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Low Volume Application of Pesticides in Cotton Aphid Control

Author: ZhuYuKun
Tutor: WangKaiYun
School: Shandong Agricultural University
Course: Pesticides
Keywords: Aphis gossypii (Glover) low volume application droplet density deposition control effect
CLC: S435.622.1
Type: Master's thesis
Year: 2013
Downloads: 18
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Abstract


The low volume application of pesticide was studied to improve the utility of pesticides,increase the deposition rate of pesticides on cotton and reduce the run off rate of pesticides incotton field. The deposition of pesticide on cotton was studied with the spray tower of ASS-4using four hollow cone nozzles with different droplet sizes by adding tracer allura red ininsecticides solution. Droplet density was detected with a water sensitive card to investigatethe effect of action mode of pesticides on the interaction of droplet density and mortality ofcotton aphid (Aphis gossypii (Glover)). In field trials, lever-operated knapsack sprayer andknapsack mist blower were used to spray acetamiprid at cotton seedling stage andpymetrozine in adult cotton stage at different spray volumes. The deposition of the twopesticides on different stages of cotton was studied to determine the best spray method andspray volume in reducing run-off rate. And at the seedling stage, the relationship betweendroplet density of3%acetamiprid sprayed with knapsack mist blower and the control effectagainst cotton aphid was studied to provide a reference for the field spray application. Theresults are as below:1. The VMD of droplet sprayed with four nozzles were146.6,173.2,190.3and220.1μm,respectively. When pymetrozine was sprayed at150g/ha with the four nozzles at the samespray volume of225L/ha, the most deposition on cotton leaves was observed at the VMD of146.6μm. The deposition decreased as the droplet size increased and the deposition ofpymetrozine at the VMD of146.6μm was two-fold to the deposition at the VMD of220.1μm. The droplet of190.3and220.1μm almost had the same deposition. When pymetrozinewas sprayed at the dose of150g/ha with different nozzles at different spray volume, the146.6μm and153L/ha combination obtained the most deposition of2.3μg/cm~2. The depositiondecreased significantly when the VMD of droplets reached190.3μm. The deposition of220.1μm,447L/ha combination and190.3μm,354L/ha combination had no significant difference.It is beneficial to the deposition on cotton when pesticides were sprayed with a small dropletsize nozzle and low spray volume.2. Systemic acetamiprid and contact insecticide pyridaben were sprayed to control cottonaphids, and the mortality of aphids increased as the droplet density or concentration increased when the mortalities were low. The mortalities were82.8%and100%, respectively for0.05and0.1g/L acetamiprid at the density of238particles cm-2. When acetamiprid was sprayed athigher concentration of1.0and5.0g/L, the mortalities of aphid were still high even thedroplet density was reduced to43.2particles cm-2. While, the mortality of aphid was not highwhen high concentration of pyridaben was sprayed at a low droplet density. The mortalitieswere54.8%and41.6%for2and4g/L pyridaben at the droplet density of43.2particles cm-2.The results showed that systemic insecticides could be sprayed at a reduced droplet density byincreasing concentration, while plenty of droplet depositions are needed for contact pesticidesto attain a high mortality of cotton aphid.3. At the seedling stage, when3%acetamiprid EC was applied with mist blower at thedose of450mL/ha, the run-off rates were24.4%,28.9%and26.7%at volume rate of75,150and225L/ha, respectively. The run-off rates of3%acetamiprid EC sprayed withlever-operated knapsack sprayer at volume of300,450and600L/ha were35.6%,37.8%and46.7%, respectively. Efficacy of acetamiprid against cotton aphids applied with two spraymethods at different volume rates had no significant difference. At the adult-plant stage, when25%pymetrozine WP was applied at dose of300g/ha, the run-off rates of pymetrozinesprayed with lever-operated knapsack sprayer at volume of600L/ha and mist blower of150L/ha were13.3%and3.3%, respectively. The control effect of pymetrozine applied with mistblower at150and300L/ha at the dose of225g/ha had no significant difference withapplication of lever-operated sprayer at600L/ha at the dose of300g/ha. In summary, lowvolume spray using mist blower could be benefit not only to reduce the insecticide dosageused in cotton field for aphid management, it could be valuable to decrease the run-off rate ofinsecticide on soil and reduce the influence on environment risk.4. The effects of2g/L acetamiprid against cotton aphid7days after application were31.6%,49.1%,78.6%,88.6%and91.9%, respectively for the droplet density of19,62,118,191and296particles cm-2. The efficacy increased as droplet density of acetamiprid increase.When the droplet density reached191particles cm-2, the efficacy had no significant differencewith that of296particles cm-2. The effects of4g/L acetamiprid against cotton aphid7daysafter application were69.7%,86.0%,91.7%,94.2%and93.9%, respectively for the droplet density of43,72,104,166and206particles cm-2. When the droplet density reached104particles cm-2, the efficacy was not significantly different from the higher droplet densities.It’s enough to control cotton aphid at191and104particles cm-2for2and4g/L acetamiprid,respectively, when it was sprayed with a knapsack mistblower. Pesticides applicators couldrefer to the photo of droplet density and adjust their operation when spray acetamiprid tocontrol aphid in cotton field.

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CLC: > Agricultural Sciences > Plant Protection > Pest and Disease Control > Crop pests and diseases and their prevention > Economic crop pests and diseases > Fiber crop pests and diseases > Cotton pests and diseases > Insect pest > Cotton aphid
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