Pests That Attack California Oaks

Oaks are famous for the food they provide local wildlife. In fact, oaks help to sustain everything from squirrels and jays to black bear and deer. But while most animals primarily feed on the acorns of oaks, other animals – primarily several types of insects – feed on the leaves and other parts of oak trees.

These pests often cause significant damage to living oaks, and they may even cause enough stress to kill the tree outright. Others may not cause substantial damage via their feeding activities but still represent a threat, as they can transmit fungi, bacteria and diseases to the trees on which they feed.

Some of these insects can be managed, while others are more difficult to control. But in all cases, you’ll have a better chance of saving your oaks if you solicit professional help quickly before the infestation grows out of control. To help you do so, we’ll discuss some of the most important pests of oak trees below.

1. California Oakworm
California oakworms are 1-inch-long, when fully grown, black-and-yellow caterpillars who are found throughout the coastal regions of our state. Their feeding activities cause severe defoliation, but fortunately, they rarely kill the trees they infest. Close inspection of oakworm-damaged leaves will reveal that the bottom surfaces of the leaves have been eaten, but the top portions are left intact (although the top portions of the leaves will turn brown).

2. Fruit-Tree Leaf Roller
The fruit-tree leaf roller is found throughout California, and it attacks almost all of our native oaks. These small, light-colored caterpillars feed on new leaves in the spring. They also roll the leaves up into bizarre shapes, which serve as their cocoons. Most healthy oaks can survive low-level infestations, but trees that have been stressed by drought or previous attacks may decline and eventually die.

3. Tent Caterpillars
Tent caterpillars are 2-inch-long caterpillars that are usually covered in tufts of hair. They are named for their tendency to construct large silk “tents” in oaks and fruit trees. Fortunately, tent caterpillars rarely cause significant stress for oak trees, although some homeowners consider them to be nuisances. Some people also find their nests to be eyesores.

4. Western Tussock Moth
Named for the white hair tufts on their backs, larval tussock moths (caterpillars) feed on oaks and a variety of other tree species in California. These pests often cause serious defoliation. In addition, these caterpillars also cause problems for people, as they produce quite a bit of frass (droppings) and their hairs can be irritating to the skin.

5. Gall Wasps
Gall wasps are small insects who deposit their eggs in the tissues of oak trees (and many other species). This causes the oak tree to create a swollen, typically brown chamber in which the eggs and larvae will develop. Some gall wasps are capable of depositing eggs in many different oak species, while others have evolved to favor a single one. Although the galls they create often cause homeowners quite a bit of concern, gall wasps rarely cause damage to the trees they use. Rarely, they’ll cause damage to individual branches or twigs.

6. Oak Pit Scale
Pit scales are small insects that cause depressions to form on the surfaces of branches and twigs. The actual insects are barely more than 1 millimeter in length, so they’re hard to spot, but their pits are often quite apparent. Pit scale insects are found throughout California, although they rarely reach high population densities in forested areas – they more commonly infest isolated trees in home landscapes. Pit scales typically prefer deciduous oak species to live oaks, and they can cause serious damage to trees.

7. Bark Beetles
There are a few different oak bark beetles that attack California’s oaks, but they all exhibit relatively similar biology and feeding habits. These beetles, which may reach about 2 millimeter in length, feed on the inner bark of the trees by tunneling through the outer bark. They also lay their eggs inside these tunnels. While the beetles can cause damage and accelerate the decline of stressed trees, the biggest threat they pose is their tendency to be associated with the pathogen responsible for sudden oak death.

8. Carpenterworm
Carpenterworms are off-white to pinkish-white caterpillars (larvae) that can reach about 2.5 inches in length. They are found throughout the state, and they attack ashes, aspens, willows and elms in addition to oaks. These larvae, which feed on the inner bark of trees, create small tunnels in the bark, which are about ½ to ¾ inches in diameter. Carpenterworms may cause branch girdling themselves, but they may also make trees vulnerable to fungal attacks, thanks to the tunnels they make.

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If you think that one of your oak trees is suffering from an insect infestation, you’ll need professional help, so give your friends at Evergreen Arborist Consultants a call. We’ll have one of our certified arborists visit your property, inspect your trees and identify the insects that are causing the problem. We’ll then recommend a prudent course of action that may save your tree and prevent the insects from infesting your other trees.

