Composição química da manipueira e sua potencialidade no controle de Meloidogyne incognita em tomateiro no oeste do Paraná

Abstract

The tomato crop is strongly affected by the root Knot nematode Meloidogyne incognita. This nematode species is widespread in the Western region of Paraná State, Brazil. The strategies currently adopted on the control of this nematode emphasize the search for alternative methods specially those that contributes to the environmental preservation. Manipueira is a waste liquid residue produced by the cassava industry and found in large amounts at Western Paraná. The aim of this work was to study the chemical composition of the manipueira produced in Western Paraná and its nematicide effect on M. incognita, parasite of tomato crop. The chemical analyses were performed with homemade manipueira and industrial manipueira. The industrial manipueira were collected from three cassava industries in the Western Paraná. The homemade manipueira were extracted from four cassava cultivars. The chemical analysis showed presence of nutrients such as N, P, K, Ca, Mg, Fe and Mn in different concentrations from samples of different sources. The pH of the samples ranged from 6.0 to 6.6, DBO from 1.600 to 1.986 mg L-1 and free cyanide (CN-) from 25 to 40 ppm. The nematicide effect of manipueira on M. incognita was tested in vitro, in pots and in the field. in vitro tests followed the completely randomized statistical design with 12 replications. The treatments were manipueira 100%, and manipueira diluted in water at 75%, 50%, 25%, 15%, 10%, 8%, 6%, 4% and 2%, besides water as the negative control and the nematicide Carbofuran 50 mg L-1 as the positive control. Each replication was composed of one eppendorf containing 1 ml of each solution and 500 second stase juvenile stages (J2). After 24 hours, the living and dead nematodes were counted and inoculated on tomato plants cv. Santa Cruz Kada. In total, it was inoculated 1.500 J2/pot in four replications per treatment. The evaluation 45 days after inoculation was based on the number of galls formed per tomato. The in vitro tests showed that the manipueira treatments until 10% dilution had 100% mortality, being statistically different from the other solutions. The nematicide had a better performance than the negative water control. The essay developed in pots was carried out with the treatments manipueira 10%, 25%, 50%, water control and Carbofuran 2 g per pot. The experimental design was completely randomized with 4 replications. Tomato plants were inoculated with 5.000 J2 and rested for 60 days before starting the treatments. After adding the solutions into the pots the tomato plants were cut at the soil level, being replaced by new ones. Variables such as plant height, dry mass, root length, number of galls and eggs per root and the reproduction factor (RF) were analyzed. The results showed that the manipueira treatments had a better performance than the others considering the most of features studied. The best treatments from the pot test were manipueira 10 and 25%. However, manipueira 50% was superior to the others as a nutritional source. The field experiment with tomato plants cv. Santa Cruz Kada,was performed from May to August 2007 in an area infested with M. incognita. The experimental design was completely randomized containing 4 treatments and 4 replications. The assessed variables were plant height, dry and fresh shoot weight, number of galls and eggs per root and fruit yield (g). The best treatments against M. incognita, in the field experiment, were manipueira 10 and 25%. The treatment manipueira 50% was also the most effective in field conditions as a nutritional source. In terms of crop yield, no statistical difference was detected among the manipueira treatments, which were statistically different from the water control and the nematicide. The results suggest that manipueira at 10 or 25% should be alternated with manipueira 50% in order to maximize its effect on M. incognita