Category Archives: about models

NEWA webinar provides training for the Northern Grapes Project

New York State IPM Program staff members Tim Weigle and Dan Olmstead got together and gave a 1-hour webinar for the Northern Grapes Project on 10 April 2018.

Dan provided a 20-minute boot camp on NEWA basics including history, navigation, general tool categories, and future directions. Tim gave in-depth 40-minute that covered NEWA grape disease and insect risk assessment tools. These included phomopsis, powdery mildew, black rot, downy mildew (DMCast), powdery mildew, and grape berry moth.

Tim Weigle is the Statewide Grapes IPM Specialist at NYS IPM and is located in Portland, NY with the Lake Erie Regional Grape Program.

Dan Olmstead is the NEWA Coordinator at NYS IPM and is located in Geneva, NY on the Cornell AgriTech NYSAES campus.

Learn more about the Northern Grapes Project by clicking here.

Implementing NEWA Weather and Pest Model Information into a Vineyard IPM Strategy

Readers choice: degree day report options

Alan Teach of Sunrise Orchards in Gays Mills, WI wrote in this week asking what the differences are between degree day reports shown on weather station pages (Figure 1). Let’s talk more about degree day models and the differences among those offered on NEWA.

Figure 1. Three standard degree day reports are offered on NEWA weather station pages.

What is a degree-day model?

A degree-day model is used to estimate insect or plant development through different life stages. Basic parameters of a model include the minimum temperature at which growth can occur. This is termed the base temperature or lower development threshold. Sometimes a maximum temperature is also used, called the upper development threshold.

The simplest way to calculate degree days is a subtraction of the base temperature from the average temperature over a period of time. Consider the following example.

Day X has a minimum recorded temperature of 46F. Maximum temperature was 67F. Insect Y has a minimum development temperature of 50F. We calculate degree days on Day X for insect Y in the following way.

  1. Day X average temperature = (min TEMP + max TEMP)/2 = (46+67)/2 = 56.5F
  2. Insect Y degree days on Day X = average temp – base temp = 56.5F – 50F = 6.5 degree days

6.5 heat units are calculated for Insect Y on Day X. If temperatures are warmer, more units accumulate. If temperatures are colder, fewer. No heat units are accumulated if degree days are calculated to be less than 0. Development stops but does not reverse.

You can also review our overview of degree-day models on the NEWA website.

What’s the difference between model reports on weather station pages?

Allen’s question asks about differences between base 50F, base 50F BE, and base 85/50F reports. With a better understanding of how degree days are calculated, this question is more easily answered.

Base 50F

This model uses a base temperature of 50F. The example above calculated degree days in this manner. This is a common and straightforward method.

Base 50F BE

50F is also used as the base temperature in this model. BE is a reference to the Baskerville-Emin method of calculating degree days. The calculations look similar to the standard methods at temperatures well above threshold. For example when min temperature is 65F and max temperature is 85F.

But Baskerville-Emin is better at calculating accumulation on days where temperatures are close to the threshold. For example, consider a day when the minimum temperature is 40F and the maximum temperature is 60F. A basic degree calculation would show an accumulation of 0. In reality, some degree days are likely to have accumulated because a good portion of the day was in fact above 50F. Base 50F BE accounts for these close margins and should provide a more precise measurement of actual degree-day accumulation.

Base 85/50F

This model is similar to a base 50F model but also restricts accumulation by imposing an upper-temperature threshold. In the same way that degree day accumulation is restricted by a base temperature, accumulation of heat units is restricted when the maximum daily temperature approaches 85F. An 85/50F model is particularly suited to measurement of corn development for example.

Other degree day models

The most common degree-day models are directly available from weather station pages but the NEWA degree day calculator has many more options with a total of 14 available iterations of this model type (Figure 2).

Figure 2. Fourteen degree-day models are available in the NEWA degree-day calculator.

This feature is available using data from any active NEWA location. Select the ‘Weather Data’ drop-down menu from NEWA’s main navigation bar and select ‘Degree Day Calculator.’ Choose your State, Weather station, Degree day type, accumulation start, and end dates and click ‘Get report.’

Figure 3. Snapshot report of customized degree day calculations from the NEWA degree-day calculator.

The output report provides a snapshot of your chosen degree day model accumulation for the past two days as well as a 5-day forecast. This model also works with historical dates, relabeling ‘5-day forecast’ as ‘Ensuing 5-days’ to indicate historical data.

