Bob Westerfield is an Extension horticulturist.

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First Aid for Summer Squash
by Bob Westerfield       #Advice   #Disease   #Pests

Old, maturing squash left on the vine too long will attract pesky insects, which in turn can damage your plants. Be sure to harvest frequently before the fruit matures.

As we enter mid-July with August right around the corner, there are some pretty rough-looking summer squash patches that I have visited around the state in my role as a vegetable specialist. From backyard gardens to commercial growers, everyone that has grown summer squash knows the challenges that the late season can dish out. It takes a dedicated and persistent gardener to keep summer squash looking good all summer long until the plants finally play out in the coolness of fall. By being diligent and keeping a very close eye on your plants, it is possible to produce this delicious summer vegetable all season long.

In order to better combat the issues that face your summer squash, it helps to have an understanding of what can actually affect them. Poor gardening practices from the start are the fastest ways to shorten the lifespan of your zucchini and crooked necks. No amount of pesticides or fertilizer will overcome bad gardening management. With that being said, try to grow the healthiest squash you can by fertilizing them properly and maintaining a soil pH of about 6.5-6.8. Proper irrigation is also critical if your squash are to stand a chance against all the summer critters that want your squash as bad as you do.

The best defense against the several insect and disease problems you may encounter with squash is a good offense. Scout your plants frequently from about the time they emerge to the time they stop producing. Diseases such as powdery mildew and downy mildew are very common problems that will cut down on the vigor of your plants and overall lifespan of production. These fugal pathogens appear on the broad leaves of squash plants. Powdery mildew looks almost as if a white talc powder has been sprinkled over the leaves. Downy mildew produces angular white and yellow blotches on the leaves. Both of these diseases can be held to a minimum by avoiding overhead irrigation and spacing plants so they have plenty of room for good air circulation. When needed, spray plants with a labeled organic or synthetic fungicide at the first sign of disease presence. High humidity and heat play a big role in disease formation and unfortunately, you cannot control these. But once again, keeping the plants as healthy as possible will allow them, in many cases, to grow through these diseases if they are encountered.

Powdery mildew is a common disease issue that can weaken squash plants and reduce yield.

Perhaps nothing is more devastating to our summer squash plants over the last few years than the squash vine borer. I am not sure if it is just the increase in more people growing their own squash, but this pest has been an epidemic around the Southeast. The adult moth, which actually more closely resembles a wasp, emerges out of the ground in the spring and begins looking for its host plant squash somewhere between the middle and end of June. Adults continue to fly for several months as they deposit their egg close to the base of vulnerable squash plants. From the single egg, a tiny larva emerges and bores into the stem of the squash plant. Like a child let loose in a candy store, these voracious feeders munch on the inside of the stem, tunneling upward and downward as they go. Most people do not even realize they are there until they see their squash plants suddenly droop over, like they severely need water. By this time, the squash borer may have riddled the plants beyond repair. This is probably one of the hardest insects to control because they stay so well hidden from our eyesight. The best control is accomplished by spraying approved organic or chemical options at the base of your plants soon after they have emerged. You will need to continue to make frequent reapplications every week or so to have any chance at controlling this pest. On occasion, you might see the red-colored adult sitting on the squash leaf, and you should destroy her immediately. Keep a careful eye on the base of your plants and look for any entrance holes and sap oozing from the plants. If you catch it early, you can use a sharp razor blade to vertically slice the stem near the penetration hole. Use your fingers to pull back the hollow stem and look for this beastly caterpillar. You can carefully cut him in half with the razor blade or extract him and exile him to parts unknown. Close up the wound that you created by pinching it back together, and then pile some soil over the wounded area to help in the recovery process. As long as you do not allow the grubs to feed for an excessive amount of time, your squash plant should recover.

Perhaps the worst problem for squash growers is the squash vine borer. Difficult to detect at first, they can take out an entire planting of squash quickly if left unchecked.

Squash bugs are another prolific pest that frequents the summer garden. They can rapidly multiply and cause substantial damage by feeding on both the foliage and maturing crop. Leaf-footed bugs can also invade squash and other vegetables, and they look a lot like squash bugs. While there are other insects that can munch on your plants, these two, along with the squash vine borer, will be your greatest challenges. Organic products such as neem oil and pyrethrin will do a pretty good job of controlling both leaf-footed bugs and squash bugs. There are also a number of manmade products labeled for vegetables that will work well to help control this enemy. Most of these insects have multiple generations, so you need to stay diligent in your defense. It is very important, as well, that you harvest your squash as early as possible and not allow any of the fruits to become over-mature on the vine. Over-mature squash left in the garden will be ringing the dinner bell for all the bad bugs on the block.

With all this talk about controlling diseases and insects, make sure you correctly identify the problem. There are also plenty of beneficial insects out there that help control the bad guys and help perform the task of pollination. Be careful when you spray that you do not wipe out more of the good guys than the bad. Avoiding early morning sprays will help with this.

Squash bugs are one of the most common pests that can invade your plants.

Care should be taken to correctly identify insects to prevent spraying and harming beneficial insects, such as this ladybug.

Squash is certainly a favorite among home gardeners, but I have heard too many gardeners say that they have given up on it because of all the challenges to keep it healthy. One way to help yourself out is to continue to plant successions of new squash every few weeks during the first part of the growing season so that you have different stages of maturity going on in the garden. By spacing your planting times and controlling a few of the more troublesome diseases and insects, you should be able to harvest this delicious table fare all season long.

Photos by Bob Westerfield.


Posted: 07/24/14   RSS | Print


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