INTERAÇÃO ENTRE PLANTAS DE COBERTURA E AGENTES DE BIOCONTROLE NO MANEJO DE NEMATOIDES NA CULTURA DA SOJA

Abstract

The soybean is the most important oilseed cultivated in the world and Brazil is the largest producer. In the Brazilian cerrado, phytonemaoids have increasingly become a challenge for agriculture and the association of control tools is the best strategy to be used in their management. Thus, the present work aimed to evaluate the efficiency of phytonematodes management in soybean crop using cover crops and biological control agents. Thus, experiments were carried out under greenhouse conditions for the genera H. glycines, Meloidogyne incognita and Pratylenchus brachyurus. The first study aimed at the efficiency of nematode management in soybean crop using cover crops and biocontrol agents. For each genus under study (Meloidogyne incognita and Pratylenchus brachyurus) two trials were developed under greenhouse conditions where different specimens of cover crops (millet ADRG 9050 and ADR 300, U. ruziziensis, C. ochroleuca and C. spectabilis) and DKB 290 corn treated or not with Bacillus subtilis and B. methylotrophicus (1x106 per seed) in different assays. After the cultivation of cover crops, soybeans were sown and cultivated for 45 and 60 days. At the end of the tests, the fresh mass of roots, total nematode population and the number of nematodes per gram of root were evaluated. The association of microorganisms with C. spectabilis, U. ruziziensis and ADR 300 millet conferred an additional effect on reducing the population of P. brachyurus. For the species M. incognita the association was successful only for the combination of C. spectabilis with B. methylotrophicus. Although DKB 290 corn is not a cover crop, it is noted that when previously treated with B. methylotrophicus, the nematode population per gram of sequentially planted soybean root is reduced by 90% compared to plants that did not receive the previous treatment of corn with the microorganism. The second study aimed to evaluate the efficiency of biological treatments T. koningiopsis and B. methylotrophicus, associated with off-season crops for the control of Heterodera glycines race 3 in soybean crop. Two trials were carried out under greenhouse conditions where different specimens of cover crops (ADR 300 millet, U. ruziziensis, C. spectabilis) and DKB 290 maize treated or not with T. koningiopsis (1g per kg-1 of seed) and B. methylotrophicus (1x106 CFU per seed) in different assays. After the cultivation of cover crops, they were subjected to a water stress of 60 and then soybean seeds were sowed and cultivated for 30 days. At the end of the tests, the number of cysts/vessel and the number of eggs per cyst were evaluated. The association between top dressings and the biological products T. koningiopsis and B. methylotrophicus did not confer additional effect on the control of H. glycines evaluated in the subsequent soybean. The control effect of the combination between cover crops and biological products has unique interactions and behaviors, which is also influenced by the nematode genus. The association of control tools will always be the best alternative to manage and contain the multiplication of phytonematodes in the soil.