| Monolepta hieroglyphica Motschulsky (Coleoptera: Chrysomelidae ) has been a severe boring new pest of cotton plants in China's Uigur Autonomous Region in recent years, M.hieroglyphica differed quickly in Sin kiang and damaged more and more severely. Form 2005 to 2007 which the paper had studied systematically the morphic character, habitus, life history, threshold temperature, effective accumulative temperature and population dynamic by room and field experiments. At five constant temperatures of 19,22,25,28 and 31℃,it had been investigated the growth, propagation, longevity and so forth in laboratory. Study on the Capability of adult adapt to high-temperature and cold-temperature and population difference of M.hieroglyphica form different regions on Esterase electrophoresis,We had selected out two insecticides which high Toxicity to M. hieroglyphica and the effective synthetic control measure was drawn up preliminarily. The results are as follows:1. Biological charactersThis insect occurs only one generation in one year. The female deposited their eggs into soil that the depth range form 0 to 15 cm and eggs over-wintered in the soil. Next year, in the second or last ten days of April, Over-wintered eggs started to incubate. The larva have three developmental stages and mature larvae constructed the chamber around itself to pupation. The larvae feed on roots of cotton, corn and weeds (Convolvulus arvensis L, Setaria viridis subsp virids,et al) completed to their development, Adult primary eat cotton leaves maintain their life. Adult can fly in short distance about 2 to 5 meters, adult can mate and lay many times all the life.Adult started to emerge and damage cotton leaf in late-may or early-June, the population will increase to climax in late-June or mid-July, then the population gradually decline and the damage will decrease, we nearly couldn't found the adult in field at first ten days of September. This insect had only one peak damage period during all generation of cotton.2. Ecological characters(1)Effective accumulative temperature: In range of 19-31℃, the growth speed of M. hieroglyphica goes up with the rising of temperature. The relationship between growth speed and temperature accords to Linear model and logistic model. The result showed that threshold temperature of egg, larva, pupae and pre-oviposition were estimated to be 9.8, 10.8, 12.6 and 10.1℃, respectively. And the effective accumulated temperature was 1182.2, 401.2, 111.9 and 269.0 degree-days.(2)Effect of temperature to fecundity: in the range of temperature 19 to 31℃, the female adult productions is the highest at 22℃to 25℃.When the temperature is higher than 25℃or lower than 22℃,eggs productions decrease gradually and reproductive period decreased evidently. A female can lay average 93.8 eggs at 25℃, with the rising of temperature, the pre-reproductive period is shorter and the date of laying eggs is earlier, the pre-reproductive period is only 13.5 days at 31℃. (3)Effect of temperature to adult longevity: With the rising of temperature, the adult longevity becomes more and more short. The entire populations of the colony averaged at different constant temperatures (19, 22, 25, 28 and 31°C) were to be 64.1, 60.8, 55.6, 42.1 and 34.7days, respectively. The female average longevity is longer than male. The Weibull model was set up about the relationship between adult longevity and temperature, the model as following: y=63.5583*[1-EXP (-((x-17.3229)/11.6200) ^-1.6141)].(4) Clustering for M.hieroglyphica form different regions on Esterase electrophoresis, the populations form 125 Tuan and 133 Tuan of Sin kiang are very similar, the difference of population between Sin kiang and Shanxi are very indistinctive, but the population form Gansu are dissimilar to others.3. The experiment of insecticide effectWe selected nine insecticides which used to management cotton pest in Sin kiang, the toxicity of Pesticides to adult of M. hieroglyphica were determined in room by leaf-dip method. The results showed that 5%fipronil SC, 25% thiamethoxam WG, 25% endosulfan EC, 3%Acetamiprid EC,10% imidacloprid WP and NPV had higher activities, their LC50 were 0.3593, 1.9896, 3.3681, 7.4012, 8.906mg/L and 1.31×10~8PIB/L, respectively. The results of field trial showed that 5% fipronil SC 112.5g/hm~2 and 25%thiamethoxam WG 225g/hm~2 had better control effects, 5%fipronil SC and 25% thiamethoxam WG had longer persistence against the insect, their controlling efficiency both exceeded 90% after 7 days, and safe to laidbug Coccinella septempunctata (Linnacus).4. Evaluation on comprehensive control measuresMethods Combining the survey of insect pest of M. hieroglyphica in the main producing region, with the environmental protection policy of protecting the environment and maintaining the ecological balance, and combining the principle of prevention first and integrated control, taking measures to agricultural prevention and cure, chemical prevention and cure methods and biological control, And postpone the resistance to pesticide. |
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