Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Apricot Tree Showing Signs of Brown Rot
by Chantal Guillemin , Master Gardener
Request: My Royal (Blenheim) apricot tree usually produces delicious fruit, but this year almost all had brown discoloration. Globs of golden sap ooze out in many places along branches and the ends of some branches have brown, withered leaves and dead flowers. What kind of disease is affecting my apricot tree? What can I do about it?
Photo by Jack Kelly Clark, courtesy UC Statewide IPM Program
Response: Thanks for contacting the Help Desk of the UC Master Gardener Program of Contra Costa County about the problems with the brown spots appearing on your apricot fruit.
Expanding dark brown, firm, circular spots on apricots are symptomatic of a very common and serious disease of stone fruit called brown rot. The exudation (oozing) of sticky droplets of gum (sap) from the base of dead flowers and the bark of infected twigs is further indication that Monolinia spp., the brown rot fungus, is present on your apricot tree. Brown rot can also infect other stone fruit such as almond, peach, plum, cherry, nectarine and quince (a pome fruit).
The first symptom of brown rot is the browning and withering of blossoms. These infected blossoms cling to twigs for months. Cankers, which are sunken brown areas, may develop around twigs at the base of infected flowers, causing leaves at tips of twigs to become dark brown and shrivel up.
Photo by William W. Coates, courtesy UC Statewide IPM Program
Gardeners in Contra Costa County can practice the following sanitation measures to decrease the spread of brown rot fungal disease: frequent checking of stone fruit trees for signs of brown rot, timely and appropriate pruning, furrow or drip irrigating versus overhead sprinklers, and planting disease tolerant varieties.
Inspect your apricot and other stone fruit trees nearby often for symptoms of brown rot. Do this during the bloom period, as fruit turn green, and when they begin to ripen. Consider harvesting fruit before it is ripe but once it is soft will lessen the risk of brown rot. After harvest, remove all fruit left on trees or destroy them because they are potential overwintering sites for brown rot. Ensuring that gardening sanitation tasks are performed on a regular basis will go a long way to minimizing the development of spores from mummified fruit hidden beneath weeds and debris on the ground.
As for apricot trees, pruning should never be done during winter dormancy. That's our wet season, and atmospheric moisture carries airborne spores and pathogens. Apricot and cherry trees are particularly susceptible to Eutypa dieback, a disease which causes whole branches to wither away. Do not inflict pruning wounds on apricot trees at this time. Pruning diseased twigs and dead blossoms still clinging to branches of apricot trees should be done after leaves drop but before the first fall rains.
Other stone fruit require the same removal of infected plant tissue but this can be done as soon as these are detected. Burn, bury or bag all diseased branches and leaves. Destruction of these affected parts and the removal of mummies from the tree and from beneath the tree prevents the buildup of brown rot inoculum. This applies to flowering cherry, plum and quince as well. Do not put diseased plant parts in compost. Remove broken or diseased branches. Prune trees from the time they are planted to allow good ventilation in the canopy.
Avoid wetting blossoms, foliage, and fruit during irrigation by using furrow or drip irrigation. As far as prunes are concerned, drying them immediately after harvest kills the brown rot fungus.
Some plant varieties are known to be least susceptible to brown rot. Apricot cultivars Tilton, Harcot, and Harglow are touted to have some brown rot resistance. Royal, Blenheim, Perfection, and Derby Roal are most susceptible to this fungal infection.
If left unmonitored, brown rot fungal infection of apricots and other stone fruit can thwart homeowner's plans for a harvest of healthy fruit. Familiarization with brown rot symptoms and taking action to remove sources of brown rot spores can alleviate the problem of brown rot fungal infection on apricots and other stone fruit.
