Zucchini, a type of summer squash, grows best in warm, moist conditions, which makes it susceptible to numerous disease, insect, animal and fungal problems that can decrease yields or quickly kill the plant. Because zucchini depends on bees for pollination, use of pesticides must be limited, which further encourages insect problems.
Because zucchini is a short-lived annual, it must have the right growing conditions from the time the seed is planted to maturity. Anything that interferes with the growing process can affect yield and plant health.
Types of Problems
Types of zucchini problems include fungal diseases, insect and worm problems, animal pests, and poor pollination.
Fungal disease are of three types: fungal diseases that affect seed germination, fungal diseases that affect the plant after it is growing and fungal diseases that affect the fruit after it forms. Fungal diseases in seed are simple to diagnose because the seed does not sprout. A zucchini plant should sprout from seed in warm, moist soil within five days.
Powdery mildew affects the leaves of the plant anytime during the growing process. It looks like the plant was dusted with talcum powder. It thrives when night temperatures are around 75 degrees F.
Blight affects plants and fruit and shows up as brown sunken spots. The plant will suddenly die when affected.
Wet rot is another fungal disease, which appears as fuzzy gray mold on young fruit and blossoms.
The most common insects to affect zucchini plants are squash bugs and the squash vine borer. Squash bugs can be seen around the base of the plant and look like gray stink bugs. In a bad infestation they are seen in all stages of maturity. Leaves of affected plants are brown around the edges and may be wilted.
The squash vine borer burrows into the base of the stem. Excrement and plant dust is visible where the worm enters the plant. The plant will wilt or be near death.
Animal pests such as rabbits, squirrels, rats and raccoons leave small nubs where they break off the squash and carry it away.
Poor pollination results in deformed or non-existent squash.
If fungal disease is preventing seed germination, use seed that is treated with a fungicide before planting. Most non-organic seeds are treated. Seeds treated with a fungicide have a bright pink or bright green color.
Fungal diseases on growing and producing plants are prevented by planting in a well-drained area and avoiding overhead watering. Neem oil can be used to control powdery mildew. Apply every three days at first sign of powdery mildew.
Squash bugs are controlled by spreading pyrethrum dust around base of plants in the evening when bees are not active. Avoid applying pyrethrum dust to flowers or blossoms.
Kill squash vine borers by carefully slicing the stem of the plant and removing the worm. Cover wound and base of plant with soil. Piling soil around base of other plants will discourage infestations.
Control animal pests with an electric fence around the garden area.
Resolve poor pollination by encouraging bees to visit the garden by planting more flowering plants. Also, hand pollination can be done by taking a male flower, gently pulling off the flower petals, and dabbing the pollen onto the female flower. The female flowers are identified as the flowers with a tiny zucchini forming at their base. Zucchini plants produce male and female flowers on the same plant.
Organic growing methods are best for growing zucchini because of the risk to bees. Contact your county extension agent to find varieties that are best for your area. Plant at the right time of year and use natural or plastic mulch to keep the zucchini from resting on the ground. Don't use sulfur on zucchini plants for mildew problems as it causes the leaves to shatter. Control weeds around plants so bugs can't hide from natural predators.