4 Easy Tips to Prevent and Manage Pests and Diseases

By Nisha Joglekar, Communications Intern

As a new gardener, I would be puzzled at seeing browned, drooping or half-eaten leaves on plants that had looked healthy before. Making some simple changes in my gardening went a long way in managing these problems. With the help of the The Garden Hotline, here are four easy tips to prevent and manage some common pests and diseases.

1. Don’t over-water or under-water plants

Fungus gnats emerging from the soil.

Initially, I over-watered my plants, which invited all sorts of trouble like root rot, mold and pesky fungus gnats, which love a wet, humid environment. Too much water saturates the soil, not giving plant roots room to breathe. They will develop root rot if they remain sitting in water. To check soil dryness, stick your finger about two inches into the soil. If it feels dry, then it needs watering.

On the other hand, insufficient or irregular watering can stress out plants and dry out its roots. Stressed plants don’t withstand attacks from pests and diseases as well as hydrated and healthy ones. It is also better to avoid overcompensating for missed watering and just get back on schedule.

How frequently you need to water depends on the plant, seasonal weather, soil medium and the choice of potting material if planted in containers. For instance, clay and wooden pots dry out quicker than plastic ones.

2. Water the soil, not the leaves

Watering just the soil ensures it gets absorbed where the plant needs it the most, at the roots. Avoiding water on the foliage will also prevent diseases from forming due to wet leaves. According to Laura Matter, a Garden Hotline educator at Tilth Alliance, “watering in the morning is more beneficial as the plant leaves will dry out during the day and the whole plant will be well hydrated during the heat of the day”. Young seedlings in seed starting cells or cups can also be ‘bottom-watered’ by putting them in a water-filled tray or saucer. This prevents the top layer of the soil around the seedlings from staying constantly wet.

3. Prepare and store healthy soil

Having used bags of wet potting soil in the past, I would notice a white fuzzy growth on it, soon followed by the appearance of fungus gnats. As I was to learn through The Garden Hotline, potting soil has compost in it which breaks down over time. The white growth on wet soil was part of that natural process and likely a fungal hyphae, which the fungus gnats were attracted to. The trick was in knowing what to do with the bag of wet soil. The Garden Hotline suggests stirring the soil to break it up and putting it somewhere dry to air out like a covered porch, patio, garage or basement. Any remaining soil can be stored in a cool, dry, dark place.

4. Create a diverse garden

Creating a healthy, diverse garden that attracts beneficial insects is a better preventive measure over using pesticides. This year I am experimenting with companion planting to manage pests. Using native plants is even better as they are recognizable to native insects.

Plants from the Daisy family (marigold, sunflower, cosmos, zinnia, calendula), Mint family (lavender, thyme, mint, oregano, sage), Carrot family (fennel, dill, cilantro, lovage, sweet cicely) are some examples of plants that attract beneficial insects and can be planted close to or between vegetable crops. Others like Nasturtiums attract aphids and can be used as trap plants (their leaves and flowers are edible too!) to keep black bean aphids off green beans.

Remedies for pests and diseases

Identifying the cause of an unhealthy plant can be perplexing as a new gardener. The Garden Hotline can help determine what the problem is – whether cultural, pest or disease related. Knowing some simple remedies for common pest infestation and disease also comes in handy. Here are a few tips that you can try:

  • Light dusting of cinnamon on the soil around the plant.

    I found that lightly dusting cinnamon on the top of the soil helped limit my fungus gnat issues. Being a natural fungicide, cinnamon destroys the fungus in the soil on which fungus gnats feed. Care should be taken to avoid getting cinnamon on the plants.

    You can also put a thin layer of grower’s sand, the kind used in cactus soil mixes, to prevent fungus gnats from laying their eggs in the soil.

  • Baking soda spray can be used for powdery mildew prevention on plants like squash, pumpkins and cucumbers. In one gallon of water, mix 1 tablespoon of baking soda, 1 tablespoon of oil (vegetable oil is OK) and 1 or 2 drops of dishwashing liquid (non-detergent like Dr Bronner’s castile soaps). The mix can then be sprayed on the leaves of plants.
  • When purchasing any pre-made pest management product look for organic certification on the label, generally from the Organic Materials Review Institute (OMRI). Follow all label directions and do not spray on a hot sunny day. These products are made from soaps and oils and can burn plant leaves. They also are non-selective and will kill beneficial insects and their eggs as well.
  • Slug traps can be made from used plastic containers (like cottage cheese size), and sunk into the ground around plants getting eaten by slugs and snails and filled with cheap beer or baking yeast and water.
  • Wash off aphids with water – spray off aphids on your plants with a strong stream of water, being careful not to damage your plants.
  • Use floating row covers to prevent flying insects from laying eggs on or near your plants. This can prevent damage from Imported Cabbage Worm, Leaf Miners and Carrot Rust Fly.
  • It is best to test out a small area of the plant with any new sprays or remedies and wait for 24 hours before proceeding.

If you have any questions on pests or diseases affecting your plants, call The Garden Hotline, a FREE service offering individualized solutions to gardeners throughout Seattle and King County. You could also try Tilth Alliance’s Secrets of Companion Planting and Organic Pest Management classes to learn about creating a diverse, healthy and organic garden.


5 responses to “4 Easy Tips to Prevent and Manage Pests and Diseases

  1. Thanks, Nisha.. I’ll be using some of these techniques. I also ‘sprayed’ away, with water, the majority of the white flies on my plum… then a vireo turned up to dine on the remainder ! 🙂

  2. Love this guide! Thanks for sharing. Many of the tips you mention I’ve picked up over the years from friends and family, and they’ve worked wonders 🙂 Would def recommend to others.

    If I could suggest my own tip, it would be to try and identify which pests are affecting your plants / veggies, too. And early, if possible. I’ve found guides like this one super helpful for this – http://www.leicesters.co.nz/soil-borne-diseases/ . Makes them a whole lot easier to treat if you know what you’re up against 😀

    Thanks again for sharing!

  3. Thanks for your comment and glad you found this article helpful! Absolutely, learning to identify pests is a great (and fascinating) practice. Thanks for that.

    I’d be hesitant about that site (from the link you shared) for two reasons. First, the info might be helpful if you’re from New Zealand, but if not, it’s be better to use a resource that is closer to your bioregion. So for us in the Pacific NW of the US, it’s not necessarily a great match.

    Second, the site sells toxic chemicals that can cause a host of human health, animal, aquatic life and soil damage. A great local resource to get customized information about solutions using healthy practices if you’re having pest problems is the Garden Hotline. They’re managed by Tilth Alliance, garden educators here in our office (sponsored by Seattle Public Utilities and King County) who you can email/call and send photos and discuss your situation. Help@Gardenhotline.org or (206)633-0224.

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