Evaluating Pochonia chlamydosporia in a double‐cropping system of lettuce and tomato in plastic houses infested with Meloidogyne javanica

The effect of Pochonia chlamydosporia , a facultative fungal parasite of nematode eggs, alone or in combination with oxamyl was evaluated in a double‐cropping system of lettuce and tomato in unheated plastic houses infested with Meloidogyne javanica at two sites for two consecutive growing seasons. An additional treatment of methyl bromide fumigation was included to compare crop yield in nematode‐free vs. nematode‐infested soil. Final population densities, reproductive rate, root gall rating, and egg production were determined after each crop. Pochonia chlamydosporia was isolated from nematode eggs up to nine months after application to soil. The fungus survived in the rhizosphere for the entire growing season at one site, but only at low densities. Final population densities of M. javanica decreased after cultivation of lettuce and increased after tomato, and this pattern of population fluctuation was unaffected by treatment, experiment or site. The reproductive rate on lettuce was equal to or below 1, and it was similar among treatments in both experiments at both sites. Eggs were not found on lettuce roots. On tomato, the reproductive rate in the fungus + oxamyl treatment was significantly lower ( P < 0·05) than other treatments in experiment 1 at both sites. Fungus + oxamyl consistently reduced root gall ratings on tomato in all cases, but numbers of eggs per g root varied depending on treatment. Methyl bromide‐treated plots remained free of M. javanica at the end of the 2‐year study.