Effects of hatching factors on potato cyst nematode hatch and in-egg mortality in soil and in vitro

The exogenous application to three Globodera pallida-infested fields of tomato root leachate (TRL) containing hatching factors increased nematode hatch and in-egg mortality, particularly in a highly organic soil, and in a sandy but not in a clay soil. The most active concentrations of TRL (7.5-12.5 mg m(-2)) resulted in a reduction of between 69 and 79% in the number of viable eggs per cyst recovered 12 weeks after TRL application. At high hatching factor concentrations, supra-optimal inhibition of both hatch and in-egg mortality was observed; generally, hatch and in-egg mortality exhibited similar dosage-responses to TRL. A significant TRL dosage-hatch response was observed at 4 weeks after TRL application only in the sandy soil. In vitro, a G. pallida population exhibiting moderate hatch gave similar hatching and in-egg mortality responses as in the held experiment. The response of the PCN populations in vitro was found to be dependent on the physiological state of the egg/juvenile complex, with egg populations in diapause responding to the presence of natural and artificial hatching factors by exhibiting increased in-egg mortality but not increased hatch. The results are discussed in relation to novel G. pallida control measures.