Exotic Beetle Killing Oak Trees

Exotic Beetle Killing Oak Trees

An exotic beetle has invaded Southern California and targeted coast live oaks. The tiny western oak bark beetle has long been a threat to the oaks but this variety brings a fungus with them that is now wreaking havoc on the iconic oaks. These pests are about the size of a grain of rice. Beetle infestation is identified by the red sap and cream colored foam that pours from holes in the trunks and branches. This is the first symptom of infestation as the sap leaks from the insect entry holes. The beetles lay eggs which grow into larvae beneath the bark and feed on the widespread fungus rather than the tree itself. A single tree can be infested with many beetles at once which greatly increases the chances of death. If just the branches are infected, they can be pruned to stop the spread of the disease. The fungus called foamy bark canker disease blocks water and nutrients from circulating inside the oaks which causes the evergreen tree to turn brown. Once the sap and foam stop flowing, the only evidence of a problem is the small holes. The beetle is infecting trees in Los Angeles, Thousand Oaks, Orange, Santa Barbara, and Monterey counties. The disease is raising wildfire danger concerns as dead trees provide wildfire fuel. In addition to killing the prized trees, the wildlife that depend of the habitat of the oaks is also affected. Species include the Red-shouldered hawks, big, flycatcher’s mule deer, rodents, and quail. Additionally, these oaks are in danger of widespread wife fires due to the drought. Researches from the University of California have been unable to discover the origin of this insidious pest, but they are determined to find and eradicate the source. The insects can be further spread by moving infested firewood.

Orange County Register, Sunday May 11, 2014. Brooke Edwards Staggs, Staff Writer.

Hurricane Sandy Downs Historic 400-Year-Old Oak

oak-tree

oak-tree

The city of Shelton, Connecticut, recently lost a historic oak tree believed to be at least 400 years old when Hurricane Sandy blew through the area in early November. It was not only the oldest tree in the city, but the tallest, at approximately 85 feet. Winds first blew off the top branch of the tree, which fell into power lines and cut off power to the neighborhood. John Miller, who lives across the street from the tree, said he heard a loud “crack” at about 6 p.m. “It sounded like thunder,” he said. Twenty minutes later, the entire top of the tree was taken off by another gust of wind.

Residents said that they were saddened by the loss, but not surprised. One resident said that the tree was a little hollowed out, although from outward appearances there was no indication of decay. The tree had been impacted by construction, which may have damaged its roots, and in the 1970s a construction crew planned on cutting it down until they discovered its historic nature.

“It’s sad to see it come down. There should be some kind of tribute for it,” said resident Lin Mulford.

Evergreen Arborists Consultants, Inc. has experience in examining thousands of trees. We evaluate a tree’s signs and symptoms ranging from decay, poor branch structure, poor pruning and maintenance practices, and roots. Please call us today for a consultation.

Care of California’s Native Oaks

Big tree

A big tree

Young native oak trees are much more tolerant and adaptable to environmental changes, while mature, established oaks are intolerant of change. This means that any major change in a mature oak’s environment may weaken the tree or kill it. To reduce the chance of this happening, leave the tree’s RPZ, or root protection zone, undisturbed. The RPZ is defined as one and a half times the area from trunk to drip line. A healthy root system for a mature oak begins with the formation of a tap root when the tree is a seedling. This allows the tree to have assessable moisture. As the tree grows, lateral roots extend horizontally (sometimes up to 90 ft.) past the dripline. This root system also forms fine roots typically within the top three feet of the soil, and these roots absorb moisture and nutrients. To support the natural dry weather conditions in the summer, the tree also grows deep vertical roots, usually within ten feet of the trunk, which helps support the mature tree. Therefore, mature oaks need protection from excessive water, inadequate drainage, over fertilizing, filling, paving, over pruning, and trenching within the root zone.

Excessive water and inadequate drainage can smother roots and encourages crown and root rot fungi. Conditions should be dry during summer months, therefore only drought-tolerant plants that require no summer watering should be planted around mature oaks. Even then, plants should be planted no closer than six feet from the base of the tree. Groundcovers such as cobbles, gravel, and wood chips can also be used because they don’t interfere with getting the right amount of moisture and oxygen. Usually, mature oaks don’t require any irrigation, except in cases where there is an impervious surface within the RPZ. If this is the case, occasional watering may be helpful – as an extension of the normal wet season. Otherwise, oaks should be watered only outside the RPZ. Moist, warm soil at the base of the tree encourages crown and root rot. If a tree needs to be watered, water only once or twice during the summer with a slow, all-day soaking. Shallow watering promotes shallow root growth and also encourages crown and root rot. Rot and root drowning may also be caused by placing a swimming pool, which acts as a dam, downhill from a mature tree.

Mature oak trees usually need no supplemental fertilization, because they get nutrients from the leaf litter that breaks down around the tree. If fertilizing is to be done, it should be done in late winter or early spring. Trees that have undergone recent severe pruning should not be fertilized. Sometimes when leaves yellow, it is not a sign of nutrient lack, but rather a sign of crown or root rot.

