1. Large Patch

2. Knowledge Requirements
What are the best diagnostic signs and symptoms of large patch?
Is the pathogen a spore-former or a non-spore-former?
How does the pathogen survive adverse conditions?
How does the pathogen infect turfgrass plants?
What species of turfgrasses are susceptible?
What effects do nutrients such as N, P & K have on the disease?
What environmental conditions are required for large patch to develop?
8. What species of turfgrass are resistant or immune to large patch?
9. What turf nutrients suppress large patch?
10. In what ways can the environment be manipulated to suppress
large patch?
11. Name a contact, systemic and penetrant fungicide that will
control large patch.
12. During what season(s) are preventive applications of large patch
fungicides applied in GA?

3. What was once consider one disease (Brown Patch) in now considered as three.
In this section we will review Large Patch.
BROWN PATCH
Brown Patch
Cool Season Grasses
Rhizoctonia solani
(strains AG 1 and
AG 2-2IIIB)
Rhizoctonia Large Patch
Warm Season Grasses
Rhizoctonia solani
(strain AG 2-2 LP)
Yellow Patch
Cool Season Grasses
Rhizoctonia cerealis

4. RHIZOCTONIA LARGE PATCH
caused by
Rhizoctonia solani
(strain AG 2-2 LP)

5. (strain AG 2-2 LP) Rhizoctonia solani Nonspore-forming fungus.
Survives as sclerotia or dormant mycelium
in thatch, soil or dead tissue.
Initial infection occurs on leaf sheaths when
night temps at 40-60°F and crowns of
plants have been wet for more than 10 hrs.
Note how Large Patch occurs at a lower temp. than Brown Patch

6. RHIZOCTONIA LARGE PATCH
Susceptible Grasses
All warm season grasses.
Note that large patch occurs only on warm season grasses while brown patch
occurs on cool season grasses.

7. RHIZOCTONIA LARGE PATCH
Favorable Environment
Night temps <60°F.
High soil moisture.
More than 10 hr. of crown and stolon
wetness per day for several days.
Lower temp. than
brown patch

8. Large patch on St.Augustinegrass – Patches can be
About 8 ft. in diameter
Large patch on St.Augustinegrass – Patches can be
15 or more ft. in diameter.

9. Large patch on hybrid bermudagrass.
Symptoms occur in the spring and fall
when the turf is either coming out of
dormancy or going into dormancy.

10. Large patch on zoysiagrass. Note how disease does not
perennial rye
Large patch on zoysiagrass.
Note how disease does not
spread to perennial ryegrass
at top of photo. Perennial rye,
a cool-season grass, is not
susceptible to the strain of
of R. solani that causes Large
Patch.
Large patch on zoysia

11. Large patch on hybrid bermudagrass
Outer margins of patches are
yellow to orange in color when
the large patch fungus is actively
growing and infecting turf.
Large patch on a zoysiagrass fairway

12. Large patch on recently sodded
zoysia lawn.

13. Large Patch on zoysia. Note how
weeds develop in center of patch.
Note orange border indicating active
disease development.
Large Patch on St. Augustinegrass.

14. Large patch beginning to develop on zoysia in the fall.
Patches (<1 ft. in diam.) of yellow-orange leaves are
an indication of early infection. As patches increase in
size, leaves in the center of the patch turn gray.
Look at leaf sheaths to make diagnosis

15. No lesions on
leaves.
Note lesions on
this leaf sheath
of St. Augustine.
This is where
the fungus is
infecting.
Development of
brown lesions on
leaf sheaths is the
best diagnostic
symptom of large
patch

16. Leaf turns yellow due to poor
translocation of nutrients and water
up through leaf sheath.
Lesion forms on leaf
sheath, not on leaf.

17. Lesions often coalesce to consume whole leaf sheaths Note how lesions
do not form on
leaves, just on leaf
sheaths.
This is a difference
between large patch
and brown patch.
Lesions often
coalesce to
consume whole
leaf sheaths

18. ligule
Fungus rots leaf sheaths and leaves shrivel and die do to poor translocation of
water and nutrients. Fungus seldom grows past ligule and into the leaf.

19. Lesion on leaf sheath
of centipedegrass

20. Dark lesion on outer leaf
sheath of zoysiagrass
When outer leaf
sheath is stripped
away, inner lesion
may appear bleached.

21. MANAGEMENT OF
RHIZOCTONIA LARGE PATCH

22. RHIZOCTONIA LARGE PATCH
MANAGEMENT OF
RHIZOCTONIA LARGE PATCH
Cultural Management
Avoid N fertility in spring prior to mid-May and in fall
after Sept. 1st.
- Maintain moderate to high P & K according
to soil test.
Decrease shade and increase air circulation.
- Improve soil drainage.
Avoid irrigation in late afternoon and in
evening prior to midnight.
- Maintain thatch at ½ inch or less.

23. RHIZOCTONIA LARGE PATCH
MANAGEMENT OF
RHIZOCTONIA LARGE PATCH
Resistant Species and Cultivars
All warm season species are susceptible, but in
in general, bermudagrass will recover
faster than either zoysia, St. Augustine, pasalum
or centipede.
- No cultivars are known to be resistant.

24. Management of Large Patch
Chemical Control
Contact fungicides – chlorothalonil, mancozeb,
thiram, polyoxin. 14 days control
Localized penetrants – iprodione, vinclozolin,
trifloxystrobin, pyraclostrobin. 21 days control
Acropetal penetrants – azoxystrobin, flutolanil,
thiophanate-methyl, propiconazole, triadimefon,
fenarimol days control

25. Management of Large Patch
Chemical Control
Preventive or early curative* fungicide applications are recommended in
spring and fall when night temperatures are between 35 and 60°F.
*when patches are less than softball size.

26. End of Large Patch Section