LONG

Long-term management for disease control in lawns emphasizes good basic
turfgrass management practices. These practices include the selection of
the best adapted grass for the site, proper site preparation, proper
management and the use of pesticides if needed.

Environmental conditions vary greatly throughout North Carolina. The
northwest mountain region has a climate similar to the northeastern United
States where cool-season grasses such as bluegrass are best adapted. The
southeastern region is the opposite extreme with a climate suitable for
the warm-season grasses such as centipedegrass or bermudagrass. The
region in the central part of the state is the transition zone which is
often too cold in the winter for the warm-season grasses and is often too
hot in the summer for the cool-season grasses to grow well. Microclimates
of sites in the transition zone determines which turfgrasses are best
adapted to particular lawns. The warm-season grasses are best adapted for
lawns with sunny southwest exposures while the cool-season grasses are
best adapted for lawns with northern exposures in this zone. The use of
warm-season grasses, such as zoysiagrass or bermudagrass, for good quality
turf in the summer and overseeding in the fall with cool-season grasses,
such as ryegrass or tall fescue for green color in the winter can be used
in highly maintained lawns with good sun exposure in the transition zone.
Evaluation of the climate or the exposure of the lawn will help determine
the best type of turfgrasss to grow to avoid severe disease problems in
the future.

Inadequate soil preparation before planting contributes to many disease
problems in the future even if the proper grass is selected for the site.
Most of the soils in the state have a low pH and low phosphorus levels if
the area was wooded just before the lawn was planted. Soil tests should
be taken from the site early enough to know how much lime and phosphorus
should be incorporated into the soil before planting. The pH of many of
the soils may be 4.0 or lower where trees have been growing for years.
All of the turfgrasses used in the state are not native to this area and
grow best in soils with a pH near 6.5 except centipedegrass which prefers
a pH near 5.5. The pH scale is logarithmic which means that a pH of 4 is
1000 times more acid that a pH of 7. The soil pH determines the
availability of nutrients in the soil to the plants. The soil test is
often omitted and not enough, if any, lime and phosphorus is applied.
These nutrients move very slowly in the soil and should be incorporated 6
to 8 inches deep before planting. Tall fescue lawns in the Raleigh area
have been observed to grow well and not need any reseeding for as long as
10 years where the proper amounts of lime and phosphorus was incorporated
into the soil before planting. Whereas, adjacent lawns that did not
receive proper amounts of lime and phosphorus have to be reseeded yearly.
The depth of incorporation of the lime and phosphorus determines the depth
of rooting of the turfgrasses. A good deep and healthy root system
results in a healthy plant that can better tolerate environmental
stresses, compete with weeds and recover from insect and disease damage.

Time of planting, the amount of seeds and varieties of grasses used are
important long-term disease management practices. The cool-season grasses
grow better and conditions are less favorable for diseases if planted in
the fall. The temperatures are cooler at this time and the fungi that
cause many of the diseases are less active during cooler weather. High
seeding rates of tall fescue, 10 pounds per 1000 square feet or more,
usually result in rapid greening of lawns but often contribute to poor
survival the following summer. Many small seedlings do not develop deep
root systems and are very susceptible to diseases such as brown patch and
drought stress. Lower rates of seeds, as low as 4 pounds per 1000 square
feet, would result in slower greening of the lawn after planting but will
result in stronger plants that can survive disease and drought stresses
the following summer. Using mixtures of several varieties of tall fescue
and mixing bluegrasses with the tall fescues will help to reduce damage
from diseases. The warm-season grasses should the planted in late spring
or early summer to allow enough growing time for the grasses to become
well established to reduce the chances of winter damage.

Management of the established lawn can affect the damage from diseases.
Some disease is likely to occur in all lawns sometime during the year, but
a good management program can reduce the amount of damage. Fertilization
based on recommendations for the specific type of grass and soil test
results is the best method to use. High rates of nitrogen in the summer
on tall fescue will increase the severity of brown patch. Tall fescue
should be fertilized in the fall, winter and spring and not during the
summer. Small amounts of nitrogen fertilizer with iron can be used in the
summer to improve color and may not increase susceptibility to brown
patch. A lighter green color in the summer may be less acceptable to the
homeowner, however, it would help reduce the severity of brown patch.
Irrigation practices can affect the damage from diseases. Turfgrasses in
lawns should be irrigated about once a week during dry weather to wet the
soil 6 inches deep. Frequent, light irrigations keep the foliage wet and
provides favorable conditions for diseases to develop. Turfgrasses should
be mowed when the foliage is dry. Mowing when wet can spread the disease
causing organisms from infected to healthy leaves more rapidly.

Environmental changes in lawns over a number of years often contribute to
conditions that are more favorable for diseases and less favorable for the
growth of turfgrasses. Shade and root competition from trees increases as
the trees enlarge. Also, hedges become larger and thicker which reduce
air movement in the lawn. The shade and reduced air movement cause
relative humidity and moisture levels to remain high for longer periods on
the turfgrass leaves which creates more favorable conditions for diseases.
The trees and shrubs should be pruned or removed to make conditions more
favorable for the growth of turfgrasses and less favorable for diseases.
If trees cannot be removed, the best solution to the problem will be to
redesign the landscape and use mulch or ground cover plants in the shady
areas in place of grass. Homeowners often describe the problem as "I used
to have a good lawn in the area", and my response is that "the trees used
to be small and the turfgrasses used to have more sun exposure." The
long-term solution to this problem is to decide which is more important,
trees or grass, in your landscape because it is very difficult to grow
good quality turf in shady areas.

Pesticides should be considered as a last resort for a long-term disease
management practice. Fungicides are available that can be used to control
diseases on turfgrasses in lawns. However, these chemicals will be needed
frequently under favorable disease conditions, such as hot-wet weather for
brown patch on tall fescue. The cost for fungicides may exceed the normal
cost of a professional lawn maintenance program and homeowners must choose
between this extra expense and less than desirable turf quality in late
summer with reseeding in the fall. Turf quality of tall fescue will
usually be acceptable in later fall with good management without the use
of fungicides. Fungicides are seldom needed on warm-season turfgrasses.

Nematodes may cause serious damage on some turfgrasses growing in very
sandy soils in the Eastern and Sandhills regions of the state. Good
fertility and irrigation practices are the only methods available to help
overcome the damage from nematodes in home lawns. Chemicals are not
labelled for use in home lawns to control nematodes.

In summary, long-term disease management for turfgrasses in lawns involves
best management practices that encourages the growth of healthy turf. A
healthy turf may have some diseases, but will have less severe disease and
can recover from the damage more quickly than poorly managed turf.
Publications are available from your county Cooperative Extension office
on the best management practices for turfgrasses in your area.