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INSECTICIDE EFFICACY: ALFALFA WEEVIL AND APHIDS IN ALFALFA, 2011

INSECTICIDE EFFICACY: ALFALFA WEEVIL AND APHIDS IN ALFALFA, 2011 Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 (F3) ALFALFA: Medicago sativa L. ‘CUF-101’ Eric T. Natwick University of California Agriculture and Natural Resources Desert Research and Extension Center 1050 E. Holton Rd. Holtville, CA 92250 Phone: (760) 352-9474 Fax: (760) 352-0846 E-mail: etnatwick@ucdavis.edu Martin I. Lopez E-mail: marlopez@ucdavis.edu Egyptian alfalfa weevil (EAW): Hypera brunnipennis (Boheman) Blue alfalfa aphid (BAA): Acyrthosiphon kondoi Shinji Pea aphid (PA): Acyrosiphon pisum (Harris) Cowpea aphid (CPA): Aphis craccivora Koch Spotted alfalfa aphid (SAA): Therioaphis trifolii forma maculata (Buckton) Sevenspotted lady beetle (SSLB): Coccinella septempunctata Linnaeus Aphid parasite (AP): Diaeretiella spp. The objective of the study was to evaluate the efficacy of the new and old insecticidal compounds used against Egyptian alfalfa weevil (EAW), Hypera brunnipennis (Boheman) larvae and aphids (Blue alfalfa aphid (BAA) Acyrthosiphon kondoi Shinji, Pea aphid (PA), Acyrosiphon pisum (Harris), Cowpea aphid (CPA) Aphis craccivora Koch) and Spotted alfalfa aphid (SAA) Therioaphis maculate (Buckton) on alfalfa grown for hay production under desert growing conditions. A field study was conducted during the spring of 2011 at the UC Desert Research and Extension Center. A stand of alfalfa, VAR. CUF 101, was used for the experiment. The experimental design was RCB using four replicates with ten treatments. Plots measured 33.3 ft by 50 ft and insecticide treatments listed in the tables were applied on 8 Mar 2011, using a broadcast application with a tractor mounted boom. Broadcast spray applications were made with a Lee Spider Spray Trac, tractor mounted spray boon, operated at 20 psi delivering 31 gpa, delivered through 17 nozzles (TJ-60 11003VS). EAW and aphid populations were measured in each plot with a standard 15-inch diameter insect net consisting of ten, 180 sweeps. Plots were sampled on the indicated dates and days after treatment (DAT), 2 Mar (7DPT), 11 Mar (3DAT), 15 Mar (7DAT), 22 Mar (14DAT), and 29 Mar (21DAT). Sweep samples were bagged, labeled, and frozen for later counting of EAW larvae and aphids by species. Data sets were analyzed using a 2-way ANOVA and means separated by protected LSD (P ≤ 0.05). All insecticide treatments had means for EAW larvae that were significantly lower than the means for the untreated check on all post- treatment sampling dates except for Centric at 14DAT and 21DAT (Table 1). Danitol provided the highest level of EAW control and residual activity through 21DAT. Pretreatment aphid levels were high and there were no differences among the means for CAP, BAA, and PA for sweep samples (Tables 2-4). Aphid levels diminished quickly over the three weeks following treatments including in the untreated check plots due to high levels of predation from SSLB, Coccinella septempunctata Linnaeus and parasitism by AP, Diaeretiella spp. All insecticide treatments had means for PA that were significantly lower than the means for the untreated check 3DAT and 