Spatial distribution of thrips (Thrips tabaci) in onion (Allium cepa) under cold arid region of Jammu and Kashmir

Abstract

A field study was carried out during 2003-04 at Ladakh at to study the spatial distribution of onion thrips (Thrips tabaci Lindeman) in 'Brown Spanish' onion (Allium cepa L.). The various indices of dispersion, viz variance mean ratio, exponent k and common k (Kc), Lloyd's indices of mean crowding ( x* ) and patchiness idex ( x* x) and Taylor's power law revealed that the onion thrips exhibited aggregated or contagious pattern of distribution in the field. The value of Taylor's aggregation index (b) was 1.3778 and 1.4186 during 2003 and 2004 respectively. In study of Iwao's m* - m relationship it was found that contagiousness coefficient value (a = 1.002 and 1.038 respectively) was &gt 1. This also indicated that thrips population followed negative binomial distribution pattern as an alternative of poisson or random distribution. The intercept also justified that the distribution of thrips was contagion in nature.