- Author: Denise Godbout-Avant
(From old proverb)
I love to stroll under the shade of majestic Valley oak trees in the oak woodland riparian habitat along the Stanislaus River at Caswell State Park in Ripon. I visualize Lakisamni Yokut women (the indigenous people who lived in Stanislaus County area for millennia) as they gathered acorns.
Vital Roles
Early humans built their homes, created tools, built shelters and ships from oak wood. Oak galls were used to make dyes, writing ink, and tan leather. Today we use its strong wood to construct furniture, flooring, cabinets, and wine barrels. If you like truffles, thank oak trees, since truffles have a close relation with the roots of oak trees. Truffles are almost impossible to grow. Instead, truffle farmers plant oak trees, hoping to create favorable conditions conducive to the growth of truffles.
California Oaks
- Valley oak (Quercus lobata) – One of California's iconic species, it is the largest oak tree found here, living up to 300 years. The Valley oak grows where there is a water table within reach of the roots, often near creeks and rivers. They grow quickly, reaching 20 feet in 5 years and up to 60 feet in 20 years. A deciduous tree, it's distinguished by deeply lobed shiny green leaves and long, narrow acorns.
- Interior live oak (Quercus wislizenii) – An evergreen tree, growing up to 25-80 feet tall, it is found in hilly or mountainous areas, near creeks and streams, living up to 200 years. It can produce two types of leaves at the same time, one with a serrated edge and the other with a smooth edge, and produces small, thin acorns.
- Blue oak (Quercus douglasii) – A deciduous tree found in the hot, dry foothills, it grows to be 20-60 feet tall with blue-green leaves which vary in size and shape. With a lifespan of 200-500 years, their acorns are fat and stubby.
Oaks tolerate fire due to their thick, furrowed bark and tough leathery leaves. During wildfires, the larger oaks in areas cleared of fuel may scorch, but rarely burn completely. Damaged trees will resprout from the root crown.
Acorns
An oak tree can produce millions of acorns during its lifetime, but only one in 10,000 acorns grows up to be an oak tree. Acorns are highly nutritious, carbohydrate-rich, and were a diet staple of the Californian indigenous people. Mammals and birds who eat acorns include the Acorn woodpecker, Yellow-billed magpie, California ground squirrel, and Mule deer. However, acorns are toxic to dogs and horses.
The indigenous people called the California scrub jay the “gardener bird” because of its propensity for caching thousands of acorns and not eating all of them, which helped replenish and expand oak forests.
Oak Galls
A favorite oak gall of mine is “jumping galls,” the size of poppy seeds, round with a dot in the center. Some years large numbers of them drop and litter the ground and sidewalks. The galls “jump” each time the larva moves inside. You can see this in action in this YouTube video: https://www.youtube.com/watch?v=0VI7USm4J5I
Oak Challenges
Today, oak trees face many challenges. Disease, drought, and fire can all destroy oak seedlings. Young oaks are stepped on by grazing animals or run over by machinery. Full grown oaks are often damaged or killed when new homes, roads, stores, or businesses are built. Sudden Oak Death is a disease caused by the pathogen Phytophthora ramorum,discovered in Mill Valley in 1995. Causing a rapid color change from green leaves to brown in infected oaks, it has killed thousands of live oak, black oak, tanoak, and Shreve oak in 14 California counties. Climate change is also putting pressure on oak trees.
To maintain a forest or woodland, each oak tree needs to produce just one replacement tree in its lifetime. You can help regenerate California oak habitat by caring for an acorn seedling and protecting it from harm while it grows into a mighty oak.
All photos by Denise Godbout-Avant unless otherwise noted.
/h3>/h3>/h3>/h3>/h3>- Author: Ben Faber
There are always new things to see in the field. Some things show up on occasion, but reliably, like citrus leafminer starts damaging new leaves in the fall. You start to see the leaf spots from Persea mite in the fall, even though they started their nesting/feeding activities in the late spring. Then some things show up irregularly. There's a fungus that hits citrus and other plant species – oleander, bottlebrush, holly, Natal plum, Brazilian pepper, eucalyptus – but mostly landscape species.
