Authors: Karen Delahaut, UW-Madison Fresh Market Vegetable Program

Last Revised: 04/20/2015

D-number: XHT1087

Common Vegetable Insects That Can Be Monitored Using Degree Days or Indicator Plants

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

 

 

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

 

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

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

European Corn Borer
Base temperature = 50^oF
1^st spring moths at 375 DD₅₀
(Spiraea x vanhouttei in full bloom)
1^st 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)
1^st eggs at 1450 DD₅₀
1^st 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 = 50oF
150-200 DD50
(Norway maple late bloom, Amelanchier blooming, redbud early bloom)
Imported Cabbageworm
Base temperature = 50^oF
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^oF
680, 1950, 3230 DD₄₀ for 1^st, 2^nd, & 3^rd generation flies
1^st generation eggs laid 230-280 DD₄₀

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

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

 

 

 

Common Fruit Insects That Can Be Monitored Using Degree Days or Indicator Plants

Apple Maggot*
Base temperature = 50^oF
1^st adult fly emergence 900 DD₅₀
1^st 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^oF
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 1150 DD₅₀
2^nd generation peak moth emergence 1600 DD₅₀
2^nd generation peak egg laying 1700 DD₅₀

Obliquebanded Leafroller
Base temperature = 43^oF
1^st generation moth emergence 600 DD₄₃
1^st generation peak moth emergence 800 DD₄₃
1^st generation peak egg laying 1250 DD₄₃
2^nd generation moth emergence 2050 DD₄₃
2^nd 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.

 

This Fact Sheet is also available in PDF format:

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Thanks to Michelle Miller and Susan Mahr for reviewing this document.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.wisc.edu.