Micronutrients' foliar fertilization and releasing green lacewing chrysoperla carnea (stephens) could efficiently suppress sugar beet insect pests

Sugar beet is attacked by many mischievous insect pests. To avoid too much reliance on pesticides, many studies have been conducted to search alternative methods of sugar beet pest control. In the present study, we evaluated whether pant fertilization and biological control could be efficacious techniques to suppress insect pests of sugar beet. In two successive growing seasons of 2015-2016 and 2016-2017, we investigated the impacts of Nutrimix® complete, a foliar fertilizer with concentrated micronutrients including nitrogen and sulfur, and also release of the common green lacewing Chrysoperla carnea larvae, a generalist predator of insect herbivores, on insect pest infestation in the sugar beet fields. Applications of the foliar fertilizer significantly decreased the percentages of plants infested by cotton leaf worms or sugar beet beetles, while the infestations by sugar beet flies and the sugar beet moths were less influenced. Releasing the predator C. carnea in sugar beet fields was found to effectively reduce pest populations though the effectiveness depended on the seasons. The plants in lacewing-released plots were attacked by fewer aphids, sugar beet moths, leafhoppers and sugar beet flies than those in control plots. Aphid populations were the most influenced, and the reduction percentages reached 100% in the 2015-2016 season and 97.08% in 2016-2017 after 14 days of release, while the sugar beet flies were the least influenced with 64.84% and 49.88% reduction in the first and second seasons, respectively. Our study demonstrated the usefulness of micronutrient application and C. carnea larvae for suppressing insect pest populations in sugar beet fields.