Category Archives: fruit tree diseases

Do I Really Need to Dormant Spray and Prune my Fruit Trees?

Gummosis canker on dwarf nectarine- Photo courtesy of Sherry Austin
Gummosis canker on dwarf nectarine- Photo courtesy of Sherry Austin

A Facebook friend recently posted a picture of gummosis on her dwarf nectarine. While pruning her fruit trees she found the sticky stuff and shared her plight. While some folks post pictures of babies and political opinions on their Facebook page, my friends post pictures of plants and their fruit trees. Yes, if you haven’t already done so, this is the time to winter prune fruit trees and apply dormant spray to fend off diseases and insect pests. With rainfall expected throughout the spring this is not the year to omit this important task.

Why prune your fruit trees in winter? The reasons to prune fruit trees are to increase fruit production, develop strong 45-degree branch angles to support fruit load, remove limbs that grow down or straight up, maintain tree size and maintain fruit spurs. The dormant season is the best time to train a fruit tree during its first three years. Pruning trees during the dormant period tends to have an invigorating effect on the tree. Good for a young tree, not so good if you are trying to control size.

Gummosis on plum in summertime
Gummosis on plum in summertime.

Pruning of dead or diseased branches can be done anytime, however, the sooner the better. And don’t prune suckers in the winter. This insures they will grow back in the summer. Over zealous winter pruning can result in waterspouts so go easy at this time of year. Summer pruning, done in June or July, decreases size and vigor which helps to slow the growth of a tree.

Often I’m asked whether to paint a wound with sealing compound after pruning. This is no longer recommended as it encourages wood rot. A tree is best protected by proper pruning technique and timing. With this in mind, don’t prune during late spring or fall as a tree is most vulnerable during those times. When you cut away part of a plant, a would is left, susceptible to pests and diseases. To avoid trouble always prune so as to make small wounds, rather than large ones. Trimming a bud or twig produces a smaller wound than waiting until it is a large limb. Rubbing off a sucker bud leaves a smaller wound than if you want until it has a year’s growth or more.

My friends sticky amber gum oozing from her dwarf nectarine branch is the tree’s reaction to stress. Cankers or sunken lesions covered with gum may be caused by mechanical injuries, such as lawnmowers or pruning, insects, winter damage, sun scald, herbicide injury or various fungal or bacterial infections. Practice good sanitation by removing and destroying cankered limbs.

You can prevent or control many diseases and overwintering insects by applying a dormant spray this month. This can be the most effective spray of the season. Fungal diseases such as peach leaf curl, fire blight, scab and anthracnose as well as insects including aphids, San Jose scale, bud moth, leaf roller, coddling moth and whitefly larvae, mealybugs and mites can all be controlled.

There are several types of dormant sprays and all three types are considered organic. Lime-Sulfur or copper can be mixed with horticultural oil which smothers overwintering insects and eggs. This spray is good for all fruit trees except apricots which should be sprayed in the fall with copper and this month with horticultural oil.

Apply dormant spray when the temperature is above 40 degrees. Make sure you cover every nook and cranny of each branch and trunk until the tree is dripping and spray the surrounding soil. Spray only plants that have suffered from pests or disease. Sprays, even organic, can kill beneficial insects as well. Even though they’re organic, dormant sprays can be irritating to skin and eyes, Wear long sleeves and gloves and eye protection.

I hope I don’t find any pictures on Facebook of your plant pests or diseases but post away if you something wicked your way comes and I’ll try to help.

A Little Slice of Heaven in the Santa Cruz Mountains

toolsOutside of the historical agriculture exhibit at the Santa Cruz County Fair I have never seen so many antique farm implements and tools. Vintage tractors and parts were tucked underneath massive black walnuts. The winding driveway was dotted with more equipment, tractor wheels and parts. A storage shed displayed a collection of vintage chain saws and other small tools. California poppies bloomed in small clusters. I was here to visit an old friend in the hills above south Felton near the Toll House resort to see if I could help with advice about his ailing plum trees.

Al HIley has lived in this idyllic location since Vista_from_house.2048he was a boy and that’s a long time as his 92nd birthday is this month. His father bought the 18 acres in 1906. The original house still stands shaded by a grape vine arbor that protects the door and windows in the heat of the day. He lives close by in another house where he enjoys a vista which includes Mt. Umunhum, the Summit and Boulder Creek. Al says he used to be able to see downtown Felton but the redwoods have grown since the late 1800’s when this area was logged.

I had to laugh that Al was asking me for advice. He’s been farming this land starting since WWII ended. His father pAl_Hiley_in orchard2.1600lanted the original walnut trees in the hopes of making a profit from his land but “he was no farmer”, according to Al. I glanced at the catalogs on the 12’ long redwood burl coffee table. You can tell a lot about a person from what they read. Strewn about were several tractor catalogs, Popular Mechanic magazines, Heartland cataantique_chainsaws.1600logs, miscellaneous tool catalogs and a book entitled ‘Chainsaws: A History” which touts to be the first book on the worldwide history of the chainsaw.

With his lab, Sonny, at his side, Al and I went out to the orchard to take a look at the fruit trees. Originally in the 1960’s he had about 95 fruit trees. He grafted different kinds of apples onto his father’s trees and planted peaches, and pears as well as plums and prunes. We passed the blueberry bushes which were starting to show some fall color. Nearby grew a fig with a gnarled trunk the likes I have never seen. Loaded with hundreds on hundreds of ripening figs he invited me back to pick some when they ripened.

Al couldn’t verify the exact variety of red apple that caught my eye. It also was  loaded with beautiful fruit. He red_apples.1600got me a bag to pick as many as I wanted to take home and they are crispy and juicy. He grows a yellow delicious apple also but after eating the red variety I didn’t think anything could rival them.

The plum trees weren’t doing as well. They all had some yellow leaves and golden colored sap oozing along the branches. This condition is called gummosis and occurs often in stone fruit trees like cherry, apricot, peach and plum. It can be caused by several very different things.

The tree may have gumming from a pathogen that invades and kills bark and cambial tissue through a wound such as a pruning cut, sun scald or hail. If you scrape the outer bark under the sap the dead phloem will appear cinnamon brown in color Prevention is the key to managing this problem. Keep trees healthy with optimal watering, mulching and nutrition.

gummosis_on_plum.1600Borers can also cause gumming. In a plum tree, weakened trees or places where wounds have occurred will be susceptible. Ooze is often clear. Management of these pests is difficult and may include bark sprays during the growing season.

If you are not sure that a pathogen is causing the gummosis, scrape the outer bark away. If the inner bark is still cream colored and healthy, the oozing is caused by non-living factors and there is nothing you should do. If the wood is tan to brown, it is dead, and was most likely killed by a pathogen.

For my friend, Al’s plum trees I determined that the gummosis was caused by excessive irrigation. Due to the drought, Al had tried to limit watering during the summer. When he saw the trees being stressed he deep watered several times in the past month or so. The apple trees loved it but not the plums. He is happily going to deep water much less often until the trees go dormant.

I left Al and Sonny with the promise that I’d be back when the figs ripened. I’m sure I’ll be needing a fresh supply of apples, too.