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

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

Date DeKalb Monmouth Urbana Perry

Sep 20 0 17 0 2

Sep 27 2 80 71 284

Oct 4 38 62 13 133

Oct 11 7 3 4 9

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.

7/4 7/11 7/18 7/25 8/1 8/7 8/15 8/22

Free-

port0 21 176 112 787 1,912 1,810 1,347

De-

Kalb0 1 131 940 6,755 4,890 286 264

Mon-

Mouth0 0 1 59 71 569 1,403 ---

Eureka 0 0 2 142 401 4,920 1,090 921

Urbana 0 0 0 2 9 163 602 1,131

Perry 0 0 0 4 8 232 1,560 ---

Brns-

Town0 0 0 3 1 18 1,535 ---

Dixon

Sprngs0 0 0 1 0 0 31 2

Captures of soybean aphids in suction traps, Illinois, 2003

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

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?

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

Yield difference primarily due to pod number

Bean weight & # of beans not significantly different.

Before 2003, thresholds were based on some research conducted atMichigan State University in 2001.

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 onmain 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)

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

Insecticides labeled for controlof 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 Countysoybean field

Not treated

120 feetcheck strip

Sprayed withWarriorat stage R21,000 to 2,000aphids per plant

+ 10.75 bu/A

Summary UnknownBefore Aug 1

1st Week Aug

2nd Week Aug

3rd Week Aug

After Aug 24

Yield (Treated) Range 39–48 40–50 28–56 42–48 42–49

Average 43.5 45.2 49.2 44.6 45.3 61.6

Yield(Not treated) Range 29–39 38–41 21–40 29–37 34–43

Average 34.1 39.5 34.2 31.6 38.2 30.9

Difference in Yield Range 9–10 7–9 7–26 7–18 5–11

Average 9.4 7.8 14.9 13.2 7 30.7

Soybean yields from people who reportedFields 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 apartSamples 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, 2003

2001 A 5.50 91.94 4.84 3.50

2001 B 0 0.82 0.94 5.28

St. Joseph 0.39 7.60 1.06 1.95

2002 A 0 0 0.19 ---

2002 B 0 3.02 2.74 ---

St. Joseph 0 0.23 0.33 ---

2003 A 0 0.12 13.40 923.10

2003 B 0 0.02 26.04 6,064.00

St. Joseph 0 0.02 33.33 1,829.03

(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, 2003

2001 A 0.02 12.68 14.76 12.64

2001 B 16.24 57.26 14.56 2.22

Kendall 0.39 7.60 1.06 1.95

2002 A 0 1.66 15.84 78.38

2002 B 0.58 3.76 40.82 7.14

Kendall 0.19 5.09 34.37 20.94

2003 A 6.86 326.42 2,235.80 14.16

2003 B 9.30 109.70 191.06 3.38

Kendall 3.44 268.73 843.02 20.92

(from D. Onstad)

0.41.6

7.6

16.5

1.1

19.8

2

6.1

0

5

10

15

20

25

St. Joseph Kendall

1st2nd3rd4th

Mea

n no

. ap

hids

per

pla

nt

Data from 2001

(from D. Onstad)

0 0.190.2

5.1

0.3

34.4

20.9

0

5

10

15

20

25

30

35

40

St. Joseph Kendall

1st2nd3rd4th

Data from 2002M

ean

no.

aphi

ds p

er p

lant

(from D. Onstad)

0 3.40.02

269

33

843

1,829

210

200

400

600

800

1000

1200

1400

1600

1800

2000

St. Joseph Kendall

1st2nd3rd4th

Data from 2003M

ean

no.

aphi

ds p

er p

lant

(from D. Onstad)

0.4 0 07.6 0.2 0.021.1 0.3 33.32

1,829

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2001 2002 2003

1st2nd3rd4th

Data from St. Joseph TownshipM

ean

no.

aphi

ds p

er p

lant

(from D. Onstad)

0.4 0.2 3.41.6 5.1

268.7

16.5 34.4

843

6 20.9 21

0

100

200

300

400

500

600

700

800

900

2001 2002 2003

1st2nd3rd4th

Data from Kendall Township

Mea

n no

. ap

hids

per

pla

nt

(from D. Onstad)

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

Soybean aphid efficacy trial Kendall County, IL, 2003

ProductRate of

application

Aphids per trif.

21 DATAphids per trif.

14 DATAphids per trif.

7 DAT

Nufos 4E 2 pt 0.32 d 2.53 c 0.46 d

Nufos 4E 1 pt 4.62 c 10.48 b 0.75 d

Asana XL 8 oz 17.30 b 26.60 a 10.45 bc

Asana XL 6 oz 20.67 b 22.37 a 9.67 bc

Asana XL 7 oz 24.95 b 48.09 a 8.96 bc

Warrior 0.025 lb a.i. 31.17 b 38.93 a 7.26 c

Untreated --- 99.35 a 60.42 a 44.39 a

Lannate SP 0.45 lb a.i. 104.58 a 43.03 a 15.97 ab

Average of 48 aphids per trifoliate when treatments applied on July 23.

0.34.6

20.725

31.2

99.4104.6

17.3

0

20

40

60

80

100

120

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

Soybean aphid efficacy trial Pope County, IL, 2003

ProductRate of

application 14 DAT 7 DAT

Lorsban 4E 2 pt 22.6 de 28.8 d

Asana XL 9.6 oz 47.6 cd 52.9 de

Warrior 3.84 oz 76.4 bc 57.5 cde

Mustang Max 4 oz 91.0 b 97.4 bc

Untreated --- 142.4 a 159.1 a

Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC

Soybean aphid efficacy trial Pope County, IL, 2003

ProductRate of

application Yield(bu/A)--NS

Test Wt(lb/bu)

Lorsban 4E 2 pt 56.5 51.5 b

Asana XL 9.6 oz 54.3 51.9 ab

Warrior 3.84 oz 55.3 52.0 ab

Mustang Max 4 oz 53.8 52.1 a

Untreated --- 56.8 51.8 ab

Trial established on R5 soybeans by Ron Hines, Senior Research Specialist, DSAC