Bioecological attributes and physiological indices of invasive fall armyworm, Spodoptera frugiperda (J. E. Smith) infesting ginger (Zingiber officinale Roscoe) plants in India

Abstract

Invasive fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) of American origin, has recently arrived in Asian countries, found damaging maize and other host plants including ginger (Zingiber officinale Roscoe) in India and China. The ginger is an economically important spice and a medicinal cash crop of Asia. However, apart from just an occurrence, no other information is available hitherto on interaction of FAW and ginger plants. This is the first comprehensive report unfolding the FAW infestation to the ginger crop, including its bioecological and physiological aspects. FAW identity was confirmed at the molecular level by comparing the sequences of the CO I gene of mitochondrial DNA. FAW infestation was higher during mid-July (0.2 larvae/m2), when ginger plants were in rhizome initiation stage (critical stage of growth). Besides generalist predators, four natural enemies were found causing a total of 74.03% fortuitous biocontrol of FAW larvae. Biological attributes and nutritional indices of FAW were studied on ginger for 3 consecutive generations. The larval duration has significantly extended; however the body weight and lifetime fecundity were considerably reduced in ginger fed larvae than maize. The Consumption Index (CI), Relative Growth Rate (RGR) and Approximate Digestibility (AD) were significantly lower (Mann-Whitney U Test, P < 0.001) in ginger fed FAW larvae compared to its regular host ‘maize’. Nevertheless, the higher tissue growth (ECI) and more assimilation (ECD) of FAW on ginger indicate it as a suitable alternate host plant and FAW may cause economic damage under certain circumstances. Insights on ginger plants as a new host of FAW and fortuitous biocontrol aspects of FAW are discussed.