Understanding the cold tolerance of the salvinia weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae), and its implications for biological control of giant salvinia in temperate regions

For over a decade Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) has been utilized in Louisiana for the biological control of giant salvinia, Salvinia molesta D. S. Mitchell.  Infestations of giant salvinia reduce the habitat for game birds, disrupt boating activities, clog irrigation canals, displace native vegetation, and reduce dissolved oxygen levels. Despite localized success in southern Louisiana, the biological control of giant salvinia has proven to be problematic in central and northern parts of the state, where winter temperatures are colder compared to more southern latitudes. To improve the management and control of S. molesta in temperate climates, a better understanding of the overwintering adaptations of C. salviniae is needed. The objective of this study is to determine whether photoperiod and temperature induce physiological changes in C. salviniae. The variables measured after the 30 day duration of treatments; fresh weight, water content, lipid content, glycerol levels, and reproductive status, will be compared to a baseline assessment of variables before treatments. Results of this experiment will reveal what environmental conditions cue C. salviniae to change in preparation for winter in the field. Understanding the physiological adaptations of C. salviniae will provide valuable information to plant managers and researchers pertaining to the long term control of S. molesta.

Key words: aquatic weed, seasonal adaptations, photoperiod