Colorado potato beetle is less susceptible to steinernematid nematodes than many other insect species because the beetle feces repel infective nematodes and the host can prevent invading nematodes from developing. Even so, these nematodes still have potential for managing late-season beetle populations.
In greenhouse trials, a single application of Steinernema carpocapsae at a rate of 5 million/m2 resulted in 100% mortality of 4th instar larvae, pupae and adults. Not all larvae or pupae were infected initially, but the nematode persisted in the soil long enough to kill any adults that developed from those immatures that escaped infection.
Nematode applications were not nearly as effective in the field, however. A higher rate (7.6 million/m2) reduced Colorado potato beetle populations by about one third at one location in one year of testing, but the nematode had no significant effect on the beetle at lower rates. Repeated applications of nematodes, higher rates, or improvement in application technology would probably be necessary to obtain consistent control.
Stewart, J. G., G. Boiteau, and J. Kimpinski. 1998. Management of late-season adults of the Colorado potato beetle with entomopathogenic nematodes. Can. Entomol. 130(4): 509-514.
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