Melodie Putnam cares for about 2,000 plants a year. Most of them are dying, and some are already dead. It could be depressing, but she says there is an element of detective work that makes her job as chief diagnostician at Oregon State University's Extension Plant Disease Clinic interesting.
The "patients" come through the door in the form of whole trees, single leaves or, sometimes, plastic bags full of rotting goo. Some have fungal problems, others viral infections, while still others just look odd.
Despite the caseload and the condition of some of her patients, Putnam enjoys the job because she's able help people solve problems. Seldom does she have to administer "last rites," and sometimes she even discovers a new disease.
She's sort of a plant doctor of last resort. Before reaching her, Oregonians must first take their questions to an OSU Extension Service county office. If agents there don't have the answer they can refer the case.
In addition to many questions that originate with homeowners and gardeners, she gets hundreds from commercial growers, and occasional questions from Agricultural Experiment Station scientists. "They send me stuff that people bring to them and they can't identify, or things they've noticed and they can't identify," says Putnam, a plant pathologist.
Most of the easy-to-diagnose cases get handled at county extension agents' offices or branch experiment stations. "So the samples I get usually have people stumped," she says. "There are about 330 different crops being grown in Oregon. Some, like corn, have been studied to death. Others are more exotic."
"Just like people, some of the plants that come in have viruses," she says. "And, like viruses that attack humans, these cannot be cured. Some are not deadly, but there usually isn't much you can do once the plant is infected. Some viruses will kill plants--it may just take a while."
Sometimes no treatment is necessary. Many of the plant problems that come to her lab are "abiotic," that is, not caused by living organisms. The plants may have an abnormality or be suffering from too much fertilizer or general stress.
"Some people make jokes about studying stress in plants as if it were somehow a frivolous waste of money," says Putnam. "No, plants don't experience stress over divorce, mortgage or loss of income. But like humans, plants that are stressed are more likely to contract diseases. Is plant stress frivolous? Not when we depend on plants for food, fiber and building materials.
"The stress that plants experience can be from things such as cold injury, drought, transplanting or being taken out of their natural environment," she adds. "Take a sycamore tree that is adapted for growth near a stream bed and transplant it to the middle of a park with no provision for irrigation and you're going to have a problem.
"The good news is that most plants are resilient," says Putnam. "I usually give people a 'cultural' and a 'chemical' prescription for their plant's disease. A cultural treatment might be pruning off the diseased tissue or simply rotating crops or planting sites. A chemical approach might be applying a commercial fungicide."
Be cautious about cultural controls that you just "hear about somewhere,"she warns. For instance, one disease remedy includes a large dose of baking powder and Epsom salts. It may scorch all the leaves on your plants.
"Your best defense against plant disease is to buy healthy, disease-free and disease-resistant stock," says Putnam. "Look for statements of resistance in seed catalogs or ask at the nursery. The next step, if your plant still develops a problem, is to have it correctly diagnosed before you start any type of treatment.
"One of the best home diagnosis books is Westcott's Plant Disease Control Handbook," she adds. "Another option is to take as large a sample as practical to an OSU Extension Service county office. This is a free service. You can save time, effort and a lot of money by getting the correct diagnosis. For example, you could purchase an expensive fungicide only to discover later that your plant has a bacterial problem."
Just like doctors who treat humans, plant doctors sometimes have to deliver bad news. Occasionally Putnam has to tell people it is too late to do anything. Or, in the case of Dutch Elm disease, she may have to say that immediate removal of the tree is necessary.
"There are no Jack Kevorkian plant doctors," she says, "but telling someone to remove a large living tree that may have been part of their yard for years can be pretty traumatic."