POSITIVE INFLUENCE OF INTERCROPS ON COCCINELLID AND SPIDER FAUNA IN GROUNDNUT

ABSTRACT: Groundnut, (Arachis hypogaea L.) is one of the major oilseed cum valuable cash crops for millions of small scale farmers in the semi-arid tropics. The insect pests of groundnut inflicts serious losses both directly as defoliators, sap suckers, root feeders etc and indirectly as vectors to dreaded viral diseases of the crop. Chemical control is being recommended with success but the awareness of deleterious effects of chemicals led to the thinking about alternatives to chemicals. Cultural operations in agriculture have well established history for their role in insect pest management. Of these, inter/mixed cropping systems have been considered as important components and constitutes the most practical oriented approach. A field trial in RBD was conducted at S.V.Agricultural College, Tirupati to study the influence of intercrops on natural enemies of groundnut insect pests during kharif 2011. The systems studied were groundnut + red gram, groundnut + castor (at 7:1 ratio), groundnut + cowpea, groundnut + field bean (at 6:1 ratio) and pure groundnut. Coccinellids and spiders were predominant during crop growth period. Various species of coccinellid predators were considered as a group, and their presence was recorded in all the cropping systems. All the spiders, irrespective of the family to which they belonged, were recorded together as one unit. Among the coccinellids, Chelomenes sexmaculata was the predominant predator which accounts for 70 per cent of the population. Spiders belonging to Lycosidae family were predominant. Population of coccinellids and spiders was increased up to 60 -70 DAS and declined later. This may be due to availability of sufficient prey like aphids, jassids etc during vegetative stage of the crop. Change in microclimate due to shredded/shrinked foliage at later stages of the crop also may not favour the natural enemy fauna. The data shows that coccinellid population was comparatively high in groundnut + cowpea system (2.44 per plant). Aphids that prefer cowpea might have attracted the grubs and adults of coccinellids towards the crop, as coccinellids are the major predators of aphids. In the remaining intercrop systems also, significantly higher lady bird beetle population was observed. Spider population was comparatively higher in groundnut + field bean system (1.66 per plant) followed by groundnut + cowpea system (1.32 per plant). Other systems had nearly 0.8-1.3 spiders per plan