The influence of thrips incidence,Thrips tabaci Lind. (Thysanoptera: Thripidae) and the yield in onion on conventional and organic system.

Abstract

The objective this research was to evaluate the influence of the thrips incidence in yield of onion in organic and conventional systems. The study was based in the historical survey in plots without control methods in 10 and 17 experiments, respectively in conventional (from 1991 to 1997), and organic (from 2004 to 2009) systems, in the Epagri, Ituporanga Experiment Station, Santa Catarina State, Brazil. The cultivar used was the Crioula. In conventional system the relationship between nymph thrips incidence with yield was negative, y= -0,03x2+ 0,796X+ 10,06 (R2= 0,80). In organic system the relationship between insect was linear and positive to variables, total yield, y= 0,365x + 9,93 (R2= 0,27), bulb weight general, y= 1,264x + 52,12 (R2= 0,136), weight of bulb commercial, y= 0,809x + 88,49 (R2= 0,145), and commercial weight,y= 0,827x + 6,634 (R2= 0,253). The both systems differed mainly by soil management practices. In organic system ecological practices were adopted, such as no tillage, cover crops, organic fertilizers and rock phosphate.