BioControl 47: 231–243, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands. Field efficacy and predicted host range of the pickerelweed borer, Bellura densa, a potential biological control agent of water hyacinth ∗ Ted D. CENTER 1∗ and Martin P. HILL 2 1 USDA-ARS, Aquatic Plant Control Research Unit, 3205 College Avenue, Fort Lauderdale, Florida 33314, USA; 2 Plant Protection Research Institute, Private Bag X134, Pretoria 0001, South Africa ∗ author for correspondence: e-mail: tcenter@eemail.com Received 22 December 2000; accepted in revised form 27 April 2001 Abstract. The North American noctuid moth Bellura densa offers promise as a biological control agent for use in Africa and other countries invaded by water hyacinth. An augmentative release at a pond in Florida, USA, eliminated water hyacinth within a few months. Labor- atory studies, though, indicated that oviposition was indiscriminate and that development was completed on taro (Colocasia esculenta [Araceae]) as well as on several Pontederiaceae. Acceptability of taro as a larval food plant was confirmed in the field when larvae were found in isolated stands of taro in Florida. Evidence of use of Peltandra virginica (Linnaeus) (Araceae) was noted at another site. The distribution of larval damage was compared at a site containing a mixture of 97% taro and 3% pickerelweed (Pontederia cordata). Larvae damaged 87% of the pickerelweed compared to only about 5% of the taro, suggesting spillover onto taro. In another study, 416 larvae were liberated into a concrete tank containing water hyacinth (818 plants) surrounded by taro (96 plants). Three months later, taro accounted for only 4% of the damaged plants, less than the 11% expected if host selection had been random. In a similar study, larvae were liberated onto water hyacinth in a large tank divided into thirds, with pickerelweed or taro at either end and water hyacinth in the middle. The distributions of F 1 egg masses and incidence of damage 3 months later indicated that pick- erelweed was preferred over taro, but 26% of the taro plants were damaged. We conclude that while B. densa prefers plants in the Pontederiaceae, it is not restricted to this plant family. Plants in the Araceae would be at risk if this insect were released outside of North America, particularly in cropping situations near water hyacinth infestations. Bellura densa could be useful for water hyacinth management in the U.S. if effective augmentation strategies were developed. Key words: Araceae, Bellura densa, biological control, host specificity, Lepidoptera, Noctu- idae, pickerelweed, Pontederiaceae, taro, water hyacinth ∗ The U.S. Government’s right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged.