Appraisal of spinning disc technology for the application of entomopathogenic nematodes

Abstract

We assessed the efficacy of low and very-low volume spraying systems, using two spinning disc sprayers (Micron Ulva + and Micron Herbaflex), specifically for the application of infective juveniles (IJS) of entomopathogenic nematodes ( Steinernema spp. and Heterorhabditis spp.) for potential use in sprays against larvae of Plutella xylostella, a serious cosmopolitan pest of crucifers. Studies showed that significant numbers of IJS/cm 2 could be deposited, although most droplets contained no nematodes. The negative binomial distribution generally provided a good model for the distribution of IJS in the droplets. Increasing flow rate (i.e. increasing the application rate) and/or concentration of IJS significantly increased deposition of IJS from the sprayers. Numbers of IJS deposited per cm 2 were generally not affected by length of IJS, which ranged from approximately 600 to 1100 μm. The theoretical proportions of droplets capable of carrying IJS, under a series of different application regimes, were calculated and compared with the observed proportions, the latter being significantly less than the theoretical. Addition of IJS to the spray did not affect the spray spectra produced by either sprayer, irrespective of flow rate, concentration of IJS or disc rotational speed.