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Root damage caused by Diabrotica virgifera virgifera LeConte larval feeding used as a predictor of maize plant lodging and yield loss

It is proposed that western corn rootworm (WCR) larval damage can be an indicator of plant lodging and yield loss in Croatia. The aim of the investigation was (1) to find out if WCR larval damage correlates with plant lodging, (2) to determine the regression curve between WCR larval damage and percent plant lodging and (3) to determine if the root damage rating can predict plant lodging and yield loss. Ten maize fields were selected for this study in 2010 in the region of northwest Croatia. In each field, four areas containing 100 plants were inspected. Plants were grouped in one of the following three categories: up straight plants (USP), partially lodged plants (PLP) - plants lodged up to 45° when compared to USP and fully lodged plants (FLP) - plants lodged between 45-90° when compared to USP. For each category, roots were rated according to the Oleson et al. (2005) 0-3 Node-Injury Scale. Based on the average root rating (RR) of each plant category and on the ratio of each plant category for each field, an average RR was calculated. In each of three selected fields from each grouping, four samples containing ten plants were harvested. The average yield was determined for each category and based on the ratio of each category in a particular field the average yield was calculated. The yield loss was calculated by comparing obtained yields with the yields of USP plants in each of the selected fields. The average RR of USP was 0.42 and did not significantly differ from those of PLP (0.88), while the average RR of FLP (1.78) was significantly higher. The correlation between plant category and RR can be described as strong (r=0.7413, P=0.0001). We found differences between fields in the percentage of FLP, as well as in average RR. A significant (p=0.0001), strong correlation (r=0.8938) between the average RR and percentage of FLP was determined. The regression curve was linear and the regression coefficient was 37.45. The yield loss in the field where 65.5% of the plants were lodged ranged from 0 to 57.16%.

maize; plant lodging; root damage; yield loss; WCR

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