ALL ABOUT SQUASH: Squash Bugs and Diseases

As with most vegetable plants, squash bugs and diseases can quickly eliminate a garden crop without regret. Keep your eyes peeled for damage to leaves, flowers, or fruits to halt a garden takeover before it is too late!

The good news is that most diseases and pests that attack squash plants can be controlled with organic treatments rather than using chemicals, which can leech toxins into the very squash plant you’re trying to protect.

If your squash plant is looking a little under the weather, note its symptoms and consult this list:

  • Aphids – Curled or yellowed leaves indicate an aphid infestation by these little bugs that literally suck the juice out of a plant. Use a pyrethrin-based spray, such as Safer® Brand Tomato and Vegetable Insect Killer, to kill insects on contact without harming plants. You can find the actual aphids by looking at the undersides of your squash plant leaves. The tiny bugs can be black, green, or pink.
  • Cucumber Beetles – Are there holes in your plants? That’s usually a sign of cucumber beetles. Officially named Spotted Cucumber Beetles because of the black spots on their yellow backs, these insects have a taste for many of your favorite garden vegetables! They are especially destructive to squash because they spread several plant diseases, namely bacterial wilt and mosaic virus. Using an insecticidal soap will control an infestation. Safer® Brand Insect Killing Soap, for example, kills insects on contact without damaging the integrity of your organic garden.
  • Bacterial Wilt – This affliction usually appears in a plant in the form of a partially wilted or dead leaf. The disease is often spread by cucumber beetles and can be managed by regularly treating for these insects. To control the spread of bacterial wilt, check your squash (and other vegetables) for signs of cucumber beetles and bacterial wilt, and then treat for the insects.
  • Mosaic Virus – This seed-borne disease can be incredibly troublesome for squash growers. In fact, if you discover it in your plants you should destroy them immediately and not use seeds collected from infected plants.  To identify the virus, look for the symptoms — distorted, mottled leaves — during the early part of the growth cycle. As the plant matures, these symptoms will go away, but the virus won’t. Instead, the virus will create dome-like swellings on your plant’s fruit. Your best treatment is to eliminate the cucumber beetles that carry the disease.
  • Powdery Mildew – Although often mistaken for dirt, powdery mildew is a strain of fungi. Yellowing or stunted leaves, a dirt-like presence on leaves and vines, or premature leaf drop all indicate a possible powdery mildew presence. To add insult to injury, the stunted leaves will expose the squash fruit to sunscald! Unlike most fungal conditions, powdery mildew tends to spread during hot, dry conditions, often traveling from plant to plant by the wind. Once the spores come in contact with a new host, it takes only three to seven days for symptoms to appear. Safer® Brand Garden Fungicide is compliant with organic gardening and effective in powdery mildew control.
  • Squash Borers – Wilted plant leaves and stems are caused by squash borers. These bugs will eat their way into the stem of the plant and lay their eggs. When the eggs hatch, the larvae hollow out the roots of the plant. If you realize your squash is being ransacked by these creatures, you can eliminate the egg layer by finding the caterpillar’s entry wound near the base of the plant, which is often marked with a green frass.  With a sharp knife, cut a slit over the opening and kill the caterpillar inside. To help your squash plant recover from these intrusions, pile up a mound of dirt up to and over the borer’s entry wound.

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