Commercial development and efficacy of a viral insecticide for beet armyworm, Spodoptera exigua

Beet armyworm, Spodoptera exigua (Hubner), is a widely distributed agricultural pest in tropical and subtropical regions and a key pest on high value vegetables in Thailand. Decades of intensive use of insecticides to control this pest has resulted in widespread resistance and product failure. In view of the threat posed by resistance and the growing concern for maintaining quality of environment, food safety, and human health, there is a need to identify safe and effective insecticides for best armyworm. In the mid-1980 a S. exigua multiembedded nuclear polyhedrosis virus (SeMNPV) (Baculoviridae, subgroup A) was isolated from beet armyworm larvae in commercial shadehouses in Florida, USA. The virus was specific and highly virulent to beet armyworm larvae and showed considerable potential as a microbial control agent. A commercial formulation of this Florida SeMNPV isolate was recently registered and introduced in the United States and the Netherlands as SPOD-X and has attained some commercial success. Registration is expected shortly in Thailand with product launch scheduled on high value vegetables in early 1996. Small-scale field trials were conducted in the Kanchanaburi province of Thailand between December 1994 and June 1995 to gather efficacy data to support a registration dossier for SPOD-X. Our data confirm the efficacy of SPOD-X against chemically resistant beet armyworm on several major vegetable crops. SPOD-X applied at 3.1*10**(11) OBs/ha provided exceptional control on snow peahowever, on shallot and kale, these data support the recommendations that SPOD-X should be applied at 6.3-12.5*10**(11) OBs/ha at the volumetric rate used in these trials. In general, SPOD-X performed as well or better than the Bacillus thuringiensis standard, Centari. These data are in general agreement with the results of efficacy trials conducted with SPOD-X in the United States, Mexico, and Europe on vegetable and ornamental crops. High efficiency, coupled with long shelf life, and environmental safety indicate the potential of SPOD-X as a biological insecticide where beet armyworm is a predominant or primary pest. Moreover, the selectivity of SPOD-X and its unique mode of action are ideal attributes for resistance management programs and sustainable agriculture initiatives.