Evaluation of spinning disc technology for the application of entomopathogenic nematodes against a foliar pest

Two spinning disc spray application systems, the Micron Herbaflex and Micro n Ulva+, were assessed for their potential for the application of infective juveniles (IJs) of entomopathogenic nematodes (EPNs) against larvae of the diamondback moth (DBM), Plutella xylostella. The effect of initial concent ration of IJs on subsequent infection was examined for three species of EPN s: Steinernema sp. (M87), Steinernema sp. (SSL85), and Heterorhabditis sp. Increasing the concentration of Ids generally resulted in a significant inc rease in both DBM mortality and the mean number of nematodes per larva foll owing spray application with the Micron Herbaflex sprayer. Application with the Micron Ulva+ was examined using two different initial concentration of Ids, which generally resulted in an increase in DBM mortality and intensit y of infection. The effect of changing the flow rate to the Ulva+ was also examined. This generally resulted in increased DBM mortality as how rate wa s increased but there was little change in the mean number of nematodes per host larva. The effect of addition of a number of adjuvants to the spray s olution on subsequent infection showed that DBM mortality by the Ids was no t significantly affected but that the mean number of nematodes infecting wa s significantly enhanced by some of the adjuvants. Desiccation survival stu dies with IJs of Heterorhabditis sp. following application with both spraye rs onto Chinese cabbage leaf discs, with or without the addition of an adju vant, showed that the survival time of 50% of IJs was over 3 h. Infection o f DBM larvae was also assessed following desiccation on Chinese cabbage lea f discs. High levels of infection were attainable, in terms of resultant DB M mortality, for at least 150 min following spray application. (C) 1999 Aca demic Press.