We found that neem extract did not inhibit the growth of the microorganisms tested in this study, with the exception of B. megaterium, for which 1 gmL-1 or more of neem extract could inhibit growth (Table 3). As expected, azadirachtin exhibited greater antimicrobial activity than the neem extract. Azadirachtin applied at a concentration of 0.3 mgmL-1 or more could
inhibit the growth of Rhizobium sp. and X. campestris pv. campestris. The growth of B. megaterium, P. aeruginosa, and P. carotovorum could be inhibited by azadirachtin applied at concentrations of at least 0.1, 0.4, and 0.5 mgmL-1, respectively. Neither azadirachtin nor neem extract could inhibit T. asperellum and F. oxysporum. Azadirachtin applied at concentrations of 0.4 mgmL-1 or more resulted in late sporulation only in T. asperellum (data not shown).