Garden Journal | Ron Kujawski: Fungus, rust cause of leafless apple trees


The question I've been asked most often of late — besides "Are all your clothes that shabby?" — has been in regard to the defoliation of crabapple and apple trees. Many of these trees have been dropping their leaves since early August and look almost as shabby as my wardrobe. Most now stand naked, or nearly so, and people have been asking, "Why?"

An examination of the leaves, either those that have fallen or ones still clinging to the trees, will reveal the answer to the question. Actually, there are two answers. The first is called apple scab, a fungus disease that appears initially as olive green spots, later as dark gray and somewhat velvety spots on the leaves, and often on the fruit. Eventually, the leaves turn yellow and drop. The second answer is a disease called cedar-apple rust. One phase of this disease's life cycle appears as orange-yellow spots on apple and crabapple trees. In spring, another phase occurs on red cedar trees as a gelatinous gall with orange tendrils — quite impressive, if such things excite you. Both of these diseases were rampant this summer, aided by the rainy weather of July and early August.

While fungicide application in spring, at the time leaves are expanding, will help reduce incidence of these disease infections on existing apple and crabapples, the best long-term solution is to plant varieties with resistance to these diseases. Fortunately, there many resistant varieties and you should have no trouble finding them at local nurseries. In the meantime, rake up and destroy the infected leaves on trees as soon as they fall. How do you destroy these disease ridden leaves? Burying them is one way. Tossing them onto a compost pile is another, but only if it is a hot compost pile, that is, one that is kept moist and turned over frequently so that temperatures within the pile rise to 145 F to 160 F. A long probe compost thermometer can be used to measure the internal compost temperature.


Probe this list of gardening tasks:

Article Continues After These Ads

- Continue planting trees, shrubs and herbaceous perennials, but be sure to water all newly planted specimens should Mother Nature take a break from her rain-making duties. Monitor the amount of rainfall each week. If less than an inch, get out the hose or watering can and apply enough water to soak soil to a depth of 6 to 8 inches.

- Don't get your hackles up at the sight of insects, such as the fall webworm or the tussock moth caterpillar, feeding on leaves of deciduous trees in your home landscape. The impact on the health of these trees this late in the season is negligible. Besides, leaving these pests alone now will likely enhance the population of their natural predators.

- Be patient with winter squash and pumpkins. Don't harvest the fruit until they are fully mature as they do not ripen after picking. Wait until the fruit has developed its full color and the rind is hard. Usually, the stem attaching the fruit to the vine will also be hard. With some varieties, such as acorn squash, the development of a yellow ground patch, that is, the part of the fruit in contact with the soil, identifies it as being ripe for the picking. If there are any fruit with soft, sunken or water-soaked spots, don't bother storing them as they will rot. The spotted area may be cut away and the squash or pumpkins can be cooked right after harvest. Make a note not to plant squash, pumpkins or cucumbers in that area of the garden over the next two years.

- Pinch out the tops of Brussels sprouts. This will hasten the growth of the buds or sprouts and most will be ready for harvest at the same time. While frost is not good for pumpkins and squash, cool weather is great for Brussels sprouts. Cool, even frosty, temperatures promote firmer, sweeter sprouts.

- Allow grass in newly seeded lawns to reach a height of three inches before cutting it back to 2 or 2 1/2 inches. Alter the mowing pattern each time you mow to prevent ruts from developing in the lawn. There are few things worse than being in a rut.

- Be alert to the home invasion of ladybugs, boxelder bugs, stink bugs and seedbugs, who seek shelter in the warm comforts of your home over the next several months. Though these insects cause no harm to your house, they can be a nuisance as they show no remorse in crawling over your windows, walls, furniture, and house guests. To prevent this intrusion, seal gaps around windows, doors, and foundation.     


If you'd like to leave a comment (or a tip or a question) about this story with the editors, please email us. We also welcome letters to the editor for publication; you can do that by filling out our letters form and submitting it to the newsroom.

Powered by Creative Circle Media Solutions