Temperature-mediated growth thresholds of Acrobasis vaccinii (Lepidoptera: Pyralidae)

Authors: Chasen, Elissa; Steffan, Shawn

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2016
Publication Date: 5/11/2016
Publication URL: https://handle.nal.usda.gov/10113/62684
Citation: Chasen, E.M., Steffan, S.A. 2016. Temperature-mediated growth thresholds of Acrobasis vaccinii (Lepidoptera: Pyralidae). Environmental Entomology. 45(3):732-736. doi: 10.1093/ee/nvw053.

Interpretive Summary: The cranberry fruitworm is the top insect pest for Wisconsin cranberry growers, who provide greater than 60% of the country’s cranberry crop. This manuscript reports research conducted to isolate key biological parameters relating to this insect’s development. We have derived the upper and lower developmental thresholds for the cranberry fruitworm. Isolating the temperature-mediated growth thresholds represents a critical step in the creation of a phenology model for a pest. Phenology models allow for growers and pest management professionals to use weather data to accurately estimate insect developmental status. Such information has innumerable applications and has long been known to improve IPM programs. With respect to the cranberry fruitworm, this work is especially critical because the window for treatment timing is extremely narrow due to the fact that larvae are protected for most of their lives, residing within the berry. All larvae were reared within cranberries, which represents a novel and ecologically realistic approach to the isolation of growth parameters among cranberry pests. Further, only wild, field-collected larvae were reared. Impact: Our work is an important first step towards creating a degree-day model for the most important pest of Wisconsin cranberries. Thus, we have completed the foundational work in the process of characterizing the temperature-mediated growth of this major cranberry pest.

Technical Abstract: Degree-day models link ambient temperature to the development of insects, making such models valuable tools in integrated pest management. Phenology models increase management efficacy by quantifying and predicting pest phenology. In Wisconsin, the top pest of cranberry production is the cranberry fruitworm, Acrobasis vaccinii Riley (Lepidoptera: Pyralidae). Control of this species is often complicated by the fact that the larvae feed entirely within the fruit. Timing of control tactics, therefore, is critical and generally targets the adult and egg stages. However, the commencement of oviposition and egg-hatch are extremely difficult to track empirically, forcing pest management strategies to rely on proxy events that are more apparent but less informative as indicators of cranberry fruitworm egg presence. This research provides the upper and lower growth thresholds of this pest, which represent the first steps towards the creation of a degree-day model. Using wild, field-collect A. vaccinii, we reared the larvae within cranberry fruit and monitored larval growth at nine different temperatures. We determined the average growth rate at each temperature and modelled the growth rates as a function of temperature. We then calculated the precise upper and lower developmental temperature thresholds of this species. Future work will be able to use these thresholds to generate degree-day accumulations, which can then be used to link degree-day accrual to discrete biological events in the field.