Temperature-based phenology models can be used to forecast the life cycles of insects because their development is largely dependent on the temperatures they experience. If you know how many heat units have accumulated, phenology models can predict things like when eggs will hatch and how many generations of the insect will have occurred that year. Dr. Abigail Cohen, a recent graduate of Dr. Dave Crowder's entomology program at WSU, spent years developing and validating a phenology model for potato psyllids in the Columbia Basin. The model is now available for all to use on the Potato DAS website. Since it is a temperature-based model, users need to select a nearby weather station in order to see the output for their location(s) of interest. The model shows when: 1) adult psyllids are emerging from overwintering sites, 2) the first generation of eggs are hatching, 3) second generation adults are emerging, 4) second generation eggs are hatching, and 5) the third generation adults are emerging. This information should enable more effective and efficient use of insecticides to control potato psyllids. The phenology model can help growers decide when to start a foliar insecticide program to control adult psyllids that migrate into potatoes from overwintering hosts. It can also help growers select insecticides based on which life stages are likely to be in the field, since many insecticides that control adults will not control eggs, and vice versa.
The graph above shows the psyllid phenology output for the Mae station (west of Moses Lake) on September 2, 2021. It shows that 2,176 degree days (DDs) have accumulated at this location since January 1. The model estimates that all eggs are hatched and 90% of third generation adults have emerged. It also forecasts that by next Tuesday, about 2,243 DDs will have accumulated and 95% of third generation adults will be emerged.