Zucchini Plant Fungus


Cucurbita pepo, more commonly known as zucchini, belongs to the family Cucurbitaceae and is a kind of summer squash that is coveted by home gardeners for its tender, edible skin and quick growth. Even though zucchini plants are generally simple to cultivate and take care of, they are susceptible to three types of fungal infections: plectosporium blight, downy mildew, and powdery mildew. These are the same types of fungal infections that commonly affect a wide variety of other Cucurbit species.

Plectosporium Blight

Pumpkin and squash plants are susceptible to a fungal illness known as Plectosporium blight, which is caused by the Plectosporium tabacinum fungus and may be found in decomposing plant matter and soil. The leaf veins, stems, and fruits of zucchini plants can all become infected with this fungus, which can be recognised by its telltale symptoms and cause of infection. Diamond-shaped stem and leaf vein lesions are modest and white initially, but eventually combine and cause the whole surface of the leaves to become white. Defoliation and ultimate death of leaves and stems caused by a severe infection are also possible outcomes. Lesions on the fruit are more spherical and continue to be modest even if they are there.

Powdery Mildew

Powdery mildew is a fungal disease that affects zucchini plants, as well as cucumbers, muskmelons, gourds, and pumpkins. It is one of the most common diseases that affect cucurbits. Podosphaera xanthii, a species of the fungus Golovinomyces cucurbitacearum, is often responsible for its development; however, Golovinomyces orontii and Golovinomyces cucurbitacearum are other potential culprits. Patches of white mycelium on the top and lower leaf surfaces, petioles, and stems of your zucchini plant are a telltale sign that the plant is infected with powdery mildew and is suffering from the disease. These white spots spread quickly and combine with surrounding ones to generate a powdery white covering. In the event of a serious infection, the leaves will first become yellow, then brown, and finally shrivel up. Powdery mildew will often begin to show up on older leaves first, and once it does, it will be spread by the wind to other leaves and plants.

Downy Mildew

According to the University of California Extension, downy mildew, caused by the fungus Pseudoperonospora cubensis, affects all cucurbits and is more prevalent in circumstances that are wet and chilly. These conditions are more typical later in the growing season. The first sign of downy mildew on your zucchini plant will be the appearance of small, angular spots that range in colour from light green to yellow. The dots give the leaf foliage a mottled look and eventually blend together to form larger patches. The damaged leaves may gradually become brown, and the undersides may be covered with a growth that ranges in colour from white to purple. The elder leaves of a plant are generally the first to be affected by downy mildew, which may spread to other parts of the plant through the wind or by water splashes.


Good cultural practises, such as keeping the garden free of weeds and debris and controlling insect pests that can spread disease, such as aphids, mealy bugs, and other honeydew-secreting insects, are often effective in preventing Plectosporium blight and mildews from developing on zucchini plants. This is especially true of mildews, which are caused by Plectosporium blight. Mildews may be further managed or avoided by ensuring that your plants get appropriate hydration and that there is adequate air circulation around them. Plectosporium blight may be efficiently controlled, according to research conducted by Cornell University, by using either the fungicide chlorothalonil or the pesticide trifloxystrobin. For the most efficient management of powdery mildew, use a fungicidal treatment with trioxystrobin, myclobutanil, azoxystrobin, or a combination of boscalid and pyraclostrobin. Fungicides that are not systemic, such as sulphur and copper, have the potential to provide some level of control. Fungicides such as cyazofamid, flupicolide, propamocarb, mefenoxam, famoxadone and cymoxanil, fenamidone, mancozeb, or chlorothalonil should be used as soon as the signs of a downy mildew infection manifest, and the treatment should be repeated if the symptoms grow more severe. Handling, application, and disposal of fungicides should always be done in accordance with the product label.