The Tomato Leafminer (Tuta absoluta) is an important pest on solanaceous crops such as potato, tomato and eggplant. Overwintered Tomato Leafminer pupae typically emerge as adults in spring. Depending on weather and location, there may be many generations in a season. The Tomato Leafminer Growing Degree Day Model, developed by researchers, and available on the Pest Prophet app, is a tool growers can use to predict larvae emergence from leaves and egg hatch after adults have been observed, based on temperature data.

Initiating the Biofix

To properly use the model, the biofix must first be set. This is the date that will serve as the starting point for growing degree day accumulation. For this type of model the biofix date should be set to January 1st for the Northern Hemisphere.

Growing Degree Day Accumulation and Treatment

After the biofix is set, growing degree day accumulation can begin, using a lower threshold of 46F  and an upper threshold of 95C. This can be done using daily high and low temperatures, or using hourly temperature data using the Pest Prophet app. First spring egg-laying occurs at approximately 45 GDD (F) after biofix date with the peak at 95GDD(F). First generation adults emerge at approximately 900 GDD(F) following the biofix date. The model can then be used to predict up to 8 generations in a season.

Source:

Barker, B. Coop, L. 2020. Tuta absoluta (Lepidoptera: Gelechiidae) Phenology/Degree-Day and Climate Suitability Model Analysis for USPEST.ORG. Oregon State University.