Sunflower - Disease Management    Pat Donald, MU  (573) 882-2716

                               KEY
                          1 = Symptoms
                    2 = Registered Pesticides
                           3 = Remarks

Downy Mildew   Plasmopora halstedii
   1.  Pre-or post-emergence damping off; plant malformation;
       stunting; chlorosis along veins and white mycelium on
       underside of leaf when systemic.
   2.  Apron 25W (4oz/cwt); Apron 50W (4-7 oz/cwt.)
   3.  Plant in well-drained soil; rotate to non-host crop such as
       small grains, corn, soybeans. Cool, wet weather early in the
       growing season favors disease in poorly-drained soils. See
       North Dakota State University Bulletin 25.

Powdery mildew   Erysiphe cichoroacearum
   1.  White mycelial growth on surface of leaves.
   2.  Sulfur.
   3.  Maintain good weed control. See North Dakota State
       University Bulletin 25.

Leaf spot and blights   Septoria helianthi Alternaria spp. 
       Phoma macdonaldii
   1.  Dark lesions on leaves, stems and heads.
   2.  None.
   3.  Maintain good weed control. Rotation to nonhost crops will
       reduce inoculum levels. See North Dakota State University
       Bulletin 25.

Rust   Puccina helianthi
   1.  Red powdery spots on leaves, stems and heads which can be
       rubbed off.
   2.          
   3.  Plant resistant cultivars for races present in area. See
       North Dakota State University Bulletin 25.

Sclerotinia wilt and head rot   Sclerotinia sclerotiorum
   1.  Wilt usually observed during flowering and seed development
       stages. Diseased plants initially occur singly and the
       pathogen spreads via root contact. The root system rots and
       a wet lesion, often covered with white mycelium, occurs at
       the stem base. Head rot is dependent on rain during the
       growing season. Rotting usually starts as a water- soaked,
       light brown wedge at the outside of the green head. Cool
       weather aids in partial or complete rotting of the head.
   2.  None.
   3.  Use certified seed or cleaned seed harvested from healthy
       heads. Plant minimal population with a wide row spacing (16
       in.); grow sunflowers once out of 5 years on same land;
       rotate with small grains, corn and other grasses. Monitor
       fields for wilt. See North Dakota State University Bulletin 25.

Seedling blight and seed rot   (many fungi)
   1.  Plants die pre- or post-emergence within one month of planting.
   2.  
   3.  Plant when conditions are favorable for plant growth. See
       North Dakota State University Bulletin 25.