Sphaeropsis tumefaciens pops up here and there, this year and then not for several years. I've only seen it in Ojai, but Craig Kallsen in Kern Co. says that it's not uncommon in Bakersfield backyard citrus. It creates knobby growths, galls or tumors along branches. I've seen it on mandarin (‘Pixie'), lemon, Valencia and ‘Late Navel'. Whenever I see it, I immediately think of glyphosate damage.
A lot of times, you can see twisted leaf growth coming out of the galls. Classic herbicide phytotoxicity symptoms. But symptoms are just that, they don't tell you what caused that symptom to happen. In the several cases I've, seen only one out five has been an orchard that used herbicides. So it wasn't a reaction to glyphosate that caused the unusual growths.
These woody growths take several years to form. They don't show up just after an herbicide spray. It probably take a few years for them to show up. It's not until someone is pruning that they probably notice the galls.
In fact, it might be the pruning that is spreading the spores that causes the infection. Moisture helps spread the fungus. Another reason not to prune citrus during the rainy season.
While looking through the literature, I came across a reference to galls forming in avocado caused by Sphaeropsis – this in Mexico, http://www.avocadosource.com/WAC2/WAC2_p129.pdf. I have seen symptoms like that here
Also causing a whole fruit to form a gall. Truly a bizarre sight
But of course, this is my speculation, since these symptoms have not been tested foe their cause, as far as I know.
What causes the symptoms in Mexico might be different in California.
How to treat these galls in citrus? Cut them out if you can, but in many cases they are right in the middle of a structural branch. It is desirable to get it out of the orchard to prevent its spread. With the limited experience we have with this disease, it doesn't seem to impair yield at the levels of infection i have seen.
- Author: Scott Oneto
A recent find in El Dorado County has weed scientists, land managers, foresters, botanists, and plant conservationists throughout Northern California very excited over a tiny mite.
The broom gall mite has recently been observed attacking the invasive plant Scotch broom (Cytisus scoparius) in California's natural landscapes. Scotch broom, desired for its bright yellow flowers and rapid growth, was first introduced into North America as an ornamental and for erosion control. However, its ability to outcompete native plants and form dense stands has also made it one of California's worst wildland weeds (Figure 1).
The mites cause galls, small abnormal growths on the plant's buds, to form during feeding, greatly reducing Scotch broom's ability to grow and reproduce (Figure 2). This mite is considered to be an ideal biological control agent due to its specialized feeding habits and the debilitating damage it can cause to invasive weeds. In some areas, the gall mite has already killed large stands of broom (Figure 3).
The Scotch broom gall mite, more closely related to spiders and ticks than insects, is a type of eriophyid mite that is nearly invisible to the naked eye, measuring roughly the width of a human hair (Figure 4). Although the mite is tiny, the galls formed by plants in response to the mite's feeding are quite noticeable. The small fuzzy masses occur along the length of the stem and can be quite numerous.
Native to Europe, the mite was first found on Scotch broom in the Tacoma, Washington, and Portland, Oregon, regions in 2005. Since that time the mite has become established throughout western Washington and Oregon and even into parts of British Columbia. Up until 2013, the mite had only been found as far south as Ashland, Oregon, with no occurrences in California.
However in March 2014, a landowner in El Dorado County brought a sickly
Since the first detection in El Dorado County, USFS, UCCE, and the California Department of Food and Agriculture have been on the lookout for other occurrences of the gall mite on Scotch broom. Surprisingly, the mite has since been found in many areas throughout El Dorado, Placer, and Nevada counties; but how it got there is a mystery. Mites are known to travel long distances using wind currents and by hitching rides on animals, humans and equipment. It is likely that many more finds will be forthcoming.
Since the mite is a beneficial biological control agent and not a pest, do not apply pesticides to kill it! The broom gall mite can help greatly in the fight to control Scotch broom plants that have invaded wildlands throughout California. If you or your neighbors see evidence of Scotch broom gall mites, please report it on the University of California Cooperative Extension website: ucanr.edu/broomgallmite.
Alternatives to Scotch broom
Although some retail nurseries still sell a variety of broom species, homeowners should avoid planting them. Depending on your climate, a number of alternate plant species with similar attributes that are are not invasive weeds may be available. See the PlantRight article from our April 2015 Retail IPM Newsletter about alternative plants to recommend to your customers or contact your county UC Master Gardener program or UC Cooperative Extension office for a list of local recommendations.