Submit your ideas

If you have an idea or question for the NEWA blog, send a request to or submit a request by following the ‘Help‘ link found in the main navigation bar at

Apple Tools made Easier to Use

NEWA now (1) will save your apple biofix dates, (2) has a button to click out of apple biofix dates that are too early, and (3) provides the full interface for apple pest forecast tools accessed from the Station Pages. You may need to clear your browser’s cache to enable local storage and see these changes.

(1) Biofix and orchard characteristics
Tired of entering green tip dates, bloom dates, etc., over and over again? We’re now caching that! The apple diseases, apple carbohydrate thinning, and apple irrigation tools on NEWA will now save the green tip date, first blossom open date, orchard blight history selection, bloom date, petal fall date, trees per acre, and age of orchard, that you entered when last using the tool.

Here’s what’s saved after you enter it:
Apple Scab – green tip date (50% green tip on ‘McIntosh’ apple or closest equivalent)
Fire Blight – first blossom open date on variety of interest & orchard blight history selection for block of interest
Sooty Blotch/Flyspeck – 90% petal fall on variety of interest
Apple Carbohydrate Thinning – green tip date & bloom date on variety of interest
Apple Irrigation – green tip date, trees per acre, & age of orchard for variety of interest

The dates and orchard characteristics cached are specific to the weather station location and the year used. The information saved is what you last entered when using the tool for that weather station and year.

This information is saved locally in your browser’s cache. Local storage from your browser is not backed up, so if it is cleared (deleted), it will need to be reentered. Always keep a record of your biofix dates and orchard characteristics. We developed an Apple Biofix Record Sheet to help growers keep track of the apple disease and insect biofix information. Feel free to adapt this to benefit your operation and use of NEWA tools.

***You may need to clear your browser’s cache to enable local storage and see these changes. Remember, though, that clearing your browser’s cache will delete your saved biofix dates and you may not want to do that if NEWA is already saving them.***

(2) Biofix has not occurred yet
Is the NEWA-estimated biofix date too early and you want to eliminate it? Now you can! On the Apple Diseases tools for apple scab (green tip date), fire blight (first blossom open date) and sooty blotch/flyspeck (90% petal fall date) a “Click if <biofix> has not occurred” button returns you to the pre-biofix IPM information for that apple disease tool.

Screen shots of the new button that can be used if biofix has not yet occurred. (A) For apple scab green tip. (B) For fire blight. (C) For sooty blotch/flyspeck.

This is especially important for locations south of New York where apple phenology can be estimated incorrectly from the historical data collected at Cornell AgriTech at NYSAES, Geneva, NY. In particular, for fire blight, the pre-biofix IPM message contains fundamental information about scouting for oozing, overwintering fire blight cankers. For apple scab, the pre-biofix message informs you about the upcoming primary infection season.

***You may need to clear your browser’s cache to see these changes. Remember, though, that clearing your browser’s cache will delete your saved biofix dates and you may not want to do that if NEWA is already saving them.***

(3) Full interface access from Station Pages
Do you want to see what happened last year or change the biofix date on an apple disease or insect tool when accessing it from a Station Page? Now you can! Previously, the Station Page Pest Forecasts for apple diseases (apple scab, fire blight, sooty blotch/flyspeck) and insects (spotted tentiform leafminer, oriental fruit moth, codling moth, plum curculio, obliquebanded leafroller, apple maggot) provided current day results only.

Now, those links will take you to the current day results in the fully functional interface, including the map, results, and more info tabs. The left-hand part of that interface allows you to select dates in the past to look at what the tool predicted for last year or prior years. You also can select an alternate weather station location and see the map of weather stations. A link below the model results will return you to the Station Page for the weather station of interest.

Screen shot of the NEWA fire blight tool accessed from the Geneva Station Page. The full interface has the Map, Results, and More Info tabs and the left-hand selection tools to access different dates and locations. Return to the Station Page using the link at the bottom of the web page display.

***You may need to clear your browser’s cache to see these changes. Remember, though, that clearing your browser’s cache will delete your saved biofix dates and you may not want to do that if NEWA is already saving them.***

Most of these upgrades are operational on the NEWA server now. Finalizing the local cache to save the orchard characteristics for the apple carbohydrate thinning model and the apple irrigation model will be operational by Monday, April 2, 2018.

Juliet Carroll, Fruit IPM Coordinator, NYS IPM Program, wrote this article with input from Keith Eggleston, Regional Climatologist, Northeast Regional Climate Center, and Dan Olmstead, NEWA Coordinator, NYS IPM Program