Symptoms
With beginning boll development and ongoing deficiency, chlorosis and marginal necrosis occur on medium aged leaves, too. Interveinal areas show a bronze-orange tint.
Reasons
Late-season potassium deficiency
K and Mg deficiency both cause interveinal chlorosis. With Mg deficiency the green leaf veins are well-defined against the chlorotic tissue whereas with K deficiency the color gradient is rather diffuse. Verticillium wilt causes interveinal necrotic lesions with well-defined borders.