The lone voice of horticultural reason

Pests & Disease

7-15-1999 — Eight years ago, a dear friend presented my garden with a lovely gift: a miniature hollyhock plant. Unlike its taller brethren, it thrived in my garden’s less-than-full-sun scenario, bloomed upper-class pink in great profusion, and quickly became one of my absolute favorites. It didn’t need staking, bloomed for a month, responded well to deadheading, and shimmied like a go-go dancer when given a light summer breeze.

By the start of last season I had divided it twice, and so had in my arsenal four robust, four-foot vertical slashes of delicate yet commanding pink with which to paint my garden. This spring I moved all four (each larger than the original plant) to the perfect spot, envisioning a mid-bed wave of rich pink spires set off by the taller, steel-blue globes of echinops to their side and rear.

Instead, today, gone. Gone, gone, gone. The roots are there, and four little tufts of life, still groping, hoping to rise, trying to create enough green mass to survive, but the stems of May and early June are dead, gone, joining the earliest leaves as the brown and withered trash I’ve been picking and pruning out of my garden nearly all season. My first encounter with hollyhock rust, you see. It is a dastardly thing.

This is and will continue to be a tough gardening season due to plant fungi, rusts (a form of fungi) and viruses. Our wet, cool spring, and the ample rains since, have many gardeners with whom I’ve spoken reeling from the effects of powdery mildew, tomato blight and a host of other heart-breaking diseases. Here’s a run-down of the most common problems, and some solutions.

First and foremost, proper, basic gardening practices are always your best deterrent. There are hundreds of garden fungi and rusts, many more than I could possibly discuss here. Moisture, in the forms of rain, humidity, and the watering we do, is their main ally. Rain and humidity you can’t control; how you water your garden, you can. Water the soil, not the plant; watering flowers or vegetables by running your lawn sprinkler in or beside a garden bed is suicide. Getting leaves and stems wet when you water, and allowing water to splash off one leaf to another, breeds fungal spores plus allows them to explore new areas of your garden. Water sparingly but water deep, using a watering wand held only an inch or two above the soil. Water early in the morning when possible, lessening the effects of mid-day evaporation while allowing the rising sun to dry and sterilize lower leaves that inevitably get wet.
Winged pests such as aphids exacerbate the problem by carrying fungus spores from plant to plant and garden to garden; so you see, controlling bad garden bugs, as discussed in the previous column, is part of the puzzle.

Holding off until June 15 to apply top-dressing to the garden, be it compost, hay, dried grass or cocoa bean shells, allows the sun to fully sterilize the top inches of your garden soil, which can harbor fungus and rust spores from year to year. Keeping the garden weed-free, and removing unhealthy plants or plant parts, are also essential practices.

Powdery mildew is a white, powdery fungal growth commonly seen on the leaves of tall phlox, monarda, and a host of other perennials. Early and twice-monthly use of a fungicide containing Daconil is the best recourse. If you spray after the problem is noticed, infected leaves will not recover but new growth will be healthy; remove affected leaves and burn them or toss in the trash (never the compost bin).

Tomato blight runs rampant in wet, humid seasons, curling and turning leaves dry and brown. Choose resistant cultivars in the first place (ask when you buy) and spray tomato plants with a copper-based fungicide right after pinching and before blossoming.

Viruses are the great heart breaker. Put simply, they are untreatable, living within the plant cells. They don’t always kill the plant, but they take the enjoyment out of growing it. How do you discern viruses from fungi? Go to the University of Minnesota. and get a four-year horticulture degree. For the rest of us, proper garden maintenance, use of fungicides as needed, buying disease-resistant cultivars, and growing plants that seem to cause us the least amount of trouble are our best pursuits.

Don Engebretson
The Renegade Gardener