Rotational management of Meloidogyne javanica and effects on Pasteuria penetrans and tomato and tobacco yields
Madulu, J.D.; Trudgill, D.L.; Phillips, M.S.
Nematologica 40(3): 438-455
ISSN/ISBN: 0028-2596 DOI: 10.1163/003525994x00319
Pot tests identified a range of plant species and cultivars for use as poor on non-hosts in rotations to control Meloidogyne javanica in Tanzania. In two field trials which examined their effect on levels of infection and on tomato and tobacco yields respectively, the rotational crops were grown in the second season and the susceptible crops in the first and third seasons. The legume Crotalaria ochroleuca was tested in both trials and in the third season it increased the yields of the tomato and tobacco more than any of the other crops tested. In the tomato trial it suppressed galling by M. javanica in the third season by as much as Tagetes erecta, and more than a bare fallow. Groundnut (Arachis hypogaea) was tested only in the tobacco trial where its use in the second year increased yields of the tobacco in the third year more than sesame (Sesamum orientale), even though the latter was marginally better at reducing the subsequent infection of the tobacco. Maize was a relatively poor rotational host, halving the subsequent root gall index on tobacco but only marginally increasing tobacco yields. In the plots which grew tobacco continuously for three seasons gall indices progressively increased and yields progressively decreased. In those which grew continuous tomato, the yields were more variable due to blight infection, but gall indices increased little in the second season and decreased in the third. Further investigations at the end of the third season revealed a high level of infection (75%) of juveniles with Pasteuria penetrans in the continuous tomato plots but lower levels (25%) in the continuous tobacco. Levels were lower where a poor host had been grown in the second season than in those where the susceptible was grown for all three seasons.