What's wrong with my plant?
This summer's weather has been so strange: hot and dry, cool and wet, and every combination in between. Vegetable gardens have been enjoying the moisture and warm weather, but so have many leaf spot pathogens. If you are seeing unusual leaves in your vegetable bed, here's a quick primer on what may be causing your problems.
Many leaf spots are produced by fungi and bacteria that enter your garden through contaminated seed and transplants; wind and insects. Some have been deposited in the soil by last year's infected plant debris and have overwintered there. Splashing rain or overhead watering contaminates healthy plants with the soil-borne pathogens, and in no time, you see the beginnings of new leaf spot infections. The good news is that there are several steps you can take to prevent these infections from entering your vegetable bed.
Purchase disease free transplants or seed from a reputable source.
Rotate your crops so that no vegetable family inhabits the same place in your garden for three to four years.
Water the soil, not the plant. Avoid overhead watering, and water in the morning to allow any moistened leaves to dry before nightfall.
Stake and prune plants to keep their leaves from touching the soil.
Mulch to protect plants from soil-borne pathogens.
Regularly inspect your plants, and remove and destroy any affected plant material to keep pathogens from spreading to healthy plants.
Some common spots you may be seeing this summer include:
Peppery leaf spot on turnips, cauliflower, broccoli and Brussels sprouts: Pinch off severely infected leaves and remove them from the garden.
Black spot and gray spot on cabbage, cauliflower, Chinese cabbage, broccoli, Brussels sprouts, kohlrabi, kale, turnip, and rutabaga: Remove diseased leaves from the garden and till in infected plants at the end of the season.
Early blight on tomatoes, potatoes, eggplant and peppers: stake plants; allow space between plants for good air circulation, pinch off lower leaves and prune plants to a few stems. Deeply mulch the soil to help reduce disease problems.
Bacterial brown spot on beans: space plants to allow for good air circulation. Stake pole beans. Avoid working with plants when leaves are wet. Remove infected leaves on a cool, dry day.
Septoria leaf spot on lettuce: when growing successive crops of lettuce, be sure to seed the next crop in a location away from any currently diseased plants. Annually rotate lettuce plantings.
For more information on plant problems, visit "What's Wrong with my Plant" at http://www.extension.umn.edu/gardeninfo/diagnostics/index.html, or call Douglas County Extension at (320) 762-3890.
Until next time, happy gardening!
"It doesn't get any better than fresh from the garden!"
- Ed Crankshaft