Advances in the rearing of two biological control agents against common reed, Phragmites australis

European common reed, Phragmites australis, has become invasive throughout much of North America, displacing native endemic P. australis americanus genotypes. This invasion puts at risk endemic wetland plants and animals, including threatened and endangered species. After 20 years of research on host range testing, life history, impact and behaviour of nine potential agents; the release of two agents, Lenisa geminipuncta and Archanara neurica (Lepidoptera: Noctuidae) was granted in Canada and recommended for the US. Both species are univoltine. The eggs overwinter under P. australis leaf sheaths and hatch soon after the shoots begin to elongate in early spring. Both species have severe impact on plants and early attack can result in stem mortality, while later attack causes wilting of tips. Rearing these biological control agents on cut stem sections is an effective method but very labour intensive and time consuming, and thus not ideal for mass rearing. The aim of this project was to develop more efficient rearing methods using artificial diet. Initial studies using the McMorran artificial diet successfully produced adults of A. neurica, however they were not as fit as insects produced on cut stems. Lenisa geminipuncta were not able to complete development on diet alone. However, combining both methods, i.e. rearing early instar larvae on stem sections and later instar larvae on artificial diet, proved to be more successful and less time consuming. Using this method, we are currently able to produce over 20’000 eggs and up to 1’000 pupae per year, while on stem sections alone we only produced less than 10’000 eggs and a few hundred pupae. To date, a total of 17’600 eggs, larvae, pupae, or adults have been released at 13 sites in southern Ontario, Canada. Initial survivorship, damage and overwintering results for the insects are very encouraging and monitoring is continuing to confirm establishment.
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