Scotch broom currently infests millions of acres throughout California, causing loss of native plant biodiversity and an increased fire risk. The USFS and other agencies spend a considerable amount of time and taxpayer money each year treating Scotch broom plants either by applying herbicides or prying them up by the root. With the mites' help, we'll make much greater progress toward reducing Scotch broom infestations.
For more information about Scotch broom and other brooms, read UC IPM's Pest Note: Brooms. For plant alternatives, see PlantRight's list.
/span>- Author: David H Alosi
By Yvonne Rasmussen, U. C. Master Gardener
This time of year, as the weather starts to cool and we get a little more moisture in the air, we start to see some fungi in the garden. These might be mushrooms growing in the lawn or at the base of a tree, or conks growing out from the trunk. Other smaller fungi can produce white, black or orange spots, fuzzy material or residue on leaves. Still others make strange forms we might not recognize as fungi, such as puff balls, earth stars, galls or masses on branches or soil.Some of these peculiar protuberances are caused by the closely related slime molds, such as the so-called “dog vomit” slime mold seen in the spring. This mold produces a bright yellow, frothy-looking growth on soil, often near the base of trees or other plants.
Fungi play an important role in the environment. They help decompose plant material that cannot easily break down otherwise.
But they can also cause plant diseases and problems in the garden. Fungi generally need moisture for reproducing, which they do by means of spores. Generally spread by wind or water, spores are a little like tiny seeds. The powdery substance you feel on the underside of a rose leaf infected with rust is the rust spores. You can sometimes see spores on the underside of a mushroom, or in the smoky substance from a puffball.
Althought some fungi are edible, others are deadly poisonous and some are major allergens.
In the fall, powdery mildew often develops on the leaves of vegetables and ornamentals. It may look like white spots or a dusty coating on the leaves. Leaves infected with powdery mildew will eventually turn yellow, die and fall off.
Powdery mildew prefers cool, moist places. It does not do well in full sun and heat, so it appears first on plants in shady areas.
To avoid powdery mildew, plant in sunny locations and provide good air circulation. Keep plants pruned properly to encourage air circulation and don’t over fertilize. Too much fertilizer promotes fast, weak, leafy growth that will need more water. Excess nitrogen in the soil—what the plants can’t use—washed into our waterways and promotes algae growth.
For many vegetable crops and deciduous plants, there’s no good reason to treat for powdery mildew since the plants will soon be removed or go dormant. Most treatments can prevent the fungus, but they don’t cure it. This means you need to treat before you see symptoms.
Treatments need to thoroughly cover all susceptible plant parts. Mild to moderate symptoms can be treated with horticultural oils or plant-based oils. Follow package directions carefully. These oils can damage plants if used within two weeks of a sulfur application, or when temperatures are high, or if plants are drought stressed.
University of California Cooperative Extension has three free “Pest Note” publications related to controlling powdery mildew. You can read these publications online or pick them up in the Napa County Master Gardener office (address below).
Mushroom are generally beneficial in the garden because they break down organic matter. They grow on buried wood, dead roots and other plant debris. Removing the mushrooms will not remove the fungi from your yard because most of the fungus is actually underground or in the plant tissue. The mushroom is only the fruiting body.
It’s like harvesting an apple from a tree. You remove the seeds but the tree lives on. For fungi, spores are the equivalent of seeds. They can travel great distances on the wind.
Because some mushrooms are toxic, you may want to remove them to keep them from being eaten by small children or pets. If you suspect mushroom poisoning, contact California Poison Control at 800-222-1222. If possible, keep a piece of the suspect mushroom or take a photo of it so you can accurately describe it to poison-control or medical personnel. If you suspect your pet has eaten a toxic mushroom, contact your veterinarian.
University of California Master Gardeners do not identify mushrooms, nor can we determine if they are edible or not. But we do have Pest Notes available on mushroom control.
To learn more about the biology of mushrooms and other fungi, consult the websites of the Mycological Society of San Francisco (http://www.mssf.org), the Bay Area Mycological Society (http://www.bayareamushrooms.org) or the Sonoma County Mycological Association (http://www.somamushrooms.org).