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Title: Comparative infectivity of homologous and heterologous nucleopolyhedroviruses against beet armyworm larvae

item PUDJIANTO - Clemson University
item SHEPARD, B - Clemson University
item SHAPIRO, M - Clemson University
item Jackson, D
item CARNER, G - Clemson University

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2015
Publication Date: 2/9/2016
Citation: Pudjianto, Shepard, B.M., Shapiro, M., Jackson, D.M., Carner, G.R. 2016. Comparative infectivity of homologous and heterologous nucleopolyhedroviruses against beet armyworm larvae. Journal of Agricultural and Urban Entomology. 32:13-24.

Interpretive Summary: Beet armyworms are a major cosmopolitan pest of many vegetable and field crops. Vegetable crops often are sprayed to control this pest, but results are sometimes unsatisfactory due to poor timing or coverage of the spray or to resistance of the armyworm to several insecticides. Thus, there is a need for new biologically-based methods, such as insect viruses, for control of beet armyworms on vegetable crops. Therefore, we evaluated nine homologous and heterologous nucleopolyhedroviruses (NPVs) to determine the most effective isolate for controlling beet armyworm larvae. These isolates were from three beet armyworm populations, three closely related species, and two moth species in the same family, and a moth in another family. Similar isolates from South Carolina, Florida, and Maryland were most virulent. More variable isolates from closely related species differed considerably in activity, and isolates from distantly related species showed little activity on beet armyworm larvae. Both pathogenicity and speed of kill were key criteria for measuring the effectiveness of NPVs on beet armyworm larvae. This study contributes to our knowledge about how the relatedness of NPV isolates to the host affects their efficacies, which could be important for pest management decisions on beet armyworms.

Technical Abstract: Homologous and heterologous nucleopolyhedroviruses (NPVs) were assayed to determine the most effective NPV against beet armyworm larvae, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)(SeMNPV). Included were three isolates from S. exigua, one isolate each from S. littoralis Boisduval, S. litura (F.), and S. ornithogalli (Guenée), two isolates from other noctuids, Helicoverpa armigera (Hübner) and Rachiplusia ou (Guenée), and one isolate from Plutella xylostella (L.) (Lepidoptera: Plutellidae). Based on median lethal concentration (LC50), homologous SeMNPV isolates from South Carolina and Maryland, the registered isolate SPOD-X® (commerical formulation), and the heterologous NPV isolate SpliNPV from S. littoralis were most virulent. SeMNPV-SC and SPOD-X® were most virulent, based on median lethal time (LT50). Based on LC50, the least active NPVs were from P. xylostella, S. ornithogalli, and S. litura. The slowest acting NPVs were from S. litura, S. littoralis, and S. ornithogalli, based on LT50.