Potato Leafhopper

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Potato Leafhopper
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Forage
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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.
Forage Resources
Potato Leafhopper
Proboscis
Forage Resources
Potato leafhopper migrates from
Louisiana each spring
Forage Resources
Forage Resources
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
Forage Resources
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
Forage Resources
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.
Forage Resources
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
Forage Resources
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
Forage Resources
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.
Forage Resources
Glandular-haired alfalfa and
normal alfalfa
Forage Resources
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.
Forage Resources
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.
Forage Resources
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
Forage
Resources
Paul Peterson
University of Minnesota
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