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Leaf Spot and Melting Out
Disease
Mary Small
Extension Agent, UIP
Jefferson County
Leaf spot and melting out are diseases of
stressed turf caused by several species of fungi. The symptoms of leaf spot are
small purple spots on leaves. If the spots extend across the leaf blades, they
die. Melting out first appears as a purple leaf spot that works its way down to
the base of the plant, infecting the crown and roots. The tissues near the
ground turn brown and rot. Lawns appear yellow and thin with irregular patches
of dead grass. Leaf spot is active during cool moist weather and the melting out
is active during warm weather. Dry periods that alternate with cloudy, wet and
cool to moderate temperatures favor both diseases.
To manage leaf spot and melting out,
use good cultural practices to keep turf plants healthy and reduce their
susceptibility to infection. Use disease resistant varieties when establishing
or re-establishing a lawn. Core aerate the lawn at least once per year (spring
or fall) to decrease thatch build up and improve soil condition. Mow the lawn at
a height of 3 inches. Water deeply and infrequently. Avoid excessive nitrogen
(more than 1 pound of nitrogen 4 times per year). High amounts of nitrogen
produce tender succulent growth that is more susceptible to infection.
Fungicides are rarely needed to manage the disease and they are best used in
conjunction with good cultural practices.
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