Variation in reproductive attributes and diapause behaviour among six populations of Zygogramma bicolorata Pallister.

Zygogramma bicolorata Pallister is an effective biocontrol agent of Parthenium hysterophorus L. We evaluated the variability in reproductive attributes and diapause behaviour among populations of Z. bicolorata from six geographical locations of India, viz. Jammu, Poonch, Rajouri, Almora, Jabalpur and Coimbatore. This was done to optimize its augmentative rearing. We collected the adult insects from these locations and reared them in the laboratory. The eggs obtained from these adults were reared from egg-hatch to adult emergence to determine the development, reproduction, diapause and the influence of extremes of temperature on survival. The percentage of pupation (84.30 ± 1.41%), adult emergence (86.75 ± 1.11%), egg viability (77.30 ± 2.02%) fecundity (2159.5 ± 8.45 eggs), and longevities of males and females (86.5 ± 4.8 and 146.9 ± 6.1 days) were greater in the Coimbatore population of South India experiencing tropical climatic conditions than the other populations. In addition, this population had the lowest incidence of diapause in adult males (26.1 ± 1.0%) and females (26.1 ± 1.0%), and shortest mean diapause durations. The Coimbatore population had the highest survival when adult females were exposed to three suboptimal temperatures with the highest survival at 35 °C, followed by 45 °C and – 5 °C, while the Jabalpur and the Almora populations survival was the lowest. The adult survival percentage of this tropical population declined with an increase in the duration of exposure to the temperature extremes. We conclude that tropical climatic conditions favour development and reproduction, and minimize the prevalence of diapause in Z. bicolorata than the colder habitats of northern India. The findings may help mass rearing of parthenium beetle under controlled conditions and to manage parthenium across various geographical habitats. [ABSTRACT FROM AUTHOR]