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Monday - August 06, 2007

From: Greenville, AL
Region: Southeast
Topic: Diseases and Disorders, Trees
Title: Diagnosis of problem with Parsley hawthorn
Answered by: Barbara Medford

QUESTION:

I have a Crataegus marshallii (Parsley hawthorn) that is about 3 years old. It leafed out this spring and flowered lightly. As the summer has progressed, though, the leaves have been dropping prematurely from the top branches down and some branches are even bare now. The lower branches still have green leaves, but some of the leaves are turning brown on the end. We've been having extreme drought in this area, but this tree is in an area that gets watered by drip irrigation. Given that it is drip irrigation, it is hard to measure exactly how much water it gets. Could it be suffering from insufficient water despite the irrigation? Thanks

ANSWER:

Crataegus marshallii (parsley hawthorn is a really lovely ornamental tree, naturally occurring in your state of Alabama. We at the Lady Bird Johnson Wildflower Center are always in favor of using native plant materials, because they ordinarily will better survive the weird things local weather can do. However, sometimes very extreme conditions or diseases can, indeed, damage even sturdy natives. The parsley hawthorn is a member of the Rosaceae family and, therefore, a cousin to roses and susceptible to some of the same diseases. Here are links to two of the diseases that are commonly blamed for declines in the Rosaceae family: fire blight, leaf blight, twig blight and cedar-hawthorn rust.

Any number of insect pests find plants in this family tasty. Aphids, spidermites, scale, leaf-miners, borers and girdlers could all be involved in your tree's problem. Close inspection is required to rule in or rule out pests. You might consider taking an affected limb to your county's Cooperative Extension Service agent for examination and diagnosis. Many states offer excellent and generally inexpensive plant disease and pest diagnostic services.

As you will see when you go to these sites, there really is no cure for these fungal diseases, but prevention of spread to other plants in the area is strongly recommended. However, the good news is that the cause of these diseases, since they are both fungal in nature, seems to be more a case of too much rain, overhead watering, etc., none of which seems to be the case in your drought conditions and with drip irrigation. So, let's talk about a slightly more obvious reason: too little water. Most young trees will benefit from deep irrigation, which usually involves sticking a hose into the dirt, and letting water slowly run in until the tree well is full. If your parsley hawthorn is in full sun, this is probably even more important, because parsley hawthorns do well in some light shade. A plant subjected to dry conditions will protect itself from further dehydration by curling leaves or dropping them altogether. The fact that your leaf drop is beginning at the top, farthest from the roots and water source, is another clue that lack of sufficient moisture at the root system could well be the problem.

Do be sure to go to the web links on diseases and establish as well as you can that those are NOT your problem. Then, we'd suggest a little more water, at the base of the plant, and a lot of love, and hope your tree will rise and bloom again next Spring.