Zucchini Leaves Turning Yellow – Why Are The Leaves on My Zucchini Plant Turning Yellow

Zucchini leaves turning yellow may be a recurrent problem when growing zucchini. Yellow leaves on the zucchini plant can be caused by several different factors. Some common causes of zucchini yellowing leaves are related to water issues, nutrient deficiencies, and pests.

To diagnose what causes yellow leaves on zucchinis you should take a look at all the plant leaves. Although it is not accurate 100%, this tip could be helpful. If only a few leaves are turning yellow is likely due to pests or disease. If all the leaves are turning yellow then it is probably a water issue or a nutrient deficiency. Let’s move forward to understand What Causes Yellow Leaves On Zucchini Plants.

yellow leaves on squash plants
Zucchini Leaves Turning Yellow – Why Are The Leaves on My Zucchini Plant Turning Yellow – Some common causes of zucchini yellowing leaves are related to water issues, nutrient deficiencies, and pests. . If only a few leaves are turning yellow is likely due to pests or disease. If all the leaves are turning yellow then it is probably a water issue or a nutrient deficiency.

Zucchini Leaves Turning Yellow – Zucchini Care Tips

Firstly, for a good diagnosis of what causes yellow leaves on zucchini plants, you should review the following care tips this plant needs.

Overwatering, lack of sun, and lack of nutrients are common causes of zucchini leaves turning yellow and any plants.

Being a plant that develops quite a lot, the distance between zucchini plants must be large or plant zucchini on a trellis to make the most of the space in our garden.

When planting zucchinis in the ground, plants should be separated by 35” and 40” (90 cm and 100 cm) between them. Be sure to double-check the distance between zucchini plants. Otherwise, the lack of sunlight reaching the leaves would result in yellow zucchini leaves.

As far as major maintenance goes, I trellis and prune the zucchini plant to increase aeration and ensure that fungus does not impact it by being far from the ground.

Zucchinis are a low-maintenance crop that may produce a large harvest if properly watered. Watering should be done on a regular basis to minimize water stress in the plant, which might cause the flowers to fall off before fruiting.

When the zucchini plant begins to form fruit, we should try to increase the amount of water per irrigation. Always be careful not to flood the soil because it can rot the fruits or even lead to the appearance of fungi. Overwatering causes yellowing leaves on zucchini.

Zucchini Leaves Turning Yellow – Why Are The Leaves on My Zucchini Plant Turning Yellow
Zucchinis are a low-maintenance crop that may produce a large harvest if properly watered. When the zucchini plant begins to form fruit, we should try to increase the amount of water per irrigation. Overwatering causes yellowing leaves on zucchini.

Yellow Leaves on Zucchini Plant

Yellow leaves on Zucchini Plant. The Zucchini plant is one of the most prolific and easy-to-grow crops. They grow quickly and easily in the garden, especially on a trellis, guided by our help.

However, it can happen that at some point yellow leaves, yellow spots on zucchini leaves, and even yellow and curled leaves appear on the zucchini plant. These chlorotic leaves can appear for different reasons.

Below you will find out what causes yellow leaves in zucchini, how to solve it, and how to prevent it for future zucchini crops.

Zucchini Leaves Turning Yellow Due to Lack of Sun

Zucchini Leaves Turning Yellow Due to Lack of Sun. Sunshine is essential for the development of zucchini.

Zucchini requires a lot of sunlight to grow and develop properly. You should place zucchini in a place where they receive at least six hours of direct sunlight, ideally eight hours.

To avoid having yellow leaves on zucchini plant due to lack of sunlight, you should choose the right place to plant your zucchini to make sure it gets enough sunlight.

If you have a potted zucchini, just move it to the best spot with plenty of sunlight. If the zucchini gets enough sunlight, zucchini will not have problems with yellow leaves due to lack of sun.

Zucchini Leaves Turning Yellow  Due to Watering

Zucchini Leaves Turning Yellow  Due to Watering. Zucchini is a plant that consumes a lot of water and the soil must therefore be able to meet this high demand. Either through rainwater, irrigation, or, more often, both. Overwatering causes yellow leaves on zucchini plants.

Depending on the type of soil in question, it will be necessary to act in one way or another to ensure that constant humidity is maintained near the zucchini plant.

I would recommend making frequent irrigations of low intensity. How often watering zucchini depends on the type of soil, location, and temperature.

