What Preventative Strategies Stop Garden Pests Before They Attack?

“What is best to use to be on the offensive and keep pests from coming into your garden?” Question from Marilyn of Roseburg, Oregon

Answer: You cannot keep pests from visiting, especially if you are growing their favorite foods. But, cleanliness, monitoring, and planting robust pest-resistant varieties are three excellent tools for keeping pests at bay. Planning ahead for potential pests is another tactic. Let me flesh out these tips a bit more.

Give Good Plants a Good Head Start

Stressed plants emit hormones that attract potential pests, so keeping plants happy and healthy is important. When choosing vegetable starts at your local nursery, select disease and pest-resistant varieties, pick large plants with no leaf damage, and avoid highly root-bound plants. (Bound roots have a dense, interwoven network of roots with little potting mix. Gently lift plants from their pots to see the roots.) Bound root systems must be cut and separated at planting time, which puts undue stress on transplants.

Choose (or raise) the healthiest plants you can. Large, robust seedlings have a greater chance of resisting pests and diseases and producing high yields. If growing plants from seed, be sure to give your seedlings plenty of light and room to develop stout, dense growth, and ample root systems. Planting one seedling per pot will help avoid competition. Fertilize starts lightly, so they are as strong at planting time. (Click here for seed starting tips.)

Keep Plants and Beds Clean

A clean, weed-free garden with open spaces between plants yields better fruit by increasing light exposure and airflow. Under clean, open conditions, pests and diseases are slower to take hold and easier to manage. Walkways covered with straw, leaf mulch, or compost also make is nicer and easier to walk through the garden and care for plants in all weather.

Keep plants clean! Bushy veggies, such as tomatoes, peppers, and eggplant, are especially important to clean and prune to minimize the spread of disease and pests. (Click here to learn how to prune tomatoes.) Remove dying, diseased, or infested leaves and stems or any unwieldy branches that inhibit airflow and light where it needs to reach. When pruning, clean your pruners from one plant to the next by dipping them in a 10% bleach solution to reduce the chances of any cross-contamination of potential diseases. At the end of the season, remove all garden litter and plant material from the garden soil that may harbor overwintering pests and diseases.

Plan For Pests You’ve Experienced Before

If your cabbages have had cabbage loopers or your petunias have had budworms in the past, expect them to return. Apply pre-emptive applications of OMRI Listed BT to stop them in their tracks. By learning the life cycles of different pests that have plagued your garden in the past, you can plan precise strikes with the correct pesticides. (Reach out to the Oregon State Extension Service for more information and to take advantage of their many online resources for Oregon vegetable gardeners.)

Happy gardening,

Jessie Keith

Black Gold Horticulturist


How Do I Stop Powdery Mildew?

This zinnia has a severe case of powdery mildew.

“Every year I get white mold on the leaves of various plants in my vegetable garden. I don’t use any fertilizer or pesticide, other than an organic compost in the soil. It usually doesn’t cause a great deal of problems but is there something I could or should be doing?” Question from Lynda of West Warwick, Rhode Island

Answer: It sounds like you have powdery mildew, a common fungal infection that attacks leaves, causing white, powdery looking surfaces and blotches, particularly towards late summer. Some flowers and vegetables are more prone to it than others. For example, squash, melon, zinnia, and cosmos leaves typically develop powdery mildew, unless you have chosen mildew-resistant varieties.

The disease acts on leaf surfaces, disabling a plant’s ability to respire and gather sunlight. This weakens them and reduces productivity. Severe cases will kill plants. Here are four things that will stop or reduce the disease.

1. Choose powdery-mildew resistant varieties. Before buying a garden flower or vegetable that typically gets this disease, search for resistant varieties. Choosing vigorous, highly disease-resistant varieties will always result in a happier garden. You can often find lists of resistant varieties at university websites, like Cornell University (click here to view).

2. Provide plenty of sun, water, and airflow. Take good care of your plants and give them lots of sun and air, two things that discourage mildew development. Refrain from planting too closely together.

3. Remove diseased leaves as you see them. Simply prune off bad leaves on sight. Be sure to clean your pruners well after cutting any diseased plant.

4. Apply an organic fungicide. The all-natural product, Green Cure, stops powdery mildew. Apply it when you first see any signs to stop the disease in its tracks.

I hope that this information helps!

Happy gardening,

Jessie Keith

Black Gold Horticulturist