关键词: 化学防治, 虫害, 拟轮枝镰孢, 玉米穗腐病, 产量, 伏马毒素

Abstract:

【Background】 Fusarium verticillioides is responsible for ear rot occurrence and quality degradation in maize. It gives rise to the production of fumonisin and poses a threat on food security. Ear borers inculding Ostrinia furnacalis and Conogethes punctiferalis can cause severe yield loss and lead to an increase in ear rot occurrence. 【Objective】 The objective of this study is to evaluate the efficacy of two insecticides (emamectin benzoate and chlorantraniliprole) combined with three fungicides (phenamacril, tebuconazole and difenoconazole) in promoting yield, reducing ear rot severity and fumonisin kernel contamination under natural conditions, clarify the effect of artificial inoculation of F. verticillioides on insecticide efficacy, define an effective schedule for the control of maize pests and provide a theoretical basis for the pesticide field application. 【Method】 Hybrid Zhengdan 958 typically cultivated in China was selected in this study. Field experiments were conducted in Langfang, Hebei Province. Pesticide treatments were conducted 5 d and 20 d after silking, and artificial inoculation of F. verticillioides was conducted 7 d after silking. Insect damage, ear rot occurrence, ear length, kernels per row, 100-grain weight and ear weight were investigated and recorded at harvest phenological stage. Fumonisins B1 and B2 level in kernels was analyzed by LC-MS/MS. 【Result】 Compared with controls, emamectin benzoate and chlorantraniliprole application could significantly reduce borer damage, ear rot occurrence and fumonisins level. While insecticides have been shown to give advantages in their application, adding a fungicide didn’t lead to a significant lower insect damage, ear rot occurrence or fumonisins level. Additional fungicide didn’t lead a significant higher control effect or yield. After inoculating F. verticillioides, chlorantraniliprole application led to a significant decrease in fumonisins level, ear rot incidence and severity. Control effect of 25 g·hm ^-2 chlorantraniliprole and its combinations on insect damage was 82.1%-92.7% and 94.2%-95.0% in spring and summer maize, respectively. Control effect of 30 g·hm^-2 emamectin benzoate was significantly lower, at the level of 57.8%-78.0% in spring maize and 83.1%-89.9% in summer maize. Control effect on ear rot occurrence was >60% in spring maize and >88% in summer maize. No significant difference was found among pesticide treatments. Regarding yield, insecticide application had no significant effect on ear length or kernels per row, while significantly promoted ear weight compared with controls. No significant difference was found among insecticide treatments and mixture treatments. Artificial inoculation of F. verticillioides had no significant impact on yield after insecticide application. The yield of spring and summer maize increased by 5.49%-13.49% and 9.20%-13.95% after applying insecticides or mixture of insecticides with fungicides, respectively. Kernel fumonisins level was lower than 500 μg·kg ^-1 after insecticide or mixture of insecticides with fungicides application, while the level in controls was 2 817 μg·kg ^-1. Kernel fumonisins level after inoculating F. verticillioides reached up to 8 710 μg·kg^-1, while the number could be reduced to 1 500 μg·kg ^-1 after insecticide application. 【Conclusion】 These results indicated that 25 g·hm^-2 chlorantraniliprole and 30 g·hm^-2 emamectin benzoate application can reduce ear rot occurrence and fumonisin level, improve maize yield and quality by controlling insect damage. No significant difference was found in insecticide treatments and mixture of insecticide with fungicide treatments. Insect infestation plays a decisive role in the F. verticillioides infection. Taking all aspects into consideration, 25 g·hm ^-2 chlorantraniliprole is relative ideal in maize pest control.

Key words: chemical control, pest, Fusarium verticillioides, maize ear rot, yield, fumonisin