 Alternaria leaf spot
Identification tips: Small, dark specks develop on leaves and later enlarge into circular, tan spots (0.25–0.5 inch in diameter). Spots may develop concentric rings of dark green spores. Old leaf spots may tear, producing a shot hole appearance. This disease is usually not an economic concern except for cole crops marketed for the leaves. |
 Cabbage looper
Identification tips: Larvae are green, smooth-skinned, and up to 1.5 inches long. They have a narrow, white stripe down either side, and several white lines down their back. They crawl by arching their bodies. These caterpillars occasionally damage seedlings by eating ragged holes into leaves. |
 Downy mildew
Identification tips: Infection begins as irregular, yellow patches on leaves that later turn light brown. White fluffy growth can develop on the undersides of leaves. If cotyledons or the first true leaves are infected, the young plants may die. |
 Imported cabbageworm
Identification tips: Larvae are green, with fine hairs that give their skin a velvetlike appearance. Older larvae are up to 1 inch long and move slowly. They chew large, irregular holes in leaves, often feeding along the midrib. |
 Vertebrates (birds)
Identification tips: Birds will feed on seeds and seedlings. Look for holes in the soil and seedlings that have been nipped off. Also look for droppings near plants. |
 Wind damage / Wind whip
Identification tips: High winds cause girdling and death of small seedlings. Surviving plants may wilt and fail to form a flowering head. Stems become brittle. Seedlings are most susceptible after weeding. |
