If you have witnessed a healthy looking zucchini suddenly die, and see yellow leaves on zucchini plants throughout your garden, you might want to think about checking for squash vine borers. These little pests use squash and gourds as hosts. Sometimes watermelons become their hosts as well.
Vine Borer Causing Zucchini to Suddenly Die
If you have zucchini leaves wilting, it is probably the vine borer. These are larvae of a moth. This particular moth has clear wings and is sometimes mistaken for wasps. The vine borer overwinters in cocoons in the soil and come out as adults in late spring. They deposit eggs on the underside of the leaves. When they hatch, the larva cause yellow leaves on zucchini and the zucchini to suddenly die. If you find your zucchini dying, check under the leaves for signs of the borer. If you find zucchini leaves wilting, the borer is probably present in the stem.
The eggs of this vine borer are deposited on the underside of the leaves toward the base of the plant. Once they hatch into larvae, these larvae will bore into the stalks of the plant at the base. When there, they tunnel through the stem and eat it. Once they are mature, you will find them exiting the plants and burrowing into the soil where they overwinter until mature in the spring.
It is unfortunate that this vicious cycle begins because you could have a healthy looking zucchini plant suddenly die and not know what caused it if you aren’t aware of the existence of this pesky moth. There are ways to control the attack if you catch it early enough, when you find zucchini leaves wilting or yellow leaves on zucchini instead of your zucchini dying.
You can use insecticides when the vines are young. Do it right as they start to run. Some of the chemicals used are pyrethrum, malathion or Sevin. You can apply these as dusts. You can even buy sprays. Both will work. You should apply these things every 7 to 10 days to keep the borers at bay. Do this for about five weeks and your zucchini should be free of vine borers for the duration, preventing zucchini suddenly dying.
For those plants already affected, you can keep the damaged bored area on the stalk covered with soil and make sure to water the plant regularly. You might be able to save them and change yellow leaves on zucchini back to green in no time.