It is a challenge to diagnose a diseased plant if you can’t see all the symptoms.
The only solution will be a shotgun approach to diagnosis.
I got an email from a reader a few weeks ago. They asked me what was killing their squash and even sent me a picture.
Last week I talked about insects that do their best to feed on our zucchini and the reasons that you see the wilt. Vine Borers feed on the stem on the inside and the Squash Bug sucks the nutrients out of the leaves.
Both deprive the sap from flowing through the plant.
Bacterial Wilt or Erwinia tracheiphila is a disease that is spread by a Stripped Cucumber Beetle or Acalymma vittatum. The two previous plant pests mentioned are large compared to this vector.
This disease overwinters in the stomach of the cucumber beetle.
As spring arrives these beetles feed on young plants like squash and more and infects their stems and leaves. Affected squash plants may first wilt in their leaves, which eventually spreads downward until the entire squash plant is affected.
Typically an entire vine can wilt within only a couple weeks after infection. Fruit of infected plants will be wilted or poorly shaped.
One of the unusual things you may see is the plant may ooze a sticky, milky substance when the stem has been cut.
Once a squash plant has this disease and begins to wilt, it cannot be saved. When you can easily remove the vines get it out of the garden and make sure that they don’t stay on the soil over the winter.
I would take the infected leaves and plants to the curb. The problem is that the vines intertwine with healthy plants and can create a problem removing the infected plant parts.
If you have to wait until the fall and remove the vine and all the infected plant parts then, at the end of the season take it all to the curb.
These plants will dry-out until the end of the season. Remember that if you think that you would like to compost this plant material, you may not get your compost pile hot enough to kill the disease.
Future infections may kill all of the squash plants that are in your garden from having reinoculated soil with this disease.
A cover crop over the young plants will help distract the beetle from attacking your squash plant.
If you have seen these beetles in your yard from the year before, you can also record where you first saw the disease in your journal. One of the best ways to help discourage these beetles is to perform normal maintenance job of reducing weeds between the plants.
Cucumber beetle control will be the best control for this disease. If you can do it early in the season when the vine crops emerge the pests also emerge.
If you delay planting your cucumbers by a few weeks the beetles won’t find them and their food source will be gone.
Striped Cucumber Beetle must feed right away to survive and will leave when they emerge from their eggs, if a food source is unavailable.
So by delaying your plantings any cucumber beetle that overwintered in your garden will have to fly away before the plants come up.
The second round of beetles may yet be a problem; but if the first generation has found another food source, you will be safer and the plants will be more established.
Diatomaceous earth, a non-toxic fine powder, spread around your plants will cut into the feet of insects that crawl on your plants. Under a microscope this powder looks like tiny glass shards.
Sprinkling this powder on your plants and on the ground will prevent most insects from harming your plants. Both lady bugs and lace wings have cucumber beetle eggs on their menu.
Attracting both lady bugs and lacewings will go a long way to solve most insects pest problems.
Greenhouses have used yellow sticky traps for many years as a scouting trap. Yellow seems to attract most insects.
Therefore, provide a modicum of control for this cucumber beetle as you would place them close to your squash.
If you plant a trap crop of Hubbard squash in the perimeter of your garden, these beetles will go there first. There are a variety of insecticides that you can use to dispatch this pest.
My hope is that if you have a wilty zucchini in your garden that you will have the proper ammunition to dispatch this disease properly.
I hope that you have a great stroll through your garden this week. If you see any challenges send me an email at ericlarson546@yahoo.com.