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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

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Potato leaf hopper and damage

V-shaped damage on leaf

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Potato Leafhopper DamageDamage caused by Potato leafhopper

0

5

10

15

20

0 20 40 60 80 100 120# of Leafhoppers

Hei

ght o

f pla

nts

(inch

es)

Potato leafhopper effect on % Crude Protein

18

20

22

24

26

0 20 40 60 80 100 120# of Leafhoppers

% C

rude

Pro

tein

Source: Improving Alfalfa Forage Quality, CASC

Yield is reduced with plant stunting

Forage quality is lowered because crude protein is reduced

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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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MonitoringWhen: 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 LeafhoppersHeight per sweep(inches)

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% resistanceCrop Value of $80 per ton

Cost of TreatmentCanopy Height $8 $10 $12 $14 $16 $18 $20

4 29 37 44 52 60 68 768 33 41 48 56 64 72 80

12 37 45 52 60 68 76 8416 41 49 56 64 72 80 88

Crop Value of $120 per ton

Cost of TreatmentCanopy Height $8 $10 $12 $14 $16 $18 $20

4 18 24 29 34 39 54 698 22 28 33 38 43 58 73

12 26 32 37 42 47 62 7716 30 36 41 46 51 66 81

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 Cost of TreatmentCanopy Height $8 $10 $12 $14 $16 $18 $20

4 71 87 103 119 136 153 1708 75 91 107 123 140 157 174

12 79 95 111 127 144 161 17816 83 99 115 131 148 165 182

Crop Value of $120 per ton

Cost of Treatment Cost of TreatmentCanopy Height $8 $10 $12 $14 $16 $18 $20

4 49 60 71 82 93 104 1158 53 64 75 86 97 108 119

12 57 68 79 90 101 112 12316 61 72 83 94 105 116 127

Source: Rice and Lefco, IA State.

HR* = Highly Resistant (>50%)R = Resistant (31% to 50%)MR = Moderately Resistance (15% to 30%)LR = Low Resistance (6% to 14%)

PLH Resistance Level CategoriesOnly a percentage of plants within a variety

have resistance to PLH‘Early generation’ glandular haired alfalfa

varieties were Resistant (Less than 50% level)

*Late generation glandular-haired alfalfa varieties have over 50% resistance (Highly Resistant = HR).

Glandular-Haired Alfalfa Variety PLH Resistance Ratingswww.uwex.edu/ces/forage

Under “select forage varieties” go to the “marketers …” and then click on the green “Alfalfa”

LR116FS Growmark; Olds Seed Soln.WL 357 HQLR100FS Growmark; Olds Seed Soln.WL 348 APHR.FS Growmark; Olds Seed Soln.WL 346 LHLR104FS Growmark; Olds Seed Soln.WL 319 HQHR.Croplan GeneticsTrailblazer 5.0R103Target SeedRUGGEDR102TrelayROOT 66R.Target SeedREBEL

MR99Agripro SeedsInterceptorHR.Farm Science GeneticsFSG 400LHHR102Farm Science GeneticsFSG 300 LHHR.NK Brand SeedsEvergreen 2MR104America’s AlfalfaAmeriguard 301HR99PioneerPioneer 54H91HR.GarstGarst 6325R.GarstGarst 6310

ResistanceRating

Avg. Yield

CompanyVariety

LR116FS Growmark; Olds Seed Soln.WL 357 HQLR100FS Growmark; Olds Seed Soln.WL 348 APHR.FS Growmark; Olds Seed Soln.WL 346 LHLR104FS Growmark; Olds Seed Soln.WL 319 HQHR.Croplan GeneticsTrailblazer 5.0R103Target SeedRUGGEDR102TrelayROOT 66R.Target SeedREBEL

MR99Agripro SeedsInterceptorHR.Farm Science GeneticsFSG 400LHHR102Farm Science GeneticsFSG 300 LHHR.NK Brand SeedsEvergreen 2MR104America’s AlfalfaAmeriguard 301HR99PioneerPioneer 54H91HR.GarstGarst 6325R.GarstGarst 6310

ResistanceRating

Avg. Yield

CompanyVariety

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

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

UW Entomology/Agronomy Researchon Glandular-Haired Alfalfa Varieties

PIONEER 5454(no resistance)

DK 131 HG (53%

resistance)

EVERGREEN (79%

resistance)

Arlington 2000

David B. Hogg, John L. Wedberg and Dan J. Undersander

2000 YIELDS (Tons/acre) [Plots cut July 19]

0

0.5

1

1.5

2

5454 DK131HG Evergreen

WarriorWarrior 0.5No Spray

No PLHResistance

53% Resistance

79% ResistanceDavid 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]

Thresholds:

0

0.5

1

1.5

2

1X20XNo Spray2X

Reid B. Durtschi, David B. Hogg, John L. Wedberg and Dan J. Undersander, 2003

No PLHResistance

53% Resistance

HR = High ResistanceMore than 50% Resistance

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

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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 UndersanderDavid HoggBryan JensenEileen CullenUniversity of Wisconsin

Richard LeepMichigan State University

Paul PetersonUniversity of Minnesota