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SYSTEMIC EFFICACY OF RYNAXYPYR APPLIED THROUGH DRIP IRRIGATION ON FALL LETTUCE, 2006

SYSTEMIC EFFICACY OF RYNAXYPYR APPLIED THROUGH DRIP IRRIGATION ON FALL LETTUCE, 2006 (E25) LETTUCE (HEAD): Lactuca sativa var. capitata L. ‘Beacon’ SYSTEMIC EFFICACY OF RYNAXYPYR APPLIED THROUGH DRIP IRRIGATION ON FALL LETTUCE, John C. Palumbo University of Arizona Department of Entomology Yuma Agricultural Center th 6425 W. 8 St. Yuma, Arizona 85364 Phone: (928) 782-3836 Fax: (928) 782-1940 E-mail: jpalumbo@ag.arizona.edu Cabbage looper (CL): Trichoplusia ni (Hübner) Beet armyworm (BAW): Spodoptera exigua (Hübner) Corn earworm (CEW): Helicoverpa zea (Boddie) Leafminer (LM): Liriomyza spp. The objective of the study was to evaluate the systemic efficacy of the new compound Rynaxypyr when applied to head lettuce using drip irrigation under desert growing conditions. Lettuce was direct seeded on 14 Sep 2006at the Yuma Valley Agricultural Center, Yuma, AZ into double row beds on 42 inch centers. Stand establishment was achieved using overhead sprinkler irrigation and irrigated thereafter using a sub-surface irrigation system with emitters at 8” spacing; tape was placed 6” below the soil surface. Plots were four beds wide by 55 ft long and bordered by two untreated beds. Four replications of each treatment were arranged in a RCB design. Formulations and rates for each compound are provided in the tables. Soil applications were made by diluting formulated material in 2 gal of water and metering the total volume into the plots using a Venturi type injection system Drip chemigations were made over a 10 h period by allowing the system to run for 1 h, injecting each material through the system for 45 min duration and then flushing the system for a 8 h period. A subsequent irrigation was made 4 days following each injection. Drip chemigations were made on 6 Oct, 14 Oct and 23 Oct. Rynaxypyr treatments were buffered down to a pH of 4.7 by adding New Balance at 0.25% v/v to each solution before each injection. Evaluation of lepidopterous larvae efficacy was based on the number of live larvae per plant. Ten plants per replicate were destructively sampled on each sample date. The sample unit consisted of examination of whole plants for presence of small and large BAW, CL and CEW. At harvest (5 Dec), 20 mature plants per plot were randomly selected and assessed for presence feeding damage and frass on the heads as well as presence of larvae. A damage assessment of leafminer activity was conducted by counting all the visible mines present on leaves on 22 Nov. Assessments were made from 6 randomly selected plants and counting mines on 5 leaves/plant from the basal node positions 5-10. Treatment means were analyzed using a 1-way ANOVA and means separated by a protected LSD . (P < 0.05) Initially we had planned to measure Rynaxypyr and Admire efficacy against sweetpotato whiteflies but the population was very low during the study and data was not collected. However, BAW, CL and LM pressure was moderate-heavy. Pre- application counts for BAW were 1.3 small and 1.3 large larvae per 10 plants, and for CL were 3.3 small and 3.8 large larvae per 10 plants. At 7 d following the first chemigation, no significant differences were observed between the Rynaxypyr treatments and the untreated control (Table 1). By the second chemigation however, numbers of CL and BAW larvae were significantly reduced in both Rynaxypyr treatments compared with the check. Larval numbers in the Rynaxypyr treatments remained very low following the third application and for the remainder of the trial. At harvest (43- DAT #3), head damage and contamination was negligible in the Rynaxypyr treatments compared with the Admire Pro and untreated check which were considerably higher than the USDA grading standards for marketable head lettuce (Table 2). In addition, assessments made at 30-DAT #3 showed that Rynaxypyr provided highly significant control of LM. The results of this trial suggest that Rynaxypyr has acceptable systemic activity against key lepidopterous larvae and leafminers in lettuce when applied via sub-surface chemigation in desert growing conditions. No phytotoxicity was observed. Table 1 Mean larvae/10 plants 13-Oct 20-Oct 30-Oct Treatment Rate /acre CL BAW CEW CL BAW CEW CL BAW CEW Rynaxypyr 1.6 SC 3.4 fl oz 16.3a 0.9a 0.3a 12.5b 0.9b 0.0a 0.6b 0.0a 0.0a Rynaxypyr 1.6 SC 5.1 fl oz 12.2a 1.8a 0.6a 2.5b 0.0b 0.0a 0.0b 0.0a 0.0a Admire Pro 7 fl oz 24.1a 0.6a 0.0a 28.1a 4.3a 0.3a 15.9a 0.3a 0.0a UTC --- 17.8a 0.6a 0.0a 25.6a 4.7a 0.3a 17.5a 0.3a 0.0a Mean larvae/10 plants 6-Nov 15-Nov 22-Nov Treatment Rate /acre CL BAW CEW CL BAW CEW CL BAW CEW Rynaxypyr 1.6 SC 3.4 fl oz 0.4b 0.4a 0.0a 0.0b 0.0a 0.0b 0.0b 0.0a 0.0a Rynaxypyr 1.6 SC 5.1 fl oz 0.0b 0.0a 0.0a 0.0b 0.0a 0.0b 0.0b 0.0a 0.0a Admire Pro 7 fl oz 21.7a 0.0a 0.0a 10.8a 0.5a 0.8a 5.8a 0.0a 0.4a UTC --- 19.2a 0.0a 0.0a 11.2a 0.8a 1.0a 4.8a 0.0a 0.0a Means followed by the same letter are not significantly different, ANOVA; protected LSD (P > 0.05) Table 2. Lep feeding damage Leafminer % Heads infested with larvae damage % damaged % heads Treatment Rate /acre (mines/leaf) heads with frass CL BAW CEW Total Rynaxypyr 1.6 SC 3.4 fl oz 0.06b 2.5b 0.0b 0.0b 0.0a 0.0b 0.0b Rynaxypyr 1.6 SC 5.1 fl oz 0.01b 2.5b 0.0b 0.0b 0.0a 00b 0.0b Admire Pro 7 fl oz 1.72a 72.5a 75.0a 12.5a 0.0a 7.5a 20.0a UTC --- 1.94a 75.0a 82.5a 7.5a 0.0a 10.0a 17.5a Means followed by the same letter are not significantly different, ANOVA; protected LSD (P > 0.05) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arthropod Management Tests Oxford University Press

