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Potato Insect Management for Market Growers

Ray Rantz – M.S. Student

Zsofia Szendrei – Professor, Extension Specialist

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Outline

Pest Identification

Colorado potato beetle

Leafhoppers

Aphids

Tarnished plant bug

Flea beetle

Scouting

Monitoring

Thresholds

Management

Cultural

Biological

Chemical

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Colorado potato beetle life cycle

Summer Generation

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Colorado potato beetle defoliation

Photos by J. Obermeyer

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High Defoliation Potential

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Crop rotation

Goal: Reduce continuity in time, create gaps when there is no crop/host
Plant different crops in alternate years, seasons

1 mi

potato

corn

1mi

potato

corn

2023

2024

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Trap crop

Goal: concentrate pests on a small, well-defined area, and kill them while they are there
Potato trap crop planted earlier than main crop on the field border attracts Colorado potato beetles that emerge as soon as there is food to be had.

April

Last year’s potato field

This year’s potato field

8 rows is plenty for trap crop, the best thing to do is to have a band of potatoes that you can cover with one pass of your spray boom. Do not use any at planting insecticide. Any of the foliars listed would be fine, we recommend that you use always the high rate. Since you are applying it to a very small area, a bottle of insecticide will last you for a while. Plant the potatoes at the edge, where your old - and - new fields back up to each other. If you can, plant them at least 2 weeks ahead of the main potato crop. Sometimes its too cold for them to start growing, but any headway you can give the trap potatoes is good. Once they are up, let the beetles accumulate for a bit and don't spray as soon as you see a beetle - remember you are not trying to get yield out of your trap crops, so you should allow higher than normal beetle pressure to build up on your trap crop. This maximizes the number of beetles killed for the amount of insecticides used. Foliars on the trap crops may need to be sprayed 2-3 times in the spring, applications are typically a week or two apart (the key is to let the population build up again between sprays).

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Trap crop

8-rows or a sprayer’s width
Plant ~2 weeks before main crop
Let beetles accumulate then spray
Spray 2-3 times one week apart

8 rows is plenty for trap crop, the best thing to do is to have a band of potatoes that you can cover with one pass of your spray boom. Do not use any at planting insecticide. Any of the foliars listed would be fine (Agrimek, BlackHawk, Athena, Radiant), I recommend that you use always the high rate. Since you are applying it to a very small area, a bottle of insecticide will last you for a while. Plant the potatoes at the edge, where your old - and - new fields back up to each other. If you can, plant them at least 2 weeks ahead of the main potato crop. Sometimes its too cold for them to start growing, but any headway you can give the trap potatoes is good. Once they are up, let the beetles accumulate for a bit and don't spray as soon as you see a beetle - remember you are not trying to get yield out of your trap crops, so you should allow higher than normal beetle pressure to build up on your trap crop. This maximizes the number of beetles killed for the amount of insecticides used. Foliars on the trap crops may need to be sprayed 2-3 times in the spring, applications are typically a week or two apart (the key is to let the population build up again between sprays).

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Scouting and Thresholds

Scouting: V or W-shaped pattern
Check margins and inside
Check whole plant (under leaves)

Egg masses underneath lower leaves

20% defoliation before yield loss occurs
Threshold: Average1 large larvae or 1 adult per checked plants

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Colorado potato beetle insecticide program

Conventional:

Over-wintered generation: at-planting neonicotinoid
Summer generation: Foliar application of Blackhawk, Coragen, Agri-Mek, Delegate, Exirel, etc.
Stay away from carbamates, pyrethroids– resistant beetles

Organic:

Entrust

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Potato flamer

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Cultural management

Plant mulches deter adults from the field

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Potato Leafhopper “Hopperburn”

Photos by J. Obermeyer and Z. Szendrei

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Potato Leafhopper Management

Scouting: undersides of leaves, or sweep larger plants
Thresholds: Early signs of hopperburn

1 nymph per 10 leaves
1 adult per 2 sweeps

Yield loss potential
Some biological control
Timely irrigation
Management: Pyrethroids, pyrethrum (OMRI)

Minute pirate bug

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Flea Beetles

Photos by J Obermeyer

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Flea Beetle Management

Scouting: “bullet holes”- small and fast to jump
Thresholds: not known, economic loss rare due to defoliation
Crop rotation
Remove crop debris, weeds and other surface trash – larvae/pupae in soil
Rarely reach economic threshold
More problematic later in the season
Management: pyrethroids, neem

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Aphid Damage��Aphids

Photo by Stuart Greig

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Aphid management

Scouting: 3 leaves/plant, count aphids on top, middle and bottom leaf
Thresholds: 30/3 leaves, and for <2 weeks before vine kill, 15/3 leaves
Disease (PVY) transmitter
Hedgerows/woodlots reduce wind velocity to reduce aphid falls

Management:

Reflective mulches
Oil sprays
Biological control – reduce broad spectrum insecticide applications

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Tarnished Plant Bug

Photos by E. Banks, S. Squire

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Tarnished Plant Bug Management

Scouting: sweep net
Thresholds: 25 adults per 25 sweeps
Rarely reach threshold
Don’t mistake nymphs for aphids
Management: remove overwintering sites - common weeds

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Wireworms

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good drainage
crop rotation: most problematic in fields that had grassy weeds, sod/hay/pasture before potato (grassy crops), cereal cover crop
varietal differences: lower preference for Russet Norkotah
Organic: baits
Conventional: pre-plant neonicotinoids

Wireworm management

Scouting/Threshold

Management

More info on building traps, sampling, management

Some problems with scouting is that the wireworms can be unevenly distributed throughout the field and may only cause significant issues in a portion of the field. Important to check in previous grassy fields before planting because wireworms might be present, and once potatoes are damaged you won’t know until harvest (too late). One wireworm per trap is equivalent to 20,000 wireworms per acre. There are no foliar applications. Seems like many years of alfalfa will also lower populations allowing for safe potato planting. Don’t bring up soil fumigation

wireworms seem to dislike chipping potatoes or Shepody. (same ref as russet norkotah quote, I think. Cropwatch)

https://cropwatch.unl.edu/potato/wire_worm

https://www.uidaho.edu/extension/ipm/ag-pests/arthropods/wireworm-potato

https://s3.wp.wsu.edu/uploads/sites/2075/2013/05/Wireworm-Scouting-FS059E1.pdf

Innovative ways to control wireworms: https://www.potatoesincanada.com/new-tools-to-battle-wireworm-30168/

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Coragen,

Agri-Mek,

Blackhawk,

Entrust

Admire or Platinum - neonicotinoid at planting

Warrior or Baythroid - foliar pyrethroid

Fulfill, oils – paralyzes mouthparts, only sucking insects

An example of a potato insecticide management program

May

August

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Handy potato scouting form, including pest thresholds / methods

Scouting form

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