Client's Request: I'm a trapper in the Ag Department. We have been looking for plum bud gall mites in the county. I recently came across this plum tree with a huge growth or gall, it's 8" long and 7" wide on the underside of a branch, the tree is around 15 years old. Homeowner wants to know what it is and what should be done about it. The tree is in Pittsburg. Any ideas?
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about a very large gall on this 15 year old plum tree in Pittsburg.
I believe this is a gall caused by the bacterium Agrobacterium tumefaciens commonly referred to as crown gall mite or possibly Plum Bud Gall Mite (Acalitus phloeocoptes (Nalepa)). Crown gall, as its name implies, typically appears at the crown of a plant, where the trunk enters the soil but it also can infect the main trunk and side branches. Plum trees are among a long list of plants commonly infected by crown gall including many popular home garden fruit trees (pluots, etc.).
The surface of crown galls and wood underneath is the same color as healthy bark and wood. However, when cut with a knife, crown galls are softer than normal wood and lack the typical pattern of annual growth rings. Galls can be tiny and smooth on young plants but usually are rough and sometimes massive on older trees.
Crown gall appears to have a relatively minor effect on most older plants which is the situation you found. Since this tree is 15 years old and the gall appears to encompass a major part of the main branch I would suggest leaving it be. If the distal portion of the branch starts to decline then the branch can be removed back towards the trunk thereby removing the gall.
Without further inspection of the gall here in our office, another possibility is the Plum Bud Gall Mite (Acalitus phloeocoptes (Nalepa)) which are well described in the Santa Clara County UCCE link below.
Following is a link to a UC Integrated Pest Management website that explains crown gall http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/crowngall.html
and here is a Santa Clara County UCCE link to Plum Bud Gall Mite:
http://mgsantaclara.ucanr.edu/files/300211.pdf
We could give a more conclusive response if you would bring a sample to our offices during our office hours described at the bottom of this response.
I hope your homeowner will be relieved. Good luck.
Help Desk of the UC Master Gardener Program of Contra Costa County (EDC)
Notes: Contra Costa MG's Help Desk is available almost year-round to answer your gardening questions. Except for a few holidays (e.g., last 2 weeks December), we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 2380 Bisso Lane, Concord, CA 94520. We can also be reached via telephone: (925) 608-6683, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/. MGCC Blogs can be found at http://ccmg.edu/HortCoCo/ You can also subscribe to the Biog.
By Corinne Yoshihara, UC Master Gardener of Napa County
As I traveled through Napa Valley this spring, I made a special effort to note the progression of colors on trees lining my route. Color change (or the appearance of color) occurs every year, yet I never tire of it. It's one of my favorite aspects of spring and it's especially noticeable on trees. I enjoy watching the transformation of stark brown branches to those with pops of whites, pinks and, now, green.
Having had a good winter rain, the flowers were particularly abundant this year (as are the weeds, sigh). I first noticed the white flowers of evergreenpear trees in February. Their white flowers were striking against the grey sky, made even more pronounced by the scarcity of other flowers. Pollen-covered anthers lent a charming speckled appearance to the white petals.
With the landscape being so bare, it was also easy to spot the large white flowers flushed with purple of the saucer magnolia, one of the early blooming hybrids of magnolia. The creamy white flowers of southern magnolia didn't make their appearance until May.
When the February rains took us into March, I noticed more arboreal change. Plum trees were covered with soft pink or white blossoms. Bare maple trees sported flowers resembling little red or yellow-green (red maple and silver maple, respectively) balls of bristles. Also around this time, bright pink pea-like flowers covered the branches and trunk of the redbud tree displaying a trait called cauliflory, or “flowering on mature trunk.”
By April, many more trees were in bloom. I saw striking red clusters of the red horse chestnut flowers, white fringe-tree flowers that resembled dragonfly wings, and crabapple blossoms in colors of white, pink and red.
One tree in particular was especially beautiful in April, the dogwood, one of my favorites. Usually blooming under the dappled light of shade trees just beginning to leaf out, the dogwood's tiered branches are sheathed in white, pink or red depending on the variety. The “flowers” are actually four bracts or modified leaves and the actual flowers are tiny, forming a rounded yellowish cluster in the center of the bracts.
Leaves were out on many trees by May, late spring. It seems like they slowly peep out of their bud covers and then, while you're distracted, cover the entire tree in fresh, unmarred chartreuse. Still, I was able to pick out the flowers of tulip, cherry and hawthorn trees.
