Karen Delahaut, UW-Madison Fresh Market Vegetable Program
Revised:  8/6/2012
Item number:  XHT1087

Common Vegetable Insects that can be monitored using degree days or indicator plants

Cabbage Maggot
Base temperature = 43°F
300, 1476, 2652 DD43 for 1st, 2nd, & 3rd generations flies
1st generation eggs are laid when the common lilac is in full bloom

Colorado potato beetle, 1st generation
Base temperature = 50°F
Begin counting when first eggs appear
1st instar larva at 185 DD50
2nd instar larva at 240 DD50
3rd instar larva at 300 DD50
4th instar larva at 400 DD50
Pupa at 675 DD50

Common Asparagus Beetle
Base temperature = 50°F
Egg laying at 150 – 240 DD50
(Amelanchier full bloom, redbud early to full bloom, Black Hills spruce bud caps splitting)

Corn Rootworm
Base temperature = 50°F
Adult beetles present at 1300 DD50
(Canada thistle seed ripe, Queen Anne’s lace early bloom)

European Corn Borer
Base temperature = 50°F
1st spring moths at 375 DD50
(Spiraea x vanhouttei in full bloom)
1st eggs at 450 DD50
(Pagoda dogwood late bloom)
Peak spring moths at 631 DD50
(Black locust full bloom)
1st summer moths at 1400 DD50
(Mountain-ash fruit golden yellow, most Canada thistle seed ripe)
1st eggs at 1450 DD50
1st egg hatch at 1550 DD50
Peak summer moths at 1733 DD50
Summer treatment period at 1550 – 2100 DD50
(Queen Anne’s lace full bloom – 1500 to goldenrod early bloom – 2100)

Fleabeetles
Base temperature = 50°F
150-200 DD50
(Norway maple late bloom, Amelanchier blooming, redbud early bloom)

Imported Cabbageworm
Base temperature = 50°F
Adult butterflies at 150-240 DD50
(Amelanchier full bloom, redbud early to full bloom, Black Hills spruce bud caps splitting)

Onion Maggots
Base temperature = 40°F
680, 1950, 3230 DD40 for 1st, 2nd, & 3rd generation flies
1st generation eggs laid 230-280 DD40

Squash Vine Borer
Base temperature = 50°F
Egg laying at 900-1000 DD50
(Chicory full bloom)

Seed Corn Maggot
Base temperature = 39°F
200, 600 for 1st and 2nd generation flies

Common Fruit Insects that can be monitored by degree days or indicator plants

Apple Maggot*
Base temperature = 50°F
1st adult fly emergence 900 DD50
1st egg laying 1100 DD50
Peak fly emergence 1600 DD50
Peak egg laying 1750 DD50
End of fly emergence 2800 DD50
*These degree days assume normal soil moisture.  Under dry conditions, all apple maggot events will be delayed until the soil is moist.

Codling Moth
Base temperature = 50°F
1st generation moth emergence 150 DD50
Eggs laid 250 DD50
1st generation peak moth emergence 500 DD50
Peak egg laying 550 DD50
2nd generation first moth emergence 1150 DD50
2nd generation peak moth emergence 1600 DD50
2nd generation peak egg laying 1700 DD50

Obliquebanded Leafroller
Base temperature = 43°F
1st generation moth emergence 600 DD43
1st generation peak moth emergence 800 DD43
1st generation peak egg laying 1250 DD43
2nd generation moth emergence 2050 DD43
2nd generation first eggs laid 2300 DD43

For more information on phenology:  See University of Wisconsin Garden Facts XHT1085, XHT1086 and XHT1088, or contact your county Extension agent.

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