Economic Injury Levels and Economic Thresholds for Tibraca limbativentris (Hemiptera: Pentatomidae) on Paddy Rice Based on Insect-Days.

The rice stalk stink bug Tibraca limbativentris Stal, 1860 (Hemiptera: Pentatomidae) is an important pest of paddy rice (Oryza sativa L.) in South America. Current records of economic injury levels (EILs) and economic thresholds (ETs) for this insect are scarce. In this study, we determined EILs and ETs through cumulative insect-days of T. limbativentris adults in two phenological stages of paddy rice. Five field trials were established for the 2015/16 and 2016/17 crop season. To evaluate the relationship between insect-day and yield, rice plants were infested at V4 and R2 with adult male-female pairs of T. limbativentris. Mixed linear models were fitted utilizing the year and block as random factors to estimate the damage to plant, irrespective of the interference of environmental factors. The yield loss per insect-day was then used to calculate EILs using current market values and control costs. Rice grain yields were reduced by 5.91 kg/ha for each insect-day/m2 when infested during V4 stage, with EILs ranging from 3.88 to 11.61 insect-days/m2, while infestation during R2 stage resulted in a yield reduction of 3.16 kg/ha, with EILs ranging from 8.05 to 21.72 insect-days/m2. The results indicate that yield losses of paddy rice due to T. limbativentris infestation vary according to plant phenological stages and management should consider control cost and market value of rice. These EILs and ETs based on insect-days may be an efficient strategy for decision-making in the management of T. limbativentris on paddy rice.