Developmental Times and Life Table Statistics of Aulacorthum solani (Hemiptera: Aphididae) at Six Constant Temperatures, With Recommendations on the Application of Temperature-Dependent Development Models

Aulacorthum solani (Kaltenbach) (known as foxglove aphid or glasshouse potato aphid) is a pest of increasing economic importance in several agricultural crops worldwide, including greenhouse vegetables and ornamentals. Developmental rates and age-specific life tables for a North American population of A. solani on pansy (Viola X wittrockiana) (Gams.) were determined at six constant temperatures, and comparisons were made to previous studies of A. solani from differing geographic regions and host crops. On pansy, A. solani developed fastest at 25 degrees C, passing through the four nymphal instars in an average of 6.9 d. The highest intrinsic rates of population increase (0.410 and 0.445) and shortest population doubling times (1.69 and 1.56 d) were recorded at 20 and 25 degrees C, respectively. Average total fecundity remained high from 10 to 20 degrees C (74-68 nymphs/adult); a significant decrease to 39 nymphs/adult occurred at 25 degrees C. For calculating developmental thresholds, we present here a method of adjusting the lower developmental threshold (t(min)) using estimates from nonlinear models to provide an improved estimate of the thermal constant (K, in degree-days). We also call attention to the necessity of using a simulation method to estimate the true upper developmental threshold (T-max) and optimum developmental temperature (T-opt) from the Lactin-2 model of temperature-dependent development.