Effect of fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) strain and diet on oviposition and development in the parasitoid Euplectrus platyhypenae (Hymenoptera: Eulophidae)

Authors: Hay-Roe, Mirian; Meagher, Robert - Rob; Nagoshi, Rodney

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2013
Publication Date: 3/13/2013
Citation: Hay-Roe, M.M., Meagher Jr, R.L., Nagoshi, R.N. 2013. Effect of fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) strain and diet on oviposition and development in the parasitoid Euplectrus platyhypenae (Hymenoptera: Eulophidae). Biocontrol. 66(1):21-26.

Interpretive Summary: The parasitoid wasp Euplectrus platyhypenae Howard has been proposed as a good candidate for use as a biological control agent for the fall armyworm, a serious insect pest of corn, pastures, turf grasses and cotton. The fall armyworm species is subdivided into two host strains, the corn strain, mostly found in corn fields; and the rice strain, found in grasses and pastures. In this paper scientists at the USDA, Agriculture Research Service, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida, tested for female parasitoid preference and parasitoid fitness on eggs laid by fall armyworm fed corn or stargrass. We found that female wasps prefer to lay their eggs on corn strain larvae that have been fed corn plants, rather than on larvae that have been fed stargrass. Also, wasp offspring have higher mortality rates and are smaller in size, when their hosts fed on grass rather than corn. These results suggest that significant biological control by release of these wasps would be expected in corn monocultures where the corn strain is mostly present.

Technical Abstract: Oviposition tendency and subsequent development of the parasitoid wasp Euplectrus platyhypenae Howard was compared using the corn and rice host strains of Spodoptera frugiperda (J. E. Smith) fed corn (Zea mays, ‘Truckers Favorite’) or stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis, ‘Florona’ grass). In no-choice and two-choice experiments using newly molted fourth instar hosts female wasps preferred to oviposit on corn strain larvae fed corn plants. Rice strain larvae were parasitized when fed corn plants, but only after the host had reached an optimal size. The reason for this preference might be due to differences in size between host strains at a given stage. No oviposition preference for corn or rice strain larvae fed grass was observed. When female wasps were given a choice between corn and rice strain larvae, they always produced more female offspring on the corn strain than the rice strain larvae, irrespective of the host plant the larvae fed upon. Among rice strain hosts, those fed corn hosted more female offspring than those fed grass. The data also show that host quality had a direct effect on parasitoid size, since significantly larger parasitoid offspring resulted from largest host fed corn plants, and smaller offspring resulted from the smallest hosts, rice strain larvae fed stargrass. Furthermore, E. platyhypenae larval mortality occurred in hosts of both strains fed stargrass, which may indicate that stargrass allelochemicals might not be appropriate for this parasitoid. Implications of these results for biological control methods are discussed.