Field Crop 2024, Vol.7, No.3, 182-190 http://cropscipublisher.com/index.php/fc 183 2 Biology and Behavior of Western Corn Rootworm 2.1 Lifecycle and development The Western Corn Rootworm (WCR), is a significant pest of maize, particularly in the United States and Europe. The lifecycle of WCR includes egg, larval, pupal, and adult stages. Eggs are laid in the soil during late summer and hatch the following spring. Larvae then feed on maize roots, causing substantial damage to the plant's stability and growth. The pupal stage occurs in the soil, and adults emerge in mid-summer to feed on maize silks and leaves, completing the cycle (Figure 1) (Ferracini et al., 2021; Meinke et al., 2021). Figure 1 The agricultural region in the midwestern U.S. that is a major producer of maize is called the Corn Belt (Adopted from Meinke et al., 2021) Image caption: This figure shows the major maize grain production area within this region, a Dvv insecticide use/field-evolved resistance timeline associated with continuous maize, and the geographic location of states Nebraska and Kansas where Dvv resistance to multiple insecticides has occurred. Maize grain production area is based on USDA-NASS 2015-2019 data (Adopted from Meinke et al., 2021) 2.2 Feeding habits and damage to maize WCR larvae primarily feed on maize roots, which can lead to significant economic losses due to reduced plant growth and yield. The root damage caused by larval feeding can result in plant lodging, where the maize plants fall over, making harvesting difficult and further reducing yield. Adult WCRs feed on maize silks, which can interfere with pollination and further impact yield. Studies have shown that effective insecticide application at sowing can significantly reduce larval density and root damage, leading to increased grain yield (Souza et al., 2019; Ferracini et al., 2021; Nemkevich et al., 2022). 2.3 Resistance Mechanisms The extensive use of insecticides over time has led to the development of resistance in WCR populations. Resistance mechanisms in WCR include both oxidative and hydrolytic metabolism, which facilitate cross-resistance between different classes of insecticides such as cyclodienes, organophosphates, carbamates, and pyrethroids. Field-evolved resistance has been documented, significantly reducing the efficacy of commonly used soil and foliar insecticides. This resistance can persist in field populations even in the absence of selection pressure, indicating minimal fitness costs associated with resistance (Souza et al., 2019; Meinke et al., 2021; Nemkevich et al., 2022). Integrated pest management strategies, including crop rotation and the use of multiple control tactics, are recommended to mitigate resistance development and maintain the effectiveness of insecticides (Furlan et al., 2022).
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