Effect of the medicinal plant Withania somnifera on the development of a medico-veterinary pest Chrysomya megacephala (Diptera: Calliphoridae)

Abstract

ABSTRACT Topical administration of root and seed extracts (5, 10, 15 and 20 µg/µL) of Withania somnifera to 0, 1, 2, and 3 days post-moult third instar larvae of Chrysomya megacephala resulted in disruption of moulting and metamorphosis. This leads to several developmental aberrations, such as prolongation of larval-pupal and pupal-adult ecdysis, larval mortality, abnormal pupariation, formation of pupal-adult mosaics and adultoids, ecdysial failure, reduced pupariation and adult emergence. Treatment with seed extracts of W. somnifera was more effective as it causes greater toxicity in all the treated groups as compared to that observed with the root extracts. There was a significant interaction among all three factors viz. extract type (root and seed extracts), larval stage (0, 1, 2, 3 days post-moult third instar larvae) and concentration (5 µg/µL, 10 µg/µL, 15 µg/µL, 20 µg/µL) for prolongation of larval-pupal and pupal-adult ecdysis. The results are similar to those observed with the administration of juvenoids and hence it can be inferred that the plant extracts mimic the action of juvenoids. The results clearly suggest that W. somnifera acts as a potential IGR disrupting the moulting and metamorphosis as a consequence of interference with the normal hormonal mechanism in C. megacephala. Abbreviations: Co Sf=coarse surface; Cy W=cylindrical wings; De Ae = deformed anterior end; De W = deformed wings; Ev G = everted genitalia; Ev Pt = everted ptilinium; L Mp = larval mouth parts; Nm W = non-membranous wings; P Ab = pupal abdomen; P Cu = pupal cuticle; Pa T L = partial tanned legs; Pg E = pigmented eyes; Pm = puparium; Re W = reduced wings; Sr G = scar of genitalia; T Pm = tanned puparium; Tu L = tubular legs; Tw Pm = twisted puparium; Un Ab = untanned abdomen; Un Pm = untanned puparium; W Pri = wing primordia