Foliar applied insecticide control of the Soybean Aphid (2015)

Transcription

1 Foliar applied insecticide control of the Soybean Aphid (2015) Bruce Potter, University of Minnesota Extension IPM Specialist Travis Vollmer, Plot Technician University of Minnesota Department of Entomology, University of Minnesota Southwest Research and Outreach Center Summary During 2015, the performance of insecticides on the soybean aphid, Aphis glycines Matsamura (SBA), was evaluated at the University of Minnesota Southwest Research and Outreach Center near Lamberton, MN. Seven (7) insecticides, one fungicide, insecticide/fungicide combinations and a water treated control were compared with in a randomized block design with four replications. The insecticides and fungicides evaluated were: the pyrethroids alpha-cypermethrin (Fastac EC), zeta-cypermethrin + bifenthrin (Hero EW), bifenthrin (Tundra EC), and lambda-cyhalothrin (Warrior II); an organophosphate chlorpyrifos (Lorsban Advanced); two rates of a pyrethroid plus neonicotinoid premix lambda-cyhalothrin + thiomethoxam (Endigo ZC), and the fungicide premix pyraclostrobin plus fluxapyroxad (Priaxor). The pesticide treatments were applied on July 31, 2015 to R4 stage soybeans. The SBA population was approximately 450 aphids per whole plant distributed more or less uniformly throughout the trial area. Throughout the trial, the untreated control had higher numbers of SBA/plant than all insecticide treatments. By August 3, three days after application, all insecticides had fewer aphids than the control. The fungicide treatment had a temporary reduction in SBA populations at 3 days after treatment but this was no longer observed at the 7 DAT and later assessments. Three insecticide treatments had less SBA control than the best performing treatments. Treatments with insecticide treatments yielded more than those without. The fungicide treatment yielded more than the untreated check but the addition of fungicide to insecticide did not reduce yield. Background The soybean aphid, Aphis glycines Matsumura (SBA), is the insect pest most consistently damaging to Minnesota soybeans. In Southwest Minnesota, populations of SBA have reached the 250 aphids/plant economic threshold every growing season since the 2003 growing season, with SBA populations varying in distribution and severity each year. Over this time, insecticide performance issues were rarely reported. This trial was designed to look at aphid control and resultant yield differences between insecticide products. The products in this trial represent a range in insecticide group, and soybean aphid control efficacy. Methods This trial was located at the University of Minnesota, Southwest Research and Outreach Center, Lamberton, MN. Site, experimental design, treatments, and application methods are presented in Table 1. The growing season was characterized by moderate temperatures, timely rainfall and exceptional yields. Weather details can be found at

2 The trial was placed within a field of Pioneer 22T69 soybeans planted May 1 with a sixrow, 30-inch row space planter (John Deere 7200 Max Emerge II, John Deere, Moline, IL). Alleys between replicate blocks were cut into the bulk planted field with a 55-inch wide rotary tiller (John Deere 655, John Deere, Moline, IL) the day before insecticide application. Soybean aphid populations were reflective of neighboring fields in the geographic area with early, uniform colonization and rapid population increases beginning in mid-july. Insecticides and fungicides were evaluated in a randomized block design with four replications. Insecticide applications were made using a two-man boom sprayer pressurized with CO 2 (R& D Sprayers, Opelousas, LA) spraying the center four rows of each six row plot. Eight (8) TeeJet 8001XR nozzles (TeeJet Technologies) placed on 15-inch centers applied 15 gallons/acre water at approximately 38 PSI. Application, agronomic and site environmental information and application information are given in Table 1. Pesticide treatments consisted of the following products and per acre rates: Tundra EC insecticide at 5 fl. oz., Hero EW insecticide at 5.1 fl. oz. plus COC at 1% V/V, Warrior II Insecticide at 1.6 fl. oz., Warrior II at 1.6 fl. oz. plus Priaxor fungicide at 4 fl. oz. plus NIS at 0.25% V/V, Lorsban Advanced insecticide at 16 fl. oz., Transform Insecticide at 0.75 oz., Fastac EC insecticide at 3.8 fl. oz. plus NIS at 0.25% V/V, Priaxor at 4 fl. oz., Transform at 0.75 oz. plus Priaxor at 4 fl. oz. plus NIS at 0.25% V/V, Endigo ZC insecticide at 3.5 fl. oz. plus 1% V/V crop oil concentrate, Endigo ZC at 4.5 fl. oz. plus 1% V/V crop oil concentrate. The untreated control consisted of water alone. On July 31, the insecticide treatments were applied to R4 stage soybeans with an average of 450 soybean aphids/plant. Aphid populations at a given sample period were assessed as aphids counted on a whole plant and based on a sample of five plants for each plot. Yields were taken from the center two rows of each plot using a plot combine (ALMACO, Nevada, IA) and adjusted to 13.5% moisture. Results and discussion Aphid control and yield results by treatment are presented in Table 2. At 3 days after treatment (DAT) and thereafter, the untreated control had higher numbers of SBA/plant than all insecticide treatments. Tundra and Hero had the fewest SBA/plant. Priaxor, Fastac, Warrior II and Transform (with and without Priaxor) had the highest SBA populations but were less than the untreated control. After the initial 3 DAT reduction, the Priaxor fungicide treatment was equivalent to the untreated. By August 7, 7 DAT, insecticide treatments containing Warrior II or Fastac had more SBA aphids than others. Lorsban Advanced had the fewest SBA.

