| The red imported fire ant, Solenopsis invicta Buren is an extremely harmful insect, which not only endanger agricultural production, public facilities and public health, but also bring badly damage to the ecological environment of invasion according to its great ecological advantages. In 2005, they invaded partly southen area of our country such as Guangdong, Fujian and Guangxi, etc. In order to quickly prevent their expansion and development, governmentes of invaded sites prevented with different pesticides and methods, of which were beta-cypermethrin and spinosad used abroad in Guangdong and Fujian province, and flursulamid used abroad in Guangxi. The effects of the invasion of red imported fire ants on the communities of the native ants were investigated by bait methods in Beiliu, Guangxi from Sept. to Oct., 2005. The residual status of flursulamid was investigated in most soil sample in BeiLiu. Soil behavior, such as degradation, mobility and so on, of the three pesticides, was investigated. Purpose of present study is to predict efficacy of the three pesticides for the red imported fire ant control. The present study also head for predicting potential for ground water contamination results from field application of the three pesticides.The survey result of bait-method showed that the invasion of Solenopsis invicta caused ants on wasteland reduced 1 subfamily, 3 genera, 5 species and 95.09% of individuals; and caused ants on lawn reduced 3 species and 94.04% of individuals; on the wasteland and lawn the one and the only dominant species is the Solenopsis invicta. Because of the invasion of Solenopsis invicta that, R ,J ,H', index of ants in the invaded sites became lower, while index of ants was higher than those in the non-invaded sites, and the Solenopsis invicta were the dominate species. The results also showed that, R ,J ,H', index of ants on wasteland and lawn of the invaded sites became lower, while index of ant was higher than those in the non-invaded sites, and the influence of the invasion of Solenopsis invicta on lawn was more serious than wastelands. The similarity of ant community in each enviornment is low, the coefficient of similitarity of wasteland and lawn where the Solenopsis invicta invaded and non-invaded sites were 0.36 and 0.44, which belong to the middle dissimilarity. The above results showed that the invasion of Solenopsis invicta had brought serious influence on the native ant communities. Therefore, it is very important to strengthen the quarantine of solenopsis invicta and the dynamics of general investigation, and find new nest to deal with this problem timely. What's more, research better prevention and control effectiveness of the insecticide as soon as possible to prevent the expansion of harmful area.The results of soil survey indicated that the new discoverd place—Yalang village, the residues of flursulamid in its soil was obviously higher than Tinxing industrial area and Liudipo village. It's due to late prevention and residential area were sparied large number of pesticide. The residue of sulfur fluoride sulfonamide in each level soil of the same sample point were not only affected by organic matter and sand-carrying capacity, but also by rainfall and man-made interference. So, in the sandy farmland with low organic matter, the content of residues of flursulamid in subsoil are relatively high, so it is easily cause to enviornment pollution.The degradation status of three pesticides in field experiment was studied. Result showed that spinosad, flursulamid and beta-cypermethrin all belong to low residual pesticide, residues of which correlated to pesticide styles and soil characteristics. The effect of spinosad on environment was safe because of short half life and easy degradation. Half life of flursulamid was 7.8d, 8.2d, 9.6d, representatively in lawn, badlands, and farmland, while half life of beta-cypermethrin was 11.9d, 18.8d, and 13.8d, representatively in above 3 soils. In comparison with flursulamid, beta-cypermethrin had a longer half life. According to physicochemical properties of soils, degradation rate of beta-cypermethrin was relatively quick in high organic matter and pH, while degradation characteristics of flursulamid in soils disagreed with regularity of physicochemical properties of farmland and badlands.The result of degradation status of field test showed that spinosad, flursulamid and beta-cypermethrin belong to low residual pesticide, the residues of their were related with the varity of pesticide and the properties of soil. The spinosad was safe to environment because of its short half -life and easily degraded. It's belong to the easily biodegradable pesticide .The half-life of flursulamid in lawn, wasteland, farm soil was 7.8d, 8.2d, 9.6d, while the half-life of beta-cypermethrin in above three enviornment representatively was 11.9d, 18.8d, and 13.8d. Compared to flursulamid, beta-cypermethrin had a longer half- life of digestion in soil. According to physicochemical properties of soils, we discovered that degradation rate of beta-cypermethrin have quicker degradation rate in where contain high organic matter and pH, while the degradation characteristics of flursulamid in soils was not consistent with the regularity of physicochemical properties of farmland and wasteland.The flursulamid spried into the soil was in the form of granules, the first day after spraied pesticide the residue reached the maximum in wasteland and farmland, while after three days in lawn. From then on, they degraded gradually. Just because of flursulamid release pesticide slowly in soil, this helped Solenopsis invicta had enough time to carry toxic bait into their nest and transmit to other mostly individuals, while the quantity of residues of beta-cypermethrin reached top the day pesticide spried. If it don't put into the inside of ant nests in time, pesticide then gradually over time it would be difficult to eliminate whole nest of Solenopsis invicta.Pesticide residues were increased with the increase of the dose. Moving range of spinosad was limit in soil among 3 preventive pesticides because of degrading easily. Test by the three pharmaceutical of prevention, spinosad was easily degraded and the moving range in soil was limit. Flursulamid residues in subsoil were obviously lower than in uppersoil. It indicated the weak moving following water. The farthest distance of lateral movement can reach 60cm and it speed related with dose of pesticide. Besides, lengthways moving was seriously influenced by rainfall and flursulamid moved down to subsoil 60cm. Beta-cypermethrin pesticide residuces reached the maximum after one day and were detected in subsoil 150cm, so it moved down quikly in soil. As a result of stronge moving ability along with water, beta-cypermethrin could move to subsoil 150cm in vertical direction, while distance of lateral movement was 240cm and related with dosage. Thus, beta-cypermethrin which was used with method of pouring nest had potential influence on ground water and edaphon, and rainfall made incidence become bigger. Oppositely the toxic bait scattered with hands brought relatively little influence on surrounding living beings. However, vast dosage applied before and after rainfall could increase relatively potential threation to groundwater. |
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