Effects of NeemAzal-U on survival, host infestation and reproduction of entomopathogenic and plant-parasitic nematodes: Heterorhabditis bacteriophora and Meloidogyne incognita

Abstract

To determine the effects of neem active ingredients (azadirachtin) on the entomopathogenic nematode Heterorhabditis bacteriophora and the plant-parasitic nematode Meloidogyne incognita, the nematodes were separately treated with different concentrations of NeemAzal-U (i.e., 0.06%, 0.3% and 0.6%) and its blank formulation. Direct exposure of both nematode species to NeemAzal-U for 14 days caused 14% (control mortality = 6.5%) and 44.5% (control mortality = 14.3% ) mortality of H. bacteriophora and M. incognita, respectively. Heterorhabditis bacteriophora kept either in different NeemAzal-U solutions or water did not differ in their parasitisation efficiency of wax moth larvae Galleria mellonella. However, infection rate of M. incognita decreased with increasing neem concentration and a reduction of gall formation of up to 88% was recorded with the highest neem concentration. The number of infective juveniles (IJs) of H. bacteriophora produced per Galleria larva was not influenced by neem treatments of IJs used for host infection. In contrast, the highest neem concentration reduced hatching (85%) and increased mortality (68%) of M. incognita juveniles compared with the water control. It can be concluded that NeemAzal-U can be applied together with ento-mopathogenic nematodes for pest control without detrimental impact on the beneficial nematodes. Furthermore, NeemAzal-U can contribute to the control of M. incognita but only if high concentrations are used.