Common Disease Problems
Cercospora Leaf Blight: Small flecks which develop a yellowish halo appear on the leaves and turn brown and coalesce. They cause the leaves to wither and die. Burpee Recommends: Remove infected plants and destroy all plant debris. Rotate crops.
Damping Off: This is one of the most common problems when starting plants from seed. The seedling emerges and appears healthy; then it suddenly wilts and dies for no obvious reason. Damping off is caused by a fungus that is active when there is abundant moisture and soils and air temperatures are above 68 degrees F. Typically, this indicates that the soil is too wet or contains high amounts of nitrogen fertilizer. Burpee Recommends: Keep seedlings moist but do not overwater; avoid over-fertilizing your seedlings; thin out seedlings to avoid overcrowding; make sure the plants are getting good air circulation; if you plant in containers, thoroughly wash them in soapy water and rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes yellow spots on the upper surface of the leaves, and whitish gray patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Powdery Mildew: This is a fungus disease that causes a white powdery look on the foliage. This disease weakens plants as it inhibits their ability to make carbohydrates for themselves using sunlight. Burpee Recommends: You can remove infected plant areas, increase air circulation, and try to reduce the humidity in the room. Check with your Cooperative Extension Service for fungicide recommendations.
Rust: Lesions on the leaves are light green and become chlorotic. Yellow-orange pustules are seen on the underside of the leaves. Plants may become distorted. Burpee Recommends: Check with your Cooperative Extension Service for fungicide recommendations.
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 who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Armyworm: Holes in leaves can be singular or clumped together. Leaves can become skeletonized. Egg clusters may be evident on foliage with a cottony or fuzzy appearance. Young larvae are pale green and adults are darker with a light line along the sideand pink underside. Burpee Recommends: Introduce natural enemies to the area.
Cutworms: These insects cut off the seedlings at the soil level. Burpee Recommends: Place a paper cup collar (use a coffee cup with the bottom cut out) around the base of the plant. They are usually mostly a problem with young seedlings. You can also control by handpicking and controlling weeds, where they lay their eggs.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Whitefly:These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.
Should I eat fennel raw or cooked? Many parts of the fennel plant may be eaten, including bulb, stalks, leaves and seeds. You can cook the bulbs and stalks, use seeds in cooking and use the leaves in cooking. Leaves, stalks and bulbs may also be used raw.
Can I grow fennel in a container? Fennel can grow large, although ‘Orion’ is a smaller more compact variety. If growing fennel in a container use an 18-24 inch container and be sure to use a commercial potting mix rather than garden soil.
Can I use fennel as a companion plant? Fennel attracts beneficial insects to the garden. Otherwise is not is commonly used as a companion plant and may inhibit the growth of neighboring plants.
What do I do if I see caterpillars?? Fennel is a host plant to black swallowtail butterflies, so the caterpillars are a good thing in your garden.
I had fennel last year and it seems to be coming back, does fennel self sow? Yes, fennel is a short lived perennial plant and does tend to self sow where it is happy.