Determination of multiple-species economic injury levels for insect pests of tossa jute (Corchorus olitorius) in India

Yield loss to damage functions were established to determine multiple-pest economic injury levels (EILs) on jute, Corchorus olitoris L. (var. JRO 204) at different crop growth stages through field experiments during 2015–2017. The yield loss to damage functions were derived for two-pest combinations viz., yellow mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) and lepidopterans i.e. Bihar hairy caterpillar (BHC), Spilosoma obliqua Walker (Lepidoptera: Arctiidae) and jute semilooper (SL), Anomis sabulifera Guenee (Lepidoptera: Noctuidae). The grouping of insects was made into different injury guilds, based on the plants' physiological response to insect injury. In the present study, the damage mechanism for yellow mite as sap assimilator and Bihar hairy caterpillar and semilooper as tissue consumer were grouped. Based on yield loss functions, single-species as well as multi-species EILs were determined. Across the experiments, single-species EILs of yellow mite combined with BHC and SL, ranged from 32.73–37.20 mites/cm² on the second unfolded leaf and 8.84–9.90% plant damage, respectively. The iso-loss equations were depicted by the various two-pest incidence combinations which resulted in economic damage although each pest was below its respective EIL. The multi-pest EILs can be useful to monitor the simultaneous occurrence of two-pest species thereby helping to prevent yield losses in jute.