The effects of fluctuating temperatures on degree-day development and life history parameters of Pseudacysta perseae (Hemiptera: Tingidae).

Abstract

Pseudacysta perseae (Heidemann 1908) (Hemiptera: Tingidae) is a foliar pest of avocados. The effects of 6 fluctuating temperature regimens, which averaged 15, 20, 25, 30, 32, and 35 °C over a 24-h period, on the developmental and reproductive biology of P. perseae were investigated. Selected temperature cycles are representative of avocado production regions in California (US). Fluctuating temperature regimens had significant effects on P. perseae development times, fecundity, fertility, longevity, and survivorship rates. One linear model (Ordinary Linear) and 7 nonlinear regression functions (Beta, Brière-2, Lactin-2, Lobry-Rosso-Flandrois, Performance-2, Ratkowsky, and Weibull) were utilized to investigate the correlation between fluctuating temperature profiles and P. perseae development times. The Beta and Weibull models failed to converge. Model parameters, T _min, T _opt, and T _max, were estimated as 1.72 to 9.78 °C, 31.04 to 31.57 °C, and 34.05 to 39.38 °C, respectively. The thermal requirement for development, K, was estimated as 476.19 degree-days. At 32 °C, P. perseae females exhibited 4 egg-laying peaks around days 11, 35, 54, and 63 of life. A maximum daily average of eggs laid (i.e., fecundity) was 6.07 on day 35 and the average daily egg-laying rate was 3.08 eggs over a 69-day span. The maximum proportion of eggs that hatched (i.e., fertility) was 0.49 on day 31, and the average daily proportion of hatched eggs was 0.10. This study confirmed that P. perseae passes through 4 nymphal instars, not 5 as previously reported. In addition, sexual dimorphism with respect to the coloration of the fourth antennal segment is documented and is substantially darker in adult males.