SPUDcast is a weather based system, under development by WIN, to assist in the spray decisions of growers for controlling late blight in potatoes. Currently, the delivery aspect of the project is still in its development stage and therefore is not yet publicly accessible however, you can read about the models and their advantages below. SPUDcast has two distinct forecasting models, A and B, that assist potato producers in managing foliar diseases in potatoes when using fungicides.

Model A: Timed Interval Spraying

This model is used in regions where late blight continues to be a threat yet does not occur every year.

Model A uses a daily disease severity scale from 0 to 7. These values, called SPUD values, rate each day according to the favourability of weather conditions towards the development of disease. Growers are advised to apply an initial spray when 150 SPUD values have accumulated after crop emergence. Subsequent fungicide applications are applied after accumulating an additional 50 SPUD values since the last application.

It is the grower’s responsibility to choose which fungicide is appropriate for their region based on the weather conditions, the development of disease in surrounding potato fields, the level of seed borne late blight, and the availability of registered fungicides. The spray decision point of 50 SPUD values is only a suggestion based solely on weather conditions, however the model allows growers to alter this spray decision point based on the effective coverage of their sprayer, the efficacy of the fungicide that is used, and the growers own risk assessment tolerance.

Model B: Dynamic Dosage

This model is used in regions where late blight is a continuing threat, with local outbreaks occurring every year.

Model B, the Dynamic Dosage model, allows growers to continue with their regular spray intervals of 7-10 days, but allows for better decision making when it comes to choosing the type of fungicide needed and the proper label rate to apply. Most potato fungicide labels and provincial crop protection publications provide a range of chemical rates for early and late blight. Model B gives growers advice about when to use the lower or higher recommended rates of the protectant fungicides available, and when to switch to a late blight targeted fungicide based on weather conditions over the past seven days.

When choosing a specific fungicide, growers are advised to refer to their local provincial crop protection publications, current label recommendations and advice from their regional extension advisory service personnel. An example list of fungicides registered in Canada is provided below.

The Chart below outlines SPUDcast Model B spray recommendations:

Example list of potato fungicides registered in Canada:

Registrations and classifications of fungicides change frequently. Use the most current information available.