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The soybean aphid in Illinois before 2003

The soybean aphid in Illinois before 2003. 2000 ―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? 2003 . . . Evolution of the soybean aphid problem in Illinois in 2003.

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The soybean aphid in Illinois before 2003

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  1. The soybean aphid in Illinois before 2003 • 2000―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? • 2003 . . .

  2. 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

  3. Suction traps to capture flying aphids 9 locations

  4. Data from suction traps, Fall 2002

  5. 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.

  6. 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. Captures of soybean aphids in suction traps, Illinois, 2003

  8. The Soybean Aphid OutbreakIllinois, 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

  9. 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 1st to 2nd sample • Percentage of alatoid nymphs is <50% • Soybean growth stage is R1 or R2 But what if the soybean growth stage was past R2?

  10. Treated 2351 g 12.7% 64.6 cm 17.7 14.6 11.3 0.136 g Untreated 1414 g 12.0% 54.2 cm 14.0 11.6 10.7 0.131 g Measure yield % moisture plant height avg# pods/plant avg# pods/main stem nodes/main stem weight per bean Before 2003, thresholds were based on some research conducted at Michigan State University in 2001. Yield difference primarily due to pod number Bean weight & # of beans not significantly different.

  11. A review of soybean growth stages • R1 Beginning bloom (open flower at any node) • R2 Full bloom(open flower at one of two uppermost nodes on main stem) • R3 Beginning pod (pod 3/16 inch long) • R4 Full pod (pod 3/4 inch long) • R5 Beginning seed (seed 1/8 inch long) • R6 Full seed (green seed that fills pod cavity)

  12. Treatment thresholds forsoybean 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

  13. Insecticides labeled for controlof soybean aphids • Asana XL • Chlorpyrifos(Lorsban, Nufos) • Furadan • Mustang Max • Penncap-M • Warrior

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

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

  16. + 10.75 bu/A

  17. Soybean yields from people who reported Fields treated for control of soybean aphids, 2003

  18. 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

  19. 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

  20. 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.

  21. 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

  22. 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

  23. 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

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

  25. (from D. Onstad)

  26. (from D. Onstad)

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

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

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

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

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

  32. Sampling for soybean aphidsOther 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

  33. Soybean aphid efficacy trial Kendall County, IL, 2003 Average of 48 aphids per trifoliate when treatments applied on July 23.

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

  35. Soybean aphid efficacy trial Pope County, IL, 2003 Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC

  36. Soybean aphid efficacy trial Pope County, IL, 2003 Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC

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