Effect of Crop Matrix on Insect – Plant Interaction under Two Environmental Regimes on Cowpea

The results revealed that inland ecosystem (Srivilliputtur) during summer and winter 2017, cowpea + sorghum intercrop system recorded low numbers aphid, thrips, pod bug and spotted pod borer viz., (7.52 and 10.57/10 cm twigs, 0.96 and 2.06/10 flowers, 0.96 and 2.05/plant and 0.72 and 1.24 larvae/plant respectively) followed by cowpea + pigeonpea (8.65 and 11.64, 1.30 and 2.19, 1.04 and 2.17 and 0.99 and 2.09 larvae/plant respectively) compared to pure crop of cowpea (12.11 and 6.54/10cm twigs, 2.02 and 4.13/10 flowers, 2.08 and 3.25/plant and 1.71 and 2.99 larvae/plant respectively). In inland ecosystem during winter 2017, the mean number of leaf hopper low in intercropped with cowpea + pigeonpea (0.87/3 leaves) during summer 2017 and intercropped with cowpea+ sorghum was low (1.25/ 3 leaves).where as in coastal ecosystem (Kamudhi) during summer and winter 2017, Leaf hopper, aphid, thrips, pod bug and spotted pod borer viz., (0.57 and 1.24/3leaves, 7.06 and 8.56/10 cm twig, 0.88 and 1.76/10 flower, 0.75 and 2.09/plant and 0.8 and 1.95 larvae/plant respectively) were low with cowpea + sorghum followed by cowpea + pigeonpea (0.85 and 1.37/3leaves, 8.72 and 9.40/10 cm twig, 1.12 and 2.14/10 flowers, 0.86 and 2.19/plant and 0.78 and 1.95 larvae/plant respectively) which was significantly minimum than pure crop of cowpea (1.21 and 2.54/ 3 leafhopper, 11.39 and 14.58/10 cm twigs, 1.81 and 3.67/10 flowers, 1.86 and 3.26/plant and 0.26 and 0.30 larvae/plant respectively).