Monitoring and chemical control of canola stem-borer weevils Ceutorhynchus spp. (Col.: Curculionidae)

In order to monitor canola stem borer weevils, Ceutorhynchus spp., determining the appropriate time for control, and investigate the efficacy of insecticides, this research was conducted in a RCBD with five treatments and four replicates in Sari during 2011-2012. Yellow water traps were used for monitoring the pest. The treatments were a) chlorpyrifos EC40.8% (2 l/ha), b) imidacloprid SC35% (1 l/ha), c) diazinon EC60% (1.5 l/ha), d) fenitrothion EC50% (1 l/ha) and e) control. Four plants per plot were collected 1 day before and 5, 14, and 21 days after treatment and the pest larvae were counted. One week prior to harvesting, the numbers of healthy pods (HP) and blind stalks (BS) on three plants per plot were counted. 1 m2 of the crop per plot was harvested, and the yield and thousand kernel weight (TKW) were measured. First and last weevils were caught in early November and late December, respectively and its peak occurred in late November. Oviposition began in late November and its peak occurred in early December. The efficacies of the treatments a, b, c and d at 14 days after treatment were 88.89±6.51, 57.57±9.61, 83.20±6.00, and 91.82±6.13 percentage, respectively. Compared to ghe control, TKW and yield increase in a, b, c, d were 0.8, 0.4, 0.48, and 0.43 g; 115.5, 68.2, 79.5, and 62.8 g, respectively. HP and BS in a, b, c, d and e were 77.17±11.63, 43.58±1.93, 44±9.10, 44.75±7.06 and 31.75±3.35; 4.50±0.29, 8.75±0.98, 13.25±1.42, 18.33±3.54 and 14.83±2.76, respectively. Chlorpyrifos with appropriate efficacy, had the highest yield, TKW, HP and the smallest BS.