Bathyplectes curculionis, is a parasitic wasp that is an important insect used for biological control of Alfalfa Weevil. Researchers have developed a growing degree day model for Bathyplectes curculionis that can help predict spring emergence and timing of the following adult generation, in order to improve pest management decisions.

Calculating Growing Degree Days

The Bathyplectes curculionis model uses a lower threshold of 43F. It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field.

For this model, the “biofix” date, or date from which to start accumulating growing degree days, should be set to Mar. 1st for the Northern Hemisphere.

Spring emergence begins at approximately 425 GDD(F). Adult emergence  of the next generation occurs at approximately 1392 GDD (F) after the biofix date.

Sources:

Eklund, L. R., and R. G. Simpson. 1977. Correlation of activities of the alfalfa weevil and Bathyplectes curculionis with alfalfa height and degree-day accumulation in Colorado. Environ. Entomol. 6: 69-71.