From: Janine Hasey []
Sent: Thursday, April 13, 2006 12:36 PM
To: Janine Hasey
Subject: Pest Tracker April 13, 2006



Cankers with rust spores were found by a local PCA on April 5, 2006 on Halford in the Hallwood area. They were positively identified on April 12 by UC Riverside Plant Pathologist Jim Adaskaveg. Canker development is slow at the beginning and will occur over the next two to three weeks. Plan to apply fungicide sprays to prevent rust over the next two weeks.  Research has shown that under heavy rain conditions, the strobilurin (e.g. Abound, Pristine) and the DMI2-triazole (e.g. Elite, Orbit, Indar, Rally) fungicides will give better control than sulfur. Sulfur controls rust as well as the strobilurin and DMI2-triazole fungicides when rain is not as persistent.




The other concern now with our saturated soils, especially as the weather warms up, is the possibility of Phytophthora root or crown rot diseases and/or waterlogging damage. USDA Plant Pathologist Greg Browne from UC Davis, has researched the effects of phosphonate treatments on walnuts and almonds.  Phosphonates (inorganic and organic salts of phosphonic acid, the active ingredient) can provide systemic activity against water mold fungi and have helped manage diseases caused by Phytophthora. They are translocated both upward and downward in the plant; the mode of action is complex and not completely understood, but evidence suggests that phosphonic acid disrupts the growth of Phytophthora and increases the plant’s defenses.

There are several phosphonate products available on the market.


Dr. Brown found that using Fosphite® applied in late summer/early fall as either a foliar spray or foliar + phosphonate chemigation on walnut reduced the area of cankers caused by P. citricola compared to the untreated control trees. In another study on almonds, he found that using Nutri-Phite®P+K applied as a preventative foliar spray in the fall or spring suppressed development of Phytophthora cankers for up to 5 months. Considering the saturation of our soils, you may want to consider applying a phosphonate product on your tree crop this spring. Make sure to check the label because tank mixing with copper may result in phytotoxicity. 


Janine Hasey


Farm Advisor, Sutter and Yuba Counties

University of California Cooperative Extension

142A Garden Highway

Yuba City, CA 95991

Phone (530) 822-7515

FAX  (530) 673-5368