By C. Rae Hozer
Master Gardener training involves learning how to identify and solve plant problems. That is appropriate since problems in their yards and gardens are what my friends and neighbors most frequently ask about. I still chuckle remembering trying to do crunches and at the same time answer questions about azaleas with leaf spot and hydrangeas that would not bloom, after my exercise instructor announced to the class that Rae had just become a Master Gardener.
A three-element relationship known as the Plant Disease Triangle was part of my studies. I still use it today. The first side of that triangle is a susceptible host plant, the second a pathogen capable of infecting the plant and third a favorable environment. All three must come together to produce a problem. In other words, only if environmental conditions are right will the pathogen interact with a susceptible host plant in a way that produces disease.
That honeysuckle vine with powdery mildew growing along the north side of my neighbor’s house cited in last week’s article is a classic case. Honeysuckle (Lonicera spp.) is a susceptible host, different powdery mildew fungi cause the disease on different plants, but the fungi are common and spread by the wind (pathogen), temperatures from 60 to 80 degrees F and shade favor this disease (conducive environment).
I got on-the-job training in plant problem analysis while examining samples of infected, infested and damaged plants homeowners brought to the Ask-a-Master-Gardener desk at the University of Tennessee Cumberland County Extension office in Crossville. Sometimes after consulting available in-office research materials and conducting online searches, the identity of the plant and/or the exact nature of the problem still remained a mystery to me. In that situation, a digital camera was used to take photos of the plant material or insect pest in question (including highly magnified images taken using a microscope with the camera). A text form with environmental details and the images were transmitted to resource professionals at the Plant and Pest Diagnostic Center in Nashville through an Internet program called Distance Diagnostics. Within a day or two, we would receive an email answer giving the identity of the plant, diagnosing the problem and detailing appropriate treatment. One of the experts in Nashville at that time was Alan Windham.
Though never officially enrolled in one of professor Windham’s classes at UT, I’ve learned a lot from him over the years. I caught his presentation titled "Be a Plant Detective: Solve Plant Problems" in August during the Fall Gardener’s Festival at UT Gardens Crossville.
Plant detective strategies are:
1. Identify the host plant because plants have certain primary insect pests and diseases. Knowing the plant can lead to the problem identity.
2. Look for signs and symptoms which are clues to identifying problems.
3. Identify biotic (living) pathogens like fungi, bacteria, viruses and nematodes or non-living ones like moisture (too much, too little), temperature extremes (heat or cold), pesticide injury, soil pH extremes and nutrient deficiencies as probable causes
4. Use a digital camera to document damage, symptoms or signs associated with the unhealthy plant.
5. Collect a specimen. Helpful resources are the county Extension office, the Soil, Plant and Pest Center Facebook page (https://www.facebook.com/SoilPlantPestCenter), the online image library showing various plant problems (www.ipmimages.org), becoming a Master Gardener and the Soil, Plant and Pest Center webpage (http://soilpalntandpest.utk.edu/).
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Plateau Gardening is written by Master Gardeners for gardeners in Tennessee’s Upper Cumberland Region. Contact UT Extension Cumberland County at P.O. Box 483, Crossville, TN 38557 (484-6743) for answers to horticulture questions, free publications and how to become a Master Gardener. Send email comments or yard and garden inquiries to Master Gardener Rae, MGardenerRae@frontiernet.net.