Life History of the Mealybug, Maconellicoccus hirsutus (Hemiptera: Pseudococcidae), at Constant Temperatures

Important life history parameters of the mealybug, Maconellicoccus hirsutus (Green), were characterized on hibiscus (Hibiscus rosa-sinensis L.) cuttings at six constant temperatures between 15 and 35°C. The development of M. hirsutus was the fastest at 27°C, where the mealybugs completed development in 29 d. The lower (Tmin) and upper (Tmax) developmental thresholds and the optimal developmental temperature (Topt) for the development of female mealybugs were estimated as 14.5, 35, and 29°C, respectively. The thermal constant (K), which is the number of temperature-day or degree-day units required for development, of the females was 347 DD. The original distribution range prediction (based on Tmin = 17.5°C and K = 300 DD) indicated that M. hirsutus could complete at least one generation in all of the continental United States. However, results of this study suggested that the distribution range of M. hirsutus may expand northward because of the lower Tmin, and the predicted number of generations in a year may be lower because of the higher K required to complete each generation. The average cumulative survival rate of M. hirsutus at 25 and 27°C was 72%, which was significantly higher than 51 and 62% at 20 and 30°C, respectively. M. hirsutus reproduced sexually, with each mated female producing 260-300 eggs between 20 and 27°C but only 100 eggs at 30°C. Female longevity was reduced from 28 d at 20°C to 19-21 d at 25-30°C. At 27°C, the net reproductive rate (Ro) was estimated at 165 /, the intrinsic rate of population increase (rm) was 0.119 (//d), the generation time (TG) was 43 d, and the doubling time (DT) was 5.8 d. The life table statistics suggested that the currently released biological control agents, which have higher rm than M. hirsutus, will be able to complete more generations than the mealybug within the tested temperature range; thus, they are effective against M. hirsutus.