An Update on California Oak Issues—November 2002
By Tom Gaman
RegisteredForester
Integrated PestManagement—General recommendations for treatment
of pests in native forests
My name is Tom Gaman. I am a registered forester and live in Inverness. Thank you for inviting me to speak today. Our guest is Bob’s coast live oak tree, sadly defoliated by the California oak worm, and patiently awaiting its fate outside the window before you.
I thought I’d spend a few minutes speaking about the big picture of forestry in the oak woodlands of California. When we are fully depressed about that, we can return to Bob’s trees, and speak about forestry problems here in Inverness,including the Oak Moth. I will also try to bring you up to date on Sudden Oak Death.
Foresters are not very common, and there seem to be fewer ofthem all the time. The California Forest Practices Act, the Z’berg Nejedly Act of 1972 established the Board of Forestry and empowered it to develop Forest Practice Rules. The rules established the minimum qualifications for a Registered Professional Forester and charged foresters with management of the timber and wildlands of California. It established that registered foresters would prepare “Timber Harvest Plans” for all commercial timber activities in California, and ever since the Board of Forestry has been weaving ever more complex timber harvest regulations in response to increasing population and environmental concerns. Today a typical timber harvest plan, which is legally the functional equivalent of an EIR, includes sections, among others, regarding existing forest inventory, species,type, condition, and a detailed description of trees to be harvested. Each plan addresses, soil protection, archaelogical resources protection, fisheries, endangered species including spotted owls and goshawks, rare plants, forest fire protection, roads, stream protection, cumulative watershed impacts, forest regeneration, and long-term forest sustainability. A THP typically has 15 maps and, even for a small project, runs into the hundreds of pages. As a result most foresters, like myself, rather than spend a career sitting in front of a computer, have foundother things to do. In my case, my company, East-West Forestry Associates, based for 16 years in Inverness, is a contractor with the USFS and we provide forest, inventory, monitoring and data analysis services for the US government on the 20 million acres of National Forest lands in California. This provides me with a wonderful goal toget to know every dirt road and campsite in the state. Last week we completed our 2002 surveys ofthe Lassen and Klamath National Forests. This winter we will be working on the Southern California National Forests. In addition to these we are working on fisher and goshawk habitat redevelopment projects on National Forests in the Sierra Nevada, and the effort to establish a Sierra-Nevada Conservancy similar to the Coastal Conservancy and the Tahoe Conservancy. With Mark Switzer, also of Inverness, I developed the Natural Forests Network which deals with sustainability resource use and emerging “green” markets (http://www.naturalforests.net/ ).
Getting back to Bob’s tree, the Board of Forestry limited the scope of its endeavors to “commercial forestlands” in California, and even went as far as to identify those commercial species. Blue oak, coast live oak, valley oak, Engelmann oak, and a numberof other hardwood species are not among those species regulated by the Board of Forestry and are therefore not protected by state law. This means that 11 million acres of oak forests, fully 11% of the stateof California, are subject to the whims of their local protectors—ranchers, farmers, homeowners, commercial vineyard operators, municipalities, and others. Eighty-five percent of theseoak woodlands, are on private lands from sea level to 2000 feet elevation inthe lower watershed of the Sierra and coastal ranges, mostly in the counties that surround the central valley and along the central California coast. These oak woodlands are home to over 300 species of vertebrates, innumerable vernal pools, and hundreds of species ofrare plants, and 16 species of oaks. They provide vital ecosystem services--open space, air quality, habitat, they filter runoff water, shade vulnerable soils, protect their watersheds andaquifers below them, and are an underpinning of the ecological functions that sustain California’s wild landscapes.
Moreover, they are California.
Californian’s identify their heritage with rolling golden hills studded with grand old oaks. Many of these same old trees were here when native American people gathered acorns from the oaks surrounding their villages.
Today forest inventories have shown that these forests are not regenerating. Urbanization, grazing, gopher populations, lowering water tables, conversion of the California savannah from a perennial grassland to an annual grassland,destruction of riparian corridors, soil compaction from human and animal uses,and even documented climate change are conspiring to subtly transform California, incrementally chipping away at our irreplaceable natural resources every day of every week. These woodlands today support hundreds of millions of trees that are largely available for removal, conversion to vineyards, housing tracts and shopping centers. In the latter half of the twentieth century over 700,000 acres of oak woodlands vanished before our eyes,and the process is accelerating as California swells in population.
