Sunflower
and leaf spot. The symptoms of these diseases are given in Table 3. The severity of these
disease effects on total crop yield might be ranked: 1) sclerotinia, 2) verticillium, 3) rust
(recently more severe), 4) phoma, and 5) downy mildew. Resistance to rust, downy
mildew, and verticillium wilt has been incorporated into improved sunflower germplasm.
Table 3: Major sunflower diseases and symptoms.
Downy mildew Cottony fungus on underside of leaves. Dwarfing,
Plasmopara halstedi contrasting discoloration of yellow-green and green.
Blackening and sometimes swelling at base of stem.
Disease most severe when rain occurs before and after
emergence.
Powdery mildew Cottony fungus on green leaves late in summer - not largely
Erysiphe cichoracearum damaging.
Leaf spot Dead blotches on flower leaves before heading
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