Bioefficacy, phytotoxicity and safety of Virtako 1.5 Gr a premixed commercial insecticide against thrips, black cutworm and natural enemies in onion

Abstract

Aim: This study aimed to evaluate the relative field-efficacy, natural enemies safety and phytotoxicity of premixed soil insecticide formulation Virtako 1.5 Gr (Chlorantraniliprole 0.5% + Thiamethoxam 1%) against onion thrips (Thrips tabaci) and black cutworm (Agrotis ipsilon) infesting onion. Methodology: Two field experiments were conducted in successive years (2017-18 & 2018-19) to evaluate the bio-efficacy of Virtako 1.5® Gr against thrips, cutworms and natural enemies in onion. The desired dosage of Virtako 1.5® Gr was applied as soil broadcasting after 10 days of transplanting. Thrips population, cutworm damage, natural enemies and phytotoxicity observation were made using standard procedures. Results: The results revealed that Virtako® 1.5 Gr applied @ 105 and 90 g a.i ha-1 recorded the lowest mean thrips population, 18.03 and 19.50 thrips per plant, respectively. Similarly, Virtako 1.5 Gr at 105 a.i. ha-1 reduced cutworm damage by 88.5%, followed by Virtako 1.5 Gr at 90 g a.i. ha-1 (85.5%). Although no natural enemies’ activity (Coccinellids, Orius spp, and Spiders) was found in the early phase of onion growth, they were recorded in all treatments at later crop growth stages. All doses of Virtako 1.5 Gr had no noticeable phytotoxicity effects on onion plants. Interpretation: Application of Virtako 1.5 Gr effectively minimized thrips population and cutworm damage in onions. Further, it did not show any significant harmful impact on the activity to above-ground natural enemies. Therefore, Virtako 1.5 Gr at a lower effective dose 90 g a.i ha-1 can be recommended for onion against thrips and black cutworm. Key words: Cutworm, Onion thrips, Premixed insecticide, Phytotoxicty, Virtako 1.5 Gr