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Sternechus subsignatus (Boheman) (Coleoptera: Curculionidae): level of control and damage on soybean under the no-tillage system

This study was carried out in the 1987/88, 1988/89 and 1992/93 soybean growing seasons to evaluate the infestation levels and damage of Sternechus subsignatus (Boheman). Experiments were set on soybean under no-tillage in Cruz Alta, Rio Grande do Sul State. Infestation of one adult/m of row and two adults/m of row at V2-V5 growing stages caused significant reductions on yield when compared to uninfested plants. Increasing number of adults/m of row decreased plant population, plant height and first pod height (significant negative correlations) and increased the number of dead and damaged plants (significant positive correlations). Significant negative correlations were observed between yield and number of dead and damaged plants, and significant positive correlations between yield and plant population, plant height and first pod height. Infestation levels of 20% or more damaged plants caused significant differences on yield in relation to the check plots. Taking into account the damage caused by the insect it is suggested the level of 0.4 adult/m of soybean row as an indicator to start application of foliar insecticides to protect the soybean plants.

Insecta; damaged plants; Glycine max

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