Bacterial blight cause water soaked spots on stems, leaves and flowers. These later turn black. The plants are defoliated and are killed when stems are girdled. Infected flowers have blackened sepals and the petals fail to develop. A slimy exudate may form. The spots are scattered, circular and surrounded by yellow tissue which later turns brown. Destroy infected plants and do not plant poppies in the same area. No chemical control is listed.
Downy mildew causes pale spots on both sides of the leaves. The spots are covered by white or grayish mold. The stems are distorted and the blossoms fail to develop. As the stem bases are infected the plant collapses. Pick off infected leaves. No chemical control is listed.
Powdery mildew causes a white powdery growth on the leaves. Spray with benomyl or sulfur.
Verticillium wilt decline and death of the plants. No chemical control is available for this disease.