Redwood Reader

Reports of relatively new threats to regional forests are far more frightening than any timber harvesting. The first reports of Asian Longhorned Beetle in California were found recently in Sacramento. This pest arrived in shipping material from China, but it is known on the East Coast since 1996, where it has established itself as a major problem with 115 million dollars spent on research and control so far this year.
The real issue now is Sudden Oak Death. There is a lot of news at the California Oak Mortality Task Force website this month and most of it is not good. This is the steady trend since the site started monthly updates several years ago. Sudden Oak Death has become an industry for researchers and regulators. A lot of money has been spent and a lot has been learned but there is a lot more to understand before we can even make decisions.
First there is a third species of yew has been found susceptible to p. ramorum. This is a nursery species from Holland and joins West Coast and U.K. species as hosts of the disease.
Five more infected Oregon nurseries revealed the first known cases of infection in magnolia tree, Magnolia loebneri, rhododendron and Pieris japonica as well. Two more were found in Washington State, again Pieris and Rhododendron. Another two retail nurseries were found to have P. Ramorum contaminated camellias and rhododendron. IN all cases trace forward/baclward is being conducted. California has had 53 nurseries found with the disease as of August 1. Of these, ten ship wholesale, eight nationwide and two to Nevada only. For eight of the nurseries it is not the first time. 76 sites have been found nationwide, 53 in California, 14 in Oregon, 2 in Washington, 4 in Georgia, two in Louisiana and one in Tennessee. Three sites are known from British Colombia, and the trace forward/back is underway.
Results compiled for the federal National Nursery Survey, in 41 states show 2,433 nurseries were visited and 39,345 samples were collected. Thirty-eight sites in six states tested positive so far. Only the above mentioned seven sites were outside the already regulated three West Coast states, and these amount to all known cases not on the West Coast.
Meanwhile more trees are passing Kochs test and moving from associate host to known host. The six newly classified hosts are: Castanea sativa, Fraxinus excelsior, Quercus falcata, Quercus ilex, Syringa vulgaris, and Taxus baccata. Here we see many Mediterranean species, also under assault from extreme heat and fire. It is interesting to note that different plant parts are affected depending on the plants species. A ring test to expand testing ability to multiple sites is nearly finished.
Tracking down and destroying the plant material seems to be working, as the above given numbers for sites outside the West compare very favorably with those from the previous year, where 61 sites in 17 states tested positive in 2004’s survey. The National Plant Board met to discuss P. Ramorum. They inspected labs for testing for negative results nad approved 5, with 16 more inspected but not yet approved. They made it easier for infected nurseries to move tested and uninfected stock, and created a research committee to investigate whether certain cultivars are responsible for the movement of the disease in nurseries.
After this is a long list of current research together with synopsis of particular projects. Among the most interesting to me at least is “baiting” the disease and filtering it from watercourses, along with the fact we are looking at multiple endemic phytopthora species, setting conditions for hybridization; infection found in European chestnuts, new phytophthora species and hybrids in Minnesota, that the disease is capable of infecting roots as well as leaves and stems; its persistence in a locality weeks and months after infected material is removed; OSU found variable resistance to infection from totally susceptible to complete resistance in Viburnum; the durability of chlamydospores in various soils and roots; the effectiveness of steam for sterilization and the temperature needed for it; resistance variability in tan oak, one of the worst sufferers; a sstudy on the world of critters that live on California Bay leaves, yeasts, molds and fungi, to see if they aid the phytophthora to spread infection; rhododendron leaf baiting was used on watercourses to study spread into newly infected areas, including recovery eight miles downstream from Redway; the effect of fungicides on nursery stock as well as recycled irrigation water in nurseries; the survivability in subsurface soils in all seasons; recognition of endemic phytophthora species and possible preoccupation of niches. Several links are given for information for professional planners, those interested in S.E. asian phytophthoras, and the new APHIS sudden oak death release.
A most revealing study is done in Britain on 23 hardwood and 11 conifer species important there. We see several families of trees pretty reistent but find Douglas fir consistently hammered; A short discussion of two California look-a-like diseases is followed by an article about Elkhorn Slough National Estuarine Research Reserve and explaining the policy of cleaning shoes to each visitor there.
A discussion on the movement and economic uses of infected items repeats earlier findings that the disease does persist in the wood for months as it air dries. No processed products showed any results except firewood air dried less than six months. However, the percentage of usable product from diseased removals is very small and something will have to be done with the rest.
Finally, the Host of the Month is a hybrid yew named taxus media from Holland. It is the second European yew found infected after the UK found it in taxus baccata.
Plenty of people are working hard to discover the kikely outcome of this invasive species attack. One wonders if local species can keep the spread in check or ifsome other factor such as weather will be a contributing factor. We are surprised to hear about resistant tanoaks and should be seeking them out. We worry about transmission from boots, tires and even dust. We worry that Douglas fir seem to be so susceptible, although it is not clear if we are talking infection or mortality. Even if these trees are only impaired and some tan oaks survive, our precipitation interface and root zone storage areas will shrink considerably. This will create more runoff at the time of the event and reduce the amount of water available later in the year.