7DAT (Table 2). All insecticide treatments had means for PA that were significantly lower than the means for the untreated check 14DAT with the exceptions of Mustang and Danitol. None of the insecticide treatments had PA means that were lower than the check 21DAT. All insecticide treatment BAA means were significantly lower than the means for the untreated check 3DAT, 7DAT and 14DAT (Tables 3). None of the insecticide treatments had BAA means that were lower than the check 21DAT. There were few CPA present during the experiment and there were no differences among the CPA post treatment means except at 7DAT when all insecticides treatments except Mustang and Centric had CPA means significantly lower than the check (Table 4). Numbers of SAA were too low to give meaningful results but the treatment means are reported in Table 5. None of the insecticide treatments showed any injury to the alfalfa plants. This research was supported by industry gifts. 1 Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 Table 1. EAW larvae per 10 sweeps y xz x x x Treatment/formulation Rate/oz acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 9.75a 29.88a 13.25a 2.38a 1.63a Mustang 1.5EC 4.3 9.43a 0.25c 0.45c 0.48b 0.63b Stallion 3EC 9.25 8.50a 0.43c 0.08de 0.10bc 0.50b Stallion 3EC 11.75 13.28a 0.30c 0.05de 0.25bc 0.35bc Endigo 2.06 ZC 4.0 11.43a 0.48c 0.18cd 0.25bc 0.65b Endigo ZCX 2.71 ZC 4.0 10.78a 0.45c 0.15cde 0.15bc 0.33b Centric 40 WG 3.5 10.03a 3.73b 3.30b 1.73a 1.98a Voliam Xpress 1.25 ZC 9.0 8.20a 2.83c 0.63c 0.63b 0.28bc Cobalt Advanced 2.63 EC 24.0 6.68 0.35c 0.13de 0.20bc 0.20bc Danitol 2.4 EC 21.3 9.95 0.25c 0.00e 0.0c 0.05c Means within columns followed by the same letter are not significantly different ( LSD; P=0.05). x Log (X+1) transformed data used for analysis, actual means reported. y Pre-treatment on 2 Mar 2011 z Days after treatment. Table 2. Pea aphids per sweep y xz x x Treatment/formulation Rate oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 65.73a 40.85a 10.98a 0.85a 0.75 Mustang 1.5E 4.3 68.43a 0.58c 0.50bc 0.28abc 0.68 Stallion 3EC 9.25 65.60a 0.20c 0.03c 0.00d 0.83 Stallion 3EC 11.75 82.30a 0.33c 0.10bc 0.15bcd 0.08 Endigo 2.06 ZC 4.0 72.73a 0.35c 0.00c 0.03d 0.40 Endigo ZCX 2.71 ZC 4.0 67.08a 0.28c 0.03c 0.00d 0.23 Centric 40 WG 3.5 83.95a 0.48c 0.03c 0.05d 0.95 Voliam Xpress 1.25 ZC 9.0 73.05a 1.13c 0.28bc 0.13bcd 0.33 Cobalt Advanced 2.63 EC 24.0 84.80a 0.13c 0.15bc 0.10cd 0.40 Danitol 2.4 EC 21.3 75.90a 5.93b 1.03b 0.45ab 0.33 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 Mar 2011 Days after treatment. Table 3. Blue alfalfa aphids per sweep y xz x x Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check -- 245.53a 139.68a 28.78a 2.20a 0.83 Mustang 1.5EC 4.3 238.88a 2.43c 1.30b 0.28bc 0.58 Stallion 3EC 9.25 189.85a 0.50de 0.23cde 0.28bc 0.35 Stallion 3EC 11.75 249.13a 0.50e 0.28bcde 0.28bcd 0.63 Endigo 2.06ZC 4.0 257.03a 1.08cde 0.08de 0.18bcd 0.35 Endigo ZCX 2.71ZC 4.0 182.43a 0.83cde 0.00e 0.25bc 0.18 Centric 40WG 3.5 293.95a 2.93c 0.93bc 0.08cd 0.38 Voliam Xpress 1.25ZC 9.0 232.55a 3.50cd 1.00bcde 0.05d 0.58 Cobalt Advanced 2.63EC 24.0 205.05a 0.43e 0.23bcde 0.20bcd 0.48 Danitol 2.4EC 21.3 191.33a 12.43b 1.98bcd 0.55b 0.53 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 March 2011 Days after treatment. 