SYSTEMIC EFFICACY OF RYNAXYPYR APPLIED THROUGH DRIP IRRIGATION ON FALL LETTUCE, 2006

Arthropod Management Tests , Volume 32 (1) – Jan 1, 2007

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Publisher
Oxford University Press
Copyright
© Published by Oxford University Press.
eISSN
2155-9856
DOI
10.1093/amt/32.1.E25
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Abstract

(E25) LETTUCE (HEAD): Lactuca sativa var. capitata L. ‘Beacon’ SYSTEMIC EFFICACY OF RYNAXYPYR APPLIED THROUGH DRIP IRRIGATION ON FALL LETTUCE, John C. Palumbo University of Arizona Department of Entomology Yuma Agricultural Center th 6425 W. 8 St. Yuma, Arizona 85364 Phone: (928) 782-3836 Fax: (928) 782-1940 E-mail: jpalumbo@ag.arizona.edu Cabbage looper (CL): Trichoplusia ni (Hübner) Beet armyworm (BAW): Spodoptera exigua (Hübner) Corn earworm (CEW): Helicoverpa zea (Boddie) Leafminer (LM): Liriomyza spp. The objective of the study was to evaluate the systemic efficacy of the new compound Rynaxypyr when applied to head lettuce using drip irrigation under desert growing conditions. Lettuce was direct seeded on 14 Sep 2006at the Yuma Valley Agricultural Center, Yuma, AZ into double row beds on 42 inch centers. Stand establishment was achieved using overhead sprinkler irrigation and irrigated thereafter using a sub-surface irrigation system with emitters at 8” spacing; tape was placed 6” below the soil surface. Plots were four beds wide by 55 ft long and bordered by two untreated beds. Four replications of each treatment were arranged in a RCB design. Formulations and rates for each compound are provided in the tables. Soil applications were made by diluting formulated material in 2 gal of water and metering the total volume into the plots using a Venturi type injection system Drip chemigations were made over a 10 h period by allowing the system to run for 1 h, injecting each material through the system for 45 min duration and then flushing the system for a 8 h period. A subsequent irrigation was made 4 days following each injection. Drip chemigations were made on 6 Oct, 14 Oct and 23 Oct. Rynaxypyr treatments were buffered down to a pH of 4.7 by adding New Balance at 0.25% v/v to each solution before each injection. Evaluation of lepidopterous larvae efficacy was based on the number of live larvae per plant. Ten plants per replicate were destructively sampled on each sample date. The sample unit consisted of examination of whole plants for presence of small and large BAW, CL and CEW. At harvest (5 Dec), 20 mature plants per plot were randomly selected and assessed for presence feeding damage and frass on the heads as well as presence of larvae. A damage assessment of leafminer activity was conducted by counting all the visible mines present on leaves on 22 Nov. Assessments were made from 6 randomly selected plants and counting mines on 5 leaves/plant from the basal node positions 5-10. Treatment means were analyzed using a 1-way