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The soybean aphid, Aphis glycines Matsumura, can be a serious problem of soybean, Glycine max (L.) Merrill., production in South Dakota. The economic threshold is 250 soybean aphids on 80% of sampled plants around the R4 soybean development stage. When the threshold is reached, it may warrant an insecticide treatment to prevent potential yield loss through R5 soybean development stage. During the 2015 growing season, we conducted a field study near Brookings, South Dakota, using four foliar applied insecticides for control of soybean aphid. The insecticides were applied at 16 gallons per acre (GPA) using a bicycle push …

Soybean aphid (SA) continues to be an important pest of soybean in eastern North Dakota. Insecticide trials continue to examine the efficacy of broad spectrum compounds (primarily pyrethroids), however, new chemistries must also be tested, especially those that have the potential to reduce mortality of beneficial insects. The objectives of this trial were to test the efficacy of foliar-applied sulfoxaflor in controlling SA, and to measure the immediate impact of sulfoxaflor on adult lady beetle (LB) numbers. The trial was conducted at a cooperator’s field approximately five miles east of Moorhead, MN. Test plots were established on 2 Jun using a two-row vacuum precision planter equipped with GPS at a seeding rate of 150,000 live seeds per acre. Each plot was 10 ft wide (4 rows at 30-inch row spacing) × 25 feet long. Two “guard rows” were left between each plot to prevent spray overlap. Plots were arranged in a RCB design with four replications. Foliar insecticide applications were made on 11 Aug using a tractor-mounted CO2 sprayer with …

Soybean aphid, Aphis glycines Matsumura, has drastically changed soybean pest management in the North Central region. To date, SBA can be successfully managed by timely scouting and foliar insecticides. Host plant resistance is the newest soybean aphid management tool and is complementary to existing chemical control. In 2015, we established plots at two Iowa State University Research Farms (Northeast and Northwest) on 27 May and 27 May, respectively. NK S25-E5 soybean variety was used for all the soybean aphid-susceptible treatments, and 28ARC5 soybean variety was used for the Rag2 -containing treatments. Plots were arranged in an RCB design with four replications. Each plot was six rows in width and 50 ft in length at the Northeast location and six rows in width by 44 ft in length at the Northwest location. Treatments containing …

The Soybean aphid, Aphis glycines Matsumura, can be a serious problem of soybean, Glycine max L., production in South Dakota. The economic threshold is 250 soybean aphids on 80% of plants sampled. When the threshold is reached it may warrant an insecticide treatment to prevent potential yield loss through early R5 soybean development stage. During the 2014 growing season, we conducted a field study near Brookings, South Dakota using foliar applied insecticides for control …

This experiment was part of an effort to evaluate materials for management of SBA in Minnesota. The experiment was conducted at the University of Minnesota Outreach, Research and Education Park near Rosemount, MN. On 27 May 2014, soybean seed (variety: S17-B3) was sown 1.5 inches (3.81 cm) deep at a seeding rate of 165,678 seeds per acre (409,399 seeds per ha). Spacing between rows was 30 inches (76.2 cm). Plots were arranged in a randomized complete block design with 12 treatments and four replications. Each plot consisted of four rows 30 ft (9.14 m) long. Plots within blocks were separated by 5 ft (1.52 m) of fallow ground …

Soybean aphid, Aphis glycines Matsumura, has drastically changed soybean pest management in the North Central region. To date, SBA can be successfully managed by timely scouting and foliar insecticides. Host plant resistance is the newest soybean aphid management tool and is complementary to the existing chemical control. In 2014, we established plots at two Iowa State University Research Farms (Northeast and Northwest) on 24 May and 22 May, respectively. NK S25-E5 soybean variety was used for all the soybean aphid-susceptible treatments, and LD09-05484A soybean variety was used for the Rag1 -containing treatments. Plots were arranged in an RCB design with four replications. Each plot was six rows in width and 50 ft in length. Treatments containing a …

Foliar insecticides were compared with an untreated check and Gaucho seed treatment for SBA control and yield at the Michigan State University Entomology Farm, East Lansing, MI. The trial was a RCB design with four replications, planted on 1 Jun 06 in 10’ × 30’ plots at 117,000 seeds per acre. Gaucho was seed-applied at 2.0 oz/cwt before planting. Weekly whole-plant SBA counts and plant stages were taken before foliar treatment application beginning 16 Jun. No SBA were found prior to treating. Despite low aphid numbers, foliar insecticides were applied at the R3 growth stage on 21 Jul. This mimicked the practice of some growers to apply a ‘prophylactic’ treatment in anticipation of mid-season flights. Treatments were applied using a CO2 pressurized backpack sprayer with twin jet nozzles at 40 psi and 20 gpa. Whole-plant SBA counts and plant stages were taken on 5 plants per plot 7 and 19 DAT. Yield was taken with a Hage 125 combine with a five foot grain head. Data was analyzed using ANOVA and LSD (P = 0.05).

