) MSc

The mounting problems posed by pod sucking bugs recently in the vegetable cowpea ecosystem is emblematic of the changing pest status in favour of sucking pests in many agro ecosystems. To devise management strategies against the bugs, a project entitled “Bioecology and management of pod bugs infesting vegetable cowpea, Vigna unguiculata ssp. sesquipedalis (L.) Verdcourt” was undertaken during 2005-2006 at the College of Agriculture, Vellayani.

Nine species of pod bugs viz., Acrosternum graminea (Fab.), Clavigralla gibbosa Spinola, Cletus bipunctatus Westw., Coptosoma cribraria Fab., Homoeocerus sp., Nezara viridula (L.), Piezodorus rubrofasciatus (Fab.), Riptortus? linearis (Fab.) and Riptorus pedestris Fab. were recorded. A. graminea, C. bipunctatus, Homoeocerus sp., P. rubrofasciatus, R? linearis are new reports from vegetable cowpea in India. R. pedestris was the dominating pod bug followed by N. viridula and R? linearis.

Nine predators including four preying mantids, one black ant, a reduviid bug, three species of spiders and one ectoparasitic mite were documented as natural enemies of pod bugs. Record of the mantids, Elmantis tricomaliae (Mukharji-Hazra), Euantissa pulchra (Fabricius), Humbertiella ceylonica (Saussure), Hierodula? ventralis Giglio-Tos, the black ant Camponotus compressus Fabricius and the ectoparasitic mite are new reports of natural enemies of pod bugs in India.

Plants belonging to the family Leguminosae were the most preferred hosts of R. pedestris. Cassia occidentalis (L.), Panicum maximum (L.) and Synedrella nodiflora (L.) Gaertn. served as important weed hosts. Minimum temperature exerted significant positive effects on the population of N. viridula and nymphs of Riptortus spp.

N. viridula, P. rubrofasciatus and R? linearis completed their life cycle in 22.59 + 0.41, 20.19 + 0.20 and 22.05 + 0.25 days respectively on vegetable cowpea var. Sharika R. pedestris took 21.40, 24.00, 24.40 days to complete its development in vegetable cowpea var. Sharika, grain cowpea var. Pusa komal and coffee senna weed (C. occidentalis) respectively.

Amrutneem 5 ml l-1 proved superior among the botanical insecticides tried against R. pedestris in the laboratory bioassay and field experiment and it was followed by Nimbecidine 2 ml l-1 and Neem Azal 2 ml l-1. Beauveria bassiana @ 2.5 x 107 spores ml l-1 and Rhizopus oryzae @ 7 x 106 spores ml-1 was pathogenic to R. pedestris but the infectivity was low. Pseudomonas fluorescens P.F.I @ gl-1 showed no lethal effects on R. pedestris.

Imidacloprid 0.005 per cent and dimethoate 0.05 per cent were significantly superior in suppressing the nymphal population of Riptortus spp. All the insecticide treatments evaluated were significantly superior to control in reducing the population of Riptortus spp. Imidacloprid 0.005 per cent gave the highest benefit cost ratio.

Monitoring the population of pod bugs, mechanical destruction of eggs, nymphs and / or adults, wetting the crop canopy thoroughly during irrigation, removal of weed hosts viz., C. occidentalis, P. maximum and S. nodiflora in vicinity, trash removal after harvest in cowpea, bhendi, chilli and application of Amrutneem 5 ml l-1 / Nimbecidine 2 ml l-1 / Neem Azal 2 ml l-1 / imidacloprid 0.005 per cent / dimethoate 0.05 per cent / malathion 0.05 per cent / fenvalerate 0.03 per cent / lambda cyhalothrin 0.002 per cent / chlorpyrifos 0.03 per cent are suggested as management measures against pod bugs.