APPRAISAL OF SPINNING DISC TECHNOLOGY FOR THE APPLICATION OF ENTOMOPATHOGENIC NEMATODES

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 entom opathogenic nematodes (Steinernema spp. and Heterorhabditis spp.) for potential use in sprays against larvae of Plutella xylostella, a serio us cosmopolitan pest of crucifers. Studies showed that significant num bers 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 fl ow rate (i.e. increasing the application rate) and/or concentration of IJS significantly increased deposition of IJS from the sprayers. Numb ers of IJS deposited per cm(2) were generally not affected by length o f IJS, which ranged from approximately 600 to 1100 mu m. The theoretic al proportions of droplets capable of carrying IJS, under a series of different application regimes, were calculated and compared with the o bserved proportions, the latter being significantly less than the theo retical. 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. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.