| Material Information
||Control of Pythium and Rhizoctonia in chrysanthemum plantings
||Gulf Coast Experiment Station mimeo report
||3 leaves : ; 28 cm.
||Jackson, Curtis R
Gulf Coast Experiment Station (Bradenton, Fla.)
||Gulf Coast Experiment Station
||Place of Publication:
||Chrysanthemums -- Diseases and pests -- Control -- Florida ( lcsh )
Pythium -- Control -- Florida ( lcsh )
Rhizoctonia -- Control -- Florida ( lcsh )
||government publication (state, provincial, terriorial, dependent) ( marcgt )
non-fiction ( marcgt )
||Statement of Responsibility:
||"Nov. 16, 1959"--Leaf 3.
||Florida Historical Agriculture and Rural Life
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Copyright 2005, Board of Trustees, University
Gulf Coast Experiment Station Mimeo Report 60-3
Control of Pythium and Rhizoctonia in Chrysanthemum Plantings
C. R. Jackson
Pythium stem rot has been found in all chrysanthemum growing areas of
Florida during the summer and fall of this year. Losses from this disease have
leen unusually heavy due partly to the prolonged abundant rains. Rhizoctonia
&tem rot has not been abundant during the past summer but may appear more often
during drier weather.
More than 40 fungicides have been evaluated at the Gulf Coast Station
during the past year in an effort to find more effective materials for control
of soil-borne pathogens. Preliminary laboratory screening and field plant tox-
icity tests have been supplemented by growers' trials. Four fungicides, pres-
ently available to growers, were found to be effective when timely applications
PYTHIUM STEM ROT
(1) Sudden collapse of plants, wilting, and blackening of stem near soil line.
(2) Progressive upward blackening of stem frequently extending to the top of
(3) Spread of stem infection to leaf petioles and lower parts of leaf blades.
(4) Presence of strands of white mycelium on diseased parts during periods of
(5) Occasional "pinch" wound infections resulting in downward progress of stem
The suddenness of disease development (12-36 hrs.), a dark brown to
black color of infected tissue, and infection of leaves are characteristic
of the disease. The pathogen grows rapidly during periods of high humidity
and at temperatures of 80-100 F. Very high soil moisture is most favora-
ble for the growth of Pythium.
RHTZOCTONIA STEM ROT
(1) Gradual stunting and wilting of plants.
(2) Stem infections commonly starting at or below soil level, initially light to
dark brown with the infected stem diameter noticeably smaller than the green
stem of the same plant.
(3) Progressive upward browning of the stem for 1-6 inches, seldom reaching the
top of the plant.
(4) Presence of brownish mycelium on diseased parts.
The brown color of infected tissue, gradual development of disease
and absence of leaf petiole infection usually serve to distingu RhizoctonJ
infections from those of Pythium. Rhizoctonia grows rapidly d Fitds c
high humidity and at slightly lower temperatures than Pythium. derat Ps i
moisture is most favorable for the growth of Rhizoctonia.
Both of these fungi are soil-inhabiting pathogens that persist in the soil
as actively growing mycelium or resistant resting bodies. Preplanting soil treat-
rents commonly used by Florida growers reduce the numbers of fungi but recontamina-
tion from walks, access roads and other areas may occur. During period of heavy
r-ins, movement of water or splashing rain over treated beds may introduce disease
Effective fungicides, when applied to beds where diseased plants are ev.-
dont, eradicate or stop the growth of the pathogen. Plants which are infected at
the time of fungicide application usually die subsequently. Since infected plants
are a source of the disease fungus, they should be removed from beds and growing
areas without delay.
The following materials are recommended for the control of the specific
disease fungus. Use of the fungicides should be confined to established plants
sirce rooted cuttings are usually more sensitive to these fungicides and may not
become established when treated beds are immediately reset. Follow the msnufac-
turers'directions regarding health hazards.
I. Captain (50% wettable powder)
Rate 1 to 1 1/4 lb. in 15 to 30 gal. water per 100 sq. ft.
Application Apply as a soil drench or coarse spray directed at soil. Lightly
sprinkle plants after application to rinse foliage.
Use Entire bed or spot treatments. Captan 50W has been found to be non-toxic
at these rates but may stunt plants if used at higher rates.
If. Panogen Soil Drench (3.5% liquid)
Rate 1 to 1 1/2 liquid oz. in 15 to 30 gal, water per 100 sq, ft. for bed
treatment of Iceberg or Whitetop. For spct treatments with sprinkling
can use 1 teaspoonful in 10 gal. water.
Application Apply as a drench to beds using the low rate if only 15 gal.
water per 100 sq. ft. can be used. For spot treatments, apply about
1 pint per square foot. Rinse foliage after drenching.
Use Panogen Soil Drench is recommended at present as a bed treatment with
Iceberg and Whitetop varieties. Slight injury can result from using
Panogen Soil Drench with Blue Chip, Beauregard, or Shasta at the bed
treatment rates. A more dilute drench, as recommended above for spot
treatments may be used in rooting beds on many varieties; however,
the responses of all commonly grown varieties are not known.
Panogen Soil Drench is very effective when applied to estab-
lished plants at recommended rates but slight to severe chlorosis,
stunting, and hardening of plants will occur if excessive application
rates are used.
III. Phygon XL (50% wettable powder) SUGGESTED FOR LIMITED TRIAL
Phygon XL has proven to be effective against Pythium at rates of 1/4
lb. in 15 to 30 gal. water per 100 sq. ft. No plant injury has been noted
in field experiments during the summer using Iceberg, Whitetop, Beauregard,
Blue Chip, and Fhasta. Cuttings set into drenched beds were slightly stunted
but normal in other respects. Phygon XL can be applied as suggested for cap-
tan. Use of Phygon XL should be limited t; small trial plots at present.
I. Terraclor 75W (75% wettable powder)
Rate 1/2 lb. in 25 gal. water per 100 sq. ft.
Application Apply as suggested above for captain.
Use As a drench for entire established beds or as a spot treatment in
flowering or rooting beds.
II. Panogen Soil Drench. This material has proven to be-very effective against
Rhizoctonia when used as suggested above for Pythium control.
Nov. 16. 1959.