Why Are The Leaves On My Squash Plants Turning Yellow?

Last update: 2021-10-27

While squash plants produce tasteful fruits, they are a bit more tricky to grow than usual. They are susceptible to various diseases, cold-intolerant, and vulnerable to a nutrient deficiency – all of which commonly make the leaves turn yellow, along with other problems.

If you are wondering “Why are the leaves on my squash plants turning yellow?”, then keep reading!

Diseases

The fact is that squash plants are vulnerable to plenty of diseases, some of which can make the plant leaves dry and turn yellow. For example:

  • Downy Mildew

Why Are The Leaves On My Squash Plants Turning Yellow?

  • Fusarium Wilt

Why Are The Leaves On My Squash Plants Turning Yellow?

  • Cucumber Mosaic Virus

Why Are The Leaves On My Squash Plants Turning Yellow?

There are two common causes of these diseases – either by pests or found in the soil used for growing previous squash plants that were infected.

Cucumber beetles and aphids are typical examples; while aphids carry the zucchini yellow mosaic virus, cucumber beetles are the carrier of the squash mosaic virus.

Why Are The Leaves On My Squash Plants Turning Yellow?

Squash plants once are infected will be more difficult to handle and treat than pests, especially in cucurbit plants.

If your plants are infected with Cucumber Mosaic Virus or Fusarium Wilt, there’s no treatment for this disease. You’ll have to remove the infected plants and eliminate pests or any pathogens to stop the disease from spreading.

Pests, Insects, And Bacteria

Other common reasons causing the leaves of your squash plants to turn yellow are pests, insects, and bacteria – which usually hide under squash leaves, around the plant base, or crawl along the stem during daylight.

Some common pests, insects, and bacteria in squash plants are:

Squash Vine Borers

Why Are The Leaves On My Squash Plants Turning Yellow?

They pierce and suction the squash plant, which not only causes damage but also halts the flow of water and nutrients, therefore, making the plant leaves turn yellow.

To detect them, fill a yellow-colored container with water and place it in the garden. The squash vine borer is attracted to this color.

Now, remove it by cutting a slit in a squash vine near it, then cover the cut stem with garden soil. Take a close look at every inch of your plant to find and remove any borer’s eggs.

You should also prevent the adult squash vine borer from laying eggs by covering the plant’s stem with a barrier, such as aluminum foil or nylon stocking strips.

Bacterial Wilt (Or Erwinia Tracheiphila)

This is a bacterium spread by the spotted and striped cucumber beetles and it causes loss of squash plants. Here are some common signals to identify bacterial wilt:

Why Are The Leaves On My Squash Plants Turning Yellow?

Leaves turn dull green and wilt during daylight and recover at night, then completely wither and turn yellow with brown edges, and finally die. The symptom gradually spread to the entire plant, making it wither and end up dying.

Why Are The Leaves On My Squash Plants Turning Yellow?

The most effective way to prevent bacterial wilt is to control the beatles.

Whiteflies

Run your hands through the squash (if it’s grown on earth ground) or move it (if it’s grown in a pot) and encounter a bunch of small, white-winged insects, that might be whiteflies.

Why Are The Leaves On My Squash Plants Turning Yellow?

Whitefly immature stages suck on squash leaves for water and nutrients.

While eating, their saliva introduces honeydew – a toxin – into the plant, causing a silvery or yellowish appearance on leaves.

Here is how to eliminate the pest effectively:

Leafhoppers

The way that leafhoppers ruin your squash plants is quite similar to whiteflies.

Why Are The Leaves On My Squash Plants Turning Yellow?

The differences are that both leafhopper immatures and adults feed on squash leaves, and their toxins cause “hopper burn” conditions on leaves, making their edges die and appear scorched.

Here is how to eliminate the pest effectively:

Spider Mites

Cucumber leaves are their favorite foods and damage causes the leaves to turn yellow. Spider mites are commonly found on the underside of the leaves.

Why Are The Leaves On My Squash Plants Turning Yellow?

Here is how to eliminate the pest effectively:

Incorrect Water Schedule

Lacking water can make the leaves of your squash plants turn yellow.

Why Are The Leaves On My Squash Plants Turning Yellow?

Correct water schedule is an important factor for squash; avoid overwatering and under-watering. Make sure to provide around two inches of water weekly and even more than that during the growing season or during hot, dry months.

You don’t need to water your squash plants frequently, just focus on watering deeply each time.

Lack Of Sunlight

Squash is a sunlight-loving plant, therefore, you should take note to grow them in a full-sun spot or at least 6-hour sunlight exposure per day.

Otherwise, the plant’s photosynthesis process is impacted and the leaves will turn yellow.

A Nutrient Deficiency

Iron Deficiency

Why Are The Leaves On My Squash Plants Turning Yellow?

If you find the leaf veins of your squash plants are green but the surrounding area turns yellow plus no insects or pests detected, that might be the sign of lacking iron availability (or called chlorosis).

But luckily, this issue is easy to fix by:

  • Reducing phosphorus in soil
  • Avoid overwatering
  • Improve compacted soil
  • Adding organic matter to correct clay soil
  • Lower soil pH level

Potassium Deficiency

Why Are The Leaves On My Squash Plants Turning Yellow?

If you find the leaves of your squash turn yellow at their edges and tips, then the entire leaf gradually turns yellow while new leaves are cupped with a dull look, those are signs of potassium deficiency – which is commonly found during the flowering stage.

Nitrogen Deficiency

Why Are The Leaves On My Squash Plants Turning Yellow?

If you find new leaves of your squash plants are still green but the older leaves start turning yellow along with their tips and veins, they are probably nitrogen-deficient.

While making the leaves turn yellow, nitrogen deficiency can limit the plant growth and in the worst case, the plant might die.

Therefore, you should mix nitrogen fertilizers with compost and add them to the soil before the growing season of squash starts.

Conclusion

Growing squash plants is a bit more difficult than some other ones because they’re quite vulnerable to many outer factors. But by paying extra attention to them, you will receive an abundant crop.

I hope this article gave you the best answer for “Why are the leaves on my squash plants turning yellow?”. Thanks for reading!

Harry Ramos
Harry Ramos

Related Articles