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Degree Days for Common Insect Pests

🔍 Insect Pests by Common Name

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Y

Z

Degree Days for Common Insect Pests

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Degree days (also known as heat units or thermal units) are a way of incorporating both temperature and time into one measurement to quantify the rate of plant or insect development. All plants and insects develop in response to temperature. The warmer the weather, the more quickly they develop, and the cooler the temperature, the slower they develop.

Learn to calculate degree days

A

Apple Maggot*

Base temperature = 50°F

1^st adult fly emergence = 900 DD₅₀

1^st egg laying = 1,100 DD₅₀

Peak fly emergence 1,600 = DD₅₀

Peak egg laying = 1,750 DD₅₀

End of fly emergence = 2,800 DD₅₀

* These degree days assume normal soil moisture. Under dry conditions, all apple maggot events will be delayed until the soil is moist.

Ash Borer

Base temperature = 50°F

1^st instar larvae = 275-500 DD₅₀

Asparagus Beetle

Base temperature = 50°F

Egg laying = 150 – 240 DD₅₀
(Phenology: Amelanchier in full bloom, redbud early to full bloom, Black Hills spruce bud caps splitting)

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B

Birch Leafminer

Base temperature = 50°F

1^st generation larvae = 275-500 DD₅₀

Black Vine Weevil

Base temperature = 50°F

1^st generation adults = 400-600 DD₅₀

2^nd generation adults = 900-1,000 DD₅₀

Bronze Birch Borer

Base temperature = 50°F

Larvae = 400-500 DD₅₀

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C

Cabbage Maggot

Base temperature = 43°F

1^st generation flies = 300 DD₄₃

2^nd generation flies = 1,476 DD₄₃

3^rd generation flies = 2,652 DD₄₃
(Phenology: 1^st generation eggs are laid when the common lilac is in full bloom)

Codling Moth Degree Days

Base temperature = 50°F

1^st generation moth emergence = 150 DD₅₀

Eggs laid = 250 DD₅₀

1^st generation peak moth emergence = 500 DD₅₀

Peak egg laying = 550 DD₅₀

2^nd generation first moth emergence =1,150 DD₅₀

2^nd generation peak moth emergence = 1,600 DD₅₀

2^nd generation peak egg laying = 1,700 DD₅₀

Colorado Potato Beetle (First generation)

Base temperature = 50°F

Begin counting when first eggs appear

1^st instar larva = 185 DD₅₀

2^nd instar larva = 240 DD₅₀

3^rd instar larva = 300 DD₅₀

4^th instar larva = 400 DD₅₀

Pupa = 675 DD₅₀

Cooley Spruce Gall Adelgid

Base temperature = 50°F

Adults = 50-100 DD₅₀

Egg hatch = 210 DD₅₀

Galls forming = 250 DD₅₀

2^nd generation nymphs = 2,800-3,000 DD₅₀

Corn Rootworm

Base temperature = 50°F

Adult beetles = 1,300 DD₅₀
(Phenology: Canada thistle seed ripe, Queen Anne’s lace early bloom)

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E

Eastern Spruce Gall Adelgid

Base temperature = 50°F

Adults = 50-100 DD₅₀

Egg hatch = 90 DD₅₀

1^st instar larvae = 100 DD₅₀

2^nd generation nymphs = 2,800-3,000 DD₅₀

Eastern Tent Caterpillar

Base temperature = 50°F

Egg hatch = 50 DD₅₀

1^st instar larvae = 100 DD₅₀

2^nd instar larvae = 140 DD₅₀

3^rd instar larvae = 350 DD₅₀

Adults = 725 DD₅₀

Elm Leaf Beetle

Base temperature = 50°F

Larvae = 400-500 DD₅₀

Elm Sawfly

Base temperature = 50°F

Larvae = 365 DD₅₀

Euonymous Scale

Base temperature = 50°F

Crawlers = 500-700 DD₅₀

European Corn Borer

Base temperature = 50°F

1^st spring moths = 375 DD₅₀
(Phenology: Spiraea x vanhouttei in full bloom)

1^st eggs = 450 DD₅₀
(Phenology: Pagoda dogwood late bloom)

Peak spring moths = 631 DD₅₀
(Phenology: Black locust full bloom)

