May 12, 1995
Several new fungicide products have appeared in the marketplace during the last 6 months, and some significant label changes have occurred, too. A brief summary:
Cleary's Protect T/O. This mancozeb product now has a greatly expanded label for use on landscape plants. It is labeled for control of leaf spots, anthracnoses, blights, scabs, needlecasts, and rusts in over 150 annuals, perennials, ground covers, vines, shrubs, and trees.
The SBI fungicides (Bayleton, Funginex, Orbit, Nova, Rubigan, and Procure) are widely used for disease control on apples and stone fruits because of their protectant and eradicant properties, wide spectrum of disease control, and their low toxicity to man and other mammals. They have a potential Achilles heel, however, in that their narrow mode of action on target fungi make them vulnerable to the development of resistant strains of these fungi. Much effort by University researchers and chemical companies has therefore been devoted to minimizing the risk of resistance development.
The "millipede migration" that has caused considerable concern for the past 3 - 4 years continues this spring. Wet weather for the past several summers has favored these beneficial, organic matter recyclers to the point they are a major nuisance to many homeowners.
Moss in yards has been a common complaint this spring. It occurs in sun or shade, alkaline or acidic soils and in wet or dry sites. Moss is very adaptable and can grow in difficult conditions. In poor sites, the moss moves in as the grass dies out.
Cool, wet conditions during the spring favor the development of Phytophthora blight on peony. The fungus Phytophthora, common in most soils, initially attacks either the roots or the developing shoots at the soil level, causing a blackening and decay of stem tissue. These black often sunken areas, usually several inches long, may appear on upper stem tissue as well. Stems tend to fall over at the stem lesions. Flowers, buds, and leaves may also turn a dark brown or black color. The tissue will appear somewhat leathery.
Rhododendrons and azaleas are spectacular flowering shrubs. Unfortunately, most rhododendrons and azaleas (there are over 900 species and innumerable varieties) cannot be successfully grown in Iowa because of a lack of cold hardiness. A small number, however, possess excellent cold hardiness and grow well in Iowa. Selection of cold tolerant varieties, correct placement in the landscape, and proper planting are the keys to successfully growing rhododendrons and azaleas in Iowa. Botanically, all azaleas are actually rhododendrons.