Soybean Aphid Update

February 2004

Soybean Aphid Biology• Aphid colonization occurs earliest near wooded, protected areas; along

streams, especially when buckthorn is present. • Soybean aphids reproduce the fastest at 82º F – populations double every 1.5

days. Reproduction is slower at higher or lower temperatures.• Lady beetles, minute pirate bugs and parasitic wasps are natural enemies and

are significant in lighter infestations. Beneficials exhibit a “lag” behind aphid development and can not slow a rapidly increasing aphid population.

• Soybean aphids lay their eggs on the overwintering host plant, buckthorn. Crimson clover, red clover, and scarlet runner beans are alternate hosts if soybeans are not present in the spring.

• Heavy rainfall helps reduce numbers, however, information is largely anecdotal.• Ground application of insecticides may provide slightly better effectiveness than

air application, but the difference is not significant.• 2003 research indicates a loss of 0.5 – 0.6 bu/acre for each day that treatment

is delayed beyond the Economic Injury Level. The greatest yield advantages came to those fields treated early rather than late.

Variety TrialRoundup Ready Beans

1000 – 1500 aphids per soybean plantsprayed by ground ~R3 stage, Aug 12, 2003

1.0 pint Lorsban 4E/acre14.7 bu/acre yield improvement

Variety TrialRoundup Ready Beans

1000 – 1500 aphids per soybean plantsprayed by ground ~R3 stage, Aug 12, 2003

1.0 pint Lorsban 4E/acre14.7 bu/acre yield improvement

2003 Soybean Aphid Treatment Map Northern Iowa Area Community College - Kevin Muhlenbruch, CPAg

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 ¾ inch long)

• R5 Beginning seed (seed 1/8 inch long)

• R6 Full seed (green seed that fills pod cavity)

Soybean Aphid Management Recommendations for 2004

• Scout fields in July to mid-August during late vegetative stage through seed set (R1 – R5).

• Potential for damage is not as well understood at later growth stages (R3-R5) but yield advantages have been documented at these later growth stages.

• A scouting-based Economic Threshold has been established which signals the need for insecticide application when 25 aphids per leaflet are found on late vegetative – early reproductive soybeans.– 250 aphids per plant at R1 – R2– 1,000 aphids per plant at R3– 1,500 aphids per plant at R4 – R5

Aphids averaged 1085 per plant prior to treatment.5.34” of rainfall in the seven days following application reduced aphid populations by 80 – 90% in all treatments. This is the “crash” that can result from heavy rainfall.This trial utilized the high end of the rate range of all products tested. “Lorsban produced sig. better control than Warrior or Mustang Max,” Ron Hines, Sr. Researcher

Average Number Soybean Aphids per Planttreatment at R5

University of Illinois, Hines, 2003

020406080

100120140160180

UTC Lorsban-4E, 1 qt

MustangMax, 4 oz

Warrior, 3.84 oz

Asana XL, 9.6 oz

aph

ids

per

pla

nt

7 DAT

14 DAT

Treated August 7 at R2A “medium” level of rates were tested here.“Furadan and Lorsban provided the best control throughout the sampling period. The pyrethroids, while providing control, did not achieve the level of SA reduction provided by the other materials …. The only plots relatively clean of honeydew and sooty mold were the Furadan and Lorsban treatments” Ronald Hammond, Ohio Agricultural Research & Development Center.

Soybean Aphid Control Ohio State University

RB Hammond, Wooster, 2003

0200400600800

100012001400

1.5 pt/A 8 oz/A 2.56 oz/A 2.4 oz/A 3.5 oz/A 7.7 oz/A

Lorsban-4E Furadan Warrior Baythroid MustangMax

Asana untreated

aph

ids/

pla

nt

4 DAA

11 DAA

18 DAA

Quick Knockdown and Residual

At 21 days after treatment, there was no statistically significant difference between the esfenvalerate and lambda cyhalothrin nor between the methomyl and untreated treatments. Chlorpyrifos, at both the 0.5 #/A and the 1.0 #/ac rate, demonstrated the greatest residual of all products tested.

esfenvalerate– Asana 0.03 #ai/ac = 6 oz/ac 0.036 #ai/ac = 7 oz/ac 0.04 #ai/ac = 8 oz/ac

methomyl - Lannate 0.45 #ai/ac = 0.5 #/ac

chlorpyrifos – Nufos, Lorsban 0.5 #ai/ac = 1 pt/ac 1.0 #ai/ac = 2 pt/ac

lambda-cyhalothrin – Warrior 0.25 #ai/ac = 3.2 oz/ac*

* equivalent to 3.2 oz/ac (0.125 #ai/ac) gamma-cyhalothrin - Proaxis

Soybean Aphid Control University of Illinois, Yorkville 2003

0

20

40

60

80

100

120

0.03 #ai/ac

0.036#ai/ac

0.04 #ai/ac

0.45 #ai/ac

0.5 #ai/ac

1.0 #ai/ac

0.025#ai/ac

esfen- valerate

esfen- valerate

esfen- valerate

methomyl chlor- pyrifos

chlor- pyrifos

lambda cyhalothrin

ap

hid

s/p

lan

t

0 DAT

7 DAT

14 DAT

21 DAT

Application made between R1 and R2 on Aug 14.“Pounce and the low rate of Baythroid were not significantly different than the untreated control and technically not different from the other insecticides as well, however … the low rate of Baythroid and Pounce probably had the greatest chance for resurgence … since each left a significant proportion of the original population in the field,” Tom Clark, Dept of Entomology.

