Reproductive biology, abundance and control potential of Paramecops farinosus (Wiedemann) (Coleoptera: Curculionidae): a prospective biological control agent for Calotropis procera (Apocynaceae)

ABSTRACT

Reproductive biology, abundance and control potential of Paramecops farinosus Wiedemann, (Aak weevil) a prospective biological control agent for Calotropis procera (Aiton) W.T. Aiton, (Calotrope) were studied under field conditions in Lahore, Pakistan, from spring to winter season. Newly emerged adult pairs were introduced inside insect-proof pouches with calotrope fruits, and the life cycle and reproductive biology of P. farinosus were studied. Pre-oviposition period was 4.8 ± 0.17 days and there were 6.1 ± 0.09 eggs per clutch. A female, laid eggs about 5.4 ± 0.32 times, producing 24 offspring during its lifespan. The mortality from egg to adult was 27% and the progeny sex ratio was 3:2 (female to male ratio). The developmental period of P. farinosus (egg to adult) was 59.9 ± 0.82 days and at least two generations were produced per year. The longevity of males and females recorded was 97 ± 1.98 and 69 ± 1.41 days, respectively and the pupae overwinter inside the infested fruits. The number of eggs and larvae inside fruits increased from March to July and declined in subsequent months. The highest number of eggs and larvae per fruit were recorded in July i.e. 8.27 ± 0.65 and 6.31 ± 1.77, respectively. The developing larvae destroyed 100% seeds and internal tissue of infested fruit pods of C. procera, resulting in significant reductions in fruit size (−12%) and biomass (−26%) compared to un-infested (healthy) fruits. The high reproductive capacity and control potential of P. farinosus indicate that this insect holds promise as a biological control agent of C. procera in its invaded ranges, including Australia, the Pacific, and South America.

KEYWORDS:

• Aak weevil
• biocontrol
• calotrope
• natural enemy
• invasive species
• life cycle

Acknowledgements

Partial financial support provided by the Department of Agriculture and Fisheries (DAF), Queensland, Australia for this study is highly appreciated. The authors are also grateful to Mr. Muhammad Tayyab Rafique for his assistance during the fieldwork. All authors contributed to the study’s conception and design. Material preparation, data collection and analysis were performed by SA, AS, KD and AH. The first draft of the manuscript was written by SA and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).