Diorhabda carinulata, also known as the Greater Tamarisk Beetle, is an important insect used for biological control of weeds in the tamarisk family. Their reproduction is regulated in part by photo-period, with adult males emitting mating pheromones only under long day conditions. Researchers have developed a growing degree day model for Diorhabda carinulata that can help predict spring emergence and timing of the following generations, and predict the timing of when the beetles are susceptible to photo-period.

Calculating Growing Degree Days

The Diorhabda carinulata model uses a lower threshold of 52F and an upper threshold of 98F. 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 Jan. 1st for the Northern Hemisphere.

Spring emergence begins at approximately 230 GDD(F). Peak egg hatch of next generation will occur at 502 GDD(F), with peak larvae occurring 670 GDD(F). Peak of adult stage of the next generation occurs at approximately 1128 GDD (F) after the biofix date, this stage is susceptible to photo-period. The model can then be used to predict adult emergence for the next 3-4 generations in a season.

Sources:

Herrera, A.M., D.D. Dahlsten, N. Tomic-Carruthers, and R.I. Carruthers. 2005. Estimating Temperature-Dependent Developmental Rates of Diorhabda elongata (Col: Chrysomelidae), a Biological Contral Agent of Saltcedar (Tamarix spp.). Env. Entomol. 34:775-784.

Lewis, P.A., C.J. DeLoach, A.E. Knutson, J.L. Tracy, and T.O. Robbins. 2003. Biology of Diorhabda elongata deserticula (Col: Chrysomelidae) an Asian leaf beetle for the biological control of saltcedars (Tamarix spp.) in the United States. Biol. Control. 27:101-116