PAUL DOOCEY 0000-00-00 00:00:00
The importance of oak trees to the Viejas Band of Kumeyaay Indians is hard to put into words. After all, the majestic Coast Live and Engelmann Oaks provided the Tribe with its most staple food source, an acorn mush called shawii (pronounced shah-WEE). The trees also gave shelter and the necessary raw materials to create items that aided in survival and made life a little easier for the Kumeyaay. For these reasons, the Tribe venerates and celebrates the mighty oak till this very day. “My mother and aunties would pray and give thanks to the Creator for the tree [and] the acorns,” said Tribal Councilwoman Virginia M. Christman in the winter 2008 issue of The Kumeyaay Way. “Everything we did was done with respect to the acorn and Mother Earth in prayer.” So you can imagine the alarm when some tribal members noticed a growing number of prized Coast Oaks on Viejas lands looked, well, unhealthy—greyer in color than the normal lustrous green; thin crowns, bare branches, deeply stained bark and suffering from early leaf die-offs. The condition of these trees was brought to the attention of Viejas Fire Department Fire Chief Don Butz and other tribal government members, who contacted the United States Forest Service, described the situation, and were told the oaks, much like the ones in nearby Cleveland National Forest, were likely suffering stress from an ongoing drought. “The Forest Service initially said the oaks were hurting from the drought,” Butz said. “But we told them we were finding sick trees in good water areas, so something in addition to drought must be killing them.” When the rainy season brought no relief to the sick trees, Viejas again contacted the Forest Service, who assigned Tom Coleman, entomologist for the Forest Health Protection division based in San Bernardino, to examine the oaks. Coleman was pretty sure what the culprit was and found the proof after a quick inspection—the oaks were infested with the Goldspotted Oak Borer (GSOB), a small insect with known populations in Guatemala, Mexico and Arizona. He was not surprised by the finding—GSOB was first detected in 2004, has likely been present in Cleveland National Forest since 2002, and is now present in over 90 percent of that park’s red oak species (Coast Live, Canyon Live and California Black Oaks). The problem: the recent discovery that GSOB kills its host trees, to the tune of 50 percent in Cleveland National Forest alone. It is estimated that the bugs have killed up to 17,000 oaks on public and private land throughout the area. “Unlike the colonies in Mexico and Arizona, the California GSOB is killing the host oaks at a high rate,” Coleman said. “It’s attacking all types of red oak, mostly the older and more mature trees. We’ve never seen this type of damage from GSOB before. It wasn’t until May 2008 that we officially linked oak mortality to GSOB.” Fortunately for Viejas, the GSOB infection and mortality rate does not appear to be as bad on the reservation as in surrounding areas. Recent surveys estimate less than 50 percent of the reservation’s oaks show signs of GSOB, and the projected mortality rate of these oaks is likely to be lower than seen elsewhere, since tribal authorities know about the problem and are taking steps to identify and protect vulnerable trees, according to Coleman. And now it appears the GSOB menace is spreading throughout San Diego County. Ground zero may have been the Descanso Ranger District’s Cuyamaca State Park or Cleveland National Forest, with the pest moving on the Pine Valley and the Viejas Reservation. Every day brings new reports of GSOB infiltration, a trend Coleman expects to continue. “GSOB has popped up on red oaks along the San Diego coastline to Laguna Mountain, which is 6,000 feet in elevation,” he said. “Obviously, GSOB can withstand a wide variety of temperature and elevation. Coast Live and California Black Oaks run along the coastal range all the way up into Oregon; there’s a chance this infestation will spread farther north.” To the Viejas Band of Kumeyaay Indians’ credit, the Tribe decided immediately to face the problem head on, joining a state and federal campaign aimed at educating the public on the issues, containing the spread of GSOB and finding a long-term solution to the problem. Meanwhile, the Tribe, with the help of the Forest Service, developed a program to find and quarantine sick trees, protect unaffected oaks and attempt a cure for those plants already infested with GSOB. “In June Viejas hosted a meeting that brought together the Forest Service, county and state agricultural officers and tribal agencies to get the GSOB effort off the ground,” Butz said. “The program we developed to combat GSOB on Viejas was approved by Tribal Council and involves the Fire Department, Land Use Management, and Public Works operating with tribal members to control the problem.” The research components of these programs have already borne some promising fruit, according to