P&PDL Picture of the Week for
March 15, 2010

Dothistroma Needle Blight

By Gail Ruhl, Sr. Plant Disease Diagnostician

Dothistroma needle blight, commonly called 'red band needle blight', is a fungal disease that can cause needle death and dieback. Infection usually occurs first on lower branches and spreads upwards. Needles eventually die
from the area banded to the tip. Small black fruiting bodies break through the epidermis of dead needle tissue. Symptoms are similar to Brown Spot needle blight but Dothistroma primarily occurs on Austrian Pine and brown spot is more common on Scots pine.

Management includes promoting good air circulation by adequate spacing and weed control and improving tree vigor through mulching and watering as needed. Bordeaux mixture or other copper-containing protective fungicides are most effective when applied in mid May to protect the previous seasons' uninfected needles and again in mid-June to July to protect the healthy tissue on current-year needles. Good coverage of healthy needles with protective fungicides as well as proper timing is imperative for successful management. It is important to note that fungicides prevent new infections--they don't cure existing ones. As such, diseased needles will continue to deteriorate and fungicide applications need to occur every year for several years before improvement is actually seen. As these fungicides aren't curative, they will do nothing for last year's infected needles. Remove any dead branches, and if feasible rake up and destroy fallen needles which harbor this fungal disease.

Always read and follow all label directions when using pesticides. Invigorate the trees as recommended in the publication (HO-140) available for download at http://www.hort.purdue.edu/ext/HO-140.pdf

For additional information please refer to the following article by Glenn W. Peterson; U.S. Department of Agriculture Forest Service: Dothistroma Needle Blight of Pines

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Dothistroma needle blight

Photo by Jonathan Ferris

Closeup branch

Photo by Jonathan Ferris

Closeup needles

Closeup of needles

Closeup

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service