Update 2 – April 12, 2021
The Wisconsin Vegetable Disease and Insect Forecasting Network
Ben Bradford, Dept. of Entomology, UW-Madison – bbradford@wisc.edu, Vegetable Entomology website Russell Groves, Dept. of Entomology, UW-Madison – rgroves@wisc.edu, Vegetable Entomology website Amanda Gevens, Dept. of Plant Pathology, UW-Madison – gevens@wisc.edu
Ben Bradford: An introduction to the Wisconsin Vegetable Disease and Insect Forecasting Network (VDIFN) website
One of the pillars of modern integrated pest and disease management strategies is the use of local climatic and environmental variables to model disease and insect pest risk for a particular field or region. Rather than treating for pests on a preset schedule or waiting for symptoms to appear, growers can anticipate the onset of increased pest risk using predictive models developed and tested for specific disease and insect risks to crops. The outcomes of the use of such models would be increased awareness of current and near future pest and disease risk, as well as the reduction in the use of pesticides and increased profits. There are many such predictive tools available on the market with different costs and benefits – here we present VDIFN, a free tool for growers and residents of Wisconsin that currently includes four plant disease models (Cercospora leaf spot, early blight, late blight, and carrot leaf blight), 24 insect models, and a custom degree-day map generator. VDIFN uses gridded weather data downloaded daily from National Oceanographic and Atmospheric Administration (NOAA) servers. Data include daily min/max temperatures and relative humidity, which are fed into various models and converted into daily disease severity values (or equivalents) or degree-days. These disease severity value and degree-day accumulations are then displayed on the map as color-coded risk scores based on the estimated risk to susceptible crops. Clicking on an individual grid cell brings up the daily history of weather data and disease severity values or degree-days for that location. VDIFN does not currently have the ability to use weather forecasts to run the models out into the future.
How to use VDIFN (https://agweather.cals.wisc.edu/vdifn)
When you visit VDIFN you will see the navigation and settings pane on the left, the map and pest severity display in the center, and a legend on the lower right (see image below). You can switch between disease, insect, and custom model modes with the buttons across the top of the left panel. Pick a model using the Model Selection section, and use the question mark box to get more information on the disease or insect. After selecting a model, note that the date range boxes populate with defaults for each model, but can be adjusted if desired.
The VDIFN landing page with a disease model loaded.
The popup showing weather and model result details for an individual grid point.
The custom degree-day model map maker.
Russell L. Groves: Accumulating Degree Days and Insect Forecasting.
As previously noted in this newsletter, the emergence and periods of peak flight of selected insects can be predicted using the VDIFN website. As a good comparison, the first generation of seed corn maggot flies is now fully underway at several locations in southern and southwestern Wisconsin and is approaching several sites in central Wisconsin. Recall that this insect has a base temperature of 39.2oF and the emergence of adult fly populations are expected at accumulated degree days of 360, 1,080 and 1,800 degree days. In many portions of SW Wisconsin, several locations have just exceeded this value with the recent 4-5 days of warm temperatures. Adult seed corn maggot flies will become very active now and will begin to lay eggs at the base of susceptible (young) plants, where larvae tunnel into underground portions. In somewhat of a contrast, however, the first of three generations of onion maggots will occur when degree day totals reach and exceed 680 degree days (spring), 1950 degree days (summer), and 3230 degree days (fall) respectively, using a similar base temperature of 39.2oF. As you can see from the map, the first generation peak of egg-laying onion maggot adults has not been reached in all portions of the state.
Current status of the Onion Maggot and Seedcord Maggot models (as of April 12, 2021)
Amanda Gevens: Vegetable disease forecasting.
With recent updates to the VDIFNet site we pleased to now offer tools to forecast early blight in potato and tomato and cercospora in beet. These are in addition to forecasts for potato and tomato late blight and carrot foliar disease. As indicated, above, we can include additional models in time to further expand the utility of this forecasting network. Easy access to these forecasts across Wisconsin with use of the NOAA environmental data is a key advantage of this network. I will routinely highlight outputs of this site in the UW Madison Division of Extension Vegetable Crop Updates Newsletter to provide vegetable disease status reports and management recommendations. The models included on the site have been demonstrated as effective in our growing region. In some cases, we have further validated with on-site field research.
Example Early Blight model output from July 1, 2020.