The opening of buds raises a lot of questions for the biologist-at-heart. Here is one of mine. Did you notice that many of the earlier flowering trees had no leaves? This behavior of flowering before leafing is called hysteranthous. Although both flowers and leaves begin as buds, flower bud opening is not tied to leaf bud opening.
There are even differences in the times of flowering and leaf unfolding between tree species. Pear, plum, redbud, dogwood, magnolia and cherry trees, for example, all flower prior to leafing. On the other hand, crabapple, horse chestnut and tulip trees have both leaves and flowers at the same time.
Moreover, leaf and flower bud openings can vary within a genus. For example, for the maple genus (Acer), bigleaf maple flower buds open at the same time as its leaf buds; silver maple flower buds open when its leaf buds are still tightly closed; and sugar maple leaf buds open but not its flower buds.
Since flower and leaf bud opening behaviors are not tied, the mechanisms that control them must be distinct. In addition to climatic (chilling, light, heat) requirements, there is a genetic component to flowering. It gets complicated!
Whatever the mechanism may be, it appears that time of flower or leaf opening confers advantages to trees. Trees that produce flowers first, place all of their stored energy into the important process of reproduction before other trees have a chance to leaf out and grow. Also, since flower production, like leaf production, requires sunlight, early flowering ensures that leaves don't block sunlight, or interfere with wind pollination. Masses of flowers may also attract more insect pollinators.
Next time you're outdoors admiring nature's beauty, pay attention to the little things happening around you. You may come up with your own questions. Bring them to the Master Gardeners Tree Walks and share them with us.
The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: Hi. We have a beautiful, delicious, amazing plum tree in our backyard. Every year, we've had so many plums that we've been able to share them with friends and neighbors.
This year, our tree produced very few plums. Many were malformed. I also noticed some fungus-looking growth on the tree. Can you help me identify the fungus and/or suggest how I might fix my tree? Thank you! (pics below).
Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk about your plum tree. Your email indicates that your plum tree produced fewer plums than usual this year and that some of them are “deformed”. You also have noticed some “fungus looking” growth on the trunk of the tree.
I have what I believe will be welcome news to you (and to your neighbors who no doubt love sharing the fruit from the tree). Based on the information provided in your email and what we can see in the photos you provided, we do believe that the tree has not developed any serious long term problems.
Let me start with the “fungus looking” growth on the tree. What you are seeing are lichens. Lichens are living organisms composed of both a fungus and an algae. The fungus and algae live in a symbiotic relationship. The fungus receives some food from the algae and the algae some food and protection from the fungus. They are not parasitic on the host tree (i.e., they do not receive nourishment from the host) and are generally harmless to the tree. Lichens grow in a wide variety of shapes and colors, ranging from the gray green and yellowish colors shown in your photos to bright red for some types. Lichens are more noticeable on older trees such as your plum than they are on younger trees because the rapidly growing trunks of young trees tends to disburse the lichens. As indicated in this University of California website, it is possible to remove lichens using herbicidal soaps developed specifically to control mosses, lichens, and algae. http://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/lichens.html Since the lichens are not harmful to the tree, using such soaps is unnecessary and we would not recommend it for your tree.
Now let's turn to the question of why your plum tree produced fewer fruits this year than you have had in the past. There are a couple of possible explanations. One possible factor is the weather conditions that we experienced in the spring months when the plum tree was in bloom. This year, we had a warm and generally dry February and early March. Fruit trees tended to bloom early. Then we started having some regular rain storms and cooler weather. The rain storms may have washed off some of the blooms on your plum tree. Cool, rainy weather also tends to keep honey bees and other pollinators away. Those conditions may have held down the fruit set.
Another possibility is “biennial blooming” which often occurs with fruit trees. With biennial blooming, the tree produces a heavy crop one year, a very light crop the following year, followed by a heavy year, then a light year, etc. Hormones produced in fruit seeds are to blame for biennial bearing. The hormones present in the tree with a heavy crop suppress flower-bud formation the following year. In a year with few fruits, hormone levels stay low, so there are more blooms and more fruit the following year. To interrupt this phenomenon, you can reduce the number of fruits that are allowed to develop in a heavy year by thinning the crop.
Possibly for your fruit tree, there might have been a combination effect—the rain removed some of the blooms and held down pollinators and perhaps the tree was already in a lighter fruit production cycle since you had a good crop last summer.
Finally, let me address the “malformation” of some of the fruit. We don't see much evidence of malformed fruit in the photos you sent. We do see one fruit that looks like it has cracked. Such cracking often is a result of erratic watering while the fruit is developing. If the tree received significant water when the ground was dry, it could have taken up the water rapidly and caused the fruit to split.
