Tempo de exposição de juvenis de segundo estádio a voláteis emitidos por macerados de nim e de mostarda e biofumigação contra Meloidogyne incognita

Abstract

Although volatiles emitted by diverse sources have demonstrated toxicity to some plant pathogens, only a few studies have evaluated the effect of volatiles emitted by plants on plant-parasitic nematodes. The effects of varying exposure times of second stage juveniles of Meloidogyne incognitato volatile organic compounds (VOC) from neem and mustard were evaluated. In addition, the direct effect of macerates of these plants incorporated into a substrate infested with eggs of M. incognita(biofumigation), and the effects of the VOC released into the air and held at the substrate surface by plastic cover on juveniles were studied. Macerates of neem and mustard emitted VOC that caused significant juvenile immobility at initial exposure, and significant mortality was observed after 24-hr exposure to the volatiles. The number of root galls and eggs on tomato inoculated with M. incognitasecond-stage juveniles that had been exposed to volatile compounds decreased with increasing exposure time. These findings confirmed the nematicidal effect of the VOC tested relative to the immobilization and mortality seen in second-stage juveniles after 24-hr exposure. Biofumigation with neem and mustard macerates incorporated into a substrate infested with nematode resulted in a linear reduction of galls when macerate amounts were increased, being lower than in control only at the highest macerate amount (9.6 g). However, the number of eggs was significantly reduced in macerates above or equal to 2.4 g. Juveniles exposed to volatile compounds emitted by neem or mustard macerates incorporated into the substrate and retained in a chamber formed on the substrate surface by sealing with plastic exhibited significant immobility and mortality even at the lower macerate amount, whereas this effect was not seen in the absence of the plastic sealing.