Study On The Application Techniques Of Controlling Thrips Hawaiiensis By Drip Irrigation

With the fast deveopment of drip irrigation,it has been successfully used in pestcide and fertilizer application in some parts of the world.Numerous studies reported that drip irrigation of pesticides was shown to be effective in control of many pests,such as insects of grape vineyards,weeds of yellow nutsedge of rice,nematodes and foliar arthropods.Spirotetramat and imidacloprid have good internal absorption and conduction properties,and are often used to control various insect pests,such as aphids,psyllas and thrips.In this paper the control efficacy of spirotetramat and imidacloprid on Thrips hawaiiensis by drip irrigation was cleared and the absorption distribution and enrichment of pesticides in banana plant were analyzed,those all would provided a theoretical basis for control T.hawaiiensis.The degration dynamices and final residues of spirotetramat and imidacloprid in fruits,plants and soil were determined,it's wolud enrich theoretical research of drip irrigation and provide the scientific basis for using of pesticides safety by drip irrigation technology.The main results as follows:1 Obtained the insecticides suitable for using drip irrigation to control T.hawaiiensisThe toxicity of 7 kinds of insecticides on T.hawaiiensis was determined by leaf dipping method.The results showed that spirotetramat and imidacloprid had high toxicity on T.hawaiiensis.2 Field control efficacy of spirotetramat and imidacloprid on banana T.hawaiiensis by drip irrigation were clarifiedWhen the application dosages was 504-1008 g(AI)/hm2,the control effciency of spirotetramat on T.hawaiiensis reached 91.24%-95.86%and when the application dosages was 560-11120 g(AI)/hm2,the control efficacy of imidacloprid on T.hawaiiensis reached 85.56%-92.70%.It is indicated that spirotetramat and imidacloprid could effectively control T.hawaiiensis.3 The absorption,distribution and enrichment of spirotetramat and imidacloprid in banana plants after drip irrigation were analyzed.Two hours after drip irrigation,the concentration of imidacloprid at 1 m and 2 m of banana stems reached peak values of 0.434 and 0.391 mg/kg,respectively;and eight hours spirotetramat reached peak values of 0.252 and 0.235 mg/kg,respectively.This showed that the spirotetramat and imidacloprid could be better absorbed and distributed in banana plants after drip irrigation.At different application dosages,the residual concentration of spirotetramat in banana flowers after 1 day by drip application reached peak values of 0.239 and 0.358 mg/kg,respectively.The residual concentration of imidacloprid in the flowers of banana after 2 h by drip application reached the peak 0.414 and 0.673 mg/kg,respectively.Those all indicated that spirotetramat and imidacloprid could be effectively enriched in flowers,but the pesticides concentration in the flowers would not increase proportionally with the application dosages increased.4 The degradation dynamics of spirotetramat and imidacloprid in fruit,leaves and soil of banana after drip irrigation were studied.The degradation rates of spirotetramat and imidacloprid in soil was the fastest,followed by the leaves,in fruits was the slowest.The half-life of spirotetramat in banana leaves and the soil were not changed significantly due to the application dosages changed,and at high and low application dosages the half-life of spirotetramat in banana leaves were 5.37 days and 5.21 days,in soil were 4.59 and 4.47 days,respectively.The half-life of imidacloprid in banana leaves both were 7.00 days.At different application dosages,the half-life of spirotetramat in fruits were 9.63 and 7.88 days,respectively.The half-life of imidacloprid in fruits were 9.24 and 7.07 days,in soil were 6.86 and 5.59 days,respectively.The degradation rate of both were slower when applied at high concentrations.5 The final residues of spirotetramat and imidacloprid in banana fruits,leaves and soil after drip irrigation were assessed.The banana leaves and fruits samples of taken from on the fourteenth and seventh days before harvested had not detected the residues of spirotetramat and imidacloprid.In the soil samples of fourteenth days before the banana harvested,the residues of imidacloprid were detected 0.0042 and 0.0058 mg/kg,respectively.But seventh days before the banana harvested were not detected.