Nontarget effects of orchard pesticides on natural enemies: Lessons from the field and laboratory

Abstract

The nontarget effects of insecticide programs used to control codling moth, Cydia pomonella Linnaeus (Lepidoptera: Tortricidae), were studied in large-plot field trials in apples, pears, and walnuts in the western United States. We assessed the health of the natural enemy community by sampling the abundance of natural enemies and by monitoring for outbreaks of secondary pests. The insecticides used in the field tests overlapped those tested in laboratory bioassays. Using these parallel lab and field studies, we examined two hypotheses: 1) pesticides found to have negative effects on natural enemy fitness in laboratory bioassays will predict reductions in natural enemy densities in the field, and 2) reductions in natural enemy densities in the field will result in outbreaks of secondary pests. We found only one clear instance, Forficula auricularia (Linnaeus) (Dermaptera: Forficulidae), where laboratory results documenting negative effects corresponded to a significant reduction in field studies (apple). This same instance was the only case where a reduction in a natural enemy population was associated with a significantly increased density of a secondary pest, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae). There were several instances where secondary pest outbreaks were associated with unchanged or even increased natural enemy densities. The limited number of field trials, variability in field trial conditions among years and sites, duration of the negative effect relative to sampling interval, sampling efficiency, plot size/inter-plot movement, and compensation by other natural enemies attracted to a large host/prey resource may all have contributed to the poor predictive success. Overall, the laboratory bioassays predicted a far greater negative impact than was found in the field trials.

Biological control adoption in western U.S. orchard systems: Results from grower surveys

“…Given growers' preference for pesticide modification and the increasing availability of reduced risk pesticides with different impacts on natural enemies, we believe growers might be especially interested in the entomological findings from our USDA-SCRI project designed to enhance BC in western U.S. orchard systems. Especially notable are the results from laboratory and field research focused on the effects of reduced risk pesticides on natural enemies and strategies for selecting and timing pesticide sprays to protect natural enemies Beers et al, 2016;Jones et al, 2016;Mills et al, 2016;Shearer et al, 2016).…”

Invertebrate biodiversity in apple orchards: agrichemical sprays as explanatory variables for inter‐orchard community differences

“…However, insecticides were not so likely to explain variability in the natural enemies of those pests, suggesting that the products used by these growers were preferentially affecting the pests and not the beneficial natural enemies. These results provide some reassurance that using selective insecticides such as buprofezin, CpGV and tebufenozide or methoxyfenozide, which have few effects on nontarget insects (Rumpf et al ., ; Shaw et al ., ; Lo, ; Shaw and Wallis, ; Rogers et al ., ; Beers et al ., ), can preserve biological control services, as intended in integrated pest management systems. The involvement of fertilizers, in conjunction with insecticides, in the best models to explain pests caught on sticky traps suggests that further research to examine the influence of fertilizers on the effectiveness of insecticides against apple pests could yield useful information for optimizing pest control practices.…”

“…There is also evidence to indicate that some fungicides and plant growth regulators may have toxic effects on some invertebrates (Hassan et al ., ; Adamski & Ziemnicki, ; Dagli & Bahsi, ; Sutherland et al ., ; Martinou et al ., ). Relationships between the toxicity ratings and volumes of pesticides applied and invertebrate populations have been demonstrated in vineyards (Thomson and Hoffmann, ), kiwifruit orchards (Todd et al ., ) and apple orchards (Beers et al ., ). Studies examining the influence of fertilizers on insect herbivores have generally shown a positive response to nitrogen (especially among sucking insects) but varying responses to phosphorus and potassium (Awmack & Leather, ; Fagan et al ., ; Myers & Gratton, ; Butler et al ., ; Rashid et al ., ).…”

From planning to execution to the future: An overview of a concerted effort to enhance biological control in apple, pear, and walnut orchards in the western U.S.

“…Consequently, there are five papers in this issue that address different aspects of pesticide effects on natural enemy populations in both laboratory and field settings Beers et al, 2016a;Beers et al, 2016b;Mills et al, 2016a;Shearer et al, 2016). These papers show that, in general, laboratory bioassays based on life table response experiments and the use of a demographic approach to evaluation of the combined lethal and sub-lethal effects of pesticides on natural enemies provided an effective way to estimate the potential for disruption of natural enemy populations .…”

“…Unfortunately, the use of large-plots with suitable controls proved to be logistically difficult, expensive, and required a degree of serendipity with respect to whether there was a sufficient abundance of both secondary pests and their natural enemies at the selected field sites to differentiate treatment effects. Despite the challenges and difficulties associated with the field trials, our project represents one of the largest field and laboratory studies to test the effects of some of the reduced-risk insecticides and fungicides on a range of predators and parasitoids found in tree crops in the western U.S. Beers et al, 2016b;Shearer et al, 2016).…”