POTATO UPDATE:

As of January 2006, we are no longer updating these potato resource pages.

First reports of Early Blight are being reported. Scout all fields weekly, and apply appropriate protective fungicides, according to lable directeions, as needed. The recent hot, dry weather conditions are less favorable for disease development and may reduce the risk of spread of early blight.

Potato Blackleg samples have been confirmed in northeastern Colorado. Avoid excessive irrigation, which may increase anaerobic soil conditions favorable to Erwinia carotovora, the causal agent of blackleg.

Potato acerage is greatly reduced during 2005 in northeastern Colorado.

Potato Early Blight (Alternaria solani) and
Brown Spot [Alternata Blight] (Alternaria alternata)
Potato Psyllids

Early Blight and Late Blight Potato Disease Models

VegNet now offers an interactive interface to calculate P-day values for Potato Early Blight, and Severity values for Potato Late Blight. These computer generated disease models are currently being investigated by Colorado State University to identify environmental conditions which favor the development of both Potato Early and Late Blight in our region.

Calculate P-day and Severity values from a CoAgMet weather station near your area:

Enter the year, month, and day of emergence for your potato crop

• choose a nearby weather station
• submit your request

P-days are calculated in a similar manner to growing degree days, and only require daily maximum and minimum temperatures. Research in other regions of the United States indicate that fungicide applications are not recommended for Early Blight control until after 300 P-DAYS have accumulated from emergence and presence of the pathogen is confirmed.

Severity values are used to estimate the development of Late Blight in response to relative humidity and temperature. Research in other regions of the United States indicate that Late Blight is a potential threat 7 to 14 days after the accumulation of 18 Severity values.