Poster Presentation Science Protecting Plant Health 2017

Importance of Charcoal Rot in the Australian Strawberry Industry Following the Phase-out of Methyl Bromide (#326)

Scott W Mattner 1 , David A Riches 2 , Apollo O Gomez 3 , Dylan J McFarlane 4 , Mirko Milinkovic 1 , Ian J Porter 2 , Frank C Greenhalgh 1
  1. Victorian Strawberry Industry Certification Authority, Toolangi, VICTORIA, Australia
  2. La Trobe University, Bundoora, VICTORIA, Australia
  3. Department of Agriculture and Fisheries, Maroochy Research Station, QUEENSLAND, Australia
  4. Univserity of Queensland, Brisbane, QUEENSLAND, Australia

Charcoal rot, caused by the soil-borne fungus Macrophomina phaseolina, has recently become a serious disease of strawberry fruit crops in Australia, where it has caused plant losses of up to 50%.  Symptoms of the disease include wilting, collapse and dark brown or reddish-brown necrotic areas in the cortex and along the vascular tissues of the crown.  High soil temperatures (> 27°C) and low soil moisture favour disease development.  An extensive survey conducted in 2017 of 100 strawberry farms in Victoria isolated M. phaseolina from diseased strawberry plants at 55% of properties.  Furthermore, M. phaseolina was detected in soil at 75% of properties.  In contrast, M. phaseolina was not detected in plants or soil at strawberry nursery farms.

Fumigation with methyl bromide (MeBr)/chloropicrin previously controlled charcoal rot in strawberry crops.  Following the phase-out of the use of MeBr, however, charcoal rot has rapidly increased in importance as a serious disease of strawberry crops around the world, including in Australia.  Field trials were conducted in Queensland and Victoria where microsclerotia of M. phaseolina or infected crowns of strawberry plants were buried into soil.  Fumigation with MB/Pic eradicated M. phaseolina in infected crowns buried in soil, whereas other fumigants currently registered for use in the strawberry industry (chloropicrin and 1,3-dichloropropene) were not effective.  All soil fumigants killed microsclerotia in soil.  It is likely that the continued use of MB/Pic under a critical-use exemption has prevented outbreaks of charcoal rot in strawberry nursery crops in Australia, but these exemptions will not be granted for long periods into the future and there is an urgent need for suitable alternatives.  Our current research is evaluating improved application techniques for currently registered fumigants (e.g. use of impermeable barrier films) or new fumigants (e.g. cyanogen) for control of charcoal rot.  Results will be presented at the conference.