Prediction of occurrence of Diabrotica speciosa using the laboratory degree-day model

Abstract

The goal of this work was to determine the thermal requirements (degree-day) and the prediction of occurrence of adults of Diabrotica speciosa (Coleoptera: Chrysomelidae) under field conditions (screenhouse). The soil and air temperatures were used in a linear model of degree-day, determined for the insect under laboratory conditions. Thermal requirements for the development of D. speciosa were determined by the daily accumulation of thermal units (degree-day), starting from the base development temperature of the insect (11.04ºC), using corn roots cultivated in pots as larvae diet. The value of the thermal constant (K) was used to predict insect occurrence, based on the mean temperatures of the soil and the air recorded during the experimental period. Regardless of the kind of temperature (air or soil) employed for the thermal requirements accounting, the accumulated degree-day values for the development of D. speciosa were significantly lower than the K value achieved in the laboratory. The soil or air temperatures provided a forecast of occurrence of the insect significantly different from that observed experimentally. Nevertheless, the occurrence forecast based in the air temperature was less accurate than when the soil temperatures (registered or estimated) were used.