Title: STINK BUG THRESHOLDS: EMPLOY AFTER 2% STINK BUG DAMAGED CONFIRMED IN BOLLWORM SCOUTING
1Stink Bug and Plant Bug Management in North
Carolina Training Module
Jack Bacheler NCSU
2Bollgard Adoption in NC 1996 - 2004
( of total cotton acreage)
83.1
69.7
63.5
72.5
54.6
Bollgard Acres (x 1000)
20.2
12.6
2.8
3.0
Year
3Insecticide Applications / Acre 1996 - 2004
Conv. 2.8 Bollgard 0.9
4Insect Shifts with Bt Cottons
Bollworms Budworms Europ. Corn Borers
Thrips Cotton Aphids Early Plant Bugs
Stink Bugs Late Plant Bugs Leaf-footed Bugs
5Undamaged Open Boll
Stink Bug Damage
6Stink Bug Damage to Bolls Bollgard vs.
Conventional Cotton, 1996-2004
83
Damaged Bolls
64
55
20
72
70
13
Year
7Almost all bug damage to bolls in NC is caused by
the following
Brown Stink Bug
Green Stink Bug
Plant Bug
8Southern Green
Green
Brown
Common Stink Bug Nymphs
9Plant Bug Adult
10Plant Bug Nymph
11Pre-bloom Square Loss to Plant Bugs Generally of
Little Consequence in NC
12Post-bloom Plant Bug Damage
13Late Season Plant Bug Thresholds
15 Dirty Blooms
10 Internal Boll Damage (also varies like stink
bug)
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15Effect of Various Stink Bug Stageson Harvestable
Locks in NC
GSB Green Stink Bug BSB Brown Stink Bug
97
No SB
84
83
GSB 3rd
GSB 4th
Harvestable Locks
47
40
BSB adult
34
GSB 5th
GSB adult
Stink Bug Species and Instar
16Scouting for Stink Bugs
- Sample at least 50 quarter-sized bolls
- Crush or cut open all bolls and examine lint
and boll walls - Count warts and internal damage
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18Scouting for Stink Bugs
- Sample at least 50 quarter-sized bolls
- Crush or cut open all bolls and examine lint
and boll walls - Count warts and internal damage
19Penetrations
Wart
Wart
Stained lint
Internal Boll Damage by Stink Bugs
20Scouting for Stink Bugs
- Sample at least 50 quarter-sized bolls
- Crush or cut open all bolls and examine lint
and boll walls - Count warts and internal damage
21Current Stink Bug Thresholds in North Carolina
- 10 damaged internally-damaged bolls (first
3.5 wks. of bloom) -
- Then raise threshold based on proportion of
bug safe bolls (see next slides)
22When is a Boll Safe from Stink Bugs?
Answer at approx. 25 Days
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27Possible Boll Sizer?
Small-bolled lines 2nd positions 7-9 weeks
post-blm.
Large-bolled lines 1st position 4-6 weeks
post-blm.
28Suggested Damaged Boll Thresholds for Stink Bugs
Boll Ratio
Safe (gt 1.25 dia.)
Susceptible (lt 1.25 dia.)
Threshold ()
10
0
1
15
0.5
1
20
1
1
25
1.5
1
30
2.0
1
35
2.5
1
A BollChecker may be helpful in determining
ratios. Boll diameter approximately 1.25
inches or larger.
29Summary of Scouting Procedures
- Conduct initial boll-sizing approx. 4 wks after
1st - bloom.
- Cut open or crush 25 to 50 quarter-sized
bolls/ - field and examine for internal damage
- Count any internal damage except pin pricks
- Try to determine ratio of brown or green stink
bugs - If ½ threshold or more is reached, re-scout
field - within a few days