Evaluation of hydraulic, pneumatic and mechanical agitation for the spray application ofSteinernema carpocapsae(Rhabditida: Steinernematidae)

Abstract

The application of entomopathogenic nematodes (EPN) is generally done using standard spray application techniques. However, in contrast to chemical pesticides, these biological antagonists must remain viable during and after the application process. For the application of EPN, a good agitation system is indispensable as the nematodes tend to sediment fast in a spray tank without agitation. Three agitation systems, viz. mechanical, pneumatic and hydraulic agitation were tested for their ability to keep Steinernema carpocapsae (Rhabditida: Steinernematidae) suspended in an undamaged way. Hydraulic agitation was tested using a centrifugal and a diaphragm pump. Nematode damage was quantified based on viability and infectivity of the EPN. The ability of the agitation system to keep the nematodes in suspension was examined by comparing the nematode concentration observed in the samples taken at different agitation times. Only the hydraulic agitation using the centrifugal pump damaged the nematodes. After 120 min of recirculation, only 19.3% of the nematodes survived. Infectivity was even reduced to 0%. An additional experiment revealed that the temperature rise, from 21.7 to 45.48C, was responsible for the observed nematode damage. The concentration measurements showed that the pneumatic agitation was unstable. Agitation during 120 min using the other agitation systems resulted in a significant loss of nematodes at 15 cm above the spray tank bottom. In conclusion, mechanical and hydraulic agitation using a diaphragm pump can be recommended when S. carpocapsae is applied, although attention should be paid to possible nematode loss during application.

Field suppression of the peachtree borer, Synanthedon exitiosa, using Steinernema carpocapsae: Effects of irrigation, a sprayable gel and application method

“…Those authors did not observe differences between the uses of a lance applicator versus an airblast sprayer. In contrast, in other studies differences in nematode efficacy resulting from application equipment have been reported (Hayes et al, 1999;Nilsson and Gripwall, 1999;Brusselman et al, 2010;Shapiro-Ilan et al, 2012).…”

Improving the biocontrol potential of entomopathogenic nematodes against Mamestra brassicae : effect of spray application technique, adjuvants and an attractant

“…The spray application equipment was well suited for applying S. carpocapsae on foliage for several reasons. First, the temperature in the tank remained well below 37 °C, the temperature above which detrimental effects on the survival of S. carpocapsae can occur . Second, the high survival percentage of S. carpocapsae in the tank samples proved that the mixing system is suitable for S. carpocapsae applications.…”

“…Furthermore, end‐user education about the specific problems encountered with the application of these EPN (e.g. sedimentation in the tank suspension, damage by temperature increase due to extensive tank recirculation, drought sensitivity of EPN on foliage) is badly needed. When these conditions are met, spray applications with S. carpocapsae can be fitted into biological control schemes to prevent resistance problems of M. brassicae to Bt.…”

“…First, the temperature in the tank remained well below 37 • C, the temperature above which detrimental effects on the survival of S. carpocapsae can occur. 39 Second, the high survival percentage of S. carpocapsae in the tank samples proved that the mixing system is suitable for S. carpocapsae applications. Third, the spray pressure (4 bar) was well below 20 bar, the advised upper pressure limit for spraying S. carpocapsae.…”

Effect of spray volume on the deposition, viability and infectivity of entomopathogenic nematodes in a foliar spray on vegetables

“…Approximately 30 min before every test, two (1095 L ha −1 ), three (730 L ha −1 ) or four (548 L ha −1 ) packages of 50 million EPNs were suspended in 10 L of water before adding them to 20 L of water in the spray tank. Subsequently, the tank was filled to a volume of 40 L. Before every test, the sprayer's pump was used for 5 min to homogenise the tank suspension and ensure an equal distribution of EPNs in the spray tank 10. After this homogenisation process, a sample was taken from the top of the suspension in the spray tank.…”