Week 5: Plant Pathology and Pesticide Safety

Rose-colored glasses for … nematodes?   

Jay Pscheidt, a plant pathology specialist with the OSU Extension Service, passed around a pair of thick-rimmed, black glasses with purple lenses.

The glasses, he told our master gardener class, were made by a company that claims they can tell you if your plants are stressed. Maybe even what diseases or pests are infecting them. Pscheidt was skeptical.

Master gardener training.

A trainee in the OSU Extension Service Benton-Linn County master gardener class investigates glasses that a company claims can tell if your plant is stressed, and maybe even detect diseases. (Photo by Pami Opfer)

Some trainees donned the glasses, eliciting smiles from their friends nearby. When my turn came around, I squinted through the lenses. Even to my untrained eye, a troubled plant looked the same; it was just filtered through vivid Andy Warhol-esque colors.

It would be cool if you could slip on a pair of glasses to immediately spot the microorganism that is affecting your plant. But most microorganisms are so tiny that you can’t see them without the help of a microscope, Pscheidt said.

So, like a doctor investigating what’s wrong with a patient, gardeners use symptoms and signs as clues. Symptoms are the visible effects of disease on plants, like changes in color or shape. Signs are physical evidence of the pathogen, like bacterial ooze or nematode cysts.

I learned about several other techniques in a plant pathologist’s toolbox. But there is no one key set of questions or techniques for diagnosing plant diseases. Experience and practice are the best teachers, Pscheidt said.

To learn more, see the OSU Extension guide, Preventing Plant Disease in Your Garden and Landscape.


(Not) taking sides on pesticides

Our instructor, Dan McGrath, had a confession to make.

“I’m a recovering nozzlehead,” admitted the vegetable crops specialist for the OSU Extension Service.

And so began our afternoon class on the ethics behind pesticide use and safety precautions. As master gardeners, the public will ask us questions about chemicals, regardless of how we personally feel about them. We must be prepared to answer with impartial, research-based information.

My fellow trainees and I talked in a small group about how we would feel if a client asked us about using pesticides. Some of us believed pesticides should be used only as a last resort to control stubborn pests and diseases.

“At my age, all we used to have was pesticides,” said a fellow trainee when we gathered in a big group again. “Organic stuff has only come on the market in the last few years and has been made more affordable.”

Hands holding spray bottle. (Photo by Bob Rost)

When using some pesticides, it is best to wear gloves. (Photo by Bob Rost)

“I think one of the reasons that commercial growers use it is that when people go into the store we expect perfect fruit and perfect vegetables,” said another student. “Until we change our standards, you’re going to have to deal with some level of pesticides.”

“Would you say it is a safe assumption that commercial growers are using pesticides safely?” another trainee asked.

“I would say it is probably very high, not 100 percent,” McGrath said. “I’ve had the privilege of working with three generation of farmers. Working with a new generation of farmers in their 30s, I see they are very responsible because they grew up and came of age in the ’70s and ’80s.”

An image came to my mind that McGrath had brought up previously. He has seen homeowners spray pesticides wearing T-shirts, shorts and flip-flops. At a minimum, people should wear long-sleeved shirts, long pants and shoes with socks, he said. If they’re mixing a more dangerous concentrated pesticide, they must also wear a Tyvek suit, safety goggles and gloves.

McGrath left us with these words: “You all can play an important role in educating the public about responsible use.”

The OSU Extension Service has several guides on pesticide safety:

Using Pesticides Safely

Get to Know the Pesticide Label

Integrated Pest Management Resource Guide

Keep Pets Safe around Pesticides

Calibrating and Using Backpack Sprayers


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