Microbial control of the European skipper, Thymelicus lineola Ochs.

A research programme was initiated to develop biological control methods for the European skipper, Thymelicus lineola Ochs. (Lepidoptera: Hesperiidae) after its appearance in the Province of Quebec. A baculovirus and Bacillus thuringiensis could both be used to control T. lineola in the field. With B. thuringiensis a dose of 2·5 × 10⁹ International Units/ha resulted in 100% mortality of second- to fourth-instar larvae in 6–15 days; dosages of 5 and 10 × 10⁹ I.U./ha caused 100% mortality within 3–6 days. Field application of the nuclear polyhedrosis virus caused 50, 80 and 100% larval mortality after 15, 19 and 27 days respectively. B. thuringiensis provided a curative method of control, whereas the virus can be used either as a curative or as a preventive method of controlling T. lineola because it is transmitted to the progeny. It is suggested that the best way to control T. lineola is by the combined use of both micro-organisms.