Soybean Aphid Control University of Missouri, Tom Clark, 2003

0.00%20.00%40.00%60.00%80.00%

100.00%

Pe

rce

nt

Kill

of

Ori

gn

ina

l Po

pu

latio

n

4 DAT

11 DAT

**** LOG SCALE ****Treated July 31 at R2, >500 aphids per plantLorsban provided statistically superior control over all treatments at 4 DAT.Lorsban and Warrior provided statistically superior control over all other treatments at the one and two week intervals after application.

Soybean Aphid Control University of Wisconsin, Arlington, 2003

1.00

10.00

100.00

1,000.00

10,000.00

3.84 oz/ac 1.0 pt/ac 2.8 oz/ac 4.0 oz/ac 4.0 oz/ac 6.4 oz/ac 9.6 oz/ac 2.0 pt/ac

Warrior dimethoate Baythroid MustangMax

MustangMax + NIS

Asana Lorsban untreated

aph

ids/

pla

nt

(lo

g s

cale

)

4 DAT

7 DAT

14 DAT

Foliar applied insecticide control (product performance) for Soybean aphid.Randall Reinhart farm, Nicollet County, MN (2003).B. Potter, U of M

Rating Date Days after treatment Crop Stage

Estimated Aphids/plant 7/22/2003

4 DAT R3

Estimated Aphids/plant 7/29/2003 10 DAT

R4

Estimated Aphids/plant 8/4/2003 15 DAT

R4

Estimated Aphids/plant 8/8/2003 19 DAT

R5.5

Estimated Aphids/plant 8/21/2003 33 DAT

R6.5

Estimated Aphid days 8/21/2003 33 DAT

R6.6

Untreated 142.6 a 712.5 a 393.5 a 1260.3 a 45.1 a 26854.1 aWarrior-3.2 oz 7/18*1 0.7 c-d 2.1 c 26.4 b 346.0 b 11.6 a 6107.0 bWarrior-2.0 oz 7/18 5.9 c-d 8.4 bc 23.4 b 228.6 b 49.3 a 5289.9 bAsana XL-6.4 oz 7/18 29.2 b 19.1 bc 23.1 b 271.9 b 26.7 a 5748.8 bBaythroid-2.8 oz 7/18 31.8 b 97.5 b 35.2 b 267.7 b 47.8 a 6829.9 bBaythroid-1.8 oz 7/18 54.2 ab 10.0 bc 24.4 b 310.9 b 54.1 a 6511.2 bLorsban 4E-1 pt 7/18 0.1 d 12.1 bc 43.2 b 250.1 b 82.4 a 5939.8 b

LSD (P+0.05) *2

Standard Deviation 35.1 117.5 105.6 237.4 46.8 4023.7CV 92.9 95.5 12.9 56.6 103.4 44.5Grand Mean 37.8 123.1 81.3 419.3 45.3 9040.1Prob(F) 0.0001 0.0007 0.0001 0.0091 0.1534 0.0001Means followed by same letter do not significantly differ (P=0.05, Duncan's New MRT)Mean comparisons performed only when AOV Treatment P(F) is significant at mean comparison OSLAll insecticide applications CO2 Backpack sprayer, 20 GPA, 35 PSI*1 Respray 8/11/03 with 6.4 ox Asana XL (part of timing trial)*2Mean separation for aphid/plant estimates based on a 1-10 rating scale

Treatments applied July 18 to R2 soybeans.“The 1 pint rate of Lorsban and the 2.0 and 3.2 oz rates of Warrior provided significantly better knockdown than other products,” Bruce Potter, SWROC, U of MNLorsban-4E was numerically superior to all treatments at 4 DAT; Lorsban-4E and Warrior were statistically superior to all other treatments at that same timing.

Treatment on August 7/8, stage unknownInsecticide treatments provided 4.3 to 7 bushel yield increase over untreated.

Soybean Aphid Control Iowa State University

Northeast Research and Demonstration Farm, Nashua 2003

0

10

20

30

40

50

60

70

80

6.4 oz/ac 3.5 oz/ac 1.0 pt/ac 8.0 oz/ac 2.8 oz/ac 3.2 oz/ac

untreated Asana XL MustangMax

Lorsban-4E Furadan 4F Baythroid Warrior T

aphi

ds/1

0 le

aves

4 DAT

11 DAT

18 DAT

% Lady Beetles Left Alive After Insecticide Application in Alfalfa

University of Nebraska, Concord, 2003

0

20

40

60

80

100

Mustang Max Baythroid Warrior Proaxis Lorsban-4E untreated

% A

live

9 DAA 14 DAA

Mustang Max @ 2.25 oz/acre Baythroid @ 1.6 oz/acre Warrior @ 2.56 oz/acre Proaxis @ 2.56 oz/acre Lorsban-4E @ 1.0 pt/acre

Lorsban-4E can have a shorter depressive effect on some beneficial insects

Soybean Aphid Control with Lorsban*-4E insecticide

• Lorsban-4E is the industry standard for aphid control in many crops• Lorsban-4E provides fast, complete knockdown of aphid populations• Roughly 2.5 million acres of soybean aphids were treated with Lorsban-4E in 2003 by ground or air

• Results were excellent with either application method• The ability to tank-mix with glyphosate makes Lorsban-4E extremely versatile• In addition to aphids, Lorsban-4E also controls bean leaf beetles, grasshoppers, corn rootworm beetle adults and even spider mites in soybeans• Rapid knockdown contact activity is enhanced by fuming activity of Lorsban-4E. This fuming activity explains the quick kill and greater effective coverage; in some cases Lorsban-4E vapors move laterally short distances thus eliminating aphids on foliage not directly sprayed. This movement needs to be taken into consideration when setting up insecticide strip plots. •In the few instances where very small double crop soybeans are treated, residuality of Lorsban-4E may be compromised due to this fuming action if there is very little foliage to adhere to. In addition, late planted soybeans are the most attractive for aphid re-infestation.