Coleman. “With the help of taxonomists, we now believe the California GSOB originated in Arizona,” he said. “The GSOB is not a problem in Arizona. By studying it there, we can hopefully uncover what is keeping it in check, and ifthose means will work in California.” Understanding the enemy Unlike other tree-loving pests such as the Asian Longhorned Beetle and gypsy moth caterpillar that have decimated American woodlands in the recent past, GSOB is neither an exotic species or, until last year, considered all that dangerous to trees. First identifi ed in the late 1800s in Mexico and Arizona, the Goldspotted Oak Borer (Agrilus coxalis) is a small (1 centimeter) black insect with six distinct orange/gold spots on its wings. The adult is actually harmless; it’s rarely seen and is believed to inhabit the oak canopy. It’s the insect’s larvae, 2-centimeter-long legless caterpillars that feed beneath the bark, that cause the oaks the most harm. The larvae essentially live and eat in the tree’s phloem and cambium layers, the highway that supplies the oak with moisture and nutrients. Left unchecked, GSOB larvae will eventually scar the phloem to the point where water and minerals no longer are absorbed, effectively strangling the tree to death. “Feeding larvae eventually girdle the tree,” Coleman said. “After several years of repeated attacks, the tree succumbs to injury.” GSOB infestation is easy to identify once you know what to look for. In addition to the signs mentioned above, trees with GSOB also bear trunks with several small D-shaped holes, exit wounds inflicted by emerging adults. When the bark is peeled away, the wood will reveal “larval galleries,” dark, zigzagging lines that note where the larvae have lived. The larvae will also attract increased woodpecker activity. Technically, GSOB can infect any type of oak, but prefers red oak varieties. One thing is certain—once infested with GSOB, it is difficult for a tree to fully recover. The oak can hang on for a few years, but death will come quickly in the end. “Once GSOB hits, it takes anywhere between 18 months to two years for GSOB to stress a tree to the point where it starts to die,” Butz said. “Once this process starts, the tree is dead within two to three weeks.” The GSOB impact does not end with the death of the oak. The insect can live within the tree months after it dies or it is chopped into logs. Indeed, it is believed GSOB’s primary path into new forests is through campers careless about the origin of the firewood they’re carting from campground to campground. Attack and recover In response to this crisis, the Viejas tribal government has developed a four-phase program to detect, protect and cure its oak tree assets from the GSOB menace. Phase one entailed creating an inventory of the 343 living oaks on the Viejas Reservation, assigning each tree a number and assessing its health. Traps were set on trees that appeared ill, to defi nitely determine if GSOB was the culprit and if so, the rate of infestation. Since GSOB infection happens through an oak’s trunk, the lower portions of uninfected trees were sprayed with a Forest Service-recommended poison that kills wood-boring insects. Phase two involves cutting infested trees that are either already dead or too far gone to be saved. The wood from these trees is immediately placed under quarantine and not allowed to leave the reservation. The wood can also be passed through a chipper and safely used as mulch, a step the Tribe is contemplating, according to Butz. Phase three places wood-borer poison in the ground around both healthy and infested trees during the rainy season. The poison will then be carried up through the tree’s phloem layer in hopes it will kill larvae beneath the bark. The fourth and final stage beefs up the Tribe’s oak tree nursery program, and plants saplings to replace the trees that are lost. “It will probably take 100 years or more before a sapling grows to the size of the oaks we are replacing,” Butz said. “But the Tribe feels it is an effort worth making.” Tribal government is also working with federal and state agencies, such as CAL FIRE, to educate the public on GSOB, primarily through posters and written alerts, and assisting in Coleman’s research effort any way they can. People can visit a Web site (http://groups.ucanr.org/GSOB/index.cfm) to learn more about GSOB and report possible infestations. The good news is that this research may have already uncovered a clue on how to eventually stop GSOB. “In Mexico I found a number of native parasitoids that seem to be controlling the GSOB population,” Coleman said. “We’re now working with biocontrol experts at the University of California, Riverside, to see if we can develop a natural weapon against GSOB. It’s early, but this is the best potential solution we’ve found so far and we’re very excited about it.”
Published by Custom. View All Articles.
This page can be found at http://digitaladmin.bnpmedia.com/article/PEST+CONTROL/288958/28887/article.html.