Sunflower
Almost all North American sunflower plantings are cultivated and/or harrowed for weed
control, and over 2/3 are treated with herbicides. Postemergence cultivation with a
coilspring harrow, spike tooth harrow or rotary hoe is possible with as little as 5 to 7%
stand loss when sunflowers are at the four to six leaf stage (beyond cotyledon), preferably
in dry afternoons when the plants are less turgid. One or two between row cultivations are
common after the plants are at least 6 in. tall.
Several herbicides are currently approved for weed control in sunflowers. Information on
chemical weed control in sunflowers is available at most county extension offices.
G. Diseases:
The most serious diseases of sunflower are caused by fungi. The major diseases include
rust, downy mildew, verticillium wilt, sclerotinia stalk and head rot, phoma black stem
and leaf spot. The symptoms of these diseases are given in Table 3
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