Lady beetles are a popular biocontrol method for aphids in home gardens and landscapes. Many gardeners purchase these insects at nurseries, garden centers, and online. This publication will discuss the drawbacks to using purchased lady beetles and suggest some alternatives for attracting and retaining local species.
A Brief History of Harvesting
Every serious gardener regards the lady beetle as a companion-in-arms in the fight against aphids and other garden pests. Best known in the United States is the convergent lady beetle
(Hippodamia convergens Guérin-Méneville; Figure 1), a voracious consumer. As early as 1924, these insects were collected by the thousands from the Sierra Nevada mountain region and released in California’s Imperial Valley for aphid control on commercial crops (Davidson 1924). The results were so impressive that lady beetle harvesting and shipping has become a lucrative biocontrol business (Bjørnson et al. 2011). Adult beetles are collected from their natural habitat, placed under prolonged hibernation, and shipped to farmers and home gardeners alike. Both adult and larval lady beetles (Figure 2) not only control aphids (Figure 3), but they also prey on scale insects, mites, beetle larvae, and immature bugs (Evans 2009).
Problems with Purchased Lady Beetles
Popular literature often recommends the purchase and release of lady beetles such as Hippodamia convergens (Lind 1998). Recently, however, researchers have raised concerns over the unintended ecological consequences of importing insects for biological control (Howarth 1991; Simberloff and Stiling 1996).