Seasonal climatic variations influence the efficacy of predatory mites used for control of western flower thrips in greenhouse ornamental crops

Abstract

This research investigated seasonal climate changes within greenhouses and the impacts they have on efficacy of the predatory mites Amblyseius swirskii and Neoseiulus cucumeris. Controlled environment chamber, greenhouse small-cage, and commercial greenhouse trials were conducted to determine which biological control agent is more efficacious for control of the pest western flower thrips (WFT), (Frankliniella occidentalis) on ornamental crops.When observed under laboratory conditions, predation and oviposition were increased at higher temperatures. Photoperiod and light intensity also have an impact on predatory mites. Predation rates for both mite species were greater when subjected to short day light conditions (8 h light, 11 W/m 2 ). Climates typical of summer (higher temperature and light intensity, long day length) were most favourable in terms of predation and oviposition for A. swirskii. Neoseiulus cucumeris laid more eggs under short day as opposed to long day settings.In summer and winter greenhouse small cage trials, the performance of N.cucumeris and A. swirskii significantly reduced WFT numbers on potted chrysanthemum plants. However, in summer, A. swirskii provided significantly better thrips control than N. cucumeris. The number of adult mites recovered from plants was similar for both mite treatments in winter, while A. swirskii were present in higher numbers throughout the summer trials. Results from leaf damage assessments indicate that A. swirskii is more effective for control of heavy WFT feeding damage in both summer and winter. Results from commercial greenhouse trials yielded similar trends as those found in the summer and winter small cage trials.iii ACKNOWLEDGEMENTS

Amblyseius swirskii in greenhouse production systems: a floricultural perspective

“…In temperate climates, A. swirskii provides better thrips control than N. cucumeris in summer, whereas both predators show similar efficacy in winter. In growth chamber trials, predation and oviposition rates of both predator species showed no major differences between simulated summer and winter greenhouse conditions, so the difference in performance in summer is likely related to better survival of A. swirskii (Hewitt et al 2015). However, as N. cucumeris is significantly less expensive than A. swirskii, this predator might be the better option in winter (Hewitt et al 2015).…”

“…In growth chamber trials, predation and oviposition rates of both predator species showed no major differences between simulated summer and winter greenhouse conditions, so the difference in performance in summer is likely related to better survival of A. swirskii (Hewitt et al 2015). However, as N. cucumeris is significantly less expensive than A. swirskii, this predator might be the better option in winter (Hewitt et al 2015). Unfortunately, similar comparative greenhouse studies between A. swirskii and other recently commercialized phytoseiid predatory mites (e.g., A. limonicus and T. montdorensis) have not yet been done.…”

Integrated pest management in western flower thrips: past, present and future

“…cucumeris , A. swirskii proved to be a better WFT predator than in sweet pepper, as females showed a higher propensity to attack and kill WFT larvae . In chrysanthemum, A. swirskii provided higher thrips control than N. cucumeris in summer, likely owing to a better survival, while both predators showed similar efficacy in winter . Efficiency of A. swirskii as a WFT biocontrol agent is also influenced by host plant species, and here increased trichome densities hinder mite performance .…”

When do predatory mites (Phytoseiidae) attack? Understanding their diel and seasonal predation patterns

“…However, until recently, studies focusing on the reproductive biology or predatory activity of predatory mites had considered the influence of light intensity (quality) or day length (quantity, photoperiod) under simulated conditions in a particular season (Smith & Newsom, 1970;Maeda et al, 2000;Kazak et al, 2004;Zilahi-Balogh et al, 2007). Only recently has the effect of seasonal climatic variations on the efficacy of predatory mites for thrips control in greenhouses been addressed (Hewitt et al, 2015). Our study shows that the behavioral pattern of predation changed daily and seasonally, although photoperiod and temperature in the rearing chambers remained the same during the whole experimental period, and these changes were species-specific.…”