Western Gall Rust on Willamette Valley Ponderosa Pine

Dave Shaw, Extension Forest Health Specialist, OSU

Photo by Dave Shaw

Danny Norlander with a heavily infected tree. Galls are on the branches, which does not cause major problems. Most problems occur when the gall is on the main stem.

Western gall rust is a potentially important disease in young plantations of WVPP. To date, there is no reason for concern but the disease has caused problems in certain areas of California. One element of disease control is to understand genetic resistance in the host. It maybe possible to remove parents who are highly susceptible to gall rust from future seed collections.

Last fall the Association sent Det Vogler of the USFS Forest Genetics Institute in California seed lots from about 100 Valley ponderosa families. Det is growing the seedlings now for his future tests.

In spring of 2008 he will do a greenhouse genetic screening of 2-0 seedlings from the families sent him.He will include spores of gall rust from the Willamette Valley, and spores from other sources to determine the variation in pathogenicity of western gall rust.To screen a seedling, he uses a brush to directly apply spores to the elongating stem of the tree.It takes about 6 months to a year to determine infection.This type of test will tell him whether there is any variation in the resistance of WVPP families to infection by western gall rust.

Det will also hold back a subset of seedlings and outplant them among other trees he has growing in some test gardens. These will be naturally exposed to gall rust from the surrounding stands, and will also help inform him regarding resistance to gall rust in the field, as opposed to a greenhouse study.

On another front, a new OSU graduate student in Forest Science, Danny Norlander, will be studying western gall rust on ponderosa pine for this Masters Thesis. Danny will be involved in surveys of WVPP in addition to other studies. He plans to use the WVPPCAs native ponderosa pine stand database in his work.



Last Updated 02/24/08