ANOVA and means separated by a protected LSD . (P < 0.05) Initially we had planned to measure Rynaxypyr and Admire efficacy against sweetpotato whiteflies but the population was very low during the study and data was not collected. However, BAW, CL and LM pressure was moderate-heavy. Pre- application counts for BAW were 1.3 small and 1.3 large larvae per 10 plants, and for CL were 3.3 small and 3.8 large larvae per 10 plants. At 7 d following the first chemigation, no significant differences were observed between the Rynaxypyr treatments and the untreated control (Table 1). By the second chemigation however, numbers of CL and BAW larvae were significantly reduced in both Rynaxypyr treatments compared with the check. Larval numbers in the Rynaxypyr treatments remained very low following the third application and for the remainder of the trial. At harvest (43- DAT #3), head damage and contamination was negligible in the Rynaxypyr treatments compared with the Admire Pro and untreated check which were considerably higher than the USDA grading standards for marketable head lettuce (Table 2). In addition, assessments made at 30-DAT #3 showed that Rynaxypyr provided highly significant control of LM. The results of this trial suggest that Rynaxypyr has acceptable systemic activity against key lepidopterous larvae and leafminers in lettuce when applied via sub-surface chemigation in desert growing conditions. No phytotoxicity was observed. Table 1 Mean larvae/10 plants 13-Oct 20-Oct 30-Oct Treatment Rate /acre CL BAW CEW CL BAW CEW CL BAW CEW Rynaxypyr 1.6 SC 3.4 fl oz 16.3a 0.9a 0.3a 12.5b 0.9b 0.0a 0.6b 0.0a 0.0a Rynaxypyr 1.6 SC 5.1 fl oz 12.2a 1.8a 0.6a 2.5b 0.0b 0.0a 0.0b 0.0a 0.0a Admire Pro 7 fl oz 24.1a 0.6a 0.0a 28.1a 4.3a 0.3a 15.9a 0.3a 0.0a UTC --- 17.8a 0.6a 0.0a 25.6a 4.7a 0.3a 17.5a 0.3a 0.0a Mean larvae/10 plants 6-Nov 15-Nov 22-Nov Treatment Rate /acre CL BAW CEW CL BAW CEW CL BAW CEW Rynaxypyr 1.6 SC 3.4 fl oz 0.4b 0.4a 0.0a 0.0b 0.0a 0.0b 0.0b 0.0a 0.0a Rynaxypyr 1.6 SC 5.1 fl oz 0.0b 0.0a 0.0a 0.0b 0.0a 0.0b 0.0b 0.0a 0.0a Admire Pro 7 fl oz 21.7a 0.0a 0.0a 10.8a 0.5a 0.8a 5.8a 0.0a 0.4a UTC --- 19.2a 0.0a 0.0a 11.2a 0.8a 1.0a 4.8a 0.0a 0.0a Means followed by the same letter are not significantly different, ANOVA; protected LSD (P > 0.05) Table 2. Lep feeding damage Leafminer % Heads infested with larvae damage % damaged % heads Treatment Rate /acre (mines/leaf) heads with frass CL BAW CEW Total Rynaxypyr 1.6 SC 3.4 fl oz 0.06b 2.5b 0.0b 0.0b 0.0a 0.0b 0.0b Rynaxypyr 1.6 SC 5.1 fl oz 0.01b 2.5b 0.0b 0.0b 0.0a 00b 0.0b Admire Pro 7 fl oz 1.72a 72.5a 75.0a 12.5a 0.0a 7.5a 20.0a UTC --- 1.94a 75.0a 82.5a 7.5a 0.0a 10.0a 17.5a Means followed by the same letter are not significantly different, ANOVA; protected LSD (P > 0.05)

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Arthropod Management TestsOxford University Press

Published: Jan 1, 2007

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