Possibly the “malformed” fruit has already fallen from the tree so you cannot provide photos. In that case, we would suspect that the pollination was inadequate. Similar to the small crop this year, the rainy conditions and lack of pollinators during bloom could have been factors for the malformed fruit.
We hope that this information is helpful. If you have further questions, you are welcome to contact us again. Enjoy the plums that you do have; hopefully you'll have a better crop next year. tkl
Help Desk of the UC Master Gardener Program of Contra Costa County (TKL)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523, although we will be moving late July. We will notify you when that occurs. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Biog (http://ucanr.edu/blogs/CCMGBlog/)
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Response from the Help Desk: Thank you for contacting the UC Master Gardener Program Help Desk, and for resending the photos of your plum tree.
It looks like your tree is heavily infested with Kuno scale (Eulecanium kunoense), which is a common pest in plum trees in the Bay Area. Kuno scale females are almost spherical, resembling beads on stems. They are dark brown and shiny most of the year, turning yellow/orangish during egg production in spring. The nymphs (young scale) are yellow or brown and flattened. They feed on leaves during summer, then go to the branches to overwinter. There is one generation per year. This link will take you information from the University of California on Kuno scale: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/kuno.html. And for more information on scale management in general: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7408.html.
Scales secrete honeydew, a sticky sweet substance that attracts ants. Ants in turn protect the scales from their natural enemies that could help control their population. So, the first thing to do is to control the ants. If the tree's branches touch other plants or structures, prune those branches back so the ants don't have that access route. Use a sticky substance on the trunk to prevent ants' access that way. Wrap the trunk with a collar of heavy paper, duct tape, or fabric tree wrap and coat it with a sticky material such as Tanglefoot. Check the coating every week or so, and stir it to expose new sticky material. If left too long, ants, other insects, and debris will collect on it and obscure the sticky material, allowing access once again. You should also be aware and check to assure that birds occasionally get stuck in this substance trying to eat the trapped ants, etc.
You can also use bait stations to reduce the ant population. Borate-based products seem to be the most effective, as the bait is sugar based and should attract the honeydew-eating ants. Place the station near the base of the tree. Ant baits take a while to work, so it may be a while before you see any results. This link will take you to information on ant management: http://ipm.ucanr.edu/PMG/GARDEN/CONTROLS/antmanagement.html. For more information about ants: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7411.html.
You mus also make sure you are giving good cultural care to your tree, especially with adequate irrigation, to make it more resistant to scale damage. To immediately reduce the scale population, you can prune off the most heavily infested twigs or branches, if that's appropriate for the tree's form. Your pictures look like it is a mature plum that might benefit from a little summer pruning anyway. By opening up the tree, it may increase scale mortality from exposure to heat and predators.
Chemical controls can be used for especially bad infestations. Horticultural oils (narrow-range, superior or supreme), insecticidal soaps, neem oil, or other botanical oils have low toxicity to people and pets, and appropriately applied should have little impact on pollinators and natural enemies. Make sure you follow all instructions on the products' labels, looking especially for which plants not to use the product on. For your plum, spraying with an oil during the dormant season may be the easiest. Foliage spray can be effective to get the nymphs in their crawling stage, but it can be difficult to make sure the product covers all leaf surfaces on a large tree.
To recap: Ant control is the first thing to do. Good cultural care is next. To encourage natural enemies, grow a variety of flowering plants to help attract and support them. Adults of predatory bugs, lacewings, lady beetles, and parasitic wasps live longer, lay more eggs, and kill more scales when they have plant nectar or pollen and insect honeydew to feed on.
It will take several months of efforts (such as controlling ants) or until the next season or longer before scale populations are reduced by biological control. If the level of scales is still intolerable, then consider spraying insecticidal oils to reduce scale populations while conserving natural enemies.
Please let us know if you have further questions.
Good luck with your plum tree!
Help Desk of the UC Master Gardener Program of Contra Costa County (SEH)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
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- Author: Kathy Keatley Garvey
Some call them "soldier beetles."
Some call them "leather-winged beetles."
Some call them "Cantharids" (family Cantharidae).
Whatever you call them, be sure to welcome them to your garden. They eat aphids, lots of aphids. Like the good soldiers they are, they're ready to do battle.
We spotted five or six of them munching on aphids on our year-old plum tree.
Soldier beetles have a large thoracic shield, long threadlike antennae and beady little eyes.
According to retired entomologist Jerry Powell of UC Berkeley, there are about 100 species of them in California.
Most of them, according to the Jerry Powell-Charles Hogue book, California Insects, are "similar in appearance, red or orange with gray, black or brown wing covers."