Macrotyloma axillare ‘Java’ and Crotalaria spp. combined with biocontrol agents for the management of Meloidogyne javanica in soybean

This study aimed to investigate the effects of crop rotation with Macrotyloma axillare ‘Java’, Crotalaria spectabilis and Crotalaria ochroleuca combined with green manure application or biological treatment, on the control of Meloidogyne javanica in soybean. An initial greenhouse study was conducted in a 4 × 2 factorial design, with four rotation crops (M. axillare ‘Java’, C. spectabilis, C. ochroleuca and soybean) in the presence and absence of green manure. A second greenhouse study was carried out using a 4 × 5 factorial design, with four rotation crops and five biocontrol treatments (Pochonia chlamydosporia, Purpureocillium lilacinum + Trichoderma harzianum, Bacillus methylotrophicus, Bacillus subtilis + Bacillus licheniformis and untreated control). Both experiments consisted of two independent trials (Trials 1 and 2) conducted at different times of the year. The experimental field soil was infested by growing soybean infected with M. javanica for 50 days prior to the assays. Then, seeds of rotation crops were sown and biocontrols applied. Rotation crops were removed 70 days after sowing, and soybean seeds were sown immediately afterwards. Total nematodes, nematode per gram of root and soil biological activity were assessed 60 days after soybean sowing. In the first study, all rotation systems and green manure treatments reduced M. javanica population. In the second study, all biological treatments were effective, except B. methylotrophicus and M. axillare ‘Java’ combined with P. chlamydosporia in Trial 1 and C. spectabilis combined with P. lilacinum +T. harzianum in Trial 2. Macrotyloma axillare ‘Java’ combined with B. methylotrophicus and C. spectabilis combined with B. subtilis +B. licheniformis resulted in higher soil metabolic activity. The association of biological control agents with crop rotation generally did not present additive effects in the reduction in M. javanica populations, except for one combination of M. axillare ‘Java’ with B. subtilis +B. lichneniformis.