Impact of Trichogramma Release Regimes and Combination with Mass Trapping on Sugarcane Internode Borer (Chilo sacchariphagus indicus) Management

Abstract

Large area study on the impact of six versus ten releases of the biocontrol agent, Trichogramma chilonis, besides large plot assessment of ten releases with and without mass trapping (by pheromone traps) for eco-safe management of the sugarcane internode borer (INB) - Chilo sacchariphagus indicus Kapur were undertaken in Natems Sugar factory area, Koppedu Taluk, Chittoor District, Andhra Pradesh, South India. In 2017-18, a large contiguous sugarcane crop area of 400 hectares received six releases of T. chilonis (as Tricho cards @ 5cc.ha/release) in alternate weeks during 5-7 months age of crop, followed by four additional releases during 8-9 months age (totalling ten releases) in 40 hectares area, besides assigning a no release block of 40 hectares in adjacent area. Harvest-time sampling in each treatment block showed that the INB distribution (per cent canes infested) was 80 % in control (no release) block, while it was 42 and 27 %, respectively, for six and ten releases. The INB intensity (per cent internodes infested) was also more (6.2 %) in control block whereas it was only 3.2 % and 1.5 %, in the two respective release regimes. Based on these results the cost-effectiveness of both the regimes was ascertained. In 2018-19, the impact of ten releases of T. chilonis (@5cc/hectare /release) versus same regime plus mass trapping (@25 pheromone traps/ha) was compared in large plots (each of 2.0 ha) along with an untreated control plot. Harvest-time samples showed that INB distribution was 70.3% in control block, compared to 48.3% in Trichogramma release block versus 19.8% in block combining Trichogramma and mass trapping. The respective INB intensity was 6.04 %, 4.04 % and 2.17 % while the estimated cane yields were 81.0, 86.2 and 92.5 tons/ha, respectively. The cost: benefit ratios for Trichogramma release with and without mass trapping were comparable, so confirming that both are cost-effective alternatives to chemical insecticide use in sugarcane agro-ecosystems.