Preventing Plant Diseases - Don’t Forget Sanitation!

Many of the plant problems we diagnose on samples that come to the plant diagnostic clinic are the result of poor management practices. One of the most important management practices for plant disease control is sanitation, and sanitation becomes especially important in the fall after the growing season. Sanitation includes all activities aimed at eliminating or reducing disease inocula. Inocula (fungal spores, bacterial cells, virus particles, etc.) are materials that spread a disease to healthy plants or unaffected plants. Sanitation may include removal and burning of garden plant residues after the fall frost or tilling into the garden after harvest, raking of fall leaves, pruning infected or dead branches and removing infected fruit and other diseased plant material. While we often suggest waiting until late winter to prune trees, pruning out diseased branches also reduces inocula and prevents diseases from damaging healthy plants and plant parts. Fall sanitation practices, such as raking leaves and removing the dead plant material from the garden, are extremely beneficial in managing the fungal diseases that cause some of the blights, leaf spots, powdery mildews, etc. This is because many these fungi over-winter on plant debris. When infected plant material is left in place, inocula (spores) will be released from these tissues in the springtime that can re-infect the plants growing nearby. Burying the plant residues into the soil helps to break down the debris to destroy the pathogen. When possible (if community regulations allow), burning the residues also ensures that the inocula will not be present the following spring. Composting is another great way to recycle these old residues, provided that the compost pile is properly maintained to achieve high internal temperatures to destroy the inoculum. You can see MU guide G06956 or go to http://extension.missouri.edu/explore/agguides/hort/G06956.htm for more information on proper composting to eliminate pathogens.

So, on a nice fall day, take a walk around your garden and landscape. In the perennial beds remove old flower heads, stalks and any diseased plant parts. Check your roses, shrubs and trees for dead branches. Examine your grapes and berries for dead canes and remove them. Keep in mind that most varieties of some berries such as raspberries and blackberries will have floricanes that die after producing fruit and need to be removed as soon as possible. Pull out those old tomato vines, and make sure leaves aren’t left behind sticking to the tomato cages.

Fall sanitation is a great tool in disease management, if you can resist the urge to just let things go until motivation surges next spring. When you combine sanitation with other management tactics such as cultural practices (watering, fertilizing and spacing), disease resistant varieties and occasional chemical control if warranted, your gardening success will increase. Of course, you won’t be able to eliminate every plant problem this way, and when other problems still occur, sample submission to the plant diagnostic lab is an option available year around. We look forward to receiving your samples, which also help us to see what plant problems are occurring around Missouri. While we are often not able to diagnose plant problems from a description of the problem over the phone, you are welcome to submit a sample or photos. Please see our website at http://soilplantlab.missouri.edu/plant/index.htm for more information on plant problems, sample submission and fees.

Simeon Wright
Plant Diagnostic Clinic