关键词: 二点委夜蛾, 干燥, 温度, 取食量, 取食选择性

Abstract: 【Aim】 Surveyes showed that there was no correlation between the population density of Athetis lepigone larvae and the damage rate of maize seedlings, and the damage rate of maize seedlings cannot be accurately predicted according to the number of larvae in the field. In this study, the effects of environmental conditions such as temperature and humidity on the feeding and damage of A. lepigone to corn and the feeding habits of this insect were investigated in the laboratory in order to explore the relationship between the number of A. lepigone larvae and their injury to maize seedlings and to explain the phenomena encountered in the field investigations that maize seedlings are slightly damaged even though its larvae occur in large numbers. 【Methods】 The damage degrees of the 3rd and 4th instar larvae of A. lepigone to maize seedlings were evaluated after the larvae were subjected to the following eight treatment combinations of temperature, humidity and food, respectively, for 4 h: 15℃, 30% RH and starvation (no food supplied); 15℃, 0% RH and starvation; 15℃, 30% RH and fed with artificial diet (AD); 15℃, 0% RH and AD; 36℃, 90% RH and AD; 36℃, 0%RH and AD; 36℃, 90%RH and starvation; and 36℃, 0% RH and starvation. The food consumption of larvae on maize leaves at four different temperatures (15℃, 24℃, 28℃ and 33℃) was measured. The newly hatched larvae were domesticated by feeding on eight kinds of food (leaves of purslane, purple perilla, sweet potato, Chinese cabbage, soybean, pumpkin and maize, and wheat straws), respectively, till the 3rd instar, then the feeding preference of the domesticated larvae to the initial food for domestication, wheat straw and maize leaves was assayed. 【Results】 The damage grades of A. lepigone larvae under drought conditions were higher whether they had experienced starvation or not; especially in the high temperature and desiccation treatment group, the average damage grade of larvae to maize seedlings reached 3.1. The percentages of injured seedlings with the damage grade above grade 4 (including grade 4) were 50% and 40%, respectively, when the larvae were subjected to the low temperature and desiccation treatment and the high temperature and desiccation treatment. The feeding amount of larvae to maize leaves increased gradually with the increase of temperature between 15-33℃, with the corrected feeding amount of 12.8, 31.8, 38.0 and 60.0 mg, respectively, at 48 h after treatment. Larvae domesticated with leaves of sweet potato, cabbage, soybean and pumpkin were more likely to choose the initial food for domestication. Larvae domesticated with perilla leaves preferred perilla and wheat straw to maize leaves. Similarly, larvae domesticated with maize leaves and wheat straw had greater preference to maize leaves and wheat straw, respectively. 【Conclusion】 The results show that desiccation is a major factor in increasing the intake of A. lepigone larvae to maize seedlings. A. lepigone larvae have a strong adaptability to short-term high and low temperature, and their feeding amount increases with the increase of temperature in a short time and a certain temperature range (15-33℃). Temperature as a supplementary of desiccation also affects the damage degree of the larvae to maize seedlings. In addition, A. lepigone larvae tend to choose the food they come into contact with immediately after hatching for feeding, and the occurrence and damage of this insect to maize seedlings also largely depend on its feeding habits.

Key words:  Athetis lepigone, desiccation, temperature, food consumption, feeding preference