The soybean aphid in Illinois before ―Surprised like everyone else 2001―Economic infestations occurred, but they were not widespread. Populations within fields tended to “crash” quickly. 2002―Where did they go?

Evolution of the soybean aphid problem in Illinois in 2003 The problem in 2003 began in 2002 (some early indications of a potential problem) Low-level densities of soybean aphid occurred in 2002―nothing economic Very low numbers of the multicolored Asian lady beetle in 2002 Noteworthy flight of winged aphids in the fall of 2002

Suction traps to capture flying aphids 9 locations

DateDeKalbMonmouthUrbanaPerry Sep Sep Oct Oct Data from suction traps, Fall 2002

Evolution of the soybean aphid problem in Illinois in 2003 Conditions in 2003 were favorable for the growth and development of soybean aphids. Very few predators allowed densities of aphids to build early in the summer. Cooler-than-usual temperatures favored development of soybean aphid populations (<85°F most of the time). As many as 18 generations per season are possible.

Evolution of the soybean aphid problem in Illinois in 2003 First winged soybean aphids found on April 23 (Dr. Dave Voegtlin, Champaign County) First soybean aphids found in soybeans on May 29 (Jeff Wessel, Joliet Junior College, Will County) Populations in northern IL through July, early Aug. Populations in central IL, early to mid-Aug. Populations in southern IL, mid- to late Aug.

7/47/117/187/258/18/78/158/22 Free- port ,9121,8101,347 De- Kalb ,7554, Mon- Mouth , Eureka ,9201, Urbana ,131 Perry , Brns- Town , Dixon Sprngs Captures of soybean aphids in suction traps, Illinois, 2003

The Soybean Aphid Outbreak Illinois, 2003 Primarily in northern and central Illinois Some economic infestations in southern Illinois 750,000 to 1 million acres treated $9 to $12 million in treatment costs ~$45 million in yield loss

Guidelines and treatment thresholds for soybean aphids in July 2003 Scout at least twice during late V early R stages Apply an insecticide if... Density of aphids is 25 or more per leaflet Density of aphids increases from 1 st to 2 nd sample Percentage of alatoid nymphs is <50% Soybean growth stage is R1 or R2 But what if the soybean growth stage was past R2?

Treated 2351 g 12.7% 64.6 cm g Untreated 1414 g 12.0% 54.2 cm g Measure yield % moisture plant height avg# pods/plant avg# pods/main stem nodes/main stem weight per bean Yield difference primarily due to pod number Bean weight & # of beans not significantly different. Before 2003, thresholds were based on some research conducted at Michigan State University in 2001.

A review of soybean growth stages R1Beginning bloom (open flower at any node) R2Full bloom (open flower at one of two uppermost nodes on main stem) R3Beginning pod (pod 3/16 inch long) R4Full pod (pod 3/4 inch long) R5Beginning seed (seed 1/8 inch long) R6Full seed (green seed that fills pod cavity)

Treatment thresholds for soybean aphids were adjusted in August 25 or more aphids per leaflet 250 aphids per plant at R1–R2 1,000 aphids per plant at R3 1,500 aphids per plant at R4–R5

Insecticides labeled for control of soybean aphids Asana XL Chlorpyrifos (Lorsban, Nufos) Furadan Mustang Max Penncap-M Warrior

Not treated How did soybean aphid infestations affect yield? Insecticide applied

McLean County soybean field Not treated 120 feet check strip Sprayed with Warrior at stage R2 1,000 to 2,000 aphids per plant

bu/A

Summary Unknown Before Aug 1 1st Week Aug 2nd Week Aug 3rd Week Aug After Aug 24 Yield (Treated) Range 39–4840–5028–5642–4842–49 Average Yield (Not treated) Range 29–3938–4121–4029–3734–43 Average Difference in Yield Range 9–107–97–267–185–11 Average Soybean yields from people who reported Fields treated for control of soybean aphids, 2003

Information provided by Kevin Black, Growmark, Inc., Bloomington, IL 23 yield comparisons―Treated for aphid control vs. not treated Avg. treated yield 43.0 bu/A (range 27 to 59 bu/A) Avg. untreated yield 34.6 bu/A (range 16.9 to 55 bu/A) Avg. difference in yield, treated vs. not treated 8.4 bu/A (range -0.5 to 20.6 bu/A) Products used―Mustang Max, Warrior, Furadan 4F, Lorsban 4E, Ambush 2E

Less-than-expected soybean yields 2003 Soybean aphid infestations undoubtedly had an impact, but... Weather conditions were not ideal for optimum soybean yields, and Soybean diseases also caused yield reductions Charcoal rot Root rots

Forecast for soybean aphids in 2004? Plenty of multicolored Asian lady beetles present this fall... As well as numerous other predators this summer... No significant aphid captures in suction traps this fall... Weather next year? Soybean aphids may be at low levels in 2004.

