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Butternut Squash pests and diseases

Published: 09.04.2023
pest/disease type symptoms on butternut squash control/prevention
Squash Bug Insect Punctured leaves, wilting, discoloration, stunted growth, fruit damage Hand-picking, crop rotation, use of insecticidal soap
Squash Vine Borer Insect Wilting, discoloration, frass on stems, holes in stems Crop rotation, use of row covers, insecticidal spray
Powdery Mildew Fungal Powdery white coating on leaves, stunted growth, fruit damage Regular pruning to improve air circulation, use of fungicidal spray
Fusarium Wilt Fungal Yellowing leaves, stunted growth, wilting, fruit damage Crop rotation, use of fungicidal spray
Anthracnose Fungal Dark spots on leaves and fruit, wilting, stunted growth Crop rotation, use of fungicidal spray
Downy Mildew Fungal Yellowing leaves, white fuzz on undersides of leaves, stunted growth Regular pruning to improve air circulation, use of fungicidal spray
Cucumber Mosaic Virus Viral Mottled leaves, stunted growth, deformed fruit Use of disease-resistant varieties, removal of infected plants
Blossom End Rot Physiological Dark, sunken spots on the bottom of fruit Regular watering to maintain consistent moisture levels, use of calcium supplements
Spider Mites Insect Yellowing leaves, webbing on leaves and stems, stunted growth Use of insecticidal soap or neem oil, regular spraying with water to remove mites

Squash Bug

Squash bugs are a common pest that can attack butternut squash plants. These bugs are usually gray or brown and have a flat, shield-shaped body that is about 5/8 inch long. They can cause significant damage to the plant if left untreated.


The first sign of a squash bug infestation is usually wilting or browning leaves. This happens because the bugs feed on the plant's sap, which can cause the leaves to wilt and eventually die. Squash bugs also lay their eggs on the underside of leaves, which can lead to a sudden surge in the population.

Control or Prevention

There are several ways to control or prevent squash bug infestations. The first step is to inspect your plants regularly for signs of damage or eggs. If you find any eggs, remove them immediately. You can also try using row covers to prevent the bugs from getting to your plants in the first place.

If you already have an infestation, you can try using insecticides that are specifically designed to kill squash bugs. These should be used sparingly and only as a last resort, as they can harm beneficial insects as well.

Another effective method of control is handpicking the bugs and dropping them into a bucket of soapy water. This may take some time and effort, but it is an effective way to reduce the population without using harmful chemicals.

In conclusion, squash bugs can be a major problem for butternut squash plants, but with proper prevention and control measures, they can be managed effectively.

Squash Vine Borer

The Squash Vine Borer is a common pest that attacks various types of squash, including butternut squash. This pest is the larvae of a moth, which lays its eggs at the base of the squash plant. When the eggs hatch, the larvae burrow into the stem of the plant, causing damage that can lead to wilting and eventually death of the plant.

Symptoms of a Squash Vine Borer infestation include wilting leaves and stems, as well as sawdust-like frass around the base of the plant. If you suspect your butternut squash plant has been infested with Squash Vine Borers, it is important to act quickly to prevent further damage.

Control and prevention measures for Squash Vine Borers include covering the base of the plant with a physical barrier, such as a nylon stocking or aluminum foil, to prevent egg-laying. You can also use insecticides containing Bacillus thuringiensis (Bt) or spinosad to control Squash Vine Borers.

It is important to note that prevention is key when it comes to Squash Vine Borers. Regularly inspect your butternut squash plants for any signs of infestation and take action immediately if you suspect an infestation has occurred. With proper care and attention, you can keep your butternut squash plants healthy and thriving.

Powdery Mildew

Powdery mildew is a fungal disease that affects a variety of plants, including butternut squash. The fungus thrives in warm and humid conditions, making it a common problem for gardeners during the summer months.


The symptoms of powdery mildew include a white or grayish powdery coating on the leaves, stems, and sometimes the fruits of the butternut squash plant. Infected leaves may also curl or become distorted, and the plant may appear stunted or weakened.

Control and Prevention

To prevent powdery mildew from affecting your butternut squash plant, you should ensure proper air circulation by spacing out the plants and avoiding overcrowding. Watering should be done in the morning to allow leaves to dry out during the day. You can also use a fungicide spray to prevent or control the disease. Organic options include neem oil or baking soda solutions.

If powdery mildew does occur on your butternut squash plant, remove and dispose of infected leaves and fruits immediately to prevent further spread. Fungicides should be applied early in the morning or late in the evening to avoid sunburning of the leaves. Regularly inspecting your plants for signs of disease and addressing any issues promptly is essential to maintaining a healthy garden.

Fusarium Wilt

Fusarium Wilt is a common fungal disease that affects Butternut Squash plants. The disease is caused by a soil-borne fungus that invades the roots of the plant, blocking the flow of water and nutrients to the leaves and fruits.


The first signs of Fusarium Wilt are yellowing and wilting of the leaves. As the disease progresses, the leaves may turn brown and crispy, and eventually fall off the plant. The fruits may also become discolored and develop sunken spots.

Control or Prevention:

Preventing Fusarium Wilt involves taking measures to minimize the spread of the fungus. This includes practicing crop rotation, using disease-resistant varieties of Butternut Squash, and maintaining proper soil drainage. Fungicides can be used to control the disease, but they are most effective when applied before symptoms appear. Infected plants should be removed and destroyed to prevent the spread of the fungus to healthy plants.

