Identification of the Klambothrips myopori (Thysanoptera: Phlaeothripidae) Predator Complex in California.

To identify the predator complex of the invasive thrips, Klambothrips myopori, on its ornamental host plant Myoporum laetum, field surveys were conducted at three sites in southern California over the period of 1 y. Five insect orders and five spider families were represented in the survey. Although the most abundant groups differed among collection sites, syrphid larvae, anthocorids, Chrysoperla spp., Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae), and one spider family (Salticidae) were all collected at each site. Based on the field surveys, Orius spp. and Chrysoperla spp. were identified as possible key natural enemies of K. myopori. Laboratory studies were then conducted to determine the consumption rates of Orius insidiosus Say (Hemiptera: Anthocoridae) and Chrysoperla rufilabris Burmeister (Neuroptera: Chrysopidae) at constant densities of K. myopori and to define the functional responses of the predators. Both predators consumed more second-instar larvae than other prey stages. Orius insidious displayed a type II functional response, while C. rufilabris displayed both type II and type III depending on prey stage. Generally speaking, O. insidiosus and C. rufilabris consumed a higher proportion of prey at lower pest densities, implying that in an augmentative control program using these commercially available natural enemies, predators could be released early in the year when host plants begin to flush and thrips populations are low to suppress population growth.

Economic Benefit for Cuban Laurel Thrips Biological Control.

The Cuban laurel thrips, Gynaikothrips ficorum Marchal (Thysanoptera: Phlaeothripidae), is a critical insect pest of Ficus microcarpa in California urban landscapes and production nurseries. Female thrips feed and oviposit on young Ficus leaves, causing the expanding leaves to fold or curl into a discolored leaf gall. There have been attempts to establish specialist predator natural enemies of the thrips, but no success has been reported. We resampled the same areas in 2013-2014 where we had released Montandoniola confusa (= morguesi) Streito and Matocq (Hemiptera: Anthocoridae) in southern California in 1995 but had been unable to recover individuals in 1997-1998. Thrips galls were significantly reduced in all three of the locations in the recent samples compared with the earlier samples. M. confusa was present in all locations and appears to be providing successful biological control. The value of the biological control, the difference between street trees in good foliage condition and trees with poor foliage, was $58,766,166. If thrips damage reduced the foliage to very poor condition, the value of biological control was $73,402,683. Total cost for the project was $61,830. The benefit accrued for every dollar spent on the biological control of the thrips ranged from $950, if the foliage was in poor condition, to $1,187, if the foliage was in very poor condition. The value of urban forest is often underappreciated. Economic analyses that clearly demonstrate the very substantial rates of return on investment in successful biological control in urban forests provide compelling arguments for supporting future efforts.