6 Zucchini Diseases, Pictures, And Solutions

Fighting diseases is a part of gardening. If you plan to cultivate zucchini, make sure you know all the risks your crop may face and determine how to deal with them. 

Don’t know where to start? We will help. Our guide covers all the zucchini diseases, signs, preventions, and treatments. Let’s follow us and give your plants the best conditions! 

Common Zucchini Diseases

Infected parts can be the leaf, stem, or rot. No matter which area it is, the diseases will ruin the plant. Here are the most common ones. Please check and take note of the solutions. 

1. Cucumber Mosaic Virus

Cucumber Mosaic Virus, despite its name, affects other species too, and zucchini is among its targets. The virus severely stunts zucchini plants and reduces productivity by causing curving and a mosaic-like texture on the leaves. 

  • Signs

The first infection symptom is tiny, deformed zucchini fruits with harsh skins or weak, curved leaves. The leaves may also look lumpy, puckered, and cupped. On the surface, there may be a mild or prominent mosaic pattern in shades of yellow.  

  • Prevention

Some zucchini varieties, such as Desert, Yellow Fin, and Green Machine, are resistant to the virus. Growing them will reduce the likelihood of the Cucumber Mosaic Virus attacking your garden. 

You can also grow zucchini with fragrant herbs, garlic, and onions. These plants are good at keeping cucumber beetles and aphids away. 

Another way to prevent the virus is sanitation. After working with garden tools, always clean them with bleach or rubbing alcohol. This method can help limit the virus expansion.  

  • Treatment 

What if the virus has infected your plants? The first thing to do is remove affected plant areas. Then, mix neem oil, dish soap, and water to spray on the leaves. 

2. Powdery Mildew

The cause of powdery mildew on zucchini leaves is fungi, such as Erysiphe cichoracearum, Podosphaera xanthii, and Sphaerotheca fuliginea. They flourish in warm weather. 

Powdery mildew often results in more crop losses than other diseases. It also affects houseplants, like prayer plants and pothos. So how can you handle it? 

  • Signs

Your zucchini leaves have gray or white powdery dust, as if somebody had sprinkled flour on the plants. When the disease progresses, there will be larger white blotches, yellow dead leaves, and fuzzy mildewed stems.  

  • Prevention

Irrigation from the bottom is the most vital prevention strategy. Do not water your zucchini from above because it spreads quickly via rainfall. So keeping the zucchini leaves dry with drip irrigation and soaker hoses is essential. 

Maintaining sufficient plant spacing is another key to avoiding powdery mildew. You can use a wide spacing of 18-24 inches between the plants if your garden is extremely susceptible to fungal infections to maintain proper airflow between them.

Finally, try picking the cultivars that can resist the mildew. We recommend Sunglo and Dunja.  

  • Treatment 

The simplest solution is to cut off damaged leaves. Remember to throw them away so as not to spread the bacteria. You can also clean the leaf surface with neem oil to limit future infection. 

3. Verticillium Wilt

This cool-weather-loving disease can affect your zucchini crop. It often manifests itself around mid to late summer.

The disease has various odd traits that might make diagnosis challenging. Luckily, major seed suppliers offer some resistant cultivars. 

  • Signs

Due to the Verticillium fungus, zucchini leaves will wilt, go yellow, and perish. Sometimes, only one side of the plant wilts while the other half remains normal. 

  • Prevention

Choose the V-marked cultivars that are resistant to the fungus. Cleaning gardening tools and eliminating crop waste is also beneficial. 

  • Treatment 

Unfortunately, you can’t treat verticillium. The only solution is to remove the affected plants to prevent the fungus from spreading.  

4. Alternaria Leaf Blight

Alternaria cucumerina is an invasive fungus. It affects both cucurbits and brassicas. It endures the winter on damaged crop debris and blooms on wet leaf surfaces. 

  • Signs

This leaf disease first attacks older leaves before spreading to younger ones. Small, sharp, yellow, or brown patches with a yellow or green ring around them are its defining feature. 

The spots grow bigger and ultimately join together, causing the leaves to curve under and soon die.

  • Prevention

Only water your plants from the bottom. If rain is coming, cover your plants to prevent water from pouring aggressively on the leaves. 

Plus, always clean up the garden after harvesting your zucchini crop. Neem oil for foliar spraying may also help stop the disease. 

  • Treatment 

For Alternaria Leaf Blight, organic fungicides can be helpful. You can try compost tea, Equisetum tea, and copper sprayers. Some bio-fungicides, like Actinovate or Bacillus subtilis, can work. 

Additionally, remove the infected parts by cutting them at the base. Then, throw them in the trash to avoid disease expansion. 

5. Blossom End Rot

Blossom end rot is a very major problem that looks like a disease, although it technically isn’t. Actually, the end rot results from irregular watering or a lack of soluble calcium in the planting soil. 

  • Signs

Your plant has a blossom end rot if you see water-soaked, blackened spots on the bottom part of the blossoms. Brown, crumbled zucchini might develop when the bad end of the squash crawls up to the center.

  • Prevention

Make sure the squash beds are in good condition by giving them dolomite lime, gypsum, oyster shells, or crushed eggshells. 

For zucchini, steady moisture is also essential. Your plants don’t want to become dehydrated before receiving a large amount of water at once. Instead, employ irrigation timers to keep the soil at a constant moisture level that is neither too wet nor too dry. 

Cover it with leaves or straw to prevent the soil from getting too hot, sunny weather, or severe drought.

  • Treatment 

All you can do is select and eliminate the infected fruits when blossom end rot develops. Then, as previously said, improve the watering routines and treat your crop with nutritional fertilizers.  


We mention prevention methods for each disease because they ensure you can protect your garden at the highest level. As we often say, prevention is better than cure. 

And when mishaps occur, keep calm and follow our treatment guide to tackle the problem. Hopefully, you can save your crop. 

For any further information, please feel free to ask. Thank you for reading! 

For over eighty years the Wightman Family has been growing and selling fruits and vegetables at the farm.