Dothistroma needle blight current knowledge and knowledge gaps

1
Dothistroma needle blight current knowledge and
knowledge gaps

• Lindsay Bulman
• New Zealand Forest Research Institute Ltd

March 2005
2
Distribution

• Everywhere susceptible hosts are grown
• Severe infection has been recorded
• overseas over the last 50 years
• British Columbia 1963-66
• NW USA 1960s
• Illinois early 1960s (90 mortality)
• Kansas 1951
• Africa 1960-70s
• England 1954,1956,1960
• Croatia early-mid 1980s
• Chile 1960s-present
• The sexual stage has not been reported in
  Southern Hemisphere plantation forests

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Infection process

• Spores are released during rainfall by rain
  splash so spores do not travel far
• Prolonged needle wetness is needed to initiate
  and continue infection
• Main infection period is summer (Nov-Feb) or
  when temperatures are over 16oC
• Infection can begin at 7oC but many spores
  (gt100,000) and wet conditions are needed
• The infection cycle can be as short as 3 weeks
  under optimal conditions, but generally 6-10
  weeks
• The sexual stage appears to be less important
  than the asexual stage in disease development

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Dothistromin

• Relationship with pathogenicityor virulence in
  the field not yet established
• Production in culture variable
• Lesion development is caused by benzoic acid in
  response to Dothistromin
• There were no significant differences between
  length of lesions induced by dothistromin on
  resistant and susceptible trees

5
Stocking and thinning

• Stands grown on pulpwood regime (660-1630 sph)
  sprayed on average 5.5 timesduring susceptible
  period
• Stands on clearwood regime (pruned and 300-350
  sph) 75 sprayed 0 to 2 times during
  susceptible period

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Stocking and thinning

• Thinning also removessusceptible trees,
  therebyeliminating growth response tospraying

7
Pruning

• Spores are produced on foliage attached to the
  tree
• Needles in litter are not a source of inoculum
• Pruning may suppress disease levels for 2-3 years

8
Environmental factors
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Environmental factors

• A combination of consecutive wet summers, high
  stocking, and no spraying has resulted in tree
  mortality (12 in one experiment, but
  confounded with Armillaria sp.), and lower crown
  death
• NZ does not have the variety of damaging bark
  beetles and root diseases that can attack and
  kill trees weakened by Dothistroma

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Economic impact

• Volume growth loss is proportional to average
  disease level
• Annual loss from Dothistroma needle-blight is
  in the order of 24m
• Dothistroma needle-blight is a serious disease
  of Pinus radiata and some other Pinus spp. in NZ

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Control

• Aerial spraying is effective
• Kills fruit bodies to reduce inoculum timing is
  critical
• Protects new foliage
• The only example of successful control of a
  forest pathogen by aerial application of
  fungicide
• Resistant breeds reduce infection
• Gains of 10-12 have been reported experimentally
• Silviculture
• Pruning and thinning reduce inoculum, reduce leaf
  wetness period, and remove susceptible trees

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Knowledge gaps

• Relationship between Dothistromin production and
  virulence/pathogenicity in the field
• This is currently being studied in the UK
• Performance of resistant breeds in the field
• Existing genetics trials are being evaluated for
  needlecast fungi
• Pinpointing the optimum time to spray
• Trials are underway to monitor monthly
  development of fruit bodies and infection in
  relation to climatic variables

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Future New Zealand research priorities

• Pinpointing the optimum time to spray
• Continue monthly operational trial
• Dothistroma prediction
• Revise and update current model
• Effect of infection on wood properties
• Habitat preference modelling
• Development of a GIS-based overlay to identify
  high risk microsites at a sub-stand level
• Use of disease mapping tools (i.e.
  hyperspectural, digital photographs) with
  climate/topograhy overlays
• Leading to a DSS that enables targeted planting
  of resistant breeds or alternative species

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Future New Zealand research priorities

• Performance of resistant breeds in the field
• Surveys of field plantings of resistant breeds
  and other stock, comparison of disease levels,
  growth, and spray history
• Pathogenicity/virulence
• Keep a watching brief on overseas developments
• Maintain links with UK and Canadian researchers
• Maintain a lookout for new subspecies, races,
  formae speciales, varieties, of all forest
  pathogens not only Dothistroma pini