Bob K: “With August come some of the most intense disease pressure soybean, peanut and cotton growers are likely to experience each year. The growth of the crops are at a point where leaf wetness periods are prolonged within the canopy after rains, irrigation, or morning dew, coupled with high humidity, high temperatures, and crops in reproductive growth all add up to high risk to many fungal diseases. [We] must be vigilant for soybean rust, peanut leaf spot diseases, white mold, areolate mildew, and target spot. Falling behind in a fungicide program to control any of these diseases can be difficult to overcome.
Early leaf spot on peanut – note the scattering of light-colored, needle-like spores on the TOP of the leaf. While typically not as destructive as late leaf spot, early leaf spot CAN cause significant yield loss if not effectively managed with a fungicide regimen.
Note the bronzed color; this is Indication of a potassium deficiency. Note the spots with a dark-purple border and ashy, papery center. This is Stemphylium leaf spot, caused by the fungus Stemphylium solani. The underlying cause is a potassium deficiency which make the leaf more susceptible to infection. Fungicides will not help control this disease.”