Invasive Species Compendium

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Abstract Full Text

Coccinellids and chrysopids as native predators of sucking pests in relation to rainfed cotton production system.

Abstract

Status and dynamics of sucking pests (jassids and aphids) and their native predators (coccinellids and chrysopids) were studied for five consecutive years (2001-05) in rainfed cotton production system. The effect of cultivars, cropping pattern, fertility levels and pest management options on the activity of predators was also inferred from the observations taken from different agronomic and plant protection field experiments. The range of jassid incidence, aphid infestation, activity of coccinellids and chrysopids was 2.4 to 7.5 nymphs per three leaves, 15.0 to 38.9 percent, 0.1 to 0.4 and 0.52 to 1.87 per plant, respectively. Dynamics of the predators indicated perpetuating population of chrysopid over coccinellids with their association positive (r=0.058) but non-significant. Higher incidences of jassids and aphids and their predators were observed on the hybrids than the varieties. Long-term soil fertility changes did not have any direct influence on the predators. Significantly higher chrysopids and coccinellids (1.83 and 0.99 per plant) observed on cotton sole crop reduced the aphid infestation (19.2%) compared to the soybean-intercropped cotton (24.2%). While the occurrence of coccinellids on cotton under protected and unprotected situations was discontinuous, chrysopids continued to occur between August and November months. Recolonisation of both predators was observed under insecticidal spray situations. The paper discusses the role of coccinellids and chrysopids in the context of sucking pest management and emphasizes the need for designing cotton ecosystems favourable for higher predation by these native predators.