| In recent years, with the change of the climate and farming system, the damage of Athetis lepigone(Moschler) to summer corn is more and more serious in north China,which cause significant losses to corn production. It is very difficult to control using conventional methods of spraying pesticides, because it hides beneath wheat residues and mulch in the field. However, there is a much easier and more efficient way to control this insect by using attractant. In order to determine the components of botanical attractants and behavioral responses of A. lepigone larvae to semiochemicals of host plant. This research preliminarily studies the chemotaxis and palatability of A. lepigone larvae to nine species of plant materials(Corn, wheat, cotton, soybean, peanut, amaranthus retroflexus, gray green plant, wheat straw, wheat bran), which will provide a theoretical basis for field traps and predictions. The main results are summarized as follows:1. In this study, the behavioral response of A.lepigone larvae to botanical attractants was tested by dish method. It turned out that wheat straw and Chenopodium glaucum had higher positive taxis to A.lepigone larvae. According to the study on feeding preference of A. lepigone larvae to 9 species of plant materials, we found that A. lepigone larvae were strongly attracted by wheat straw and C. glaucum, and with preference index 0.69 and 0.63 respectively. The results indicated that wheat straw and C. glaucum not only can lure larvae of A. lepigone strongly, but also can be a great deal of persistence fed by A.lepigone.2. The toxicity of several pesticides to the larvae of A. lepigone were determined by sandwich method and dipping corn seedling method. The results indicated that emamectin benzoate showed the highest contact toxicity to this insect, with the LC50 of 9.015mg/L.Phoxim was higer, with the LC50 of 16.247 mg/L, and chlorantraniliprole was the lowest one. The results of stomach toxicity of six chemical pesticides to 5th instar larvae of A.lepigone showed that phoxim and emamectin benzoate had the highest toxicity to larvae,with the LD50 of 2.067 ug/g and 3.638 ug/g respectively. Therefore, phoxim and emamectin benzoate showed a relatively high activity both in contact toxicity and stomach toxicity.3. The volatile components and content of each plant were analyzed by HS-SPME and GC-MS. Y-tube olfactometer tests were conducted to investigate taixs responses of the larvae to six compounds, five blends of two volatiles and blends of volatiles and chemical pesticides. Results indicated that the larvae were most attracted to(Z)-3-Hexen-1-ol(0.1μl/ml) with the luring rate of 78.3%. It was showed that attraction of five blends of two volatiles was lower than(Z)-3-Hexen-1-ol. It was not significant of the attraction to blends volatiles and chemical pesticides and(Z)-3-Hexen-1-ol. The(Z)-3-Hexen-1-ol mixed with phoxim proformed a better attracttion to larvae than other mixtures, and has no significant difference to single-compound. Therefore, the mixture of(Z)-3-Hexen-1-ol and phoxim can be used as a composition of botanical attractants to larvae of Athetis lepigone.4. The amino acids components and content of wheat straw and C. glaucum were analyzed by HPLC and automatic amino acid analyzer. The behavioral feeding preference of 5th larvae of A.lepigone to five secondary metabolites(sucrose, inosito and three amino acids) was tested by leaf dish method. It was similar to inositol and sucrose on the feeding behavior of the five kinds of secondary materials. With the concentration-increase of treatment, the preference index showed an increasing trend. Feeding behavior of different concentrations of glutamate and aspartate was not a concentration gradient. The changes of cysteine concentration has no significant effect on A. lepigone larvae. Thus, sucrose and inositol were stimulating substance to A. lepigone larvae in a certain concentration. |
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