2 Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 Table 4. Cowpea aphid per sweeps y z x Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 2.38a 0.75a 0.38a 0.18aa 0.10a Mustang 1.5EC 4.3 2.55a 0.23a 0.35a 0.00a 0.03a Stallion 3EC 9.25 2.20a 0.08a 0.10bc 0.00a 0.03a Stallion 3EC 11.75 3.35a 0.23a 0.03c 0.10a 0.00a Endigo 2.06ZC 4.0 2.83a 0.20a 0.00c 0.00a 0.00a Endigo ZCX 2.71ZC 4.0 2.43a 0.10a 0.10bc 0.03a 0.05a Centric 40WG 3.5 1.58a 0.40a 0.30ab 0.10a 0.00a Voliam Xpress 1.25ZC 9.0 3.38a 0.38a 0.08bc 0.00a 0.05a Cobalt Advanced 2.63EC 24.0 3.55a 0.18a 0.03c 0.03a 0.00a Danitol 2.4EC 21.3 3.73a 0.13a 0.05c 0.03a 0.05a Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 Mar 2011 Days after treatment. Table 5. Spotted alfalfa aphids per sweep y z Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 0.05 0.13 0.08a 0.00 0.00 Mustang 1.5EC 4.3 0.28 0.08 0.00b 0.00 0.00 Stallion 3EC 9.25 0.35 0.03 0.00b 0.00 0.00 Stallion 3EC 11.75 0.85 0.00 0.00b 0.00 0.00 Endigo 2.06ZC 4.0 0.43 0.05 0.00b 0.00 0.00 Endigo ZCX 2.71ZC 4.0 0.35 0.03 0.00b 0.00 0.00 Centric 40WG 3.5 0.15 0.08 0.00b 0.00 0.00 Voliam Xpress 1.25 ZC 9.0 0.78 0.05 0.00b 0.00 0.00 Cobalt Advanced 2.63EC 24.0 0.33 0.00 0.00b 0.00 0.00 Danitol 2.4EC 21.3 0.33 0.08 0.00b 0.00 0.00 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Pre-treatment on 2 Mar2011 Days after treatment. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Arthropod Management Tests Oxford University Press

INSECTICIDE EFFICACY: ALFALFA WEEVIL AND APHIDS IN ALFALFA, 2011

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Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 (F3) ALFALFA: Medicago sativa L. ‘CUF-101’ Eric T. Natwick University of California Agriculture and Natural Resources Desert Research and Extension Center 1050 E. Holton Rd. Holtville, CA 92250 Phone: (760) 352-9474 Fax: (760) 352-0846 E-mail: etnatwick@ucdavis.edu Martin I. Lopez E-mail: marlopez@ucdavis.edu Egyptian alfalfa weevil (EAW): Hypera brunnipennis (Boheman) Blue alfalfa aphid (BAA): Acyrthosiphon kondoi Shinji Pea aphid (PA): Acyrosiphon pisum (Harris) Cowpea aphid (CPA): Aphis craccivora Koch Spotted alfalfa aphid (SAA): Therioaphis trifolii forma maculata (Buckton) Sevenspotted lady beetle (SSLB): Coccinella septempunctata Linnaeus Aphid parasite (AP): Diaeretiella spp. The objective of the study was to evaluate the efficacy of the new and old insecticidal compounds used against Egyptian alfalfa weevil (EAW), Hypera brunnipennis (Boheman) larvae and aphids (Blue alfalfa aphid (BAA) Acyrthosiphon kondoi Shinji, Pea aphid (PA), Acyrosiphon pisum (Harris), Cowpea aphid (CPA) Aphis craccivora Koch) and Spotted alfalfa aphid (SAA) Therioaphis maculate (Buckton) on alfalfa grown for hay production under desert growing conditions. A field study was conducted during the spring of 2011 at the UC Desert Research and Extension Center. A stand of alfalfa, VAR. CUF 101, was used for the experiment. The experimental design was RCB using four replicates with ten treatments. Plots measured 33.3 ft by 50 ft and insecticide treatments listed in the tables were applied on 8 Mar 2011, using a broadcast application