OREGON STATE UNIVERSITY

PLANT DOCTOR DIAGNOSES OREGON'S DIVERSE FLORA

07/15/1996

CORVALLIS - Melodie Putnam cares for about 2,000 plants a year - most of them are dying or diseased.

Depressing? It could be, but Putnam says there is an element of detective work needed for every sample she receives in her position as chief diagnostician at the Oregon State University Extension Plant Disease Clinic.

They come to this "plant doctor" in the form of whole trees, single leaves or, sometimes, plastic bags full of rotting goo.

On a good day Putnam gets a conifer that freshens the laboratory air. On other days, she receives plants that with have fungal problems or viral infections, or others that just look odd.

Despite the case load and the condition of some of her "patients," Putnam says she enjoys the job because she is able help people solve problems. Seldom does she have to administer last rights and sometimes she even discovers a new disease to add to the body of research.

Putnam is sort of a plant doctor of last resort. Before reaching her, Oregonians first can take their questions to an OSU Extension Service county office. If agents there don't have the answer they can refer the case to Putnam. In addition to many questions that originate with home owners and gardeners, she gets hundreds from commercial growers.

"Most of the easy-to-diagnose cases get handled at county extension agents' offices, so the samples I get usually have people stumped," Putnam said. "People want to know, 'Will these mushrooms poison my dog?' Or 'Will I have to cut down my pin oak tree?'

"There are about 330 different crops being grown in Oregon," she added. "Some, such as corn, have been studied to death. Others are more exotic. Echinacea and ginseng, for instance, are new high-value crops in the expanding medicinal herb business."

Echinacea is a flowering plant thought to fight colds and the flu. Marketers say ginseng boosts vitality.

"Just like people, some of the plants that come in have viruses," she said. "And, like viruses that attack humans, these cannot be cured. Some are not deadly, but there isn't much you can do once the plant is infected. There is no Ebola virus in the plant world, but some viruses will kill plants - it may just take a while."

Sometimes no treatment is necessary, Putnam pointed out. Many of the plant problems that come to her lab are "abiotic" - that is, they have a problem not caused by living organisms. They may just have an abnormality or be suffering from excess fertilizer, cold injury or general stress.

Many of the samples coming in now were injured from late-winter freezes, Putnam said. The leaves are not coming out fully or there are unexpectedly few flowers. The tissues that transport water were damaged, so after the leaves came out they wilted. Or, plants such as forsythia, didn't flower well because their buds were killed by late-season freezing.

"Some politicians make jokes about studying stress in plants as if it were somehow a frivolous waste of money," said 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? We depend on plants for food, fiber and building materials.

"The stress that plants experience can be from things such as unseasonable cold weather, drought, transplanting or being taken out of their natural environment," she added. "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," said Putnam. "I usually give people a 'cultural' and '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."

Putnam warned Oregonians to be cautious about cultural controls that "you just hear about somewhere." One disease remedy involving a large dose of baking powder and Epsom salts may scorch all the leaves on your plants.

"Your best defense against plant disease is to buy healthy, disease-free and disease-resistant stock," said 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 added. "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."

Similar to being a doctor to humans, sometime as a plant doctor you have to deliver bad news. Occasionally you have to tell people it is too late to do anything.

Or, in the case of Dutch Elm disease, you may have to say that immediate removal of the tree is necessary.

"There are no Jack Kevorkian plant doctors," Putnam said, "but telling someone to remove a large living tree that may have been part of their yard for years can be pretty traumatic."