In conclusion, Fusarium Wilt is a serious disease that can cause significant damage to Butternut Squash plants. By taking preventive measures and monitoring your plants closely, you can minimize the risk of infection and ensure a healthy harvest.


Anthracnose is a common fungal disease that affects many plants, including butternut squash. The disease is characterized by the presence of small, circular or irregularly-shaped lesions on leaves, stems, and fruit. These lesions may be sunken or raised and can be brown, black, or tan in color. Over time, the lesions may enlarge and coalesce, causing the affected plant tissue to wither and die.

The fungus responsible for anthracnose can survive in soil and plant debris, making it difficult to control once it becomes established. However, there are steps gardeners can take to prevent the disease from taking hold. One important preventative measure is to avoid overhead watering, as the fungus thrives in moist environments. Instead, water at the base of plants using a drip irrigation system or a soaker hose.

If anthracnose does appear in your garden, prompt action is necessary to prevent its spread. Infected plant material should be removed and destroyed to prevent the fungus from spreading to healthy plants. Fungicides may also be used to control the disease, but be sure to read and follow all label instructions carefully.

By taking steps to prevent and control anthracnose in your garden, you can help ensure healthy plants and a bountiful harvest of butternut squash.

Downy Mildew

Downy mildew is a fungal disease that commonly affects butternut squash plants. The disease is caused by the pathogen, Pseudoperonospora cubensis, and thrives in wet and humid environments. Downy mildew can be a serious threat to the health of your butternut squash plants, so it's important to be able to recognize its symptoms and take appropriate action.


The first signs of downy mildew are yellow spots on the upper surface of the leaves. As the disease progresses, these spots turn brown and develop a fuzzy white or gray growth on the underside of the leaves. You may also notice stunted growth, wilting, and premature death of leaves.

Control and Prevention

Prevention is key when it comes to downy mildew. To minimize the risk of infection, make sure your butternut squash plants are planted in well-draining soil and spaced out adequately to promote good air circulation. Water your plants in the morning to allow leaves time to dry before nightfall, as wet leaves are more susceptible to infection.

If you suspect downy mildew on your plants, remove infected leaves immediately and dispose of them in sealed plastic bags. Fungicides containing copper can also be effective in controlling the spread of downy mildew. Be sure to follow application instructions carefully, as overuse can lead to copper toxicity in the soil.

Cucumber Mosaic Virus

Cucumber Mosaic Virus is a viral disease that can affect a wide range of plants, including butternut squash. It is primarily spread by aphids, but can also be transmitted through contaminated tools or plant debris.

Symptoms: The symptoms of Cucumber Mosaic Virus in butternut squash include stunted growth, yellowing and mottling of leaves, and distorted or malformed fruits. Infected plants may also show signs of wilting or leaf drop.

Control or Prevention: Unfortunately, there is no cure for Cucumber Mosaic Virus once a plant is infected. However, there are steps you can take to prevent the disease from spreading:

  • Remove and destroy any infected plants immediately to prevent the virus from spreading to healthy plants.
  • Control aphid populations by using insecticidal soaps or neem oil.
  • Avoid working with your plants when they are wet to reduce the risk of spreading the virus.
  • Plant disease-resistant varieties of butternut squash, if available.

Preventing the spread of Cucumber Mosaic Virus is crucial to protect your entire garden from this harmful disease.

Blossom End Rot

Blossom end rot is a common problem that affects butternut squash and other fruiting vegetables. This condition is caused by a lack of calcium in the plant, which leads to the death of the tissue at the blossom end of the fruit.

Symptoms: The first sign of blossom end rot is a small water-soaked spot on the blossom end of the fruit. As the condition progresses, this spot will become larger and turn brown or black. The affected area will become sunken and leathery, and the fruit may become distorted or misshapen.

Control or Prevention: To prevent blossom end rot, it's important to maintain consistent soil moisture levels and ensure that your plants are getting enough calcium. You can add calcium to your soil by using a calcium-rich fertilizer or adding crushed eggshells or bonemeal to the soil. It's also important to avoid over-fertilizing your plants, as this can disrupt their ability to absorb calcium. If you notice signs of blossom end rot, remove affected fruits immediately and adjust your watering and fertilization practices accordingly.

In conclusion, Blossom End Rot is a common problem that can be prevented with proper care and attention to your plants' needs. By monitoring soil moisture levels and ensuring adequate calcium intake, you can keep your butternut squash and other fruiting vegetables healthy and free from this damaging condition.

Spider Mites

Spider mites are a common pest that can infest butternut squash plants. These tiny pests are difficult to spot with the naked eye, but their presence can be identified by the fine webs they create on the leaves and stems of plants.

Symptoms of a spider mite infestation include yellowing leaves, brown spots, and stunted growth. As they feed on the plant's sap, they cause damage to the leaves and can reduce the overall health of the plant.

To control or prevent a spider mite infestation, it is important to regularly inspect your plants for signs of pests. You can also use natural predators like ladybugs or predatory mites to control the population of spider mites. Insecticidal soaps or oils can also be effective in controlling these pests.

In order to prevent future infestations, make sure to properly water and fertilize your plants to promote healthy growth. Additionally, keeping a clean garden by removing dead leaves and debris can also help prevent spider mites from taking over your butternut squash plants.

Author: Michael Chen
Bio: I'm gardening specialist with a mission to empower people to grow their own fruits and vegetables. With my background in Plant Science from the University of California and experience working with farmers and community gardens, I'm dedicated to promoting sustainable agriculture practices and helping individuals achieve bountiful harvests. Let's get growing!