with a tractor mounted boom. Broadcast spray applications were made with a Lee Spider Spray Trac, tractor mounted spray boon, operated at 20 psi delivering 31 gpa, delivered through 17 nozzles (TJ-60 11003VS). EAW and aphid populations were measured in each plot with a standard 15-inch diameter insect net consisting of ten, 180 sweeps. Plots were sampled on the indicated dates and days after treatment (DAT), 2 Mar (7DPT), 11 Mar (3DAT), 15 Mar (7DAT), 22 Mar (14DAT), and 29 Mar (21DAT). Sweep samples were bagged, labeled, and frozen for later counting of EAW larvae and aphids by species. Data sets were analyzed using a 2-way ANOVA and means separated by protected LSD (P ≤ 0.05). All insecticide treatments had means for EAW larvae that were significantly lower than the means for the untreated check on all post- treatment sampling dates except for Centric at 14DAT and 21DAT (Table 1). Danitol provided the highest level of EAW control and residual activity through 21DAT. Pretreatment aphid levels were high and there were no differences among the means for CAP, BAA, and PA for sweep samples (Tables 2-4). Aphid levels diminished quickly over the three weeks following treatments including in the untreated check plots due to high levels of predation from SSLB, Coccinella septempunctata Linnaeus and parasitism by AP, Diaeretiella spp. All insecticide treatments had means for PA that were significantly lower than the means for the untreated check 3DAT and 7DAT (Table 2). All insecticide treatments had means for PA that were significantly lower than the means for the untreated check 14DAT with the exceptions of Mustang and Danitol. None of the insecticide treatments had PA means that were lower than the check 21DAT. All insecticide treatment BAA means were significantly lower than the means for the untreated check 3DAT, 7DAT and 14DAT (Tables 3). None of the insecticide treatments had BAA means that were lower than the check 21DAT. There were few CPA present during the experiment and there were no differences among the CPA post treatment means except at 7DAT when all insecticides treatments except Mustang and Centric had CPA means significantly lower than the check (Table 4). Numbers of SAA were too low to give meaningful results but the treatment means are reported in Table 5. None of the insecticide treatments showed any injury to the alfalfa plants. This research was supported by industry gifts. 1 Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 Table 1. EAW larvae per 10 sweeps y xz x x x Treatment/formulation Rate/oz acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 9.75a 29.88a 13.25a 2.38a 1.63a Mustang 1.5EC 4.3 9.43a 0.25c 0.45c 0.48b 0.63b Stallion 3EC 9.25 8.50a 0.43c 0.08de 0.10bc 0.50b Stallion 3EC 11.75 13.28a 0.30c 0.05de 0.25bc 0.35bc Endigo 2.06 ZC 4.0 11.43a 0.48c 0.18cd 0.25bc 0.65b Endigo ZCX 2.71 ZC 4.0 10.78a 0.45c 0.15cde 0.15bc 0.33b Centric 40 WG 3.5 10.03a 3.73b 3.30b 1.73a 1.98a Voliam Xpress 1.25 ZC 9.0 8.20a 2.83c 0.63c 0.63b 0.28bc Cobalt Advanced 2.63 EC 24.0 6.68 0.35c 0.13de 0.20bc 0.20bc Danitol 2.4 EC 21.3 9.95 0.25c 0.00e 0.0c 0.05c Means within columns followed by the same letter are not significantly different ( LSD; P=0.05). x Log (X+1) transformed