Use of entomopathogenic nematodes for control of grape Phylloxera (Homoptera : Phylloxeridae): A laboratory evaluation

The effectiveness of 2 species of entomopathogenic nematodes was examined i n the laboratory against the root-form of grape phylloxera Daktulosphaira v itifolia (Fitch). Our basic unit of measurement was survival of grape phyll oxera established on root pieces of the cultivated grape Vitis vinifera L. variety 'Cabernet Sauvignon' in the presence or absence of nematodes. In pe tri dish trials, the Oswego strain of Heterorhabditis bacteriophora Poinar reduced survival of attached grape phylloxera by up to 80% relative to the control treatment, whereas Steinernema glaseri Steiner (isolate 326) had no measurable impact and was not used in further experiments. Hb Oswego signi ficantly reduced survival of grape phylloxera on root pieces placed in smal l cups filled with soil, but only when soil moisture was high (>13% water c ontent wt:wt) and when high densities of infective nematodes were used (>15 ,000/g soil). Grape phylloxera exposed to Hb Oswego often turned a brick-re d color, indicating successful infection. However, we did not detect any ev idence that Hb Oswego could successfully reproduce within the bodies of gra pe phylloxera hosts, Therefore, although Hb Oswego can exert significant mo rtality in the laboratory, their use in the field in an augmentative releas e program may be constrained by the need to use high densities, their depen dence on moist soils, and their inability to propagate themselves within gr ape phylloxera hosts.