What happens when you combine mild weather, a day or two of rain, and fast-growing plants competing for space? In addition to the number of flowers, the leaves may have the appearance of orange spots. Natural surface watering is not only a boon to the gardener and gardener, but also creates favorable conditions for the growth of disease-causing rust.
One of the most common fungal diseases in the garden. There are thousands of rusts that affect trees, shrubs, hedges, perennials, edibles, and more, such as pears, peaches, pines, rhododendrons, roses, chrysanthemums, fuchsias, geraniums, lilies, and dragonflies. Rusts have plagued humans for centuries, including important food and fiber crops such as legumes, legumes and soybeans, asparagus, cotton, apples, and coffee. Not only are they invisible, but they can also reduce the plant's strength and, in extreme cases, kill it.
Rust fungi and their damage usually appear on the leaves, stems, and fruits of deciduous plants, as well as on the bark or needles. Pimples are characteristic accumulations of rusty, powdery spores on damaged leaves and other plant parts. They can be yellow to orange in early winter, becoming more intense to dark orange-reddish brown in summer. Orange jelly-like clusters appear on some green hosts.
Most types of rust have little effect on plant health, but some rust types can kill their hosts. Infected foliage plants may turn yellow, yellow or brown and drop prematurely. Severe rust on peach trees can rot and reduce yields. There may be black dots with small holes on the fruit that open after ripening. Other species damage the bark, causing swelling or decay of the tissue, spotting or canker, branch dieback, and death of the whole plant.
As parasitic biotrophs, these fungi require a living host. The disease cannot survive on dead plant material until they develop a special type of spore, a thick-walled cavity that allows them to overwinter and remain in plant debris season after season.
Most species of rust fungi have complex life cycles, alternating between two hosts in different plant families. Ornamental tree rust can have an alternate host, which can be an incidental plant in the landscape, or even a crop or a weed. Some species, like pink rust, have only one host.
Rust needs free water to spread, so rainy weather, nighttime dew or overhead watering without enough time to wet the leaves can create ideal conditions for the disease, especially when temperatures are 65 to 70 degrees. The infection is mainly spread by wind spores or water spray in winter.
So that rust does not enter the garden;
• Choose disease resistant varieties. Check seed catalogs, seed packets, and plant labels for resistance information.
• Before purchasing plants, carefully inspect the inner and lower leaves to make sure they are healthy before bringing them into the garden.
• Do not update alternate hosts if possible.
• Provide good cultural conditions. Arrange plants so they get plenty of sun and air circulation (don't crowd them). Maintain healthy soil and avoid excess nitrogen, which will result in soft and flat growth.
• Humidity control. avoid overhead or early day water if necessary to allow foliage to dry quickly. Use a drip irrigation system or garden hose to water the soil, not the leaves.
If you already have rust.
• Cut off the rusted leaves of the plant, but do not remove more than one-third of the plant's leaves.
• Remove and destroy affected branches, buds and fruits as soon as symptoms appear.
• Remove fallen leaves and needles from host plants.
The University of California Naval Master Gardeners, sponsored by UC Cooperative Extension, provides scientific and research information for Navy home gardeners. Send your questions to support @marinmg.org. Attach photos for plant pest or disease inquiries. The office is now open several days a week. Please call 415-473-4910 to find out when the Master Gardener will be in the office. There is a sample box near the office so marine gardeners can take samples 24 hours a day. Sign up for the free UC Marine Master Gardener e-newsletter at marinmg.ucanr.edu.
