Field evaluation of a neem (Azadirachta indica A. Juss)-based formulation Neemix® against Nezara viridula (L.) (Hemiptera: Pentatomidae) in cowpea

Field trials were conducted from 1999 to 2001 to evaluate a commercial neem (Azadirachta indica A. Juss) formulation (NeemixR 4.5 EC) against Nezara viridula (L.) in cowpea (Vigna unguiculata [L.) Walpers). Three applications of NeemixR were made in each year beginning at pod formation using 210.4 g azadirachtin per hectare. Densities of N. viridula declined in treated plots after the first spray in all years. In 1999, bug densities were significantly lower in treated plots (0.2 bugs/2-m row) than in controls (1.1 bugs/2-m row) 10 days after the first spray. Similarly, N. viridula densities in 2001 were significantly lower in treated plots (0.6 bugs/2-m row) compared with controls (3.9 bugs/2-m row) 10 days after the first spray. Adults with morphological deformities, twisted wings and scutellum that folded toward the anterior of the insect were observed in treated plots after the second spray. Seed damage was significantly reduced in treated plots (4.0 ± 0.2% and 16 ± 1.3%) compared with controls (8.5 ± 1% and 24 ± 3%) in 1999 and 2000, respectively. In 2001, significantly lower pod damage occurred in treated plots (25.6 ± 4.1%) than in controls (64.5 ± 3.2). In addition, seed damage was lower in treated plots (11.5 ± 0.7%) compared with controls (24.1 ± 3.6%) in 2001. In 2001, seed yield was significantly greater in treated (1212.0 ± 25.6 kg ha-1) than in control (887.4 ± 64.3 kg ha-1) plots. These results suggest that neem may be a useful management tool for reducing damage by N. viridula in cowpea.