There are three major concerns: powdery mildew, late-season blossom end rot, and a final wave of pests. This article will review these three issues and end with tips for knowing when your squash is ready to pick. (https://extension.umn.edu/vegetables/pumpkins-and-winter-squash). 

Powdery Mildew

Photo credit: University of Maryland Extension

https://extension.umd.edu/resource/key-common-problems-squash/

The first concern is powdery mildew. It is a fungal infection often caused by overwatering, and inadequate air flow. It lives in plant debris and may spread from other infected plants. Powdery mildew on flowers, for example, will not infect squash as the fungi are host specific. But the presence of powdery mildew on another plant is a warning that conditions are prime for infections to occur on other plants. Warm days and cool nights that may still be humid contribute to the development of powdery mildew. If you don’t address it, it can speed up leaf death and that can expose your still developing squash to sunscald. Loss of leaves can also starve the plant as it now lacks the ability to generate energy needed to support the ripening squash. To avoid this problem in future years, you will want to ensure good end of season garden clean-up by removing and destroying infected plant debris as it can host spores that survive over winter. Source : https://hort.extension.wisc.edu/articles/powdery-mildew-vegetables/ 

Blossom End Rot

The next concern is blossom end rot. You may have heard of this problem in relation to tomatoes but it is a problem that occurs in several other vegetables, including squash. The cause of blossom end rot is a calcium deficiency due to inconsistent watering. Plants need water to help them move the calcium into their system. The way to prevent blossom end rot is to continue to water your plants consistently as your squash is 

forming and ripening.

Late Season Pests

Finally, continue to be vigilant about pests on your squash plants. Squash bugs and cucumber beetles are focused on getting ready for winter and are seeking shelter and sugar. They often gather in large groups under the yellowing squash leaves and may even be found on the skin of the squash, which will result in rinds that are scarred. Other articles in previous Garden Buzz issues have discussed the types of pests that may be of concern, including squash bugs, and how to prevent and manage them, e.g., hand picking them off. 

Problem Solving

You can take actions to lessen end of season problems that may threaten your squash harvest. First, prune your squash plants for sunshine and airflow. Grab your shears and aggressively remove dead, yellow, or heavily mildewed leaves. Open up the canopy. This increases airflow to dry out morning dew and allows the weaker autumn sun to hit the fruit directly, accelerating the ripening process. Leave as much healthy foliage as possible so squash are not completely exposed to the sun. 

To avoid having your squash rot as it rests on the ground, prop them on something like a brick, flat stone, or upside-down containers. This can help break up the ‘pest highway’ and reduce the risk of fungal rot. 

Harvesting and Storage

You’ve done everything you can to protect your squash and finally it is time to harvest them. But when is the right time? You can ‘Perform the Thumbnail Test’ by pressing your thumbnail firmly into the rind. If it leaves a deep indentation or punctures the skin, the squash is not mature enough to store and must stay on the vine. If the skin is rock-hard and resists your nail, it is ready for harvest. Always cut the stem with pruners, leaving a two-inch "handle" to prevent rot from entering the fruit.

Harvesting your winter squash is only half the battle. To ensure your squash stay fresh and delicious well into winter, you must properly cure and store them. This process thickens the skin, heals minor scratches, and concentrates the natural sugars. To cure winter squash, move them to a warm, dry room with good air circulation for 10-14 days. Ideal temperatures are between 70°F and 80°F (21°C to 27°C). Lay them in a single layer. Do not let them touch each other. Acorn squash is an exception, as heat destroys its quality. Instead of curing it, move it straight to storage. 

Once the squash is cured, store them in a cool, dark, and dry space like a pantry, root cellar, or unheated closet. Keep the room between 50°F and 55°F (10°C to 13°C). Never let them freeze, and avoid cold garage floors and bare concrete floors because they draw up moisture. Instead, store them on shelves or in slatted crates. When stored properly, you will be able to enjoy your: 

• Acorn Squash: 1 to 2 months

• Spaghetti Squash: 2 to 3 months

• Butternut Squash: 3 to 6 months

• Hubbard & Pumpkins: 5 to 6 months

Follow these end of season tips and enjoy your home-grown squash!