Yet it is up to the Counties to regulate their lands, and most, even Marin County, lack the political will to do so, even in the context of vast population increases, urban sprawl and the unprecedented stand-replacing fire danger which threatens both the urban wildland interface areas, and many woodland vegetation types themselves. Over the years the California Urban Forest Advisory Council, Cal Poly, HortScience, and the CDF and many others have offered planning guidelines and, although they have been largely ignored, there have also been a few successes. The University of California established the Cooperative Hardwood Range Management Program and has oak woodland advisors available throughout the state. The Oak Foundation, MALT, the Pacific Forest Trust, and others have developed conservation easements protecting oak woodlands. The Oak Foundation, with thousands of members statewide, has also become a highly-visible non-profit political voice, and is providing technical, legal and educational support in oak conservation battleson a number of fronts. The governor recently signed AB242 which provides funding for the California Wildlife Conservation Board to protect critical oak woodland habitat. In order to be eligible for grants AB242 requires each county to prepare an oak woodlandconservation plan or policy. Prop 50 onnext week’s ballot is another example of efforts to preserve critical openspace. The California Biodiversity Council provides for high- level agency interaction and cooperation to help toaddress these issues. Watershed groups have organized throughout the state in effort to protect the heritage of local California Landscapes. CDF-funded Project Leaning Tree educates children in California’s schools about oak protection—in short Oak Conservation efforts reach into every community and county with oaks in California. We are hopeful that the Board of Forestry will soon opt to use its power to protect California Oaks under the Forest Practice Act—but the Board of Forestry is avolunteer Board with a tiny budget, and taking on regulation of an extra ten million acres of land, no matter how necessary, is a thankless task. Again the COF is requesting that the Board include a hardwood policy update as a priority for its 2003 agenda. Oak trees are threatened and everyone seems to want to save them, but their future is by no means assured.
In 1995 Marin Horticultural agent Pavel Shivra looked at the dead tan oaks above Chicken Ranch Beach here in Inverness. Other Marin callers from Mount Tamalpais area drew Pavel to Kent Woodlands also to view dead trees. Dead tan oaks began to appear in Santa Cruz, and then in Monterey County at Big Sur. By 1997 or 1998 live oaks at China CampState Park suddenly began to die in large numbers. Pavel was unsure what was causing this tree mortality, but he was shaken enough to name the disease “Sudden Oak Death”.
Since then SOD has killed thousands of trees, the California Oak Mortality Task Force has been organized, and millions of research dollars have been spent in effort to contain the culprit. In July 2000, just over 2 years ago, Dave Rizzo, UCB researcher, finally identified Phytohpthora ramorum, a new speciesof the “plant destroyer” as the culprit.
Phytophthora spp. are responsible for such famous mortality as the Irish potato blight, the Port Orford Cedar root disease currently killing POC on the north coast of California and in Oregon. The genus is not a fungus and is related tokelp. Phytophthora “sporangia” attach the cellular structure of living leaves, tree bark and cambial tissue, and they multiply via chlaydospores. A similar organism has recently been identified in nursery settings in Europe and,although exhibiting some differences, has received the same name Phytophthora
ramorum. P. ramorum, unlike otherPhytophthora appears to be distributed by wind, water and throughsoil. The COMTF monitoring committee is beginning to suspect that the origin and distribution of the disease here in California is somehow related to the world market for potted Rhododendrons.
Although the symptoms are fairly telling, SOD, is actually only identifiable from tissue culture and incubation on a Petri dish. You can, however, look at your tan oaks,coast live oaks, and, if you have them, black oaks, for symptomatic “oak blood” around the lower trunk up to 10 feet off the ground. Also look for the black round Hypoxylon cankers and the frass of the Ambrosia Beetle. You can also look for leaf mortality in the long list of associate hosts, particularly bay laurel, rhododendron, huckleberry, honeysuckle, bigleaf maple and buckeye. SOD is most prevalent in coastal areas from Mendocino to Monterey Counties, and seems to be associated with urban native forests”. If you suspect that you have SOD and need to confirm its existence you can check the website “oakmapper” at www.suddenoakdeath.org or you can consult with an arborist or other professional.
With such an extravagant name, an unknown lethal tree disease killing heritage oaks in front of two million dollar houses was sure tomake the news—and I am sure you have all seen forecasts of doomsday, likening SOD to the Dutch Elm Disease and the Chestnut Blight. Was this new tree disease going to kill of California’s billion+oak trees? Even the Point Reyes Light has predicted that all tan oaks will die. But it is now coming to light that SOD is neither Sudden, is mostcertainly not restricted to Oaks, and most of the time does not cause the deathof the organism.
SOD gains access to the cambium and bark of the susceptible oak species, kills the bark and cambial layer, and mortality results either from the canker girdling the tree, or the subsequent invasion of bark beetles girdling the tree. Since oaks sprout, they may sprout again weakly from basal sprouts.
The Board of Forestry has declared a zone of infestation, and Timber Harvest Plans must mitigate and prove that logs are “free from”SOD. However, as BOF does not regulate oak woodlands, responsibility for management and quarantine has fallen to the California Department of Food and Agriculture.
Through its system of County agricultural commissioners, who are more experienced and used to agricultural pest management, the CDFA has placed a quarantine on firewood, logs, green waste, and some nursery products. Moreover, states such as Oregon have placed quarantines on such products that originate in California. Canada has imposed an international quarantine. As you might expect, SOD ishaving tremendous economic impacts and its spread has the potential to cripplea wide variety of businesses from nurseries to landfills. Even though this type of pathogen isvirually impossible to effectively isolate via quarantine vast resources are being allocated to prevention of SOD spread. Even wildland firefighters now must utilize mobile carwash units to assure that fire equipment does not spread SOD from region to region. Muir Woods is installing a visitor wash station. Public agencies have spent $12 million dollars pm SOD to date, and Governor Davis has recently requested an additional $10 million from Washington.