3 By 14 DAT, treatments containing Endigo ZC, Lorsban Advanced and Transform plus Priaxor had the fewest aphids. By 21 DAT, treatments containing Endigo ZC, Lorsban Advanced and Transform had the fewest aphids. Hero EW and Tundra EC had more aphids than the best performing treatments but less than those with Warrior II. Table 1. Site and application information County: Redwood, MN Nearest town: Lamberton, MN Soil type: Normania loam Fertility: Soil test values (2012) 11 ppm P 152 ppm K 5.6 ph 4.0% O.M. Previous Crop: 2013 Soybean, 2014 Corn Tillage: Fall 2014, Mulch Ripper; Spring 2015, Field cultivator Row spacing: 30 Cultivar: Pioneer P22T69 Seeding rate: 160,000 seeds/acre planted 1.5 deep into a dry seedbed Planting date: May 1, 2015 Weed control: Pre None Post Cornerstone Plus 24 fl oz 6/10/15 Post Cornerstone Plus 32 fl oz plus Fusilade 3 fl oz 6/18/15 Post Cornerstone Plus 32 fl oz plus Fusilade 3 fl oz 7/2/15 Harvested: October 1, 2015 Design: Randomized complete block with 4 replications Plot size: 15 x 30 - the center 4 of 6 rows (10 ) were treated, the center 2 of 6 rows were sampled for aphid populations and harvested for yield. Application information: Date: July 31, 2015 Temperature: 78 F RH 44% DP 55.4 F Wind conditions: 5-6 mph Crop stage at application: R4 Crop height at application: 31 inches Insecticide treatments were applied with a two-man, 8 nozzle boom sprayer (R&D Sprayers), 8001 flat fan nozzles on 15-inch spacing, 20 gallons/acre and 35 PSI pressure with boom 18 above soybean canopy. All insecticide treatments yielded similar to the untreated control at the 5% level irrespective of performance. These results were expected from Cumulative Aphid Days (CADs). The yields of the Priaxor fungicide treatment yielded more than the control but similar to Hero EW, Warrior II, Fastac EC and 3.5 fl. oz. Endigo ZC and reflects an effect other

4 than insect control. The addition of fungicide to Transform or Warrior II insecticides did not increase yield. These results show the difficulty in interpreting results when pesticides effective across multiple taxa are applied. This study was in a geographic location where lambda-cyhalothrin, bifenthrin and lambda-cyhalothrin + zeta cypermethrin pyrethroid insecticide performance issues against soybean aphids were observed. In close spatial and temporal proximity to this study, a 4.0 fl. oz./acre rate of Tundra EC provided poor control indicating a higher insecticide rates may mask developing performance issues with some pyrethroid insecticide compounds, at least in the short-term. Acknowledgments Compounds used in this study pyraclostrobin plus fluxapyroxad Priaxor BASF Corporation alpha-cypermethrin Fastac EC BASF Corporation zeta-cypermethrin + bifenthrin Hero EW FMC corporation chlorpyrifos Lorsban Advanced Registered trademark of Dow AgroSciences LLC bifenthrin Tundra EC Winfield Solutions lambda-cyhalothrin + thiomethoxam Endigo ZC Syngenta Crop Protection, Inc. lambda-cyhalothrin Warrior II with Zeon Technology Syngenta Crop Protection, Inc. This trial was supported in part by FMC Corporation, Syngenta Crop Protection and BASF Corporation. Thanks to Aaron Hass and Tyler Alcorn for help with this study. The information given in this publication is for educational purposes only. Reference to commercial products is made with the understanding that no discrimination is intended and no endorsement by the University of Minnesota any specific product(s) used in this implied.

5 Table 2. Foliar applied insecticide control of soybean aphid. SBA/Plant Yield 13%) Rating Date 7/31/2015 8/3/2015 8/7/2015 8/14/2015 8/21/ /1/2015 Crop Stage R 5.0 R5.0 R5.5 R 5.5 R 5.8 CADs R8 Trt-Eval Interval 0 DAT 3 DAT 7 DAT 14 DAT 21 DAT 0-21 DAT UNTREATED a a ab a a 49.6 c TUNDRA 5 fl oz/a ef 5.9 d 70.5 d 15.4 d b 67.9 a HERO EW 5.12 fl oz/a f 6.7 d 56.4 d 20.0 d b 66.8 ab COC 1 qt/100 gal Warrior II 1.6 fl oz/a bc c c 75.4 c b 66.0 ab PRIAXOR 4 fl oz/a b 94.5 c c bc b 69.8 a Warrior II 1.6 fl oz/a Lorsban Advanced 16 fl oz/a g 0.5 e 2.6 f 2.0 e b 68.2 a TRANSFORM 0.75 oz wt/a b 65.3 c 25.6 de 3.5 e b 71.4 a PRIAXOR 4 fl oz/a bcd 8.8 d 3.3 f 0.6 e b 71.2 a TRANSFORM 0.75 oz wt/a FASTAC 3.8 fl oz/a bcd bc bc b b 63.9 ab PRIAXOR 4 fl oz/a b ab a a a 60.0 b Endigo ZC 3.5 fl oz/a de 11.1 d 10.4 ef 2.9 e b 66.8 ab COC 1 % v/v Endigo ZC 4.5 fl oz/a cde 8.5 d 14.8 def 2.4 e b 67.6 a COC 1 % v/v Grand Mean Standard Deviation t 0.40 t 0.43 t 0.39 t CV t t t t Treatment Prob(F) t t t t Means followed by same letter do not significantly differ (P=.05, Duncan's New MRT) Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSL. t = Mean comparisons based on transformed data (log n+1)