Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/21/2006
Publication Date: 2/1/2007
Citation: Lapointe, S.L., Borchert, D.M., Hall, D.G. 2007. Effect of low temperatures on mortality and oviposition in conjunction with climate mapping to predict spread of the root weevil Diaprepes abbreviatus and introduced natural enemies. Environmental Entomology. 36(1):73-82. Interpretive Summary: The distribution of the root weevil Diaprepes abbreviatus in Florida appears to be constrained by temperature. We discovered that adult female weevils stopped producing eggs at 15°C (59°C). Eggs were highly susceptible to cold. Eggs died when exposed to 12°C for 4.2 days. Probability maps to describe the current distribution in Florida and to predict areas susceptible to infestation in other states were generated using the North Carolina State University-Animal Plant Health Inspection Service-Plant Pest Forecasting System (NAPPFAST). The maps use soil and air temperatures to describe the current distribution of D. abbreviatus and that of egg parasitoids that have been introduced into Florida. The maps delineated portions of Arizona, California and Texas that are susceptible to establishment of D. abbreviatus and will be used to guide survey and control efforts in those states. Further, the data suggest that egg parasitoids will not be capable of establishing in Arizona, California or Texas due to the relatively large number of days per winter with average daily air temperature below 15°C.
Technical Abstract: The root weevil Diaprepes abbreviatus was introduced into Florida in 1964. Since then, it has colonized Florida to the south but has not expanded its range to the north. We determined the effect of cold on eggs, larvae, pupae, and adults and oviposition behavior. A lower threshold for oviposition was estimated at 14.9°C. Eggs were highly susceptible to cold with 95% mortality (LTime95) occurring in 4.2 d at 12°C. Relative susceptibility of life stages to cold was eggs>pupae>larvae>adults. More than 50% of adults survived >30 d at 6°C and LTime95 for adults at 3°C was 26.5 d. Weather data was examined to guide mapping using lower larval developmental threshold (12°C) and lower oviposition threshold (15°C) as critical temperatures for distribution of D. abbreviatus and establishment of egg parasitoids, respectively. Probability maps were generated using North Carolina State University-Animal Plant Health Inspection Service-Plant Pest Forecasting System (NAPPFAST) that examined the frequency of >10, 15, 20, 25, or 30 days per winter when soil temperature was <12°C. The area that experienced 15 to 20 days per winter of mean daily soil temperature <12°C corresponded to the northern limit of D. abbreviatus in Florida. The homologous map of Arizona, California, and Texas predicted areas in the southern portions of those states where soil temperatures are favorable for D. abbreviatus. Air temperature maps suggested that establishment of egg parasitoids will be limited to southern Florida where mean daily air temperatures <15°C occur <25 days per year. The model predicted that egg parasitoids will not establish in Arizona, California or Texas.