Assessing the potential for biological control of potato field pests in Ardabil, Iran: functional responses of Orius niger (Wolf.) and O. minutus (L.) (Hemiptera: Anthocoridae)

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and the onion thrips, Thrips tabaci Lind. (Thysanoptera: Thripidae), are significant field pests of potato in the Ardabil region of Iran. Orius niger (Wolf.) and O. minutus (L.) (Hemiptera: Anthocoridae) are locally the predominant natural enemies of these pests. This study compared the functional responses of O. niger and O. minutus to female mites and second instar thrips larvae across a range of prey densities (5, 10, 20, and 40 prey/arena) under controlled conditions of 24 +/- A 1A degrees C, 50 +/- A 5% RH and 16:8 h (L:D). The resulting data were appropriately fit to Type II functional response models in four predator-prey interactions, including: (1) O. niger to second instar thrips larvae (a = 0.009 h(-1); and T (h) = 1.62 h); (2) O. niger to females mites (a = 0.006 h(-1) and T (h) = 1.28 h); (3) O. minutus to second instar thrips larvae (a = 0.008 h(-1) and T (h) = 1.93 h) and (4) O. minutus to females mites (a = 0.01 h(-1) and T (h) = 1.1 h). The number of second instar thrips larvae attacked by O. niger was greater than that by O. minutus (P a parts per thousand currency sign 0.01); conversely, the number of females mites attacked by O. minutus was greater than that by O. niger (P a parts per thousand currency sign 0.01). These results confirm the potential for both O. niger and O. minutus to make valuable contributions to a biological control program against onion thrips and the two-spotted spider mites infesting potato fields in this region.