A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org

Date: Thu 9 Jun 2022
Source: WA Department of Primary Industries and Regional Development (DPIRD) [summ. Mod.DHA, edited]
https://www.wa.gov.au/government/announcements/oat-growers-keep-watch-plant-disease-red-leather-leaf


Oat growers are to look out for red leather leaf (RLL) in oat crops, which was confirmed in Western Australia [WA] for the 1st time in 2021. The disease has been present in south eastern Australia for many years and can impact yield and quality in oaten hay and grain crops.

DPIRD [Department of Primary Industries and Regional Development] detected the disease in samples from south western WA as part of general crop surveillance. They said, given the geographic spread, it was likely the disease had been present for more than one season. The disease is stubble borne and could easily be confused with other foliar diseases. Continuous oat crops in cooler, higher rainfall environments are at greatest risk.

There are no fungicides currently registered for RLL in oats, however fungicides registered in oats for other foliar diseases have been shown to reduce disease severity in eastern Australia.

--
Communicated by:
ProMED

[Red leather leaf (RLL) of oats is caused by the fungus _Neospermospora avenae_. It has not been reported on any other host, but may be a major constraint to oat production in affected areas. Losses are due to reduction of grain and hay yield and quality. Symptoms may include small leaf lesions surrounded by chlorotic zones; lesions later become necrotic, forming holes; red-brown ("leather") discolouration and stiffening of leaves; necrosis of leaf margins. RLL is favoured by wet seasonal conditions and was found uncommon in low rainfall zones.

RLL epidemiology and pathogen life cycle are not well understood so far. The fungus survives in stubble and other crop residue for several years; infection of new crops is likely to occur via spores produced in crop residue and infected plants. Disease management may include crop rotation for several seasons; some foliar fungicides, if applied with correct timing, found to suppress RLL symptoms but not to eliminate the pathogen for complete disease control; use of crop varieties with lower RLL sensitivity to reduce losses.

Spread of many pathogens to WA is being prevented by the extensive desert and dryland areas isolating the state from the eastern regions. WA has specific biosecurity regulations to prevent introductions from eastern areas. Nevertheless, some incursions still occur, another recent example being blueberry rust (ProMED post 20220517.8703302).

Maps
Australia (with states):
https://www.nationsonline.org/maps/australia-political-map.jpg and
https://promedmail.org/promed-post?place=8703874,289

Pictures
RLL symptoms on oat:
https://i.pinimg.com/originals/b0/11/c9/b011c9e314655ad92f38ba5b7cc9f14b.jpg,
https://groundcover.grdc.com.au/__data/assets/image/0033/436839/gc_zz_RLL05_squiz02.jpg, and
https://agriculture.vic.gov.au/__data/assets/image/0011/579017/red-leather-leaf-oats2.jpg

Links
Information on RLL of oat:
https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/red-leather-leaf-of-oats,
http://www.herbiguide.com.au/Descriptions/hg_Red_Leather_Leaf_of_Oats.htm,
https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2020/08/managing-red-leather-leaf-disease-and-preventing-weather-damage-in-oats,
https://groundcover.grdc.com.au/grower-stories/southern/researchers-profile-red-leather-leaf-disease,
https://www.bcg.org.au/red-leather-leaf-not-just-a-tongue-twister/, and via
https://www.agric.wa.gov.au/sites/gateway/files/DPIRD%202020%20Oat%20Disease%20Review_National%20Hay%20Agronomy.pdf
_N. avenae_ taxonomy & synonyms:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=838075 and
http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=838075
- Mod.DHA]

Website: http://www.isid.org

Published: June 16, 2022