Common Disease Problems
Alternaria Leaf Spot: Small, round reddish brown spots, usually with a yellow halo, form on the upper surface of the leaves. Severely infected leaves turn brown, curl upward, wither and die. Fruit are not usually infected but can suffer from sunscald due to leaf loss. This disease is worse in warm, wet or very humid weather. Burpee Recommends: Avoid getting water on the foliage. Remove infected plant parts and do not work around wet plants. Provide plenty of air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Anthracnose: This is a fungus disease that attacks the fruit as it is ripening. Irregular brown spots develop on the leaves. Infected fruit develop sunken black spots that may have white mycelia during wet weather. The spots enlarge and turn black; the fruit rots. Extended periods of heat and humidity facilitate anthracnose growth. The fungus overwinters in diseased plant debris. Burpee Recommends: Provide sufficient space between plants for good air circulation, avoid overhead watering which can spread the fungus spores, keep a clean garden, remove and discard all diseased plant material and rotate crops.
Bacterial Wilt: Leaves turn brown, stems wilt and shrivel, the infected plants die. Burpee Recommends: Remove and destroy plants showing signs of the disease. Control cucumber beetles, which spread the disease. Contact your Cooperative Extension Service for recommendations.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Seed Rot and Damping Off: This is a fungus disease that affects seeds and seedlings. Infected seeds will not spout. Infected seedlings can have brown thin stems and the plants will quickly die. Burpee Recommends: Do not sow seeds until the soil has warmed to 65 degrees. Plant seeds in a raised hill that will warm up earlier. Keep beds moist but not water logged.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cucumber Beetles: Beetles may be spotted, striped or banded and can be very harmful. Beetles are usually ¼ to ½ inch in size. Beetles start feeding as soon as they hatch and can kill or slow the growth of the plants. Beetle larva can also bore through the roots of the plants. Beetles can also transmit diseases from plant to plant. Burpee Recommends: Knock off adults into a jar of soapy water and destroy them. Spade the soil to destroy dormant beetles before you plant. Use a row cover to prevent adults from feeding on young plants. Consult your Cooperative Extension Service for insecticide recommendations.
Squash Bugs: Adults are 5/8 inch long and gray or brown. Squash bugs give off a foul odor when crushed. Young nymphs have light green abdomens and black heads and legs. As the nymphs grow they will change color. Eggs are found in groups on the underside of leaves eggs will be yellow or brown. Squash bugs will feed on leaves and fruit. Burpee Recommends: Brush off adults into a jar of soapy water and destroy them. Check for clusters of eggs on the back of leaves and destroy them. Use a floating row cover to prevent females from laying eggs on plants.
Spider mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.
Misshapen Fruit: Cucumbers can become round or misshapen when they receive too much water. Burpee Recommends: Mulch to help moderate moisture levels.
Why does my fruit have a bitter or poor flavor? Bitter flavor can be caused by a number of factors including: hot and dry temperatures, overwatering, or poor soil fertilizer. Cucumbers have shallow roots; make sure the soil is moist but never waterlogged. Test your soil for a nutrient deficiency.
Why do I have lots of leaves but no flowers? The plant is likely getting too much nitrogen, which triggers it to grow foliage, and not enough phosphorus, which favors flowering and fruiting. Choose a fertilizer that has a balanced ratio of the three major elements, such as 10-10-10, or where the middle number (phosphorus) is larger than the first number (nitrogen) such as 2-3-1.
Why do I have flowers but no fruit? Cucumbers are “Dioecious”, meaning that they have both male and female flowers on the same plant. Male flowers usually open first and female flowers have a baby fruit behind the flower. Both types of flowers must be present to have fruit set. Flowers may abort because of heat or cold or drought stress OR flowers abort because of a lack of pollination OR the plant is not ready to set fruit and the plant is self-aborting flowers to conserve and direct energy towards more growth.
Why did my green cucumbers turn yellow? The fruit has over matured and must be removed. An over ripen fruit is usually bitter. Pick fruit as soon as it is the right size to use.
Why are my cucumbers curved? Incomplete pollination of the female flower will cause deformed, curved growth, as can drought stress and being grown on the ground. Training plants on a trellis is the best way to ensure long, straight cucumbers.