Sclerotinia wilt and rot

This disease is found throughout the world where sunflower is grown. Symptoms of the disease appear in different phases as root rot, stem rot, and head rot. Water-soaked lesions appear on the taproot and fibrous roots. Small brown lesions appear at the base or any other part of the stem. The plant wilts and dries up. In head rot, a conspicuous white mycelium growth of the fungus is observed. Usually heads previously damaged by birds, insects, or hailstorms are attacked by this disease. Such heads fall off and have no seeds.

Charcoal rot

This disease is also found in most of the sunflower-growing countries of the world. Early symptoms of the disease are not visible, but sudden wilting of plants, usually after pollination, is the most common symptom. The diseased plants mature early and show a black, ashy discolouration on the stem, from which the disease gets the name 'charcoal rot', if the affected stem is split, black microsclerotia are found in the pith. Resistant cultivars should be grown.

Verticillium wilt

Infection progresses from the bottom to the top of the plant. Yellow patches appear in the centre or near the edge of the leaf. The patches enlarge and their centres become brown, giving a mottled appearance to affected leaves. The entire leaf may turn brown and wither. Affected stems have black streaky patches on them, and roots are also affected. Resistant cultivars should be grown and rotation should be practiced.

Alternaria blight

The symptoms first appear in the form of dark-brown to black, circular to oval-shaped spots on the lower leaves. The disease spreads gradually to the middle and upper leaves. Late in the season, elogated spots are found on petioles, stems, and ray-florets. High humidity favours the pathogens. The disease can be controlled by fungicides and growing resistant cultivars.

Insects

Common insects infesting sunflower are armyworms, cutworms, hairycaterpillars and budworms. These insects attack the plants at the larval stage and feed on leaves, stems, and young buds. Young seedlings are also attacked by whitefly and aphids.

Birds

Mature sunflower heads are attacked by birds. Parrots are one of the most serious pests, though the crop is also attacked by other birds like sparrows and pigeons. Attacks are severe early in the morning and at evening. The heads should be harvested as soon as they are mature. Cultivars whose heads face downwards after maturity are less affected by birds.