Threshold Temperatures and Thermal Requirements of Psyllaphycus diaphorinae (Hymenoptera: Encyrtidae), a Hyperparasitoid of Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae) and Tamarixia radiata (Hymenoptera: Eulophidae)

Abstract

The temperature-driven development rates and longevity times of Psyllaphycus diaphorinae Hayat (Hymenoptera: Encyrtidae), a hyperaparasitoid of Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) and Diaphorencyrtus aligarhensis (Shafee, Alam & Agarwal) (Hymenoptera: Encyrtidae), 2 primary parasitoids of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), were quantified. Development times and longevity were investigated at 6 average daily temperatures (15, 18, 20, 25, and 32 °C) that either were constant or fluctuated over 24 h. Thermal performance curves for egg-to-adult development of P. diaphorinae reared on D. aligarhensis were characterized using 1 linear and 2 nonlinear degree-d models (i.e., Ratkowsky and Performance-2). Daily thermal fluctuations had significant effects on development rates and longevity of P. diaphorinae adults. Psyllaphycus diaphorinae reared under fluctuating profiles completed development more slowly (20, 25, and 32 °C), and survived longer (18–32 °C) than those reared under constant profiles with equivalent mean temperatures. In addition, P. diaphorinae emerged from fluctuating but not constant profiles at 15 °C. Estimates of thermal constants (i.e., degree-d to complete development) predicted by the linear model were 36% lower for the constant temperature regimen than the fluctuating temperature regimen. Nonlinear and linear model estimations of the theoretical lower and upper thermal thresholds ranged between −3.7 to 11.9 °C and 33.7 to 34 °C, respectively. The development rate of male and female P. diaphorinae was most favorable at 30 °C. These results demonstrate the significant effects of average temperatures and daily temperature variations on P. diaphorinae life history. Key Words: biological control; development rate; Diaphorina citri; nonlinear regression model; thermal threshold Resumen Se cuantificaron las tasas de desarrollo impulsadas por la temperatura y el tiempo de longevidad de Psyllaphycus diaphorinae Hayat (Hymenoptera: Encyrtidae), un hiperparasitoide de Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) y Diaphorencyrtus aligarhensis (Shafee, Alam & Agarwal) (Hymenoptera: Encyrtidae) dos parasitoides primarios del psilido asiatico de los citricos, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Se investigaron el tiempo de desarrollo y la longevidad a 6 temperaturas promedias diarias (15, 18, 20, 25 y 32 °C) que fueron constantes o fluctuaron durante 24 horas. Se caracterizaron las curvas de rendimiento termico para el desarrollo de huevo a adulto de P. diaphorinae criados sobre D. aligarhensis utilizando 1 modelo lineal y 2 modelos no-lineales dias-grados (Ratkowsky y Performance-2). Las fluctuaciones termicas diarias tuvieron efectos significativos en las tasas de desarrollo y la longevidad de los adultos de P. diaphorinae. Psyllaphycus diaphorinae criado bajo perfiles fluctuantes completo el desarrollo mas lentamente (20, 25 y 32 °C), y sobrevivio mas tiempo (18–32 °C) que aquellos criados bajo perfiles constantes con temperaturas medias equivalentes. Ademas, P. diaphorinae emergio de perfiles fluctuantes pero no constantes a 15 °C. Las estimaciones de las constantes termicas (dias-grados para completar el desarrollo) predichas por el modelo lineal fueron 36% mas bajas para el regimen de temperatura constante que el regimen de temperatura fluctuante. Las estimaciones de modelos lineales y no lineales de los umbrales termicos inferiores y superiores teoricos oscilaron entre −3,7 y 11,9 °C y entre 33,7 y 34 °C, respectivamente. La tasa de desarrollo de los machos y hembras de P. diaphorinae fue mas favorable a 30 °C. Estos resultados demuestran los efectos significativos de las temperaturas medias y las variaciones diarias de temperatura en la historia de vida de P. diaphorinae. Palabras Clave: control biologico; tasa de desarrollo; Diaphorina citri; modelo de regresion no lineal; umbral termal View this article in BioOne