Late Season Insect Problems - John Obermeyer, from the 2018 Conservation Tillage and Technology Conference, March 6 - 7, Ada, OH, USA. More presentations at https://www.youtube.com/channel/UCZBwPfKdlk4SB63zZy16kyA

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Late Season Soybean
Insect Problems
John Obermeyer
Purdue IPM Specialist

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Mid-Late Season Soybean
Defoliators
ID, Sampling, Thresholds
Suckers
ID, Sampling, Thresholds
Pod Feeders
ID, Sampling, Thresholds
Outline

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Bean Leaf Beetle - ID

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Bean Leaf Beetle
• Native, adapted to soybeans later
• Overwinters as adult under leaf
litter in wooded areas or under
untilled soybean debris
• Adults colonize earliest emerging
soybean fields
• Adults in July - feed on leaves
• Adults in Sept. - feed on pods

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SAI - Crusier

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Crusier 5FS - Label
thiamethoxam 47.6%
“provide early season protection of seedlings against injury by:”
– 0.0756 – 0.1512 mg ai/seed
• Aphids, bean leaf beetle, seedcorn maggots, white grubs, wireworms

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Neonicotinoids
(“neonics”)
New class of insecticides, early 1990’s
Derivative of nicotine, tobacco toxin
Primary products used on field crop seeds
– clothianidin (Poncho)
– thiamethoxam (Cruiser)
Very soluble (translocated)
Short lived in plant, not environment
clothianidin
thiamethoxam

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Stage Days
post planting
Untreated Thiamethoxam
(ppb)
VE* 8 31.4 (3.6) 6509.3 (1204.3)
VC* 11 13.7 (8.2) 9075.0(4550.6)
V1* 14 8.0 (2.7) 1366.1 (405.7)
V1/V2* 18 39.3 (26.4) 151.3 (67.4)
V2 20 0.2 (0.1) 10.0 (4.3)
V2/V3 23 0.7 (1.3) 1.0 (0.3)
V3 26 2.3 (3.1) 6.7 (4.1)
V5 29 0.1 (0.1) 0.5 (0.08)
V6 32 2.0 (3.8) 0.7 (0.2)
R1 35 0.02 (0.01) 0.1 (0.07)
R1 38 0.08 (0.1) 0.08 (0.003)
No bean
leaf beetle
control
No Cruiser in
plant

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Neonics vs. BLB

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Defoliators - ID
Japanese beetle
Grasshopper
Green cloverworm
Woollybear caterpillar
Bean leaf beetle

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Soybean Defoliators:
Signature Damage
Bean leaf beetle
Green cloverworm Japanese beetle

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Defoliators - Sampling
Sampling
– “Guesstimate” % defoliation
– Stage of growth
– Sweeps
– Understand insect life cycle

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Defoliation - Threshold

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Defoliation Practice
2%
10%
15.1%
33.2%

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Defoliation

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Defoliation

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Stage of Growth

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Defoliation - Threshold

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Defoliation

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Defoliation

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Stage of Growth

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Defoliation - Threshold

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Defoliation

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Defoliation

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Stage of Growth

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Defoliation - Threshold

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Soybean Suckers - ID
Twospotted spider mite
Soybean aphid

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Other Little Suckers
Potato leafhopper
Thrips Whiteflies

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Suckers - Damage

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SBA Damage

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SBA Damage

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SBA Scouting

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SBA - Counting

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Natural Enemies

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Stage Days
post planting
Untreated Thiamethoxam
(ppb)
VE* 8 31.4 (3.6) 6509.3 (1204.3)
VC* 11 13.7 (8.2) 9075.0(4550.6)
V1* 14 8.0 (2.7) 1366.1 (405.7)
V1/V2* 18 39.3 (26.4) 151.3 (67.4)
V2 20 0.2 (0.1) 10.0 (4.3)
V2/V3 23 0.7 (1.3) 1.0 (0.3)
V3 26 2.3 (3.1) 6.7 (4.1)
V5 29 0.1 (0.1) 0.5 (0.08)
V6 32 2.0 (3.8) 0.7 (0.2)
R1 35 0.02 (0.01) 0.1 (0.07)
R1 38 0.08 (0.1) 0.08 (0.003)
No Cruiser in
plant
Aphid
arrival

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Neonics vs. SBA

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SBA Threshold

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SBA Threshold
Time
SBADensity/Plant
Economic Threshold (Prediction) = 250
Economic Injury Level (Actual $) = 1,000
7 days

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SBA Threshold
Time
SBADensity/Plant
Economic Threshold (Prediction) = 250
Economic Injury Level (Actual $) = 1,000
7 days

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Spider Mite Damage

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Spider Mites
•Flourish when insects perish!
• Hot AND dry always means more mites
• Will move from dead/dying road and field side grasses
and weeds

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• Moisture-stressed (but not dead) crop is ideal
• Protein concentrated plant sap
• Increased egg-production, shorter generation time
Spider mites

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• Heat and dryness reduce levels of most fungi – including
the pathogens that keep mites in check
Spider mites

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Growth Stage – R3
July 27
August 3

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Growth Stage – R4
July 27
August 3

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Spider Mites - Scouting
Discoloration
– Subtle stippling (field sides)
– Shake method
– Use magnifying lens

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Spider Mites
Spider mites
– Hot & dry
• >80ºF, <50%RH
– Stressed plants
• > nutrition
– Population potential
• 70 X increase 1 wk.
– Epizootics lacking
• < pathogenic fungi
– Dissemination
• > ballooning

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TSM Treatment
Decisions
Discoloration (yellow look-alikes)
– Stippling not bronzing
– Sample for spread
Positively ID mites
– Health of population
FORECASTED WEATHER
– 1+” Rain
• Temporarily changes plant sap
Don’t Mow Field Sides/Ditches

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Pod Feeders

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Bean Leaf Beetle
•Late Planted/Maturing

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BLB – Planting Date
Sampling Date
Mid-Group 3
0
2
4
6
8
10
12
14
24-Aug Sept. 6 Sept. 13 Oct. 4
14-May
30-May
11-Jun
18-Jun
Beetles/Sweep

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October 4 - Sampling
0
5
10
15
20
25
30
mid May late May early June mid June
% Pod Dmg
BLB/Sweep
Planting Time (Mid-Group 3)

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Threshold
Pod Feeding
– 5-10% damage to marketable pods
and beetles still present

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Stink Bugs
Brown marmorated and Brown stink bug
Straw-like mouthpart

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BMSB - Damage

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Green Stink Bug
Adult
Nymphs

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During R5 – R6
40 stink bugs/100 sweeps
Stink Bug Threshold
R5
R6

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Any Questions?