Blossom Rot on Squash

Squash forms from large papery blossoms.

Blossom rot is a problem that affects squash and tomatoes. Although troubling, this problem is preventable and treatable. Blossom rot is not the same as blossom drop, in which flowers do not get pollinated and drop from the plant. Blossom rot affects the plant after fruit begins to form.

Identification

The first symptoms start at the blossom end of the squash. A dark spot appears on the squash and spreads, covering up to half the fruit. Lesions may also appear along the flesh of the squash.

Causes

Squash blossom rot is caused by a calcium deficiency. Calcium is one of the building blocks that feed the cells of the squash. This disease commonly affects the bottom or blossom end of the fruit, as it grows the fastest and needs the most calcium.

Prevention/Solution

Keep the soil evenly moist as your squash plant is growing. This will keep calcium levels in the soil at a stable level. Fertilize your soil with a low nitrogen fertilizer before you plant your squash. Too much nitrogen will cause the leaves to grow quickly, using the calcium in the soil for that activity and leaving little for the fruiting.

Treatment

You cannot save a squash once blossom rot has begun. The vegetable is still edible, but the flavor will be diminished. Pick infected fruit and spray the remaining plants with a calcium-rich foliar spray to prevent further damage.

References

• Cornell University Vegetable MD Online: Blossom End Rot
• Gardening Know How: Squash Blossom End Rot Causes and Treatment