In our world of plants, one of the most dreaded words is…disease. It can cause thousands of dollars of irreparable damage, loss of income, possible quarantine and loss of reputation. One only needs to go back to the late blight on tomatoes a few years ago that swept the country because of a shipment from one company. Consumers lamented the loss of their beloved vegetable but the company suffered the loss of its reputation, as well.
So we rely on science to help us overcome these problems, and one of the driving forces helping us is Margery Daughtrey of Cornell University. She grew up in the little town of Crozet, Va., nestled in the Blue Ridge Mountains and famous for its peaches. She comes from a family that gardened, including the usual suspects of vegetables, flowers, trees and shrubs.
“My grandmother made sure I noticed the wonders of lilacs and turnips. My mother taught me about nasturtiums and watercress. My father taught me about apples and sassafras trees. My aunts taught me about sweet peas, azaleas and pussy willows, and my best friend’s mother taught me about mayapples and persimmons,” Daughtrey recalls.
Growing up, she also received inspiration from the Little Golden Books on wildflowers, rocks and minerals, as well as Science in Your Own Back Yard by Elizabeth K. Cooper. She got excited the first time that she got to look at tiny creatures through a microscope. Even as a child she was interested in what made things happen on plants, and when she was 18, her first diagnosis was discovering what caused galls on her aunt’s azaleas. After doing research she found it was a fungus called Exobasidium japonicum and realized that plants could get diseases, too.
When she went off to William and Mary College, she needed an honors project in biology and chose to use the same fungus on her aunt’s azalea. She put the fungus onto azalea cells in tissue culture just to see what would happen. She got high honors for the project. After William and Mary College, she earned her master’s in plant pathology at the University of Massachusetts-Amherst and, as she says, “I’ve looked through a microscope many an hour since.”
For almost the past 40 years she has studied what can go wrong with our plants and how to prevent it or cure it.
Reading her Curriculum Vitae is daunting, akin to reading War and Peace in another language. She authored The Cornell Guide for the Integrated Management of Greenhouse Crops and Herbaceous Ornamentals, and co-authored Diseases of Annuals and Perennial, A Ball Guide, Identification and Control; Ball Field Guide to Diseases of Greenhouse Ornamentals; Diseases of Herbaceous Perennials; The Compendium of Flowering Potted Plant Diseases; and Herbaceous Perennials: Diseases and Insect Pests. Most, if not all, of these are on bookshelves in greenhouses and nurseries across the country.
“Margery Daughtrey is in a class by herself. She is a superstar in the field of ornamental plant pathology,” says Laurence V. Madden, distinguished professor of plant protection and interim chair department of plant pathology at The Ohio State University. “She knows everything about ornamental diseases and how to control them, and can explain this to the public in a clear and concise manner. Anyone who has read her books or heard her lectures is very fortunate.”
She’s been researching diseases that pose serious threats to the nursery industry, including sudden oak death. But finding a solution will not be easy, since Phytophthora ramorum has a large host range, she says. For the consumer’s popular annual, Impatiens walleriana, which has been hard hit by impatiens downy mildew, she says there are a lot of impatiens species with no or little susceptibility, so there is a large gene pool to look for plants that are resistant to IDM. They have learned that crosses between wallerianaand other species don’t work because the hybrids tend to retain the disease susceptibility of the species. She is currently working on boxwood blight (Calonectria pseudonaviculata), a disease that is threatening one of the industry’s most profitable staples. She is part of a group of scientists who are working together to learn how to manage the disease in nurseries and landscapes, and to evaluate the plants for their level of resistance to the disease.
“Of the many, many plant pathologists who work closely with nurserymen, landscapers, arborists, and greenhouse operators on woody ornamentals and floricultural crops, Margery is just the best. Her understanding of plant diseases and the needs of her clientele are exceptional,” says Gary W. Moorman, professor emeritus of plant pathology at Pennsylvania State University.
Daughtrey has not only witnessed, but been partially responsible for, many changes in the horticulture industry.
“I do think that the horticulture industry has changed a lot since 1978, when I began working for Cornell. It’s a professional and forward-looking industry, which has caused it to change with new technologies, as well as with the new plant fashions — look at the sudden importance of succulents,” she says. “The horticulture industries are still largely relying on chemicals to supplement cultural controls for their integrated pest management programs, but the public doesn’t appreciate how much safer the modern chemicals are compared to some that were (often carelessly) applied in the past. There has been a tremendous growth of helpful biological controls for insect, mite and disease management since I entered the greenhouse and nursery world, and it seems that we are continually moving in that direction. To shift to such controls will require cleaner stock for the industry’s supply of plant material, and a high level of disease and pest resistance in the cultivars.
“Disease-prone crops can’t be grown successfully when they are contaminated with pathogens before they are received by the grower. And even if plants are clean during production, the plants must have built-in disease resistance to perform beautifully for the consumer.”
Even with advances in technology, the industry still faces challenges. With the globalization of the green industry, it is difficult to monitor the disease management practices in a source greenhouse that’s located in another country.
Denise is a professional horticulturist, garden writer and speaker based in Pittsburgh.
