Augmentative Biological Control in the Urban Landscape: Using Alternative Food Sources to Improve Predator Survival and Residency

ABSTRACT Urban landscape trees are often faced with pest outbreaks due to insufficient bottom‐up and/or top‐down regulation. As such, management interventions are frequently needed to keep pest populations under damaging thresholds. Crapemyrtle bark scale (CMBS; Acanthococcus lagerstroemiae (Kuwana), Hemiptera: Eriococcidae) is a non‐native insect that commonly reaches outbreak levels in urban areas of the southeastern United States. Augmentative biological control of CMBS using Rhyzobius lophanthae (Blaisdell) (Coleoptera: Coccinellidae) and/or Chrysoperla rufilabris Burmeister (Neuroptera: Chrysopidae) appears to be hampered by low residency and survival of released predators. Here, we investigated whether providing alternative food sources, such as Wheast and/or fructose, could ameliorate these challenges. We first determined if these alternative food sources impact the survival rates of R. lophanthae and C. rufilabris in the presence or absence of CMBS in the laboratory. We then determined if Wheast, CMBS, or crapemyrtle aphids ( Tinocallis kahawaluokalani (Kirkaldy), Hemiptera: Aphididae) are attractive to the selected predators using a Y‐tube olfactometer. Finally, we measured the residency times of R. lophanthae on CMBS‐infested plants provisioned with alternative food sources in the field. Compared with individuals deprived of alternative food sources and prey, C. rufilabris and R. lophanthae lived up to 26 and 8 days longer, respectively, when provided with these food sources. Rhyzobius lophanthae survived the longest on a mixed diet of alternative food sources and CMBS, whereas C. rufilabris lived the longest on a diet supplemented with alternative food sources, regardless of CMBS presence. Neither Wheast nor the various prey items appeared to attract R. lophanthae or C. rufilabris in the laboratory; however, fructose significantly prolonged the residency time of R. lophanthae on CMBS‐infested plants in the field. Based on these results, fructose could be incorporated with the release of these two predator species in an integrated pest management program to promote their performance in urban landscapes.