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How do you Fix Yellow Squash Leaves? (Causes & Solutions)

Yellowing leaves on your Squash plant is a bad sign, significantly because it may affect the overall fruit quality and yield.

Generally, yellow Squash leaves indicate the plant is severely stressed due to over or underwatering, essential iron deficiency, lack of sunlight, vine borer infestation, and mosaic virus or bacterial wilt problems.

However, witnessing the discoloration is easy; the hard part is figuring out what went wrong.

Yellow Squash Leaves (Causes & Easy Fixes)

Squash, also known as Cucurbita, is a popular backyard plant for its watery, fleshy fruit.

However, getting the fruiting to become 6-8 inches long may not be accessible when the plant is under some form of duress.

Yellow squash leaf is a serious problem which indicates many different problems
Yellow Squash leaf is a serious problem that indicates many different problems.

Therefore, one of the earliest indications of Squash plant problems is the yellowing leaves, which may require immediate diagnosis and treatment.

1. Insufficient Water

Squash plants drink a lot of water to attain significant growth of foliage and juicy fruits.

Insufficient water leads to slow root growth and smaller, discolored foliage.

In fact, water-deprived Squash will later develop deep yellow leaves and underdeveloped fruits.

Remember, the plant needs frequent watering during the fruiting stage and hot, dry summer to engage in photosynthesis.

Along with yellowing leaves, check for other vivid signs of dehydration, such as wilting of foliage, dry or compact soil, dead leaf tips, and slower growth.


  • Immediately water the Squash plant to provide the much-needed moisture to the soil and roots.
  • Continue the process every few days until the leaves seem to revive.
  • Generally, Squash needs watering about 2 inches (5 cm) of water every week.
  • Using a sprinkler to moisten the leaves will also help prevent excess transpiration and abate dry spells.

2. Overwatering Issue

Too much watering will drown the Squash roots, preventing the plant’s supply of oxygen and nutrients.

Overwatering causes yellowing leaves and losing new growth simultaneously. The wilting of foliage, browning leaf, and edema (blisters) will indicate a severe overwatering problem.

An overwatered Squash plant is less likely to bear new fruits or maintain a healthy-looking yield due to root rot.

Generally, you should provide 1-2 inches of water per week to Squash to prevent dry spells and maintain healthy water intake.

Excess watering is less likely to be processed by the overgrowing Squash roots.


  • Immediately cut back on watering and wait for the plant leaves to revive.
  • It may be best to uproot the plant to detect root rot and discard them before it spreads to adjoining Squash plants.
  • For potted plants, transplant the Squash into the soil with good drainage.

As a precaution, insert your finger about a few inches into the soil to check for moisture. Water only when it feels dry.

3. Lack of Sunlight

These hardy plants thrive in full sunlight, at least 6-8 hours per day, to attain healthier growth of foliage and fruits.

Therefore, the lack of sunlight will affect chlorophyll production, leading to yellowed, pale leaves.

Similarly, the summer Squash would need temperatures above 70°F to maintain healthier growth.

Keep an eye out for long, lanky leaves and paler foliage to identify a sun-deprived Squash plant.

Check out for droopy squash leaves which indicates sunlight problems
Check out for droopy Squash leaves, which indicate sunlight problems.


  • Start with removing severely wilted and discolored Squash plants from the garden.
  • Transplant the affected plants to the entire sunlight area in the garden by uprooting them and planting them in the south-facing window or area.
  • Consider keeping them outdoors or near the window that receives at least 6 hours of sunlight for potted plants.

However, too much sunlight, usually during summer, can damage the plant, requiring introducing some shade.

4. Iron Deficiency

Iron deficiency is a serious condition for garden plants like Squash which need it in excess to produce chlorophyll.

Without an adequate supply of iron, Squash plants will produce bright yellow leaves that may look suspicious.

Iron Deficiency will ultimately reduce plant vigor and affect fruit production. Remember, vegetables experiencing iron chlorosis will produce low-quality fruits.

Check for a bright yellow shade on the youngest leaves and whether the area between the leaf veins is yellow or white.

However, there is more than one reason your Squash plant fails to obtain enough iron from the soil.

