Spodoptera exigua Nuclear Polyhedrosis Virus as a Candidate Viral Insecticide For the Beet Armyworm (Lepidoptera: Noctuidae)

Abstract

A technical grade lyophilized preparation of the Spodoptera exigua multinucleocapsid nuclear polyhedrosis virus (SeMNPV) was field-tested, in small plots and compared with Bacillus thuringiensis subsp. kurstaki (Berliner) for control of the beet armyworm, Spodoptera exigua (Hubner) on tomatoes, peppers, and garbanzo beans in the Central Valley of California and tomatoes in the Guasave Valley of Sinaloa, Mexico. Weekly application of SeMNPV at rates of 2.5 × 1011and 12.5 × 1011 occlusion bodies (OB)/ha gave season-long control of beet armyworm and provided significant reductions in plant damage compared with untreated control plots. On pepper and garbanzo bean, respectively, the level of beet armyworm reduction and foliar protection was significantly greater in plots treated with 12.5 × 1011 OB/ha of SeMNPV than in the plots treated with B. thuringiensis . However, the degree of control achieved at the low rate of the virus was similar to the high rate of SeMNPV and B. thurillgiensis on all crops tested. Bioassay of chrysanthemum leaves sprayed with the SeMNPV killed >98% beet armyworm immediately after application and retained 50% of its original pathogenicity 7 d after treatment. Both Orzan LS and skim milk improved virus persistence. The results of these tests confirm the efficacy of the SeMNPV for control of the beet armyworm on several vegetable crops.