Trees that have fill or paving placed with the RPZ are more likely to have problems with soil compaction, which prevents water from soaking into the soil and inhibits gases from being exchanged between roots, soil, and atmosphere. Fill can also trap moisture in the soil and cause crown and root rot. Paving also usually requires excavation to create a stable base for the paving material. Both excavation and the compaction adversely affect the root system. If any paving is needed, decking on piers is the least intrusive to the oak’s root system. It’s also best to leave the natural soil grade within the RPZ and, if necessary, use retaining walls to keep soil out of the RPZ.

Another aspect of oak care is pruning. Excessive pruning affects an oak tree in a number of ways, from exposing interior branches to sun damage, encouraging new growth that is more easily attacked by mildew, and possibly causing decline in the health of the tree. Pruning should be done during winter dormant periods and only weak, diseased, or dangerous branches should be removed. Any wounds should not be sealed, as recent research shows sealants do more harm than good. It is recommended that pruning should only be performed by a certified arborist.

Oak trees also need protection from trenching within the RPZ. Trenching can sever important tree roots when underground utilities are installed. Especially detrimental is when multiple trenches are cut through the roots. If utilities are installed within the RPZ, they should be dug by hand or they should be bored at least three feet below the surface.

Oak tree care also includes being aware of diseases and insects, which can impact the health of the tree. The tree can usually be saved if the disease is caught early. Crown rot is caused by a microscopic fungus and is promoted by saturated soils and poor soil aeration. Symptoms of crown rot are decline in tree vigor, twig die-back and wilting, lesions that ooze a dark-colored fluid, and abnormally yellow leaves. Oak root fungus, or Armillaria root rot, is almost always found in California oak trees, but doesn’t usually affect the tree unless the tree is over watered or weakened in some way. Trees affected by root rot can have branch die-back or yellowing and thinning of foliage. To avoid these symptoms, avoid summer irrigation. Mistletoe is a parasitic plant that can harm oak trees, usually be causing structural weaknesses and branch breakage. Major infestations are difficult to control and it’s best to consult an arborist for advice on mistletoe or any unexplained decline in an oak tree. Insects can also harm oak trees; especially pit scales, oak moths, and other leaf eaters. These insects weaken the tree and make it susceptible to disease. Consult an arborist when insect infestation causes a change in leaf color, twig die-back, substantial leaf loss, or sticky or sooty foliage and branches.

If all of these issues are addressed in an oak tree’s care, the oak should be healthy and last a considerable amount of time.

Oak Trees

Donna Giustizia in Ontario, Canada, is asking that the oak trees near her daughter’s school be cut down due to the risk of a nut allergy reaction from the acorns off the trees. Because she felt strongly about the possible hazards, she appeared before the Vaughan, Ontario, City Council to ask the council to remove the trees. Giustizia heads the school’s allergy committee, and although the school says it is nut-free, she feels that the school isn’t doing enough to protect its students.

The Vaughan City Council has said that they will prepare a report about the nut problem that will be read at their next meeting. Giustizia has said that she is not requesting that the entire town become nut free, but wants the school to be free of all nuts, including acorns.

When asked about the possibility that acorns are a hazard to children with nut allergies, Dr. Clifford Bassett, medical director of allergy and asthma care at New York University, said he has never encountered a case of an allergic reaction by playing with acorns found on the ground. “There’s no relationship between acorns and peanuts,” said Bassett.

 

Sherman Oaks Trees

Laurel Canyon Boulevard trees in Sherman Oaks were trimmed in a project to help reduce the danger of fires in the area. Trees along this road and in a few other Hollywood Hills areas have had limbs that hang down below 14 feet, which is the clearance requirement for fire department trucks to get through to respond to a fire emergency. “This project has been talked about for years. It’s a public safety issue, and it’s getting worse in the Hollywood Hills,” said Fire Department Fire Inspector John Novela.

The state has designated 190,000 parcels as being in a Very High Fire Hazard Severity Zone, and the tree trimming project is within this zone. Previously, 130,000 parcels were within this zone, but more development has meant more parcels are now in this zone. With the increase in residences in this high fire hazard zone, there has also been a decrease in the Urban Forestry budget to trim trees. Trees were previously trimmed on a 13-year cycle. Now they are in a 33-year tree trimming cycle. The fire department is now hiring contractors to trim trees to ensure clearance for their fire trucks and to reduce the chance of fires spreading through the tree tops.

“We learned from the Oakland fire 20 years ago that out-of-control vegetation feeds a fire, especially tree canopies where fire spreads from tree to tree,” Novela said.

An experienced arborist has been helping with the project to ensure mature trees aren’t damaged by the trimming. Trees that are found hazardous due to instability are removed entirely.

Evergreen Arborists Consultants, Inc. has examined thousands of trees. We are Los Angeles certified arborists, tree experts, and tree specialists who provide arboriculture and tree expert advice to Beverly Hills, Brentwood,  West Hollywood, Santa Monica, Malibu, Palos Verdes, Encino, Pasadena, and Sherman Oaks. We specialize in Los Angeles trees, and conducting detailed investigations and providing independent analysis. Please call us today for a consultation.

