Generalist predator contributions to the control of Tetranychus urticae in strawberry crops documented by PCR-based gut content analysis
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The contribution of generalist insect predators to the control of the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), an herbivorous pest of many crops, is poorly understood. One of the common insect predators in strawberries is the generalist predatory bug Anthocoris nemorum L. (Hemiptera: Anthocoridae), which has the potential to contribute to the control of pest populations. The feeding of adult A. nemorum on T. urticae was assessed by sampling individuals from an organic strawberry field in Denmark, and using PCR gut content analysis to detect remains of T. urticae within their gut. In the lab, we assessed that the DNA half-life detectability was 21.5 h. Significant numbers of field-collected A. nemorum tested positive for T. urticae prey DNA, with very high numbers in June (62.8%) and August (38.8%). This study presents conclusive evidence that the generalist predator A. nemorum can contribute to the decrease of T. urticae densities in strawberry fields, although the actual contribution in the present study is probably limited because predator populations were relatively low compared to T. urticae. The abundance of T. urticae did not increase significantly during the period of sampling, suggesting that a complex of natural enemies can achieve biological control of T. urticae in protected strawberries.
KeywordsSpider mites Generalist predators Anthocoris nemorum Molecular gut content analysis Predator–prey interactions
The authors would like to thank Josep A. Jaques (Jaume I University, Castellón, Spain) for collaboration, Helle Sørensen (Data Science Lab, Department of Mathematical Sciences, University of Copenhagen) for statistical support, the grower Søren Larsen for his hospitality, and the anonymous reviewers for their helpful comments to the manuscript. This study is a part of the research project IMBICONT (Improved Biological Control for IPM in Fruits and Berries) (Project number 1024151001) funded by Innovation Fund Denmark.
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