Blackwelder column: What are the spots on Indian Hawthorn shrub?

Published 12:00 am Friday, March 30, 2012

SALISBURY — Unusually warm weather and, of all things, hail, seems to have many gardeners scratching their heads as to what’s next.
Retail garden and farm outlets are very busy with customers anticipating the chance to plant vegetable transplants and maintain their landscapes. Many have questions about their gardening chores. Below are a few inquiries that may relate to your situation.
Q: (sample brought into the office) I have an Indian hawthorn shrub with spots on the leaves. What causes these spots? Can I spray and control the problem?
A: The hawthorns have Entomosporium leaf spot; the same disease that virtually eliminated red tip photinias in this area. Some cultivars of India hawthorn are as severely affected as red tip. If possible, remove fallen diseased leaves. Do not water or fertilize plants any more than necessary to avoid promoting excess new growth. Also, reduce pruning during the summer which promotes continual new growth. Severely defoliated plants may need to be pruned heavily to have a small, easier to spray plant, to reduce the source of spores and improve air movement. It may be necessary to remove severely diseased plants that have also been damaged by cold injury. Replace them with another plant species that is not susceptible to leaf spot. Several fungicides may also be helpful in the management of leaf spot in the landscape. More information on entomosporium leaf spot can be found at depts/pp/notes/Ornamental/odin011/odin011.htm
Q: When can I mow the leaves off the spent daffodils?
A: It’s not a good idea to mow the leaves of this bulb. The leaves are necessary for the plant to develop flowers for the next season.
They will eventually turn yellow and fall over. You can clip or mow them at this time. Bulbs should be fertilized and irrigated to maximize growth for showy blooms.
Q: Can I control ants or grubs in the soil now?
A: Yes, the soil is warm enough to apply recommended soil insecticides. Soil insecticides reduce grubs, which in turn drives moles to other grub-infested locations. Grubs can be controlled in the spring; however, the best month for grub control is early fall.
Q: What are the caterpillars in my plum tree? How do I control them?
A: Those are tent caterpillars. The annual infestation will vary, but it looks like a heavy number this spring. Control by disturbing the nest, opening to birds and other prey. Bacillus thuringenisis sprays (Dipel, BT’s) will control them.
Darrell Blackwelder is the County Extension Director with horticulture responsibilities with the North Carolina Cooperative Extension Service in Rowan County.
Learn more about Cooperative Extension events and activities by calling 704-216-8970 or online at
www.rowanmastergardener. com