For additional information, you can also consult:
UCANR publication 7259, Apricots: Calendar of Operations for Home Gardeners;
UCANR publication Pests in Garden and Landscapes – Brown Rot Monilinia spp.;
UCANR publication 3332, Pests of the Garden and Small Farm, pp 144-145;
UCANR publication 3382, California Master Gardener Handbook Chapter 16
UCANR publication 3311, Postharvest Technology of Horticultural Crops;
UCANR publication 3345, Diseases of Temperate Zone Tree Fruit and Nut Crops;
UCANR publication 3485, The Home Orchard
Those not available as free download UC publications are often available at your local branch library or by mail order from UCANR.
Please do not hesitate to contact the MGCC'S Help Desk if you have further questions and/or need recommendations.
Help Desk of the UC Master Gardener Program of Contra Costa County (CCG)
Note: The UC Master Gardeners Program of Contra Costa'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.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/)
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: I've managed to grow an apricot tree from seed. It's now big enough that it has produced a few apricots in prior years. However, it hasn't produced any fruit now for several years. What is preventing fruiting and what can I do to get fruit?
The apricot tree's lack of fruit production could be due to flower or young fruit damage from weather; it could be due to reduced pollination, also potentially affected by weather; it could be due to tree damage caused by a pest or pests, or it could be a nutrition issue for the tree.
Weather
Fruit trees form their flower buds in the fall. Lack of rain or high winds can damage buds before they blossom. Spring rains or late-spring frosts can also damage or kill buds and blossoms. Apricots in general perform best in climates with dry spring weather. This year we had both late frosts and spring rains in parts of the County. Last year we also had significant spring rains, and prior to that several dry years in succession. So, weather could certainly have had a negative impact on the fruit production of your apricot tree for the past several years.
Reduced Pollination
Pollination issues could also have played a role. Fruit production depends on pollination, which is the transfer of pollen from the male part (anther) of a flower to the female part (pistil) of the same or another flower usually of the same species. Apricots are self-fruitful, meaning that they may be pollinated by pollen from another flower on the same tree, or in the case of apricots, by pollen from the same flower. The transfer of pollen from one variety to a different variety of the same type of tree is called cross- pollination. Although not required, cross-pollination does improve the number of fruit that form on apricots. Pollinators, such as bees, are usually responsible for apricot pollination.
This link to a Penn State University extension website
https://extension.psu.edu/pollination-requirements-for-various-fruits-and-nuts
identifies several factors can affect pollination:
Temperatures below 55-60°F reduce bee activity
Windy and rainy weather can slow bee activity
Presence of other flowers -- the fruit plants generally are poor nectar producers and bees will naturally seek out the best nectar producing flowers
Most insecticides will reduce bee activity -- therefore do not spray them during bloom
Pests affecting apricot trees
Apricots are susceptible to a variety of pests, listed at this link:
http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/apricots.html
These include sucking and boring insects and other invertebrates, and bacterial and fungus diseases. If, after reading the descriptions, you suspect that you have any of these issues, there are controls suggested at the same link and sub-links.
Cultural care
The best prevention is good cultural care. Maintaining a good fertilization program can keep your tree vigorous and help prevent infections. Adequate irrigation will help as well.
http://homeorchard.ucanr.edu/Fruits_&_Nuts/Apricot_Prunus_armeniaca_L/
http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/apricotfert.html
http://homeorchard.ucanr.edu/The_Big_Picture/Irrigation/
With respect to pruning your tree, apricot trees should be pruned in late summer, since they are susceptible to a fungus infection if pruned during wet weather. Because of this, they should be pruned in August -- after fruit production is complete, and early enough to allow time for pruning wounds to close prior to the beginning of winter rains. Information on pruning apricots can be found at this link.
http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/apripruning.html
I hope that this information is helpful. If you have any questions about the material in these links, or anything else, please contact us again.
Good luck with your tree!
Help Desk of the UC Master Gardener Program of Contra Costa County (MCW)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer our 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 this spring. We will notify you if/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 Blog (http://ucanr.edu/blogs/CCMGBlog/)
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
