Variety of diseases hurts flowers in Utah

After you spend considerable time and money buying and growing the flowers, it is disappointing to see them die prematurely — or not bloom well — because of diseases.

As a brief reminder, diseases are separated into two general categories. The first are the nonpathogenic or environmental diseases, which include extremes in temperatures, watering excesses or deficiencies, soil problems, nutrient deficiencies, mechanical damage or similar problems.

These diseases have no causal organism involved, so they cannot spread from plant to plant — in other words, they are not contagious.

Pathogenic diseases have a contagious organism involved in their spread. These include fungi, bacteria, viruses, mycoplasmas, nematodes and even some parasitic seed plants.

While there many possible diseases that can occur in Utah, only a few are rampant. In most instances, problems are the result of environmental causes, so spraying has no effect. When you try to control pests, you must use very specific products. This means fungicides are needed for fungal diseases; bactericides for bacterial disease; and specific products for the other organisms.

Some problems are readily evident. Lack of water causes plants to wilt, as do excessively high temperatures. Various fungal and bacterial diseases, including verticillium and fusarium wilt, cause similar symptoms, so it is critical to identify the problem before starting any treatment.

Other diseases have complex reactions with the environment. For example, overwatering flowers keeps the roots from getting the needed oxygen so they grow poorly. But excess water also encourages the growth of fungi that attack the plants and kill them.

Several root-rot diseases attack flowers. Prevent problems by increasing soil drainage and watering only as needed. Preventing water molds and other fungi after plants are affected is almost impossible. Few fungicides are effective, and they are only available in commercial formulations.

Verticillium wilt affects more than 300 plant species. The soil-borne fungus enters the plant, usually through the roots, and plugs off the water-conducting tissues. The plant wilts and often dies. It usually appears with the hot weather. Since the fungus lasts for many years in the soil, using resistant plant varieties is the only practical control.