Watering should be less frequent in soils rich in organic matter or clay, because this type of soil retains more water. In contrast, in sandy soils that retain almost no water, watering should be very frequent and of very low intensity.

That is why we must water the zucchini plant correctly, as overwatering will rot the roots and insufficient watering will dry it out due to lack of water. Inadequate watering will produce yellow leaves on zucchini.

Zucchini Leaves Turning Yellow Due to Nutrient Deficiencies

Zucchini Leaves Turning Yellow Due to Nutrient Deficiencies. Zucchini needs a certain amount of nutrients to develop properly. A lack of nutrients will cause the zucchini to have yellow leaves on zucchini plant.

We recommend always checking the quality of the soil before planting zucchini.

The Zucchini plant adapts quite well to soils with pH values between 5 and 7, although prefers slightly acidic soils, with average values between 5.6-6.8.

Zucchini Leaves Turning Yellow Due to Nutrient Deficiencies
Zucchini Leaves Turning Yellow Due to Nutrient Deficiencies. Zucchini plants need fertilization twice during the life cycle. The first fertilization is before planting or sowing the zucchini seeds while preparing the soil to place the seeds. The second fertilization needed is when the zucchini plant is blooming.

Deficiency symptoms may emerge with a basic pH. However, they can be rectified with macro and microelements. First, check the pH of the soil to determine whether it has to be adjusted.

Zucchini crops need nutrients to develop properly, without the necessary nutrients the zucchini plant will not develop properly and will be more susceptible to pests and diseases.

Yellow leaves on zucchini plant due to lack of nutrients. Iron and calcium deficiency are the most common nutrient deficiency in plants that cause yellow leaves on zucchini plants. If the zucchini plant has the necessary nutrients it will not have problems with yellow leaves.

With an NPK 4-4-4 or NPK 4-6-4 fertilizer, the zucchini plant will have the necessary nutritional supply for correct growth.

Zucchini plants need fertilization twice during the life cycle. The first fertilization is before planting or sowing the zucchini seeds while preparing the soil to place the seeds. The second fertilization needed is when the zucchini plant is blooming.

Zucchini Leaves Turning Yellow due to lack of nutrients is easy to fix by adding a suitable fertilizer for the zucchini plant. I recommend removing yellow leaves on the zucchini plant and verify the soil pH is suitable for the plant.

Yellow Leaves on Zucchini Due to Pests and Diseases

The presence of pests and diseases is one of the most common causes of yellow leaves on zucchini plants, as in any type of plant.

In the case of zucchini plants, the leaves are susceptible to infection by bacteria, fungi, and viruses and can also attract certain non-beneficial insects to our gardens such as aphids and spider mites.

In the next paragraphs, we will review what causes yellow leaves on zucchini plants related to pests and diseases and how to fix yellowing leaves and prevent them.

Yellow Spots on Zucchini plants Due to Bacteria Pseudomonas syringae (Angular leaf spot of Cucurbitaceae)

Yellow Leaves on Zucchini plant Due to Bacteria Pseudomonas syringae. The angular spot of Cucurbity is a disease that affects yellow zucchinis or squash, and green zucchinis, among other fruits, which is caused by the bacteria named Pseudomonas syringae.

Yellow Spots on Zucchini plants
Yellow Spots on Zucchini plants Due to Bacteria Pseudomonas syringae (Angular leaf spot of Cucurbitaceae)

The first sign of the infection with Pseudomonas syringae is yellow spots on zucchini leaves.

Yellow Spots on Zucchini plants
Yellow Spots on Zucchini plants Due to Bacteria Pseudomonas syringae (Angular leaf spot of Cucurbitaceae)

Yellow spots appear on zucchini leaves and progress turning yellow the entire leave. It affects Cucurbitaceae (zucchini, yellow zucchini squash, melon, watermelon, pumpkin, etc.). The yellow spots on zucchini leaves spread until they are delimited by the nerves of the leaves.

How to Prevent Yellow Leaves Caused by Pseudomonas syringae

Here are a few tips to prevent yellow leaves on zucchini caused by Pseudomonas syringae

  • Use only good commercial quality seeds and certified sterile, preferably.
  • Control the humidity in the surroundings to preserve zucchini seeds.
  • Remove unhealthy leaves and plants as soon as the first indications of yellow leaves are noticed. Discard them to get rid of the germs and keep other crops from being infected.
  • Fungicide Copper treatment at an early stage may prevent the disease caused by this bacteria.   

