False codling moth (FCM), Thaumatotibia leucotreta, is one of the most important insect pests of citrus in South Africa. No treatment is currently directed towards the soil stages of FCM, with entomopathogenic nematodes (EPNs) having the potential to fill the niche. Laboratory bioassays in orchard soil, using Heterorhabditis bacteriophora, showed the LD50 to be ≈3 and the LD90 to be ≈58 infective juveniles (IJs) per FCM larva. In a field trial, after application of three concentrations (20, 40 and 80 IJs/cm2) of H. bacteriophora, mortalities of >90 %were obtained for FCM larvae, with significant difference between the lower concentrations, but not with higher concentrations. Twenty-one days after application, there was no further FCMcontrol.With the field application of H. zealandica after 6 days, no significant differences were found in FCM mortality of >80 % between three nematode concentrations (5, 10 and 20 IJs/cm2). After 21 and 35 days no significantly different FCM mortality was found for all three treatments compared to the untreated trees. In a field trial using three nematode species, treatment with H. zealandica resulted in significant control for each evaluation day, up to day 49. Results from field trials showed local EPN species to have great potential for control of the soil stages of FCM, with the added possibility of good persistence.
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Vol. 24 • No. 2