Bonus Episode: Predicting Pest Arrival using VDIFN, with Ari Abbrescia, UW Madison Extension

Resources:

VDIFN Tool Ari's tutorial on YouTube for visual aids VDIFN User's Manual Crop Risk Tool [00:00:08] Dan introduces the episode, recorded in advance while he's away, featuring guest Ari Abbrescia, Organic and Sustainable Agricultural Outreach Specialist with UW-Madison Extension.

[00:00:48] Ari provides an overview of the VDIFN (Vegetable Disease and Insect Forecasting Network), including its creators — Dr. Amanda Gevens, Dr. Russ Groves, and Ben Bradford — and its role in supporting integrated pest management across the upper Midwest.

[00:02:06] Dan and Ari dig into a real-world example: why VDIFN appears to show flea beetles absent in Iowa when growers in southern Minnesota are already seeing them.

[00:03:36] Explaining the difference between Fahrenheit degree days (FDD) and growing degree days (GDD), and what those values mean within the flea beetle model.

[00:04:50] Ari clarifies that the VDIFN flea beetle model tracks the first hatched generation — not overwintering adults — which explains the apparent gap between model output and field observations.

[00:07:08] Key takeaway: VDIFN measures risk for damage, not pest presence — an especially important distinction when interpreting disease models like late blight.

[00:07:28] Dan shares how he wants to use VDIFN as a scouting lead-time tool for growers, and discusses Spinosad as a management option against adult flea beetles.

[00:08:42] Ari walks through the seed corn maggot model as a strong example of how VDIFN can directly inform planting timing decisions based on Fahrenheit degree day thresholds.

[00:10:18] Discussion of the early blight model for tomato, including how to use the biofix date and P-day accumulation to time preventative fungicide applications.

[00:11:14] Ari explains what P-days (physiological days) are and how they relate to degree days and disease severity tracking.

[00:14:31] Introduction of the Crop Risk Tool — a newer, still-developing tool built by Ben Bradford that allows users to save named locations, upload CSV field lists, and view risk across multiple models for specific sites.