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Ascochyta
leaf blight on Kentucky bluegrass.
Here the disease is caused by drought stress, where an irrigation
head is not functioning properly. Wheel marks, from a mower, were
just an additional stress. The mower wheels did not carry the fungus
to this turf area. Turf usually recovers when irrigation is repaired
and normal turf growth resumes. |
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Ascochyta
leaf blight on tall fescue (left) and bluegrass (right).
The grass blade is usually killed from the tip down towards the base
of the plant. Infection occurs through the cut end of the leaf blade.
Can often see small, black pycnidia on the dead tissue just adjacent
to the living tissue (use a good hand lens). Symptoms are the same
on bluegrass, ryegrass, and the fescues. |
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Managing
Ascochyta Leaf Blight in the Home Lawn
- This disease
is encouraged by drought stress conditions: poor irrigation coverage,
clogged irrigation heads or nozzles, heads that are too high,
too low, or not level
- All turf species
appear to be affected by this disease
- While the turf
often appears dead, this disease usually does NOT kill the grass
(although some turf thinning will occur under severe outbreaks)
- Fungicide applications
appear ineffective in controlling this disease and are NOT recommended;
the major cause of the problem is drought and heat stress
- The turf usually
recovers when temperatures moderate, irrigation heads are repaired,
or other reasons for poor irrigation coverage/supply are addressed
- Lawns managed
with once- or twice-weekly irrigation are prone to this disease
when temperatures exceed 90-100F for consecutive days and no rainfall
occurs
- It may take
several weeks to a month for turf to recover from a severe outbreak,
even with cooler temperatures, rain and sufficient irrigation
- The disease
rarely occurs in the fall and affected turf generally recovers
completely during the fall months
- While theoretically
possible, the fungus is not significantly spread from one lawn
to another on lawn maintenance equipment or by foot traffic, but
rather by wind dispersal of the spores
- Conspicuous
wheeltracking from maintenance equipment in diseased areas is
caused by the movement of heavy equipment across drought-stressed
turf (which injures the stressed leaves), and not by "tracking"
of the disease organism from one lawn to another
- The disease
will not affect other plants in the landscape or garden; grass
clippings from affected lawns can safely be used for mulch and
in compost
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