Common Disease Problems
Bacterial Leaf Spot: This causes brown water soaked spots on the foliage which eventually makes the foliage turn yellow. It thrives in cooler temperatures. Burpee Recommends: Remove infected plants. Rotate crops with plants in a different family. Avoid overhead watering. Do not work around plants when they are wet.
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 & rinse in a ten per cent bleach solution after use.
Downy Mildew: This fungus causes 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 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.
Root Rot: This fungus causes damping off in seedlings, and in older plants, the leaves turn yellow and drop off, stunting occurs. The fungus can live in the soil for five years. Burpee Recommends: Rotate crops with plants in a different family.
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.
Cabbage Looper: These worms are green with a white stripe on either side, about 1-1.5 inches long. They tunnel through the heads. Burpee Recommends: Hand pick. Floating row covers can help prevent their laying eggs on the plants.
Flea Beetles: These small hopping beetles feed on plant foliage and can spread disease. Burpee Recommends: Rotate crops with plants in a different plant family. Use floating row covers to prevent damage to young foliage.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
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.
What is the best region to grow broccoli? Because broccoli will prematurely flower if allowed to get too warm, gardeners in cooler regions grow broccoli best in spring and early summer. Gardeners in warmer regions can grow broccoli mid-fall through winter.
Why does my broccoli have yellow flowers and no broccoli? If you see flowers, your broccoli has prematurely flowered because of warm weather, OR your broccoli is over mature.
Why won’t my Romenesco broccoli form a head? Broccoli ‘Romanesco’ is really a green cauliflower. Like cauliflower, it is very sensitive to an inconsistent growing environment (fluctuations in weather, temperature and water). Gardeners in regions that have very even growing conditions can grow this variety best, as do greenhouse or hoophouse growers. This is also a very long season plant and it does not form heads until late in the season. It may not be mature enough yet.
When should I sow broccoli in the fall? If temperatures are over 85 degrees F in your area in August, start planting indoors in the beginning of August. If temperatures are consistently under 85 degrees in August, direct sow at the end of July.
My broccoli won’t form a head (blunting) or has formed a tiny head (buttoning). Why? The early development of a broccoli plant often affects head development; potted plants that were root bound before being planted out or transplants that experienced unusually cold temperatures after being planted out may blunt or button. Both experiences are considered transplant shock.