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CONTROL OF APHIDS ON POTATOES USING FOLIAR INSECTICIDES, 2002

CONTROL OF APHIDS ON POTATOES USING FOLIAR INSECTICIDES, 2002 (E48) POTATO: Solanum tuberosum L., 'Red La Soda' Jeffrey A. Davis Department of Entomology University of Minnesota 1980 Folwell Avenue, Room 219 St Paul, MN 55108 Tel: (612) 624-2751 Fax: (612) 625-5299 davis271@tc.umn.edu Edward B. Radcliffe David W. Ragsdale Green peach aphid (GPA): Myzus persicae (Sulzer) Potato aphid (PA): Macrosiphum euphorbiae (Thomas) Insecticide trials to evaluate the control of the green peach aphid (GPA) and potato aphid (PA) were conducted at the University of Minnesota Agricultural Experiment Station at Rosemount. 'Red La Soda' potatoes were planted on 20 and 21 May at a rate of 20 bags/acre or 19,000 plants/acre. Plots were four- rows wide, 50-ft long, with 36 inch between rows and 12 inch between plants. Treatments were arranged in a completely randomized design with four replications each. All plots received a weekly application of Bravo ZN at a rate of 1--2 pt/acre for late blight control and Guthion at a rate of 1 lb/acre to control potato leafhoppers and Colorado potato beetles and flare aphids. Applications were made on 24 Aug with a CO sprayer with T-jet nozzles, a carrier volume of 30 gpa, a spray pressure of 45 psi and a ground speed of 3.5 mph. Nozzles were spaced evenly across four rows on 18" centers and the boom adjusted in height so that there was 100% overlap 12 inches below the top of the canopy. The weather conditions for the day were zero precipitation, a wind speed of 5-10 mph, a maximum temperature of 73°F and a minimum temperature of 57°F. Sampling consisted of counting aphids on 35 mid-potato plant leaves per plot. Pre-treatment counts were conducted on 22 Aug. Post-treatment counts were made on 27 and 30 Aug. Percent control was calculated as (1 - (treatment count/untreated check count)) x 100 for that day. ANOVA was performed following transformation of count data using log (x+1). The level of significance was set at P = 0.05 and the Ryan--Einot--Gabriel--Welsch Multiple Range Test was used to separate means. The results are summarized in Tables 1 and 2. At the pre-treatment count, aphid density was about 40-fold the economic threshold (based on 30 aphids per 100 potato leaves in commercial potatoes). Dinotefuran 20SG failed to control either GPAs or PAs. In fact, it seemed to flare GPAs. None of the products kept GPA populations under the economic threshold six days after treatment. Why it took six days for these chemical products to suppress aphid populations is not clear. One suggestion is that because of high humidity in the days following application, dead aphids may not have desiccated as rapidly as normal and some may have been mistakenly counted as still alive. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arthropod Management Tests Oxford University Press

CONTROL OF APHIDS ON POTATOES USING FOLIAR INSECTICIDES, 2002

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Oxford University Press
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© Published by Oxford University Press.
eISSN
2155-9856
DOI
10.1093/amt/28.1.E48
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Abstract

(E48) POTATO: Solanum tuberosum L., 'Red La Soda' Jeffrey A. Davis Department of Entomology University of Minnesota 1980 Folwell Avenue, Room 219 St Paul, MN 55108 Tel: (612) 624-2751 Fax: (612) 625-5299 davis271@tc.umn.edu Edward B. Radcliffe David W. Ragsdale Green peach aphid (GPA): Myzus persicae (Sulzer) Potato aphid (PA): Macrosiphum euphorbiae (Thomas) Insecticide trials to evaluate the control of the green peach aphid (GPA) and potato aphid (PA) were conducted at the University of Minnesota Agricultural Experiment Station at Rosemount. 'Red La Soda' potatoes were planted on 20 and 21 May at a rate of 20 bags/acre or 19,000 plants/acre. Plots were four- rows wide, 50-ft long, with 36 inch between rows and 12 inch between plants. Treatments were arranged in a completely randomized design with four replications each. All plots received a weekly application of Bravo ZN at a rate of 1--2 pt/acre for late blight control and Guthion at a rate of 1 lb/acre to control potato leafhoppers and Colorado potato beetles and flare aphids. Applications were made on 24 Aug with a CO sprayer with T-jet nozzles, a carrier volume of 30 gpa, a spray pressure of 45 psi and a ground speed of 3.5 mph. Nozzles were spaced evenly across four rows on 18" centers and the boom adjusted in height so that there was 100% overlap 12 inches below the top of the canopy. The weather conditions for the day were zero precipitation, a wind speed of 5-10 mph, a maximum temperature of 73°F and a minimum temperature of 57°F. Sampling consisted of counting aphids on 35 mid-potato plant leaves per plot. Pre-treatment counts were conducted on 22 Aug. Post-treatment counts were made on 27 and 30 Aug. Percent control was calculated as (1 - (treatment count/untreated check count)) x 100 for that day. ANOVA was performed following transformation of count data using log (x+1). The level of significance was set at P = 0.05 and the Ryan--Einot--Gabriel--Welsch Multiple Range Test was used to separate means. The results are summarized in Tables 1 and 2. At the pre-treatment count, aphid density was about 40-fold the economic threshold (based on 30 aphids per 100 potato leaves in commercial potatoes). Dinotefuran 20SG failed to control either GPAs or PAs. In fact, it seemed to flare GPAs. None of the products kept GPA populations under the economic threshold six days after treatment. Why it took six days for these chemical products to suppress aphid populations is not clear. One suggestion is that because of high humidity in the days following application, dead aphids may not have desiccated as rapidly as normal and some may have been mistakenly counted as still alive.

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Arthropod Management TestsOxford University Press

Published: Jan 1, 2003

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