Aphids:
- Type: Insect
- Symptoms: Misshapen or yellow leaves, sticky “honeydew” (excrement), and sooty, black mold.
- Control/Prevention: Grow companion plants, use water spray to knock off aphids, apply insecticidal soap, place banana or orange peels around plants, wipe leaves with a 1 to 2 percent solution of dish soap and water every 2 to 3 days for 2 weeks, and introduce native plants to attract beneficial insects.
Black rot:
- Type: Fungus
- Symptoms: Yellow, V-shaped areas on leaf edges that brown and progress toward the leaf center, eventual leaf collapse, and blackened veins visible in stem cross sections.
- Control/Prevention: Remove infected plants, select resistant varieties, ensure good drainage, eliminate plant debris, and practice crop rotation.
Cabbageworms:
- Type: Insect
- Symptoms: Leaves with large, ragged holes or are skeletonized, bored heads, dark green excrement, and yellowish eggs laid singly on leaf undersides.
- Control/Prevention: Handpick affected leaves, use row covers, incorporate companion plants to attract beneficial insects, consider planting thyme as a companion, and use Bacillus thuringiensis (Bt) spray.
Flea beetles:
- Type: Insect
- Symptoms: Numerous tiny holes in leaves.
- Control/Prevention: Use row covers, apply heavy mulching, and introduce native plants to encourage the presence of beneficial insects.