Effects of a plant extract-based nematicide (G8014S) and its components on the host finding behaviour and multiplication of Globodera pallida on glasshouse-grown potatoes

Abstract

In vitro and glasshouse studies were initiated to determine the mechanisms of action of an aqueous garlic extract, salicylaldehyde, a nonylphenol ethoxylate surfactant and a formulation (G8014S) containing these substances on the potato cyst nematode Globodera pallida. The effects of these substances on host finding and migration of second-stage juveniles (J2) were assessed by investigating their ability to migrate through a sand column and towards potato roots in Pluronic F-127 gel. The garlic extract was shown to be the least disruptive to J2 host finding, reducing attraction by between 13 and 24% at concentrations of 7840 ß\ 1~' and 983 (Ul r ', respectively. By contrast, a reduction of approximately 38% in J2 attraction to roots was achieved by treating J2 with 344 /xl r' of G8014S. Of all the substances tested, salicylaldehyde was the least attractive to G. pallida J2 (4.1%) while the garlic extract and oxamyl treatments attracted 43.5 and 28.9% J2, respectively. In glasshouse experiments, different rates of the test substances were compared with the nematicide oxamyl for their effects on the in-soil hatch, egg viability and multiplication of G. pallida. The effect of treatment with 220.16 1 ha~' of G8014S on G. pallida multiplication in the glasshouse was comparable to that of oxamyl causing a five-fold reduction in PCN multiphcation relative to the water control. These results provide evidence to support the potential of the formulation for the control of G. pallida in potatoes.