Chrysanthemum White Rust

1
Chrysanthemum White Rust
by Jane Trolinger, Ph.D.
Yoder Brothers, Inc.
2
Todays Topics

• Chrysanthemum White Rust (CWR) can impact
  chrysanthemum production
• How to recognize the symptoms/signs
• How to protect your crops

3
Chrysanthemum White Rust(Puccinia horiana)


4
Importance of Chrysanthemum White Rust

• Can spread rapidly in a greenhouse or nursery
  resulting in severe losses
• NO evidence/proof of establishment in US and
  Canada a quarantine-significant disease in both
  countries
• Introduction from overseas is a significant
  impact to chrysanthemum industry in US and Canada
  

5
First symptoms are yellow spots on upper leaf
surfaces up to 4 mm diameter
6
Prominent pustules subsequently develop on lower
surface of leaves
7
Pustules begin as pinkish buff
8
Pustules turn waxy white
9
Upper and lower leaf surfaces
10
Close up of mature pustule
11
Pustules

• Most common on young leaves and flower bracts
• Can be found on any green tissue and flowers
  this is a way CWR can move on cut flowers

12
(No Transcript)
13
Host Range 12 species of chrysanthemum
susceptible

• Pot mums, cut mums, and garden mums Chrysanthemum
  morifolium, Dendranthema X grandiflorum
  (correctly called Chrysanthemum)
• Nippon daisy or Montauk daisy Nipponanthemum
  nipponicum
• Ajania pacifica or Chrysanthemum pacificum
• Giant daisy or High daisy Leucanthemella
  serotina, Chrysanthemum serotinum
• Click here for USDA Host Range (Appendix VI) (See
  page 19)
• Note When opening links from this Webinar,
  close the link after viewing -- and before you
  try to open the next link!

14
HOW DOES CWR INFECT MUMS?

• Spores float through the air, or are carried by
  humans or by water, from an infected plant or
  flower to a new plant or flower
• Two kinds of spores
• Teliospores
• Basidiospores
• Why is that important?

15
Teliospores the survivors

• Can last for 8 weeks on dried leaves! They
  survive only one week if infected tissue is
  buried under soil so bury your cull piles!
• Are produced in pustules and remain in pustules
  unless they are aggressively brushed off
• Produce the basidiospores when conditions are
  moist for 3 hours (optimum temperature 63F)

16
Basidiospores the reproducers

• Can cause epidemic if conditions are right
• Spread from plant to plant by splashing water and
  human handling
• Must have film of water on plant surface for
  infection
• Infection (host penetration) can occur in 2 hours
  at optimum temperature of 63F
• Can travel short distances (about 1/2 mile) by
  wind currents during moist weather
• Survive
• --only 5 minutes when relative humidity is 80
• --and less than 60 minutes when relative
  humidity is 90

17
(No Transcript)
18
(No Transcript)
19
Probable sources of CWR for US and Canada

• Imported infected chrysanthemum cut flowers
• Smuggled infected chrysanthemum material

20
How do we keep white rust out of the US and
Canada?

• White rust prevention system required by USDA in
  countries exporting cut flowers to U.S.
• Inspection of chrysanthemum cut flowers at U.S.
  ports of entry (note no inspection in Canada)
• Quarantine of imported propagation material
  (cuttings) into U.S.
• Click here for more details

21
White Rust Prevention within the US and Canada

• Plant ONLY cuttings from reputable commercial
  source
• Scout crop regularly from stick to sale
• Imported flowers should never be handled in or
  near mum-growing facilities!!
• -They can be infected and not show
  symptoms or signs
• Maintain low humidity and dry foliage
• Schedule regular applications of preventive
  fungicides if you are in an area where CWR has
  been previously reported

22
Preventive Fungicides

• Heritage (azoxystrobin)
• Daconil Ultrex (chlorothalonil)
• Cygnus (kresoxim-methyl)
• Dithane 75 DF (mancozeb)
• Strike (triadimefon)
• Terraguard (triflumizole)
• Do not use Eagle or Hoist (myclobutanil) as
  preventives myclobutanil is an eradicant.
• If you are in a high risk area and conditions are
  favorable for CWR, we recommend a prevention
  program (described in CWR Bulletin).
• Click here for spray schedule (See page 5)

23
If you find white rust

• Report it this is the law
• Inform USDA, CFIA, state, or county regulatory
  officials
• Regulatory officials will supervise eradication
  and treatment program

24
Why is it important to report chrysanthemum white
rust?

• Make sure losses are minimized
• Try to keep it from spreading in the
  chrysanthemum industry
• Collect data on the location of the finds and
  document information about the disease spread to
  maximize prevention for the future

25
Eradication and treatment program

• Infected nursery (chrysanthemums) will receive an
  Emergency Action Notice preventing shipment until
  declared free
• Required destruction of symptomatic plants and
  the surrounding one-meter radius
• Three treatments, at 5-7 day intervals, with
  eradicant fungicide (myclobutanil Hoist, Eagle)
• Final inspection 5-7 days after 3rd treatment if
  no CWR, plants released for sale
• THIS CAN BE COSTLY!
• Click for US National Protocols

26
Brown Rust or Chrysanthemum Rust is distinct from
White Rust

• Puccinia tanaceti
• Present in U.S.
• Rarely causes heavy losses
• Chocolate brown pustules

27
In Conclusion

• EXCLUDE
• PREVENT
• ERADICATE
• Click Here for CWR Bulletin

28
Photo credits

• 10 John Dooley, USDA, APHIS
• 3, 5, 6, 7, 8 Pennsylvania Dept of Agric and
  USDA, APHIS (permission Anwar Rizvi)
• 9 J. L. Peterson
• 18, 26 Margery Daughtrey