- Author: Help Desk Team
Prune Apricot and Cherry Trees in August
If you have apricot, cherry, or related hybrid tree varieties such as aprium and pluot in your yard, plan to prune them before the end of August. This timing will help prevent infection by a deadly fungal disease called Eutypa Dieback that can kill these trees as well as grape vines.
When infected by Eutypa, branches or entire trees wilt and die suddenly, often with the leaves still attached.
Apricot tree with branch killed by Eutypa
Signs that your tree may be infected by Eutypa include darkly discolored cankers on the branches and oozing of amber colored gummy sap.
Eutypa cankers on apricot branch
Oozing Sap on Cherry Tree from Eutypa Infection
[Editorial Note: apricot photos downloaded from UC Repository. Cherry tree photocopied from UC ANR blog article by Chuck Ingels, UCCE Sacramento, https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16014 ]
Many other varieties of trees and shrubs can become infected with the Eutypa fungus without showing disease symptoms or progressing to the dieback stage. These other tree and shrub varieties can serve as store houses for the Eutypa pathogens that could potentially spread to your grape vines and apricot, cherry, aprium and pluot trees. Trees and shrubs that can serve as reservoirs for the disease include almond, apple, blueberry, crabapple, honeysuckle, kiwi, oleander, pear, and certain native plants such as big leaf maple, California buckeye, ceanothus, and willow.
Eutypa disease is spread from an infected tree, shrub or vine to uninfected trees by splashing water from sprinklers or rain. The splashing water allows the fungal spores to enter through pruning or other wounds. Pruning vulnerable tree varieties by the end of August allows pruning wounds to heal and close before the typical start of the rainy season in Contra Costa County in late October. Also, avoid using sprinklers near recently pruned trees since water from sprinklers can also spread infections. Using these precautions will reduce the risk of infection for your trees.
Studies have shown that the Eutypa pathogens can also be spread on pruning tools that have been used to prune infected trees and shrubs. To prevent such transmission, be sure to disinfect your pruning tools before and after pruning.
To disinfect tools, soak them for thirty minutes in a 10% bleach solution (nine parts water to one part bleach). Bleach is corrosive so be sure to rinse the tools thoroughly with water after soaking. Then oil them. The bleach solution loses 50% of its effectiveness after two hours, so be sure to use a freshly mixed batch.
As an alternative to bleach, you can disinfect pruning tools with 70% isopropyl alcohol. Just spray it on your tools and it will kill any pathogens almost immediately. Alcohol is not corrosive, so you don't need to rinse it off tools.
An internet search for “how to prune apricot [or cherry, aprium or pluot] trees” will help you find videos that demonstrate good pruning techniques. Just be aware that most pruning videos are filmed when the trees are dormant. With no leaves, the branches can be more easily shown in the video to demonstrate pruning techniques. In California, you don't want to wait until the dormant season to prune these vulnerable trees because that increases the risk of an Eutypa infection. So, you'll need to adapt the pruning techniques to a tree that still has leaves.
For more information on Eutypa disease, visit this University of California IPM website: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/eutypadieback.html
Advice for the Home Gardener From the Help Desk of the
UC Master Gardener Program of Contra Costa County
MGCC Help Desk's Response: Thank you for contacting the UC Master Gardener Program Help Desk and for sending the helpful photographs of your apricot tree. The photos show that there is severe bark cracking of major limbs extending all the way to the ground, and at least some sap ooze on smaller branches, although the leaf canopy looks rather healthy. The tree might survive and be fruitful, but because of the extensive damage to the bark and less than optimal branch structure (from improper pruning), taking it out and starting fresh is not a bad idea.
Some additional discussion of issues that could help you make this decision are below.
As we discussed, there is a common fungus disease of apricots call Eutypa die back that is spread by splashing rain and enters through pruning wounds. For this reason, apricot trees should be pruned now (early Fall), never during the wet winter. If you see oozing sites on any branches that are surrounded by sunken areas (indicating an area of infection), or see entire branches dying back, this would indicate your tree has the fungal infection and should be taken out because it will not recover. More information on Eutypa can be found at this University of California website http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/DISEASE/eutypadieback.html.
Another potential cause of the bark cracking is a vigorous and rapid growth response this spring due to last winter's rains, particularly if the tree had not been properly watered during the drought. Since you are just moving in, and do not know the history of tree care, this would be hard to determine. However, if this is the cause, the tree should be able to recover. Providing excellent cultural care for the tree would help it to recover. Apricot trees need summer water every 10 - 14 days, and should also be fertilized in the spring and after harvest as described here http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/fruitwatering.html and here http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/apricotfert.html .
If the soil at the drip line of the tree is dry to a depth of 6 inches or more, I recommend that you water it very thoroughly now and again in 7 - 10 days (depending upon whether we have more very hot weather). A soaker hose would work well to provide a long, slow application of water at the dripline that can penetrate the soil. Later, you could provide a light fertilization (half of the recommended amount) to the wetted soil. Never water near the trunk of trees since this can promote infection (described more below).
A third possible cause of the bark splitting is fungal infection of the crown area (transition zone between trunk and roots). The root flare of the apricot tree is not visible in the photos, meaning either that it is covered by mulch (which should be pulled back 4 - 6 inches from the trunk) or that the tree has sunk too deeply into the soil. When the lower part of the trunk is buried in soil, it is very susceptible to rotting by various fungi, which can kill the tree. Bark peeling and loss can be a sign of such fungal infection which would likely have been made worse by the wet conditions last winterhttp://ipm.ucanr.edu/PMG/PESTNOTES/pn74133.html . If you decide to take out the tree and plant a new one, be sure to plant the tree slightly elevated, as described and shown here http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/fruitnutplanting.html.
Finally, as we discussed, it looks as though the apricot tree was not being pruned properly by the previous owners, but it could be pruned now (early Fall... see above), if you decide to keep the tree. Specific information on how to prune apricot trees can be found here http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/apripruning.html .
I hope that this information is helpful. Good luck with your new (to you) garden and orchard. Attached to this blog post is short guidance on "Growing a Backyard Orchard" that may be of use to you. Please let us know if you have any further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (JL)
Please Join us at "Fall for Plants" on September 9 for the workshops and the plant sale.
Registration is optional, but it'll get you a free plant from the sale. We hope to see you there.
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/).
Growing a Successful Backyard Orchard
