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Down the Garden Path

Preventing vegetable diseases in the garden

Checklists can be useful garden tools to be sure projects and tasks get done in a timely fashion. Going down a checklist to lessen disease is just another part of planning what you are going to grow this season. My suggested list below covers eight points and is a great place to start. Not all will apply to every garden and some gardens may need to cover more.
  • Grow disease-resistant varieties – This is one of the easiest ways to manage vegetable plant diseases. These are most often listed in the seed catalogs and noted on the seed packets as F1 hybrids. Any variety that has a series of initials behind the name denotes disease resistance, the more initials, the more resistance.
  • Choose the best site possible – Vegetables prefer sun all day long, with 6-8 hours minimum to expect good yields. With less than full sun, leafy greens and early root crops will perform well. Vegetables that produce fruits will be delayed and have lower productivity.
  • Water properly – Even consistent soil moisture is important for sustained high quality yields. For example, critical times for water in tomatoes, cucumbers and peppers are during fruit development. Bulb onions may be limited in size if water is lacking at any point of bulb expansion. Water the soil and not the plants. Leaving plant foliage wet at night just about ensures the right environment for disease development.
  • Garden sanitation – This is done before planting, during the growing season, as well as at the end. A good clean garden bed ensures that diseased plant parts are not present. Removing fruits or vegetable plant parts that are diseased limits further spread and fall clean up removes the majority of the disease inoculum for the following year. Sanitation also includes the weeds near or around the garden. More on that just below.
  • Manage insect populations -Vegetable diseases that are spread by insects, like aphids, will feed on nearby weeds that will host the disease without showing any symptoms and then feed on our vegetable plants, spreading the disease. This is more of a concern as the growing season progresses than first thing at planting time.
  • Promote good growth – Healthy plants resist diseases better and provide greater yields. Use a starter fertilizer to stimulate roots and later consider a side dress of fertilizer as the vegetables start to flower and produce fruits. This along with the even watering will produce the best-sized and uniform yields.
  • Follow crop rotations – This is difficult to do in the smaller home gardens, as space is limited, and this is why using F1 hybrids are so important. Large to very large gardens can benefit more. Rotating plant families between the solanaceous crops (tomato, pepper, potato and eggplant) with cucurbits (cucumber, squash, melon and pumpkin) with Cole crops (cabbage, kale, broccoli, and others). A three-year rotation greatly reduces soil disease populations.
  • Fungicides – Sometimes weather conditions can go against all the good things we do to prevent vegetable diseases. When a disease is identified and caught early, fungicide applications can really help. Proper timing and very thorough coverage are critical for good control.

Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. The Kendall County Master Gardener Help Desk is open for the season, 9 a.m. to 12:30 p.m. on Mondays, Wednesdays and Fridays for the month of March. Beginning in April, and throughout the growing season, the Kendall County Master Gardeners are available Monday through Friday at those hours. Stay tuned on Facebook for more garden and yard updates at