Agri Leader

New plant diseases a threat

TRACY HODGE
Published: February 20, 2013

Central Florida is home to a variety of diseases that can wreak havoc on the plants in our landscape setting.

The U.S. Department of Agriculture is warning Florida residents to be on the look out for two relatively new diseases: sudden oak death and ramorum blight. They are of particular concern because they have a wide host range and there are currently no known cures for either condition. These diseases have not yet been identified in our state, but officials want people to report any suspicious cases to the USDA for further investigation.

Sudden oak death and ramorum blight are caused by a pathogen known as Phytophthora ramorum.

Because these diseases are fairly new, officials have little information regarding symptoms and host range. The University of Florida IFAS Extension states that approximately 75 to 100 species are thought to be at risk of contracting these damaging diseases. These susceptible species are just a few listed by the USDA: camellia, lilac, horse chestnut, big leaf maple, bay laurel, Douglas fir, European ash, mountain laurel and all oak species.

While symptoms of these diseases vary between plant species, most all infected plants appear to have healthy root systems in place. Although caused by the same pathogen, these diseases cause different symptoms.

Ramorum blight affects foliage and causes dieback. Affected plants may develop leaf lesions at the tip or around the margin of leaves. At first glance, these lesions have a water-soaked appearance, which rapidly expands to cover large portions of infected leaves. This blighted tissue may appear tan or brownish red in color.

With sudden oak death, infected trees develop trunk cankers or lesions on the trunk or branches. These cankers may be easily visible above the bark or may develop underneath bark.

Some infected trees develop cankers that ooze or bleed a sticky sap that smells foul. Some species such as viburnum exhibit only wilting symptoms that is often mistaken for drought stress. As the disease continues to progress, these plants will have reduced vigor and will eventually collapse and die from infection.

Since sudden oak death and ramorum blight are caused by a fungus, it can spread easily on the wind or through irrigation water or rain. It can also be brought into our landscape through infected nursery plants or contaminated potting soil.

Any home gardeners who feel they have plants with these symptoms are encouraged to report them. Most fungal diseases are most active during cool, moist conditions. Proper sanitation practices go a long way toward preventing the spread of dangerous bacteria and fungi. These practices include burning any plants that appear to be infected or burying them deep into the ground.

You can also prevent diseases in your yard or garden by thoroughly inspecting all plants, flowers and trees before bringing them home. Avoid purchasing any plant that appears unhealthy or infested with any garden pests. It is always a good idea to quarantine any indoor plants for 10 days or so, to be sure you aren't introducing pests such as fungus gnats into your home.

As we move into spring and cool, moist weather arrives, it is important to monitor your plants and trees for any signs of damaging diseases that can affect many plants in our environment. Always report any plant that appears to be infected to the USDA website. If necessary, allow agricultural professionals access to your home landscape for inspection.