Functional response of predatory thrips to two-spotted spider mite – influence of pesticides
2013
Pakyari, Hajar | Enkegaard, Annie
A leaf disc bioassay was used to investigate the effects of abamectin and fenpropathrin on the functional response of an acarophagous thrips, Scolothrips longicornis Priesner, to eggs of Tetranychus urticae Koch at 25 ± 1°C, 60 ± 10% RH, 16:8 h (L:D). The type of the functional response differed depending on the types and doses of the pesticides used. A type II functional response was found in all pesticide-dose combinations except for females exposed to a half-labelled dose of fenpropathrin, in which a type III functional response was observed. For type II functional responses, the search rates were similar to those found in the control treatments irrespective of predator sex, pesticide and pesticide dose. No differences in handling times across treatments were observed for males but handling times were longer for females, irrespective of pesticide and dose, compared to the control treatment. The theoretical maximum number of prey attacked by the thrips was 49.67 and 23.67 eggs per day for females and males, respectively; both maxima were attained in the control treatment. These values were reduced for males exposed to full doses of either pesticide and for females exposed to both half and full doses of either pesticide. These findings suggest that the efficacy of integrated management programmes for T. urticae involving the application of S. longicornis could be decreased by application of pesticides such as fenpropathrin and abamectin, which are often used to control pests in greenhouse and field crops.
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