1^st summer moths = 1,400 DD₅₀
(Phenology: Mountain-ash fruit golden yellow, most Canada thistle seed ripe)

1^st eggs laid = 1,450 DD₅₀

1^st egg hatch = 1,550 DD₅₀

Peak summer moths = 1,733 DD₅₀

Summer treatment period = 1,550–2,100 DD₅₀
(Phenology: From when Queen Anne’s lace full bloom to goldenrod early bloom)

European Pine Sawfly

Base temperature = 50°F

1^st instar larvae = 50-100 DD₅₀

European Pine Shoot Moth

Base temperature = 50°F

Spring larvae active = 50-100 DD₅₀

Adults = 900 DD₅₀

Egg hatch = 200-100 DD₅₀

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F

Fall Webworm

Base temperature = 50°F

Larvae = 850 DD₅₀

Fleabeetle

Base temperature = 50°F

150-200 DD₅₀
(Phenology: Norway maple late bloom, Amelanchier blooming, redbud early bloom)

Fletcher Scale

Base temperature = 50°F

Adults = 100-200 DD₅₀

Egg hatch = 600 DD₅₀

Crawlers active = 900-1,200 DD₅₀

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H

Hawthorn Leafminer

Base temperature = 50°F

Larvae = 275-500 DD₅₀

Honeylocust Plantbugs

Base temperature = 50°F

100-200 DD₅₀

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I

Imported Cabbageworm

Base temperature = 50°F

Adult butterflies at 150-240 DD₅₀
(Phenology: Amelanchier full bloom, redbud early to full bloom, Black Hills spruce bud caps splitting)

Imported Willow Leaf Beetle

Base temperature = 50°F

200-350 DD₅₀

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J

Japanese Beetle

Base temperature = 50°F

Adults = 900-1,200 DD₅₀

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M

Mountain Ash Sawfly

Base temperature = 50°F

500 DD₅₀

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O

Obliquebanded Leafroller

Base temperature = 43°F

1^st generation moth emergence 600 DD₄₃

1^st generation peak moth emergence 800 DD₄₃

1^st generation peak egg laying 1,250 DD₄₃

2^nd generation moth emergence 2,050 DD₄₃

2^nd generation first eggs laid 2,300 DD₄₃

Onion Maggots

Base temperature = 40°F

1^st generation flies = 680 DD₄₀

2^nd generation flies = 1,950 DD₄₀

3^rd generation flies = 3,230 DD₄₀

1^st generation eggs laid = 230-280 DD₄₀

Oystershell Scale (brown race)

Base temperature = 50°F

Egg hatch = 265 DD₅₀

1^st generation crawlers = 275-500 DD₅₀

2^nd generation crawlers = 1,600-1,700 DD₅₀

Oystershell Scale (grey race)

Base temperature = 50°F

1^st generation crawlers = 400-600 DD₅₀

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P

Pine Needle Scale

Base temperature = 50°F

1^st generation crawlers = 200-350 DD₅₀

2^nd generation crawlers = 1,600-1,700 DD₅₀

Pine Spittlebug

Base temperature = 50°F

1^st generation egg hatch = 145 DD₅₀

2^nd generation egg hatch = 1,500 DD₅₀

2^nd generation crawlers = 1,500-1,600 DD₅₀

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S

Seed Corn Maggot

Base temperature = 39°F

1^st generation flies = 200 DD₃₉

2^nd generation flies = 600 DD₃₉

Spongy Moth

Base temperature = 50°F

Egg hatch = 100-200 DD₅₀

Larvae = 200-350 DD₅₀

Spruce Spider Mite

Base temperature = 50°F

100-200 DD₅₀

Squash Vine Borer

Base temperature = 50°F

Egg laying at 900-1,000 DD₅₀
(Phenology: Chicory in full bloom)

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T

Taxus Mealybug

Base temperature = 50°F

275-500 DD₅₀

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V

Viburnum Crown Borer

Base temperature = 50°F

1^st instar larvae = 500-600 DD₅₀

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Z

Zimmerman Pine Shoot Moth

Base temperature = 50°F

1^st generation larvae (1^st instar) = 100 DD₅₀

2^nd generation larvae (1^st instar) = 2,700-2,900 DD₅₀

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Special thanks to Karen Delahaut (formerly UW-Madison Fresh Market Vegetable Program) for work on earlier versions of this document.