Evaluation of augmentative biological control strategy against major borer insect pests of sugarcane-a large-scale field appraisal

Background Biological alternatives to pesticides in agriculture do not harm non-targets organisms including natural enemies of insect pests. Experiments were conducted at sugarcane fields during 2015 to 2019 to assess large scale biocontrol practices, involving inundative releases of trichogrammatids against lepidopteran borers in comparison to conventional chemical-based farmers' practice. Main body Eight releases each ofTrichogramma chilonisIshii andTrichogramma japonicumAshmead were made at 50,000 ha(-1)at 10 days interval for the management of sugarcane stem borer,Chilo infuscatellusSnellen and the sugarcane top borer,Scirpophaga excerptalis(Fabricius) (Lepidoptera: Crambidae), respectively. Likewise, 10-12 releases ofT. chiloniswere made at 50,000 ha(-1)at 10 days interval for the management of sugarcane stalk borer,Chilo auriciliusDudgeon (Lepidoptera: Crambidae). The biocontrol intervention was compared with farmer's practice (chemical control) in managing these borers. The results showed that farmers' practices and biocontrol treated fields resulted in a lower incidence ofC. infuscatellus(1.1, 2.9%) andS excerptalis(1.7, 3.9%) than the untreated control fields, wherein the mean per cent incidence of these borers (6.8, 8.5%) was significantly higher. The incidence ofC. auriciliuswas also lower in augmented fields (2.8%) than untreated fields (7.3%). The yield data indicated that farmers adopting biocontrol practices were able to get comparable yield and benefit: cost ratio than farmers' practice, both being better than untreated control. Moreover, in biocontrol fields, parasitism rate on the factitious host,Corcyra cephalonicaStainton cards was estimated. Conclusion Thus, the study highlights the significance of adoption of biocontrol-based technology over a long run to provide sustainable system of sugarcane insect pest management and economic benefits to the stakeholders.