  • Higher soil pH
  • Compacted soil
  • Leaching of nutrients
  • Reduced phosphorus in soil


  • Use a liquid iron (iron sulfate or chelated iron) to spray directly onto the leaf to treat iron chlorosis.
  • Otherwise, add granulated chelated iron to the soil to provide an instant iron boost.
  • If alkaline soil is the concern, add elemental sulfur or aluminum sulfate to reduce the pH level.
  • Fertilize your plants with 10-10-10 solutions once every month.
  • Use plant food with added micro and trace nutrients to boost iron and magnesium contents.

Buy the best Squash fertilizers in the market, such as Miracle-Gro All Purpose, Miracle-Gro Shake n Feed, or Osmocote Flower & Vegetable Food.

5. Vine Borer Infestation

Did you know vine borers are moths that lay eggs on leaf stalks and later become caterpillars to feed n the leaf?

Indeed, vine borers are the biggest threat to Squash plants as they become prevalent in the growing season (early to mid-summer).

One of the earliest indications of pest infestation is yellowed leaves from the vine’s base to the tip.

Wilting leaves and a small pile of sawdust at the vine’s base may also indicate vine borer infestation.

Check out spring copper-colored eggs on Squash plants to determine whether the vine borer has laid any eggs.

These eggs will hatch after 9-11 days, upon which they will claw inside the plant stem and begin eating it.

Squash vine borer will puncture and eat leaves
Squash vine borer will puncture and eat Squash leaves.


  • The general pesticide will not work against vine borer, requiring removing the pest from the stem altogether.
  • Cut a slit in the vine, remove the borer, and cover the stem with soil.
  • Locate the visible borer and pierce it using a toothpick to kill it.
  • Spraying diatomaceous earth around the infected stalk can also help kill vine borers.
  • As a last resort, use chemical insecticides, including active contents like carbaryl, permethrin, and bifenthrin.

6. Mosaic Virus

Squash Mosaic Virus (SqMV) is prevalent worldwide, where weeds, infected seeds, and soil spread it.

You would mostly witness chlorotic mottle, green vein banding, and distortion of Squash leaves. The intense dark green mosaic and blistering will appear on leaves severely affected by SqMV.

Your garden-grown Squash is not free from SqMV disease and is always at risk of acquiring it one way or another.

Sometimes, the cucumber beetles carry the Squash mosaic virus to your garden. Other times, the infected tools will also spread the virus.


  • Start removing the infected plants, including the roots, and discard them immediately.
  • Using natural pest control such as neem oil and diatomaceous earth reduces the number of disease-carrying pests.
  • Monitor the rest of the plant closely to determine any infected plants.
  • As a precaution, disinfect your tools every time before use and remove weeds from the garden.
  • Moreover, use certified virus-free Squash seeds every time.

7. Bacterial Wilt

Although rare, your Squash plants are not free from the risk of bacterial wilt caused by the bacterium Erwinia tracheiphila.

Check out for leaves turning dull green that begin to turn yellow, wither, and eventually die.

Similarly, diagnose the plant by cutting off a piece of stem and squeezing out some juice for slimy or oozing contents.

Like the mosaic virus, bacterial wilt in Squash is spread by cucumber beetles that feed on infected plants.

Sometimes, using infected tools may also lead to bacterial wilt.


  • Start by destroying the infected plants by uprooting and burning them to prevent further spread.
  • Applying pyrethrin insecticide can effectively manage cucumber beetles to prevent further infection.
  • As a precautionary measure, always use certified disease-free Squash seeds.

Cucumber plants may also witness leaf yellowing due to similar problems so learn the causes and fix it as soon as possible.

Should you Cut Yellow Squash Leaves?

Cutting off Squash leaves will open the plant’s vascular system to further bacterial and virus spread.

Moreover, the large leaves act like sunscreen for the fruit, saving it from excess sunlight and heat.

In any case, removing Squash leaves can be a bad idea as it stresses out the plant.

Therefore, you may need to keep the plant leaves intact to ensure healthier fruit production.

In the case of infected plant leaves with excessive yellowing, consider pruning off vines that are not the main stem. Removing them will not do much harm to the plant or the fruits.

Learn here how you can increase the yield of Squash through this video below!

Final Thought

Squash are low-maintenance veggies that you can quickly grow in your garden, whereas summer Squashes are even ready to harvest within 60 days.

However, pay attention to yellowing or discolored foliage which indicates different problems with the plant.

Follow this guide to effectively diagnose your Squash plant’s yellowing leaves and apply appropriate treatments.