Controlling Fruit Tree Diseases

Joseph O’Brien, USDA Forest Service, Bugwood.org

Food gardening has never been more popular. You get to harvest fresh fruits, vegetables and herbs with incredible flavor, you have the confidence of knowing where your food comes from and just the simple joys of “growing your own” are undeniable. However, it’s also true that growing your own food can be more challenging than other types of gardening, especially when it comes to growing your own fruit.

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To produce a harvest you can be proud of, you need to give your fruit trees some special care, particularly when it comes to controlling diseases.  Fruit diseases like brown rot, scab, rust and fire blight can turn your harvest into an inedible mess and threaten the health of your trees.
 

Different Areas Usually Have Different Problems

Check with your local Cooperative Extension System office to find out which diseases are most troubling in your area. They can provide the latest information on specific disease outbreaks, variety adaptation, including which ones are resistant to local diseases, and proper timing of control measures (many states publish fruit tree maintenance calendars which are tremendously useful).
 

Plant The Best Varieties

Fruit tree adaptation varies in different parts of the country. Species and varieties that are well-adapted to your area should produce the best quality fruit but also offer better resistance to the most common diseases. Here are just a few examples of many disease resistant fruit that are commonly available:

  • Disease resistant apples like Liberty, Redfree and Enterprise resist Scab, Mildew, Cedar Apple Rust and Fire Blight.
  • Honeysweet and Kieffer pears are two among several that resist Fire Blight. There are also many Asian pears that are resistant to Fire Blight.
  • Although they might not offer the fruit quality of some of the best peaches, Q 1-8 and Frost are resist Peach Leaf Curl.
  • Because dwarf fruit trees are easier to maintain and spray, they are another good option where diseases are troublesome. Some rootstocks are also resistance to soil-borne diseases.
     

Provide Proper Growing Conditions and Care

Plant fruit trees where they get at least 6 hours of direct sunlight and in well-drained soil. They will also need regular water and proper fertilization to produce quality crops. Plant anywhere else- where there is too much shade, poorly drained, soggy soils or too much nitrogen, and you will have more disease problems. You should also thin fruit when small to insure good size at harvest. This is also a good time to remove infected fruit that may spread disease. Choosing the proper planting site and providing the right care will give you years of delicious harvest.
 

Prune Seasonally

Proper pruning opens trees to air circulation, drying and light, which will help prevent many fruit diseases. It also gives you a chance to remove diseased branches, preventing further infection. Timing is important. Most pruning is done during the dormant season when the trees are leafless, but summer pruning helps control tree size, encourages air circulation and is also a good time to remove diseased plant parts, which are usually easier to see at that time. In some cases, it helps to prune during dry weather. In California, for example, apricots are pruned in summer to prevent Eutypa Dieback, which is spread through pruning cuts by winter rains. With some diseases, including Fire Blight, sterilizing your pruning shears with a 10% bleach solution after each cut will help prevent the spread of the disease. Otherwise, you can transmit the disease from branch to branch or tree to tree via the shears.
 

Keep The Home Orchard Clean

Raking up and discarding dropped leaves and prunings from around the base of trees, along with removing mummies (overripe, unpicked fruit) from the branches, goes a long way in disrupting disease cycles from year to year.
 

Control Insect  Vectors

Not many fruit tree diseases are spread by insects, but there is one very important exception: the Asian Citrus Psyllid (ACP) and Citrus Greening Disease (known as Huanglongbing or HLB in the West). Controlling ACP is critical in controlling this devastating citrus disease, which has no cure. There are quarantines in place in primary citrus-growing states such as Florida, Arizona, Texas and California. The insect threatens all citrus in commercial orchards and home gardens in all citrus growing regions. To learn more, contact your local cooperative extension or go to www.https://www.aphis.usda.gov/aphis/resources/pests-diseases/save-our-citrus
 

Protecting Fruit Trees

Controlling diseases of fruit trees usually takes multiple approaches, including preventative fungicidal or bacterial sprays. Proper timing is critical. Dormant sprays (usually horticultural oil combined with a fungicide) can help control insects and diseases by killing overwintering pest eggs or growth stages. Natria Neem Oil can be used as dormant spray as well as to control insects and diseases during the growing season. Other Natria products are also labeled for use on fruit trees. Always be sure to read and follow label instructions.

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