with morphological, biochemical and biophysical traits, could enhance the low levels of resistance in the cowpea crop and ultimately lead to the effective management of this pest. The correlations between growth and development parameters showed that larval period had the most influence on M. testulalis survival and population build-up in the succeeding generations.