Control disease spread in your garden
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Marty Nelson
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Brown, scorched-looking leaves are symptoms of fire blight in trees in the apple and pear family. Photo: Sebastian Stabinger
For disease to occur, their first needs to be a pathogen present, secondly, a susceptible host plant, and finally, favorable environmental conditions. It’s impossible to eliminate potential pathogens from your garden. Micro-organisms abound in the environment and while some can cause disease, many are beneficial and important to plant health. Reducing plant susceptibility and controlling environmental conditions should be the focus of your disease prevention efforts.
The drooping and dying foliage on these pepper plants is symptomatic of Phytophthora root rot. Photo: Howard SchwartzThere are no vaccines for plants but there are disease resistant varieties. When you choose plants that are certified virus free or labeled as resistant to common plant diseases, there is no longer a susceptible host for those pathogens. Fungicides and bactericides can help in reducing host susceptibility in some plants but use these cautiously to avoid harm to other plants and beneficial organisms.
Eliminating favorable environmental conditions is your first line of defense. Most plant pathogens love moisture so good soil drainage and appropriate irrigation will reduce the wet conditions they favor. Splashing water can enable micro-organisms in the soil to move up onto plants. While you can’t prevent this happening when it rains, you can avoid overhead watering.
Sanitation is key in reducing disease spread in your garden. Clear out dead leaves and debris to eliminate places where pathogens can shelter and multiply. Prune off diseased areas on plants. If the entire plant is involved, remove it. Since almost all plant diseases are killed by commercial composting, dispose of infected plants in your green bin, not your home compost pile. Sanitize gardening tools used in caring for diseased plants. A solution of 10% chlorine bleach or 70% alcohol can be used to disinfect garden equipment. Soak cleaned tools in sanitizing solution for 30 minutes before using them on uninfected plants.
An excellent source of information on identifying and managing plant diseases can be found on the UC Integrated Pest Management website at ipm.ucanr.edu.