Yellow and Curled Leaves on Zucchini plant Due to Mosaic Virus ZYMV

Yellow and Curled Leave on Zucchini plant Due to Mosaic Virus ZYMV. One of the most commercially important viruses in cucurbit crops is the Zucchini Yellow Mosaic Virus (ZYMV) causing initially yellowing leaves on zucchini.

Mosaicism, blistering of the leaf lamina, deformation, and knobbed fruits are all symptoms of the ZYMV, as well as a wide variety of biological diversity.

Cucurbita pepo‘s summer crop and the winter zucchinis Cucurbita maxima and Cucurbita moschata are all affected by the ZYMV.

Diseases that target the roots, leaves, and fruit of cucurbits are common. Zucchini yellow mosaic virus (ZYMV) is a common viral pathogen that reduces the quality and yield of zucchini and the other crops it can affect (see reference).

What causes yellow leaves on zucchini plants? Infection with the Zucchini yellow mosaic virus (ZYMV) is manifested by the initial appearance of yellow and curled leaves on zucchini plants.

As a result, looking at the leaves is a vital indicator of whether or not the zucchini plant is infected with mosaicism. You’ll notice that the zucchini leaves become yellow and become curled.

The major challenge during this zucchini plant infection caused by ZYMV is that it spreads very rapidly to other surrounding crops.

How to Fix Yellow and Curled Leaves on Zucchini plant Due to Mosaic Virus ZYMV

How to Fix Yellow and Curled Leaves on Zucchini plant Due to Mosaic Virus ZYMV. There is no way to heal the plant.

However, it is possible to prevent controlling aphids and stop the progress of the disease around the infected zucchini with yellow leaves

When aphids feed on the underside of the plant’s leaves, they transmit the illness. Aphids transmit the mosaic virus, which causes reduced growth on zucchini plants, as demonstrated by yellowed and bent leaves, as well as poor fruit development.

We may, however, try to halt the disease’s progression by removing and killing any diseased plant components.

Additionally, aphids should be checked on the plants, stems, and below the leaves. As previously said, treat your plants with neem oil for plants as soon as you notice aphids.

Yellow Leaves on Zucchini Due to Spider Mites

Yellow Leaves on Zucchini Due to Spider Mites. Spider mites suck sap from leaves and cause zucchini leaves to turn yellow.

How to Fix Yellow Leaves on Zucchini plant Due to Spider Mites

How to Fix Yellow Leaves on Zucchini Due to Spider Mites. Here is the step-by-step to eliminate yellow leaves in zucchini plant due to spider mites:

  • Apply neem oil to the plants.
  • Spray the leaves from top to bottom, including the underside. Our video on how to apply neem oil to plants can be found here.
  • When spider mites are a recurring problem, introducing ladybugs that eat spider mites might be a viable ecological remedy (for aphids as well).

Yellow Leaves on Zucchini Due to Fusarium Wilt

Why Are The Leaves On My Zucchini plant Turning Yellow – Fusarium Wilt

Another disease that can cause zucchini plants to have yellow leaves is Fusarium Wilt, which is caused by the mold Fusarium. Beetles can carry the spores, which reside in the soil.

How to Prevent Yellow Leaves on Zucchini Due to Fusarium Wilt

How to Prevent Yellow Leaves on Zucchini Due to Fusarium Wilt. Fungicides are useless after the plant has been infected.

It is not possible to fix plants affected with Fusarium Wilt but we can prevent it to happen again. Remove and destroy infected plants to get rid of the Fusarium mold.

To prevent this from happening again, the soil must be treated with fungicide. Otherwise, Fusarium spores live longer in the soil and will infect your next crop.  

planting zucchini on a trellis
About Julia Morgan

We are the Morgan family, Henry, and Julia, both agronomists from the University of Michigan, where we met. We are experts in putting our hands in the soil and developing organic foods and improving production processes for decades. Likewise, we have worked for companies such as Mondelez International, BASF, Monsanto, etc. currently in our role as science writers for TheGardenStyle.com as well as advisors in promoting large scale food growing in urbanized areas. In this website, we share what we are most passionate about, gardening and farming. Enjoy and see real photos on our website. We hope that all our advice will be useful to you and that you will become an expert gardener.