If you think of the hardwood industry in the northeast, rich with a dozen species of oak including Northern red oak, Quercus rubra, whichis known to be susceptible, the impacts of the spread of SOD could be practically unimaginable in US forests.
Quarantines however, are based on the “precautionary principle” even though the science is incomplete and we do not know what is going to happen in the future, quarantines, which have to withstand contest in courts of law, can legally be imposed as a precaution.
You have probably read that SOD has now been confirmed in redwood and Douglas-fir. Think of the extent of the impact of losing California’s redwood forests!
But the good news is that every pathogen in the environment, including the feared and sensational SOD, is ecologically limited. Recent research has been leading researchers to strongly suspect that not all trees that are infected will die. There now appears to be some genetic and environmental resistance to SOD. In China Camp I believe about 25% of the trees have been killed, but of course the75% remaining trees still allow for a complete canopy. On some hillsides at Big Sur however, all the tan oaks have died. Mortality may be cyclical and it is unknown whether another round of oak mortality will occurin the near future, perhaps following a wet winter, when the water-loving pathogen multiplies more rapidly. But I think we can rest assured, that in the long-run, it is most likely that fewtrees will die. Mortality will be worst in places “predisposed” to the pathogen.
There is no recommended treatment for SOD. If your tree is infected it is probably toolate and so prevention is the best cure. Protect the root zone and do not water during the dry season. Avoid pruning during the wet season, do not collect acorns in infested areas. Do not transport firewood from infested areas (e.g Inverness).
You may even choose to fertilize your oak trees. No chemical treatments are known to be effective. Sprays, injection systems,and other “professionally recommended” substances are nothing more than somebody’s guess—there is no scientific data suggesting that any cure isavailable. The answer lies in IPM, or integrated pest management, which I will discuss in a moment.
Now we get back to Bob’s poor tree here. Those moths you saw flitting around outside as you walked in the door are oaks throughout the area are now being defoliated by the so-called California Oak worm (Phryganidia californica). As you can probably guess from the name this is the native oak moth once again at a high year in its cyclical population. A month ago millions of the caterpillars ate the oak leaves, and today they have become clouds of moths.
Residents throughout the area are saddened looking at their beloved but leafless trees and wondering what to do. Fortunately healthy oaks will generally grow new leaves after a single defoliation and my recommendation isnot to be too terribly concerned, but realize that it will take a certain amount of a tree’s stored energy to do this. For those worried about oak trees repeatedly being defoliated around their houses Bolinas Arborist Ray Moritz notes that the oak worms "generally do not do any significant damage to the trees, but they do weaken them. There are several low-cost treatments. For stressed trees try application of insecticidal soap such as ‘Safer’ or pyrethrin-based (non-toxic) insecticides." Bacillus thuringiensis (Bt), developed to combat the voracious gypsy moth in northeastern US, is a natural biological agent which is effective and, except to moths and butterfly larvae, is non-toxic. Matteo Garbellotto, famed UCB SOD professor, even believes that the oak moth may be beneficial in that a stressed plant has increased internal defense mechanisms which may help it ward off attack by pathogens suchas Phytophthora.
I do have some good news. Cures for tree problems in native forests are just about always the same—less is better. As with all tree problems, think in terms of overall tree and forest health. All trees need undisturbed root systems in well-aerated soils to support well structured stems and crowns. Favorable environmental conditions, sufficient nutrients and plenty of space and light are necessary for trees to ward off insects and disease. Although consuming a lot of soil moisture, established oak trees normally survive best without summer watering, which tends to spread damaging root fungi. Your trees naturally harbor a great variety of insects and fungi, and they have mutually beneficial relationships with many of them. If your trees show chronic signs ofstress you might want to fertilize with an N-P-K fertilizer and mulch lightly within the "drip zone". If you are concerned about a particular tree use common sense in diagnosing the problem or call Cooperative Extension agent or another experts for advice.
Like people, all trees do eventually die. Standing dead trees and fallen woody materials in native forest settings provide valuable habitat for insects and decay organisms and forage for a great variety of wildlife—although in some forest types contributing significantly to fuel loading which increases fire hazard. In fire prone areas like Inverness homeowners must be sure to maintainfire safe zone 30-100 feet around dwellings.
Remember, these trees are part of our native forest. They survived millenia without any human intervention and then adapted well to native American influences such as regular burning. The biggest killers of trees around housesare humans who compact soils, disrupt natural conditions, spray chemicals and injure trees by improper pruning and other mechanical injuries. In forested areas we have increased tree crowding and reduced tree vigor by disrupting the cycle of periodic fire and injecting our homes into previously undisturbed ecosystems. If you can help your native tree by providing a "natural"place to live, it will probably be okay.