Galerucella calmariensis L. and Galerucella pusilla Duft
Life History and Ecology
Galerucella calmariensis and G. pusilla look alike and share similar life history characteristics. With some experience and the help of a dissecting microscope, the majority of adults can be identified to species, eggs and larvae are indistinguishable. A quick reference for field identification is provided in Fig. 2 but characters can overlap widely. For details please consult Manguin et al. 1993. Adults (4-6mm) overwinter in leaf litter and emerge in spring soon after shoot growth of purple loosestrife. Adults feed on shoot tips and the main oviposition period is in May and June, but may continue through July (partial second generation!). Eggs are laid in batches of 2 to 10 on leaves and stems. Young larvae feed on developing leaf buds; older larvae feed on all above ground plant parts. Pupation occurs in the soil or leaf litter at the base of plants. New generation adults emerge from late June to August.
Both species occur throughout the native range of purple loosestrife in Europe and Asia. Both species have been released in over 27 states and 6 Canadian Provinces. G. calmariensis is more common since the species was easier to mass produce than G. pusilla. Adults are very mobile and possess good host finding abilities. Peak dispersal of overwintered beetles is during the first few weeks of spring. New generation beetles have dispersal flights shortly after emergence and can locate host patches as far as 1 km away within a few days. Long range dispersal might occur over much larger distances.
Adult feeding causes a characteristic žshotholeÓ pattern (see Fig. 1) that is particularly obvious in spring. Larval feeding can strip the photosynthetic tissue off individual plants and at high densities (>2-3 larvae/cm shoot) entire purple loosestrife populations can be defoliated causing increased plant mortality. Less severe attack will result in reduced shoot growth, elimination of seed production, and particularly reduced root growth. Galerucella attack also increases the branching pattern of purple loosestrife. Attacked plants are shorter and appear "bushier" than unattacked individuals.
Release techniques and availability
Successful, easy to use outdoor mass rearing methods have been developed for G. pusilla and G. calmariensis. For detailed instructions contact Bernd Blossey or order the purple loosestrife video. Local rearing facilities can be implemented at very little cost and beetles can also be ordered by contacting Bernd Blossey. Adults are shipped from late June to l ate July. To prevent immediate dispersal of adults, field releases require confining adults in sleeve bags pulled over plants for 2-3 days. Attacked plants serve as rendezvous sites and will keep adults closer to the release site. A standardized monitoring protocol has been developed to help assess the success of control agent releases. Please participate in this data collection.
|Hylobius transversovittatus||Galerucella calmariensis/pusilla||Nanophyes marmoratus|