The effect of hydraulic agitation on the viability of the nematode Heterorhabditis bacteriophora

The entomopathogenic nematode Heterorhabditis bacteriophora is an active ingredient of several biological plant protection products, generally applied using motorised sprayers. The effect of hydraulic agitation of motorised sprayers on the viability of the entomopathogenic nematode was investigated in three experiments, which evaluated initial liquid temperature, hydraulic agitation and rise in liquid temperature as a result of agitation at initial water temperatures of 20 and 30 degrees C and four different spraying duration times (95, 48, 32, and 24min), obtained by using various nozzle sizes (TeeJet flat fan nozzles 11008VK, 11006VK, 11004VK, and 11002VK). Viability was significantly affected (p < 0.05) by agitation, replicates, liquid temperature, and interaction between liquid temperature and agitation. The viability decreased 4.3% and 6.4% in the agitated samples at liquid temperatures of 20 and 30 degrees C, respectively. The sprayer components had no influence, but the agitation reduced viability by 5-6%. The duration of spraying reduced viability as well. No significant differences were found among nozzle sizes, but as they determine the duration of spraying, they also exhibited different ranges of viability decrease with the duration of agitation. The highest viability decrease (24%) was obtained after 95 min of spraying. The main reason for the decrease of nematode viability was the joint effect of agitation stress and increased temperature. (c) 2006 Elsevier Ltd. All rights reserved.