data used for analysis, actual means reported. y Pre-treatment on 2 Mar 2011 z Days after treatment. Table 2. Pea aphids per sweep y xz x x Treatment/formulation Rate oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 65.73a 40.85a 10.98a 0.85a 0.75 Mustang 1.5E 4.3 68.43a 0.58c 0.50bc 0.28abc 0.68 Stallion 3EC 9.25 65.60a 0.20c 0.03c 0.00d 0.83 Stallion 3EC 11.75 82.30a 0.33c 0.10bc 0.15bcd 0.08 Endigo 2.06 ZC 4.0 72.73a 0.35c 0.00c 0.03d 0.40 Endigo ZCX 2.71 ZC 4.0 67.08a 0.28c 0.03c 0.00d 0.23 Centric 40 WG 3.5 83.95a 0.48c 0.03c 0.05d 0.95 Voliam Xpress 1.25 ZC 9.0 73.05a 1.13c 0.28bc 0.13bcd 0.33 Cobalt Advanced 2.63 EC 24.0 84.80a 0.13c 0.15bc 0.10cd 0.40 Danitol 2.4 EC 21.3 75.90a 5.93b 1.03b 0.45ab 0.33 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 Mar 2011 Days after treatment. Table 3. Blue alfalfa aphids per sweep y xz x x Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check -- 245.53a 139.68a 28.78a 2.20a 0.83 Mustang 1.5EC 4.3 238.88a 2.43c 1.30b 0.28bc 0.58 Stallion 3EC 9.25 189.85a 0.50de 0.23cde 0.28bc 0.35 Stallion 3EC 11.75 249.13a 0.50e 0.28bcde 0.28bcd 0.63 Endigo 2.06ZC 4.0 257.03a 1.08cde 0.08de 0.18bcd 0.35 Endigo ZCX 2.71ZC 4.0 182.43a 0.83cde 0.00e 0.25bc 0.18 Centric 40WG 3.5 293.95a 2.93c 0.93bc 0.08cd 0.38 Voliam Xpress 1.25ZC 9.0 232.55a 3.50cd 1.00bcde 0.05d 0.58 Cobalt Advanced 2.63EC 24.0 205.05a 0.43e 0.23bcde 0.20bcd 0.48 Danitol 2.4EC 21.3 191.33a 12.43b 1.98bcd 0.55b 0.53 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 March 2011 Days after treatment. 2 Arthropod Management Tests 2012, Vol. 37 doi: 10.4182/amt.2012.F3 Table 4. Cowpea aphid per sweeps y z x Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 2.38a 0.75a 0.38a 0.18aa 0.10a Mustang 1.5EC 4.3 2.55a 0.23a 0.35a 0.00a 0.03a Stallion 3EC 9.25 2.20a 0.08a 0.10bc 0.00a 0.03a Stallion 3EC 11.75 3.35a 0.23a 0.03c 0.10a 0.00a Endigo 2.06ZC 4.0 2.83a 0.20a 0.00c 0.00a 0.00a Endigo ZCX 2.71ZC 4.0 2.43a 0.10a 0.10bc 0.03a 0.05a Centric 40WG 3.5 1.58a 0.40a 0.30ab 0.10a 0.00a Voliam Xpress 1.25ZC 9.0 3.38a 0.38a 0.08bc 0.00a 0.05a Cobalt Advanced 2.63EC 24.0 3.55a 0.18a 0.03c 0.03a 0.00a Danitol 2.4EC 21.3 3.73a 0.13a 0.05c 0.03a 0.05a Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Log (X+1) transformed data used for analysis, actual means reported. Pre-treatment on 2 Mar 2011 Days after treatment. Table 5. Spotted alfalfa aphids per sweep y z Treatment/formulation oz/acre 7DPT 3DAT 7DAT 14DAT 21DAT Check - 0.05 0.13 0.08a 0.00 0.00 Mustang 1.5EC 4.3 0.28 0.08 0.00b 0.00 0.00 Stallion 3EC 9.25 0.35 0.03 0.00b 0.00 0.00 Stallion 3EC 11.75 0.85 0.00 0.00b 0.00 0.00 Endigo 2.06ZC 4.0 0.43 0.05 0.00b 0.00 0.00 Endigo ZCX 2.71ZC 4.0 0.35 0.03 0.00b 0.00 0.00 Centric 40WG 3.5 0.15 0.08 0.00b 0.00 0.00 Voliam Xpress 1.25 ZC 9.0 0.78 0.05 0.00b 0.00 0.00 Cobalt Advanced 2.63EC 24.0 0.33 0.00 0.00b 0.00 0.00 Danitol 2.4EC 21.3 0.33 0.08 0.00b 0.00 0.00 Means within columns followed by the same letter are not significantly different (LSD; P=0.05) Pre-treatment on 2 Mar2011 Days after treatment.

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Arthropod Management TestsOxford University Press

Published: Jan 1, 2012

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