Foliar insecticides were compared with an untreated check for SBA control at the Michigan State University, Saginaw Valley Bean and Beet Farm, Saginaw. Soybeans were planted in 30 inch rows on 5 May 2005, at a rate of 148,000 seeds per acre. Plots were 10’ × 25’ and treatments were replicated three times in a RCB design. Foliar treatments were applied using a CO2 pressurized backpack sprayer with twin jet nozzles at 40 psi and 23.8 gpa. Insecticide application timing was based on SBA surpassing the threshold of 250 SBA per plant (14 Jul). Pre-treatment whole-plant SBA counts were taken on 13 Jul, sampling 24 plants over the entire trial. SBA numbers averaged 830 SBA per plant at the R2 growth stage at this time. Whole-plant SBA counts, 5 plants per plot, were taken 4 (R3), 7 (R3), 14 (R4), and 21 (R4) DAT. Yield was taken with a Hage 125B small plot combine with a five foot grain head. All products were registered for use on soybeans in Michigan except Assail, Centric, Leverage and Trimax. Data were transformed prior to analyses by log10 (x + 1.0); untransformed data are presented. Data were analyzed using ANOVA and LSD (P = 0.05).

Two on-farm efficacy trials were conducted to evaluate selected insecticides for control of SBA in soybean. 'DKB44-51' and 'DKB46-51' soybean were planted on 20 and 29 Jun at the Bob Baylor Farm in Essex Co., VA, and the George W. Sanford, Jr. Farm in Westmoreland Co., VA, respectively. Treatments were applied on 2 Sep with a CO2-pressurized backpack sprayer as a broadcast at 14.3 gpa and 18 psi through 8002VS nozzles spaced 18 inches apart on the spray boom. Each trial used a RCB design with four replicates; plots were 6 × 40 ft. Samples consisted of pulling two plants per plot and counting all SBA on each plant. Data were analyzed using ANOVA and LSD (P = 0.01).

Infestations by SA can reduce the yield of soybeans and the efficacy of various biorational spray treatments need evaluation as alternatives to chemical insecticides for SA control. The efficacy of an entomopathogenic fungal formulation, MicroAC, against SA was compared to that of a distilled-water spray check and an untreated check. Two identical efficacy tests were conducted in growth chambers at the Northern Grain Insects Research Laboratory, Brookings, SD. Each test used a RCB design with 10 replications. In each test, 30 greenhouse-raised soybean plants, growing individually in separate pots, were infested in the late VE stage (unifoliate leaves fully expanded, first trifoliate leaves expanding) with five SA (adults or late third instars) on the underside of each unifoliate leaf (total of 10 SA per plant). The plants were placed in a growth chamber (16:8 L:D photoperiod; mean temperature and R.H. of 21.4 C and 45.9%, first test; 21.3 C and 73.9%, second test). Seven days after infestation, SA were counted on each plant. Sprays were then applied 20 cm from each plant using the wide-angle mist setting on the nozzle of a handpumped squirt bottle. Sprays were applied to run-off with eight squirts (about 9.2 ml) directed per plant, four with the nozzle horizontal and four with nozzle tip pointed downward at approximately 30-degrees. The number of spores contained in an 8-squirt volume of MicroAC was enumerated by direct observation of diluted product suspensions on a light microscope using phase contrast microscopy and a hemacytometer. Sporulation rate was measured as colonyforming units (CFU) in dilution-series cultures plated on Sabouraud dextrose agar with 2 % yeast extract under growth chamber conditions; CFU were counted after a 4-day incubation period when colonies were visible and separate. After spray application, clear 10-cm-diam × 40-cm-tall cylindrical acetate cages with 16-mesh screen tops were placed over each plant, and plants were returned to the growth chamber. At 10 days after treatment (DAT), (23 Jun, first test; 11 Jul, second test), plants were clipped at soil level, and SA were counted on each plant. For each test, SA counts were subjected to ANOVA and treatment means separated using Tukey’s HSD (P = 0.05). Post-spray SA counts were log (x + 1)-transformed before analysis.