Saving 350-Year-Old Bur Oak Tree

John Sam Williamson from Missouri has been working to save a 350-year-old bur oak, probably the largest of its kind, by hauling 1,600 gallons of water to the tree each week. Missouri has had one of its hottest summers on record, with 99.29 percent of the state in extreme drought or worse. Williamson gets his water from the Missouri River and he told the Columbia Daily Tribune that he plans on watering the tree weekly for the next month or so. He hopes his efforts will keep the drought from killing the tree.

Even with his efforts, Williamson said that the bur oak has been showing signs of stress. “The leaves are beginning to curl up a little bit, and they have turned kind of brown. I think it has aborted a lot of the acorns. And the leaves turn upside down to keep from losing moisture,” he said.

Evergreen Arborists Consultants, Inc. are Los Angeles certified arborists, tree experts, and tree specialists who provide arboriculture and tree expert advice to Beverly Hills, Brentwood,  West Hollywood, Santa Monica, Malibu, Palos Verdes, Encino, Pasadena, and Sherman Oaks. We specialize in Los Angeles trees, and conducting detailed investigations and providing independent analysis. Please call us today for a consultation.

Oak Tree Damage

Cal Fire officials recently spotted a California black oak tree in Idyllwild, CA, that was infested with the gold spotted oak borer. This beetle has already destroyed 80,000 oak trees in San Diego County, but officials hadn’t expected to see it so far outside of the estimated zone of infestation. “Our concern is that it’s been found 40 miles outside the zone of infestation. That’s a long way. How did it get here?” asks Julie Hutchinson, Battalion Chief and Cal fire spokeswoman. Hutchinson thinks it was carried into the Idyllwild area in a load of firewood and cautions people to use firewood where they’ve bought it.

The adult gold spotted oak borer is about a half-inch long and forest green, with six golden spots on its wings. The larvae feed on the soft tissues of oak trees directly under the bark. This soft tissue is the supply route for water and nutrients, and the damage caused by the beetle stresses the tree until the tree dies.

The infected tree was discovered when a Cal Fire employee noticed that the tree had much smaller leaves and the leaves were starting to turn brown. When the tree was checked a few weeks later, the tree was dying and the leaves were brown. About a dozen larvae were extracted from the tree and DNA-analyzed to confirm the species. The tree was subsequently taken down and shipped to San Diego County, within the area the beetle has already infected. The extent of the infestation in Idyllwild won’t be determined until spring, when adults emerge.

Evergreen Arborists Consultants, Inc. has examined thousands of trees. We are Los Angeles certified arborists, tree experts, and tree specialists who provide arboriculture and tree expert advice to Beverly Hills, Brentwood,  West Hollywood, Santa Monica, Malibu, Palos Verdes, Encino, Pasadena, and Sherman Oaks. We specialize in Los Angeles trees, and conducting detailed investigations and providing independent analysis. Please call us today for a consultation.

Oak Trees

applegall41

Apple gall

According to Michele Warmund from the Missouri University College of Agriculture, Food and Natural Resources, galls on oak trees, frequently seen in autumn months, are harmless. Galls appear as round, brown growths, especially prevalent on oaks. Warmund has had inquiries about the growths from property owners and thinks that the unseasonably warm spring may have contributed to the increase in the production of galls this year. Property owners want to know if they should spray insecticides or trim trees to try to get rid of the galls. She says, “Do nothing. Just sit back, relax, and enjoy them. Mother Nature will probably take care of them as leaves drop and insects seek shelter underground during the winter.”

Oak galls are caused by a gall midge, which looks like a long-legged fly. Whey they first form in the spring, they are magenta or red. In the fall they turn brown and crusty, and at that time the gall bursts, releasing a larvae that buries into the soil to overwinter while pupating. In the spring, adults emerge to lay eggs and start the cycle over again.

Galls can also be found on other plant species like hickory, walnut, chestnut, and elderberry.

 

Oak Trees Damaged in Fire

Old tree

Old tree

Two oak trees on the Auburn University campus were burned in the early morning hours in November. A video showed the trees rolled with toilet paper and two men passing the trees just before the fire started. A week after the fire, most of the trees’ foliage had browned and begun to fall off. The trees were examined by members of Auburn University’s Trees Task Force and were found to have severe injury and death of most of the rootstalk and rhizomic shoots, damage to the bark of the trees at ground level, leaf scorching, and damage to surrounding trees and shrubs. Because of the timing of the fire, new leaves will probably not form on the tree until next spring.

The trees were already in severe decline due to a case of poisoning last year, and the task force said that the fire would likely further weaken the trees.  “Everyone takes a lot of pride in the oak trees and no one wants to see something like that happen” said Police Capt. Tom Stofer.

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