Potato Leafhopper
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Potato Leafhopper
• Damage
– Physical injury to phloem
– Leaves damaged
– Growth stunted, delayed
– Yield loss
• Potato leafhoppers cause
more damage than any
other alfalfa pest in North
America.
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Potato Leafhopper
Proboscis
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Potato leafhopper migrates from
Louisiana each spring
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PLH Life History
Characteristics
1. Long range migration/locally
dispersive
2. Wide range of host plants
3. Explosive growth potential
Management Implications for Alfalfa:
• At the mercy of “regional” population
• Must monitor and spray when
necessary
Potato leaf hopper and damage
V-shaped damage on leaf
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Potato Leafhopper Damage
Yield is
reduced with
plant
stunting
Height of plants
(inches)
Damage caused by Potato leafhopper
20
15
10
5
0
0
40
60
# of Leafhoppers
80
100
120
Potato leafhopper effect on % Crude Protein
% Crude Protein
Forage quality
is lowered
because crude
protein is
reduced
20
26
24
22
20
18
0
20
40
60
80
# of Leafhoppers
100
120
Source: Improving Alfalfa Forage Quality, CASC
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Potato Leafhopper Damage
• New seedings of alfalfa are particularly
susceptible to potato leafhopper damage
• Failure to control potato leafhopper in the
seeding year results in yield loss in
subsequent years.
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Monitoring
When: Mid-June until end of
season
Detection: Sweep net
Sampling: Groups of 20 sweeps
at 5 different locations,
count potato leafhoppers
per sweep
Threshold: Varies with plant
height
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Potato leafhopper scouting and
economic thresholds
Alfalfa
Height
(inches)
Leafhoppers
per sweep
Under 3
0.2 adults
4 to 6
0.5 adults
8 to 111.0 adults/nymphs
12 to 14
2.0 adults/nymphs
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Potato leafhopper scouting and
economic thresholds
If the average potato
leafhopper count exceeds the
height of alfalfa in inches
- treat
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Potato Leafhopper Economic
Thresholds
• The previous economic thresholds are a
starting point. To fine tune a treatment
decision, spray cost and economic value
of crop should be considered.
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Glandular-haired alfalfa and
normal alfalfa
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Economic thresholds for spraying potato leafhopper
in alfalfa (leafhoppers/10 sweeps),
less than 50% resistance
Crop Value of $80 per ton
Cost of Treatment
Canopy
Height
4
8
12
16
$8
29
33
37
41
$10
37
41
45
49
$12
44
48
52
56
$14
52
56
60
64
$16
60
64
68
72
$18
68
72
76
80
$20
76
80
84
88
$18
54
58
62
66
$20
69
73
77
81
Crop Value of $120 per ton
Cost of Treatment
Canopy
Height
4
8
12
16
$8
18
22
26
30
$10
24
28
32
36
$12
29
33
37
41
$14
34
38
42
46
$16
39
43
47
51
Source: Rice and Lefco, IA State.
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Economic thresholds for spraying potato leafhopper
in alfalfa (leafhoppers/10 sweeps),
greater than 50% resistance
Crop Value of $80 per ton
Cost of Treatment
Canopy
Height
4
8
12
16
$8
71
75
79
83
$10
87
91
95
99
$12
103
107
111
115
$14
119
123
127
131
$16
136
140
144
148
Co
$18
153
157
161
165
$20
170
174
178
182
Crop Value of $120 per ton
Cost of Treatment
Canopy
Height
4
8
12
16
$8
49
53
57
61
$10
60
64
68
72
$12
71
75
79
83
$14
82
86
90
94
$16
93
97
101
105
Co
$18
104
108
112
116
$20
115
119
123
127
Source: Rice and Lefco, IA State.
Forage Resources
PLH Resistance Level Categories
Only a percentage of plants within a variety
have resistance to PLH
‘Early generation’ glandular haired alfalfa
varieties were Resistant (Less than 50% level)
HR* = Highly Resistant (>50%)
R = Resistant (31% to 50%)
MR = Moderately Resistance (15% to 30%)
LR = Low Resistance (6% to 14%)
*Late
generation glandular-haired alfalfa varieties have
over 50% resistance (Highly Resistant = HR).
Glandular-Haired Alfalfa Variety PLH Resistance Ratings
www.uwex.edu/ces/forage
Under “select forage varieties” go to the “marketers …” and then
click on the green “Alfalfa”
Variety
Company
Avg.
