Comparison and Evaluation of Bagged and Structured Refugia against Cotton Bollworms

Aims: To evaluation the Refugia in bag and structured refugia against bollworm complex in cotton.

Study of Design: Bt cotton hybrid (KCH-14K59 BG II) and its non Bt counterpart was planted, following recommended agronomic practices. Six treatments were designed for the studies are detailed below: T1-100 % Bt, T2-100 % Non Bt, T3-20 % structured refugia, T4- RIB-Random (5-10 % Minimal non Bt seeds), T5- RIB-Fixed pattern (5 % Minimal non Bt seeds), T6- RIB- Fixed pattern (10 % Maximum non Bt seeds).

Place and Duration of Study: Department of Entomology, College of Agriculture and Main Agricultural Research Station, Raichur, during 2021-22.

Methodology: Observations regarding infestation of cotton bolls by different bollworm complex at 60, 80, 100, 120 and 140 days after sowing (DAS) were recorded along with observation on yield parameters of cotton. For pink bollworm, cotton bolls were randomly collected from the respective treatments, as described in cotton pest scouting method and put them in laboratory for further counting of PBW larvae.

Results: The results in commercial RIB, fixed 5% RIB and Fixed 10% RIB were observed at par with respect to good boll opening (GBO), Bad boll opening (BBO) and locule damage among the all treatments while highest seed cotton yield was observed in T1 (21.64 q/ha), followed by T4 (17.04 q/ha) and T5 (16.74 q/ha), with the least yield recorded in T2 (4.23 q/ha).

Conclusion: There was no infes of Helicoverpa on Bt cotton in the different treatments of refugia in bag and structured refugia, However, the pink bollworm incidence and green boll damage caused by PBW was recorded in all the treatments of both Bt and non Bt cotton.