Baseline susceptibility of major sucking pests of hill crops in north western Himalayan region

Abstract

Greenhouse whitefly (Trialeurodes vaporariorum), green peach aphid (Myzus persicae) and cabbage aphid (Brevicoryne brassicae) are the three major sucking pests that infect hill crops in North Western Himalayan region and cause severe yield losses. Chemical management tactics are the widely practiced methods for management of these pests in the locality. However, knowledge about the efficacy of different pesticides against these native populations is lacking. In view of this, seven insecticides against whitefly and six against aphids were tested for their bio-efficacy under laboratory conditions. The results showed that, field populations of greenhouse whitefly were highly susceptible to three insecticides; Thiomethaxam> Imidacloprid> Pymetrozine with LC50 values 12.30, 18.62 and 22.38 ppm respectively. Whereas, LC50 values of botanical insecticides NSKE and nimbicidine were very high; 524.81ppm and 4365.16ppm respectively, indicating their non-suitability against greenhouse whitefly management. The susceptibility for B. brassicae, a major pest of crucifers is in the following order; Thiomethaxam> Imidacloprid> Indoxacarb> Pymetrozine> Nimbicidine> NSKE and Thiomethaxam was the most toxic insecticide with LC50 and LC90 values as low as 0.024ppm and 0.25ppm respectively. Green peach aphid (M. persicae) was highly susceptible to Thiomathaxam and was followed by Pymetrozine, indoxacarb, Imidacloprid, Nimbicidine and NSKE respectively. The LC50 values of Thiomethaxam and Pymetrozine were at par with a recorded value of 2.54ppm and 2.57ppm, respectively. The three sucking pests under study are well known for their resistance development mechanisms against several groups of insecticides. But, the level of susceptibility that was recorded in our study indicates presence of susceptible population of these sucking pests in Indian Himalayan region that could help to maintain a refugee or buffer populations against development of insecticide resistant strains.