The brassica family of vegetables, which includes broccolini, Brussel sprouts, cabbage, cauliflower, collards, kale, and kohlrabi, are susceptible to various pests and diseases. See our lists below of (1) common pests and diseases affecting brassicas in Northern Illinois and (2) safe organic pesticides best used to control them.
Common pests and diseases in Northern Illinois
It's important to note that while these pesticides and biofungicides are considered safe for use in organic gardening, they should still be used judiciously and according to label instructions. Overuse or misuse can harm beneficial insects and other non-target organisms. Regular monitoring and cultural practices such as crop rotation, soil testing, and good sanitation can also help prevent pest and disease problems in your brassica garden.
Swede Midge Fly: The swede midge (Contarinia nasturtii) is a small, invasive fly from Europe that attacks plants in the Brassica family, including broccoli, cabbage, cauliflower, collards, and kale. We have an entire post dedicated to this new pest - see Swede Midge Fly Management.
Cabbage Worms: These are small green caterpillars that chew on the leaves of cabbage, kale, and other brassicas, leaving large holes in the foliage. They can quickly defoliate the entire plant.
Aphids: These tiny, pear-shaped insects suck the sap from the leaves, stems, and buds of brassicas, causing stunted growth and distorted leaves. They also produce a sticky substance called honeydew, which can attract ants and other insects.
Flea Beetles: These small, shiny black beetles jump like fleas and feed on the leaves of brassicas, leaving tiny holes and making the plant vulnerable to other diseases.
Clubroot: This soil-borne disease is caused by a fungus that attacks the roots of brassicas, causing them to swell and become deformed. Infected plants often wilt and die.
Downy Mildew: This fungal disease causes yellowing and wilting of the leaves, along with a grayish-white mold on the undersides of the leaves. It can quickly spread from plant to plant, especially in humid conditions.
Prevent and control brassica pests and diseases
To prevent and control these pests and diseases, it's best to use a combination of cultural practices and safe organic pesticides and biofungicides. Here are some options:
Floating Row Covers: These lightweight, permeable fabrics can be placed over young brassicas to protect them from cabbage worms, flea beetles, and other pests. They can also help prevent the spread of diseases like downy mildew.
Neem Oil: This natural pesticide derived from the neem tree can be sprayed on brassicas to repel aphids and other pests. It works by disrupting the insect's hormonal balance, making it difficult for them to feed and breed.
Bt (Bacillus thuringiensis): This natural bacteria-based pesticide is effective against cabbage worms and other caterpillar pests. It works by producing a toxin that is only harmful to certain insects, leaving beneficial insects unharmed.
Copper-based Fungicides: These biofungicides can help prevent and control diseases like downy mildew and clubroot. They work by creating a protective barrier on the plant's surface that prevents the fungus from taking hold.
Beneficial Insects: Ladybugs, lacewings, and parasitic wasps are all natural enemies of aphids and other pest insects. By releasing these beneficial insects into your garden, you can help keep pest populations in check.
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