How VegEdge Monitors Moth Flights and Calculates Degree-Days

Updated

VegEdge (vegedge.umn.edu) tracks two things during the growing season to help vegetable growers time pest management: moth flight activity and accumulated degree-days for key insect pests. Each year it monitors European corn borer (ECB) and corn earworm (CEW) moth catch throughout Minnesota and posts updates on a Weekly Moth Flight page, while separately calculating degree-days for key insect pests and publishing state and region-wide updates. Both tools exist to support integrated pest management (IPM) decisions — they tell you when a pest is active and how far its development has progressed, not just that it exists.

The Moth Flight Network

The Moth Flight Network is a season-long monitoring program. Each year, ECB and CEW moths are trapped across the state, and the catch data is compiled into activity updates.

  • What is monitored: European corn borer (ECB) and corn earworm (CEW) moth catch.
  • Where updates appear: The Weekly Moth Flight page, with activity updates posted through the season.
  • Why it matters: Moth catch is a direct signal of adult activity. For pests like CEW, which migrate in and can't overwinter in the Upper Midwest, trap catch is often the first indication that pressure is building in a region.

The page evidence describes this as: "Each year we monitor ECB and CEW moth catch throughout the state. We will provide updates on their activity on the Weekly Moth Flight page."

Degree-Days for Pests

Degree-days are a running measure of heat accumulation. Because insect development is driven by temperature rather than calendar date, degree-day totals let you estimate which life stage a pest has reached — and therefore when a control measure will actually work.

VegEdge calculates degree-days for key insect pests and provides updates at both state and region-wide levels throughout the growing season. The site points readers to a Degree-Days section for these updates.

The practical value: a calendar date tells you it's mid-July; a degree-day total tells you whether a given pest has reached the stage where scouting or treatment is warranted in your area. Because the updates are broken out by region, growers in different parts of Minnesota can act on conditions closer to their own fields rather than a single statewide average.

How the Two Tools Work Together

Tool What it measures What it tells you
Moth Flight Network Adult moth catch (ECB, CEW) Whether adult activity is occurring and where
Degree-days for Pests Accumulated heat units How far pest development has progressed

Used together, they cover two different questions. Moth flight data answers "are the adults flying?" Degree-day data answers "how far along is development?" A management decision typically needs both — knowing moths are active is useful, but knowing the pest has reached a susceptible stage is what determines whether an action is timed correctly.

Where This Fits in the Broader VegEdge Site

VegEdge is a University of Minnesota resource providing objective information on all aspects of vegetable crop IPM, focused on the Midwestern U.S., drawing on 25+ years of University of Minnesota research. Alongside the moth flight and degree-day tools, the site carries:

  • News & Pest Alerts — time-sensitive notices, such as the Winsome Fly fact sheet (a biocontrol agent for Japanese beetle now spreading naturally in Minnesota) and a citizen science project led by entomologist Bill Hutchison.
  • Weekly Vegetable Update — weekly field observations from IPM Extension Educators Natalie Hoidal and Marissa Schuh, published on the Fruit and Vegetable News site.
  • Topical articles — for example, a Spring 2023 FSMA update on agricultural water for produce growers, and a piece on tomato transplants and bacterial disease (bacterial spot, speck, and canker), noting that control begins during transplant production.

Using These Tools in Practice

If you're a grower, processor, or crop consultant, the workflow the site supports looks like this:

  1. Check the Weekly Moth Flight page during the season to see whether ECB or CEW activity is being recorded in your region.
  2. Check the Degree-Days updates for the pest you're managing to gauge its developmental stage in your area.
  3. Combine both signals with your own field scouting before deciding on treatment timing.
  4. Watch News & Pest Alerts and the Weekly Vegetable Update for emerging issues and observations from around the state.

Sampling remains the foundation — as the site notes, sampling is a key component of IPM because it lets you estimate the population density of the pest or pest complex in your own field. The moth flight and degree-day tools sharpen the timing of that sampling; they don't replace it.