High dilutions ofNatrum muriaticumand shell lime to manage of the thrips, downy mildew, and yield in the organic system of onion crops

Abstract

The aim of this research was to evaluate doses of high dilution preparations of shell lime and Natrum muriaticum onThrips tabaci Lind. (Thysanoptera: Thripidae), downy mildew, Peronospora destructor (Berk.) Casp., and yield, under organic systemof onion crops. Two experiments were carried out in the field of Ituporanga Experiment Station at Epagri (Agricultural Research and Rural Extension Service Agency of Santa Catarina State), Brazil. Plantlets were transplanted in 08/17/2009, and bulbs were harvest in 11/30/2009. Natrum muriaticum (experiment 1) and shell lime (experiment 2), both at 6CH (centesimal hahnemanniana dilution) were tested at doses of 0,1, 0,5 and 1%. For both experiments untreated plots were the control. The experimental design was in completely randomized blocks with four replications. The experimental replications were composed by 200 onion plants transplanted in a line of 20m. High dilution preparations were sprayed 54, 60, 67, 76, 83, 90 and 96 days after transplanting. Yield of onion bulbs was evaluatedin 100 bulbs per replication. Weekly thrips assessments were made on five onion plants per replication by counting all the nymphs on leaves with hand magnifier of three times. The doses of shell lime did not differed on thrips incidence and the yield of bulbs. However, doses of 0,5 and 1% of Natrum muriaticum reduced thrips incidence, respectively, at 94 and 87 days after transplanting but did not affected the bulbs yield. The incidence and severity of downy mildew were not affected by treatments.