Step 1
Rust causes humble cinnamon bark - colored erect musca volitans to develop on the leaf of septic sunflowers . These blisters ordinarily first appear on the bottom sides of the lower leaves , but they can also show up on bracts , petioles and stalk . Leaves with a slew of spots may wilt and the spots may run together to take shape turgid , irregularly shaped areas of infection . A yellow border may also surround billet and the spots become black late in the season . The inglorious spots are the overwintering point of the fungus . Once they appear , that infection is over for that time of year .
Rust Control
sunflower are more susceptible to rust infections when the temperatures are tender and there ’s water on the leaves . Leaves only have to be wet for two hour in ordering to become septic . Because rust fungus spore can survive in flora debris from the previous time of year , sunflowers should n’t be planted in the same shoes two years in a wrangle . nullify gamey - nitrogen fertilizer , which encourage the ontogeny of a thick canopy that will snare dew and keep the leaves wet . works hybrids that are resistant to corrode . Consult your local county university extension for advice about chemical restraint , since fungicides do n’t have Union favourable reception for use on sunflowers .
Step 2
Alternaria
Symptoms of alternaria foliage office let in dark circular spots on the folio . Sometimes the spots play together , causing the leaves to shrink and die . Some spots may have xanthous halos . Dark streaks , scrap or adamant - mold berth may appear on the stems or petioles . Sometimes these lesions can cause the root word to better . Dark spots can also seem on the back of the promontory . Alternaria infection are worse during strong , wet weather .
Alternaria Control
Control alternaria by removing septic works rubble and bury it . Rotate crops . Fungicides are n’t ordinarily necessary but , when they are used , they should be applied when lesion first appear .
Phoma
Phoma dark stem is the most coarse sunflower disease , according to the National Sunflower Association and is do by a grunge - borne fungus . Symptoms admit the show of large dark spots on the stem . spot can also look on the back of the chief and at the axil of the leaves , making the industrial plant look wilt . A disgraceful orbit may encircle the bow at or just below the soil line , cause the helianthus to die . Phoma black stem is worse when there ’s sloshed atmospheric condition during efflorescence . This fungus is spread by the lead and by splashing rainfall and irrigation water .
Phoma Control
Rotate harvest on a four - year basis with crop , like small grains , that do n’t serve as a boniface for this fungus . command shank weevil to reduce their power to fan out phoma . Plant hybrids that are more tolerant to this disease . No fungicides are registered for use on this disease .
References
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