- Author: Ed Perry
Fruit color is a poor indication of ripeness, because many fruits have fully colored rinds a long time before they can be eaten.
Don't expect citrus fruits to increase in sweetness or ripen more fully once you've picked them, as do peaches and some other fruits. When picked at any stage of maturity, citrus fruit does not change after picking, except that it may decay or slowly dry out.
When you're picking citrus fruit that you plan to store for awhile, be careful not to bruise or break the skin. Fruits that are cut or scratched during harvesting will rot fairly quickly in storage. Citrus fruits with perfectly sound skin are fairly decay proof, and will last in cool, moist storage for several weeks (38 to 48 degrees F, 85 to 95 percent relative humidity). Under dry conditions at room temperature, fruits develop off flavors and shrivel within a week to 10 days.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
Citrus trees need care throughout the year, including cultural practices to keep trees healthy and pest management. During the fall season, several pests can attack citrus trees in many California regions.
Brown Rot
Monitor for this disease by checking for damaged fruit on your tree, as well as fruit in storage. Sometimes affected fruit develops a pungent odor and can ruin fruit held in storage. See the UC IPM web page on Brown Rot to learn more.
If you see what look like small “tunnels” on your citrus tree leaves, your tree might have citrus leafminer. The adult stage of this pest is a small, light colored moth; the larval stage feeds and develops inside the leaves of young citrus and other closely related plants.
Citrus leafminer rarely causes problems for mature trees, however, it can seriously damage very young trees. Read the UC IPM Pest Notes: Citrus Leafminer for recommendations for prevention or management.
Snails and Slugs
Asian Citrus Psyllid and Huanglongbing
You may have heard of the Asian citrus psyllid (ACP) and the deadly disease huanglongbing (also called citrus greening) that has been featured in the news. This disease doesn't pose a threat to humans or animals, but is deadly to citrus trees. Once a tree develops huanglongbing, there is no cure, so for this disease prevention is key.
UC IPM Web Site
For information on managing other citrus pests in the garden, see the UC IPM webpage on Pests in Gardens and Landscapes: Citrus.
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/)
Apricot trees need to be pruned in summer instead of fall to avoid a disease called Eutypa dieback. It causes limbs and twigs to wilt suddenly and die. Shot hole disease is another common apricot pest which appears as purplish or reddish spots on new buds, leaves and shoots. The disease is most severe in years with rainy winter and spring weather.
Plums and other stone fruit can be attacked by brown rot, a disease that causes flower blossoms to turn brown, wither, and stay on the plant. Fruit that does develop turns brown or has tan spots that can appear sunken over time.
Peach and nectarine trees are susceptible peach leaf curl. Tree leaves have reddish areas that thicken and pucker, causing leaves to curl. In rare cases, fruit develops reddish, wrinkled areas that become corky and tend to crack.
Many vertebrate pests such as tree squirrels, birds, rats, and others also enjoy snacking on stone fruits. Visit the vertebrate Pest Notes to learn ways to keep them from ruining your harvest.
You can find more information about caring for stone fruit trees, as well as a list of the common pests, disease and disorders that affect these trees at the following links:
Apricot Nectarines and Peaches
![Infestation of brown rot on lemon. (Jack Kelly Clark) Infestation of brown rot on lemon. (Jack Kelly Clark)](http://ucanr.edu/blogs/UCIPMurbanpests/blogfiles/48284.jpg)
Brown Rot
Monitor for this disease by checking for damaged fruit on your tree, as well as fruit in storage. Sometimes affected fruit develops a pungent odor and can ruin fruit held in storage. See the UC IPM web page on Brown Rot to learn more.
Citrus Leafminer
Citrus leafminer rarely causes problems for mature trees, however, it can seriously damage very young trees. Read the UC IPM Pest Notes: Citrus Leafminer for recommendations for prevention or management.
Snails and Slugs
Asian Citrus Psyllid and Huanglongbing
You may have heard of the Asian citrus psyllid and the deadly disease huanglongbing (also called citrus greening) that has been featured in the news. This disease doesn't pose a threat to humans or animals, but is deadly to citrus trees. Once a tree develops huanglongbing, there is no cure, so for this disease prevention is key.
UC IPM Web Site
For information on managing other citrus pests in the garden, see the UC IPM webpage on Pests in Gardens and Landscapes: Citrus.