Impact of silicon-based fertilizer and salicylic acid on the population density of Brevicoryn brassicae (Hemiptera: Aphididae) and its parasitism by Diaeretiella rapae (Hymenoptera: Braconidae)

The cabbage aphid, Brevicoryne brassicae (Hemiptera: Aphididae), is an important pest of rapeseed. In this study, the effects of a silicon-based fertilizer, silicate potassium (SP), and salicylic acid (SA) on inducing resistance in rapeseed to the aphid were studied under field conditions. The rapeseed plants were directly sprayed with SP and SA at two application rates, and the population density of alive and parasitized aphids by Diaeretiella rapae (Hymenoptera: Braconidae) was recorded every three days. The results showed that the aphid population densities in SP and SA treatments were significantly lower than in control (2.21 and 3.53 folds, respectively). The lowest population density was observed in the SP treatment (1200 g/ ha). Moreover, the parasitized aphid densities in the treatments were significantly increased, and the highest parasitism was recorded in the SP treatment (1200 g/ha). The rapeseed yield in the SP-treated plants was significantly more than control, and the highest yield increase was observed in SP treatment (1200 g/ha). According to the results, SP at 1200 g/ha is recommended for cultural control of B. brassicae in the rapeseed fields.