Yield
Resistance
Rating
Garst 6310
Garst
.
R
Garst 6325
Garst
.
HR
Pioneer 54H91
Pioneer
99
HR
Ameriguard 301
America’s Alfalfa
104
MR
Evergreen 2
NK Brand Seeds
.
HR
FSG 300 LH
Farm Science Genetics
102
HR
FSG 400LH
Farm Science Genetics
.
HR
Interceptor
Agripro Seeds
99
MR
REBEL
Target Seed
.
R
ROOT 66
Trelay
102
R
RUGGED
Target Seed
103
R
Trailblazer 5.0
Croplan Genetics
.
HR
WL 319 HQ
FS Growmark; Olds Seed Soln.
104
LR
WL 346 LH
FS Growmark; Olds Seed Soln.
.
HR
WL 348 AP
FS Growmark; Olds Seed Soln.
100
LR
WL 357 HQ
FS Growmark; Olds Seed Soln.
116
LR
Glandular Haired Alfalfa
• History
– early development in public sector
– commercial development & ultimate
release (1997)
– trait from “exotic” Medicago, but not
GMO
• Mechanism of resistance?
Mechanisms of Plant
Resistance to Insects
• ANTIBIOSIS: plants are “toxic”
• NON-PREFERENCE: insect will go
elsewhere when given choice
• TOLERANCE: plants can withstand
more injury without yield loss
Three “Snapshots” from Arlington,
Wisconsin, in the Evolution of
Glandular Haired Resistance
• 1997, 1st production year (part of 4
state trial)
• 2000, seeding year
• 2003, seeding year
UW Entomology/Agronomy Research
on Glandular-Haired Alfalfa Varieties
Conclusions from 1997
• Overall performance of GH varieties
in WI was disappointing (variable but
“low” levels of resistance)
• Resistance to hopperburn was
apparent, and GH varieties supported
fewer PLH, but this did not translate
into a yield advantage
• GH varieties also showed yield “lag”
in absence of PLH
PIONEER 5454
(no resistance)
DK 131 HG
(53%
resistance)
EVERGREEN
(79%
resistance)
David B. Hogg, John L. Wedberg and Dan J. Undersander
Arlington
2000
2000 YIELDS (Tons/acre)
[Plots cut July 19]
2
1.5
Warrior
Warrior 0.5
No Spray
1
0.5
0
5454
No PLH
Resistance
DK131HG Evergreen
53%
Resistance
79%
Resistance
David B. Hogg, John L. Wedberg and Dan J. Undersander
Conclusions from 2000
• Performance of GH varieties
definitely improved
• Clear yield advantage of GH
varieties in untreated plots, and
no yield lag in absence of PLH
• But GH varieties still lost yield
when not protected
David B. Hogg, John L. Wedberg and Dan J. Undersander
2003 YIELDS (Tons/acre)
[Plots cut July 30]
2
HR = High Resistance
No PLH
53%
Resistance Resistance More than 50% Resistance
Thresholds:
1.5
1X
20X
2X
No Spray
1
0.5
0
o
Pi
4
5
4
5
D
1
K
H
91
L
H
6
4
4
5
o
L3
i
P
W
G
H
1
3
Reid B. Durtschi, David B. Hogg, John L. Wedberg and Dan J. Undersander, 2003
Conclusions from 2003
• Performance of GH varieties further
improved
• Yield responses similar to 2000, but
yield loss gap narrowing in
unprotected plots*
* plus this was under the most
extreme conditions – new seeding
with heavy PLH pressure
Reid B. Durtschi, David B. Hogg, John L. Wedberg and Dan J. Undersander, 2003
Summary
• GH-based PLH resistance has improved
substantially since its (premature?)
commercial release in 1997
– % resistance has increased from 30’s to >
80
– agronomic traits, disease resistance also
improved
• Monitoring still needed for PLH in new
seedings
– Evidence from ’03 suggests using 2X
threshold
– timing might be the more important issue
Potato Leafhopper Resistance
• New seedings should be sprayed at
same threshold as non-resistant
varieties
• With potato leafhopper resistance
greater than 50% thresholds can be
increased up to 2 times before spraying
is necessary.
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Credits:
This presentation was created from a
collaboration among the following
individuals:
Dan Undersander
David Hogg
Bryan Jensen
Eileen Cullen
University of Wisconsin
Richard Leep
Michigan State University
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Paul Peterson
University of Minnesota