Tobacco Budworm

Tobacco Budworm (Helicoverpa virescens) is an important pest on cotton, soybean and tobacco in many areas. Adult Tobacco Budworm emerge from overwintered pupae in spring when they can be targeted by traps or insecticide treatments. The Tobacco Budworm Emergence Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict adult emergence in spring, and a separate model, the Tobacco Budworm Growing Degree Day Model, can be used to predict larvae and adult emergence of following generations.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date from which growing degree days begin to accumulate. For the Spring Emergence model, January 1st is the recommended biofix date, in order to predict adult emergence in spring, as well as larvae and adults of following generations. After adults have been observed, this date should be used as the biofix for the second, in-season, model.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 55F, and an upper threshold of 86F for the spring emergence model. The in-season model uses a lower threshold of 54.7F, and an upper threshold of 91.9F. Calculating these can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. First adults will emerge in spring at approximately 270 GDD (F) and be nearly complete by 592 GDD (F).

For the in-season model, Egg hatching / larvae emergence will occur at approximately 72 GDD(F) after the biofix date, with pupation at 438 GDD(F) and adult emergence of following generations at 760 GDD (F) after the biofix date.

Source:

Potter, M. F., R. T. Huber, and T. F. Watson. 1981. Heat unit requirements for emergence of overwintering tobacco budworm, Heliothis virescens, (F.), in Arizona. Environ. Entomol. 10: 543-545.

Hartstack, A. W., Jr., J. P. Hollingsworth, R. L. Ridgeway, and J. D. Lopez. 1976. MOTHZV-2: A computer simulation of Heliothis zea and virescens population dynamics. User manual. 1976. U.S.D.A. ARS-S-127.