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In recent years, with the large-scale implementation of conservation tillage measures and crop straw crushing in North China, the winter wheat and summer corn are planted in two crops per year, creating a favorable environment for feeding and habituating for the Pleonomus canaliculatus. As the temperature in autumn, winter and spring of Gucheng Station in Hebei Province alternates between cold and warm from 2018 to 2019, the minimum temperature is significantly higher, inducing the explosive occurrence of the Pleonomus canaliculatus in the wheat field. According to the investigation of spring wheat field excavation, the maximum density of insect population is 144 heads·m-2, the maximum weight of insect population is 18.764 g·m-2. Among 58 investigation points, densities of 57 points exceed 5 heads·m-2, which calls for control measures. The density of insects in the jointing-harvest period is the highest during the booting period, followed by the jointing period, and that of the harvest period is the lowest. The oldest larvae have a maximum length of 34.68 mm, and a maximum width of 4.9 mm, 4.68 mm longer and 0.90 mm wider comparing to existing record respectively. The density of insect populations in the continuous cropping winter wheat and summer maize gramineous crops is 35.3 to 40.4 heads·m-2, which is significantly higher than that of soybean, corn, and winter wheat recreation grounds. The peanut and spring corn lands are more than 5 times higher than the soybean insect population density, and the weight of insect population is more than 10 times higher. Yield measurement in mature wheat fields shows the grain yield is reduced by 36.8%. When the insect population density increases by 10 heads·m-2, grain yield decreases by 4.824%. When insect population weight increases by 1 g·m-2, grain yield reduction increases by 3.871%, and 10% increase of plant pest will make the grain yield reduction rate increase by 11.587%. |
