Problems With Butternut Squash Diseases?

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Many people make the mistake of misidentifying pest problems as butternut squash diseases. Most varieties of butternut squash have been bred to be resistant to many diseases. However, no varieties are resistant to insects. In most cases, troubles in your squash patch are directly related to insect problems.

Most butternut squash "diseases" are caused by three main insects:

  • Vine Borers
  • Squash Bugs
  • Cucumber Beetles

Vine borers are a common garden pest and can do some serious damage. They will attack any summer or winter squash plant, along with cucumbers and pumpkins. They will bore into the main stems at the base of your butternut squash plants, sucking out the juices and eating the plants themselves.

Butternut Squash Plant

Once inside the stems, they will continue eating away at your plants from the inside out. Many times this damage is not noticed until significant and irreversible damage has already been done. The squash growth will suddenly slow and the plant will wilt, shrivel and die. Many backyard vegetable gardeners see the plant wilting and assume that the problem is lack of water. If the plants continue to wilt after a thorough soaking, you're definitely battling vine borers. You will also notice something that resembles a small pile of sawdust at the base of your plants. There are several products on the market that will prevent vine borer infestation. It's important to apply these products before your butternut squash plants become infested.  We typically apply a small amount of spray to the base of our squash plants when the stem is almost as big around as a pencil.  Read the labels on products that contain Diazinon to make sure that the spray is effective against squash vine borers. Follow the manufacturers directions. Most of these insecticides can be applied soon after the seedlings first emerge. Once the plants stay consistently wilted, you've probably lost the battle. At this point, it's best to pull the plants out of the garden and start over by planting more seeds. 

Baby Butternut Squash

Squash bugs are a common pest, and can cause butternut squash diseases. They are usually gray or brown in color, although some are almost black. Squash bugs are usually about the size of a dime and travel in packs. They will suck the juices from the plant and will actually attack the squash itself, although they usually lay their eggs on the underside of the leaves. It's easier to prevent a squash bug problem than cure it. Many of the same products that prevent vine borers and cucumber beetles will also prevent squash bug infestations. You can begin spraying soon after the seedlings emerge. By the time the blossoms appear and the plants begin to set fruit, you should have the problem under control. Most of these insecticides are available at most garden centers and should be applied according to the manufacturer's instructions. If you are trying to grow organically, soap sprays are also available. Be sure to also keep your garden free of weeds and other plant debris. You can also cover the stems of the butternut squash plants with cardboard tubes to discourage pests.

Butternut Squash Seedling

Many butternut squash problems are caused by cucumber beetles. The striped cucumber beetle has black and yellow spots on its back. The spotted cucumber beetle has a yellow back with black spots. They love to chew on young butternut squash leaves and stems. Cucumber beetles also carry wilt diseases from plant to plant. Fortunately, these pests can be controlled with common insecticides including sprays and dust. Diazinon and Malathion are common chemicals that will kill cucumber beetles. Apply products that contain these pesticides according to the manufacturer's instructions. Most can be applied soon after the seedlings emerge and throughout the growing season. Organic products including soap sprays are also available at most garden centers.

We've had good results in our own garden by implementing a preventative spray program for pests using a homemade soap spray.  We mix together 2 gallons water, 4 tablespoons hot sauce and 4 tablespoons liquid dish soap in a 2 gallon pressure sprayer.  We spray this mixture all over our squash plants every 7-10 days or after every heavy rain.  This soap spray doesn't actually kill any bugs, but it does encourage them to move elsewhere.  If we still end up with a problem, we switch to a commercial product.

If you are sure you don't have pest problems in your garden, there's a small chance you might actually be dealing with butternut squash diseases. Some diseases that affect squash plants are wilt disease, powdery mildew, downy mildew and scab disease. These are usually identified by a powder like substance on the leaves or stems. There may also be visible black spots or splotches on the leaves themselves. Most butternut squash diseases can be avoided by choosing disease resistance varieties and by controlling pests and keeping the garden clean and weeded. They can also be controlled with soap sprays or fungicides that are usually available at most garden centers.

To help prevent butternut squash diseases, we implement a preventative spray program in our own garden using a homemade fungicide.  We mix together 2 gallons water, 4 tablespoons baking soda and 4 tablespoons hydrogen peroxide in a 2 gallon pressure sprayer.  We spray this mixture all over our squash plants to the point of runoff every 10 days or so, or after every heavy rainfall.  If we still end up with a fungal infection, we switch to a commercial fungicide product.

Remember, when dealing with most garden pests and diseases, "an ounce of prevention is worth a pound of cure". We hope these tips will help you to avoid most butternut squash diseases.

Click on the following links to learn more about growing your own butternut squash.

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Click here to learn about planting butternut squash

Click here for information about watering and fertilizing butternut squash plants

Click here for help diagnosing and curing common butternut squash plant problems

Click here to learn about harvesting
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