Research on the soybean aphid in Illinois Biology, overwintering strategies, movement, other hosts, biological control―David Voegtlin Population dynamics, sampling―David Onstad Resistant soybean cultivars―Glen Hartman Management―Kevin Steffey

Sampling for soybean aphids (D. Onstad) Two counties, one township per county Kendall County, Kendall Township Champaign County, St. Joseph Township 14 soybean fields randomly selected per township 7 fields in norhtern half of township 7 fields in southern half of township

Sampling for soybean aphids (D. Onstad) Fields sampled every 3 weeks from late June or early July to early September Almost all fields sampled 4 times each year Exceptions St. Joseph Township―low numbers in 2002 Kendall Township―hail damage or insecticide applications in 2003

Sampling for soybean aphids (D. Onstad) Two 50-m transects, at least 10 m apart Samples every 2 m = 25 samples per transect

Field or Township July 5, 2001 July 1, 2002 June 23, 2003 July 25, 2001 July 22, 2002 July 14, 2003 Aug 17, 2001 Aug 18, 2002 Aug 4, 2003 Sep 6, 2001 No observation Aug 25, A B St. Joseph A B St. Joseph A B , St. Joseph , (from D. Onstad)

Field or Township July 5, 2001 July 2, 2002 June 24, 2003 July 26, 2001 July 23, 2002 July 16, 2003 Aug 15, 2001 Aug 12, 2002 Aug 5, 2003 Sep 4, 2001 Sep 6, 2002 Aug 29, A B Kendall A B Kendall A , B Kendall (from D. Onstad)

Mean no. aphids per plant Data from 2001 (from D. Onstad)

Data from 2002 Mean no. aphids per plant (from D. Onstad)

Data from 2003 Mean no. aphids per plant (from D. Onstad)

Data from St. Joseph Township Mean no. aphids per plant (from D. Onstad)

Data from Kendall Township Mean no. aphids per plant (from D. Onstad)

Sampling for soybean aphids Other findings (D. Onstad) Significant variability in densities of aphids among fields No apparent effect of row spacing on aphid densities Probability of finding an infested field by mid-July when mean density in the township is <2 aphids per plant 50% in Kendall County, 11% in Champaign County Must sample at least 2 fields (Kendall Co.) or 14 fields (Champaign Co.) for 75% chance of finding aphids in 1 field No relationship between aphid density and distance from the field edge

Soybean aphid efficacy trial Kendall County, IL, 2003 Product Rate of application Aphids per trif. 21 DAT Aphids per trif. 14 DAT Aphids per trif. 7 DAT Nufos 4E2 pt 0.32 d 2.53 c 0.46 d Nufos 4E1 pt 4.62 c b 0.75 d Asana XL8 oz b a bc Asana XL6 oz b a 9.67 bc Asana XL7 oz b a 8.96 bc Warrior0.025 lb a.i b a 7.26 c Untreated a a44.39 a Lannate SP0.45 lb a.i a a ab Average of 48 aphids per trifoliate when treatments applied on July 23.

Soybean aphids per trifoliate, 21 DAT, Kendall Co., IL, 2003

Soybean aphid efficacy trial Pope County, IL, 2003 Product Rate of application 14 DAT7 DAT Lorsban 4E2 pt 22.6 de 28.8 d Asana XL9.6 oz 47.6 cd 52.9 de Warrior3.84 oz 76.4 bc 57.5 cde Mustang Max 4 oz 91.0 b 97.4 bc Untreated a a Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC

Soybean aphid efficacy trial Pope County, IL, 2003 Product Rate of application Yield (bu/A)--NS Test Wt (lb/bu) Lorsban 4E2 pt b Asana XL9.6 oz ab Warrior3.84 oz ab Mustang Max 4 oz a Untreated ab Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC