That means more cotton per acre at less cost. The narrower rows leave more crop residue in the fields at harvest. The disease first moved into the central and western Corn Belt about 10 years ago, but significant yield losses were only found recently, esp. in 1996 and 1997. GLS starts as a small lesion on the lower leaves of corn plants, spreading quickly as it kills leaf tissue and moves up the plant stalk. The airborne spores can also take hold when rain kicks them up in surrounding soil, said Ernie Newquist, agronomist with Aurora Cooperative in Nebraska.
Weather plays a large role in the disease's spread.
Hot, humid weather early in the summer creates the right conditions. Shredding or tilling will break that tissue down and can reduce the probability of an outbreak of leaf spot. These units help speed up the organic process, providing better insect and corn borer control. Now, these shredders make it easier for farmers to bury residue infected with gray leaf spot spores.