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: Tue 17 Sep 2019
Source: Farmers Weekly [abridged, edited] <https://www.fwi.co.uk/arable/wheat/advice-on-minimising-the-damage-from-bydv-in-cereals>
Winter cereal growers are being urged to focus on cultural controls to ward off a major virus disease without a now-banned seed dressing. The aphid-spread barley yellow dwarf virus (BYDV) can cause yield losses in wheat and barley of up to 60%, and growers this [2019/20] season will not be able to use neonicotinoid insecticide seed treatments.
Experts say the focus needs to be on drilling as late as possible to try to miss the main aphid migration and destroying the "green bridge"
of volunteer cereals from the previous harvest, which can harbour aphids. Without neonicotinoid dressings, the only chemical control is via pyrethroids, but grain aphids are becoming resistant, while bird cherry-oat aphids are still susceptible. These insecticide sprays have only a short period of activity.
"Now we are going to have a much more integrated approach with BYDV, as, if we get it wrong, we cannot correct later, and the disease will stay with us for the rest of the season," [a farmer] says. "We are likely to be using 2 glyphosate [herbicide] sprays, rather than one, as we did before."
[Byline: David Jones]
--
Communicated by: ProMED-mail <promed@promedmail.org>
[Barley yellow dwarf (BYD) disease occurs worldwide and affects a wide range of grass species (Gramineae) including cereal crops like barley, wheat, oats, rice, maize and rye. It is the most destructive of the virus diseases for wheat. Grain yields may be reduced by one-third.
Symptoms include leaf discolouration from yellow to purple (depending on the host species), stunting, reduced tillering and empty seed heads. Plants infected in autumn may not survive the winter or show severe symptoms when growth resumes. Diseased plants often occur in circular patches within a field, which are associated with colonisation by the aphid vectors.
BYD viruses have now been split into several species in the family Luteoviridae (mostly in the genus _Luteovirus_). They are differentiated by their ability to be transmitted by various aphid species (family Aphididae) and their virulence on a selected variety of oats. Some of the viruses are transmitted equally well by several aphids, whereas others can be transmitted by only one or 2 species.
The bird cherry(-oat) aphid (_Rhopalosiphum padi_) and grain (wheat) aphid (_Sitobion avenae_) are vectors of the severe _Barley yellow dwarf virus-PAV_ (type member of genus _Luteovirus_). Coinfections of several BYD viruses may occur in one plant, which can result in either more severe (synergistic) or milder (due to cross protection) symptoms, depending on the virus partners.
The viruses cannot be transmitted by seed, pollen or mechanical means and cannot survive in stubble or in the soil. Volunteer cereal plants or grassy weeds may serve as pathogen reservoirs ("green bridge").
Disease management includes use of crop cultivars with reduced sensitivity to the viruses and control of the aphid vectors.
To protect beneficial insects such as bees or other pollinators, some neonicotinoid insecticides have been banned in a number of countries.
However, as the report above shows, in order to keep the same level of crop production, taking out one group of agrochemicals can lead to increased use of another, in this case glyphosate herbicides, which are also under debate for potential environmental implications.
Maps
UK:
<https://legacy.lib.utexas.edu/maps/europe/united_kingdom.gif>
Pictures
BYD symptoms on cereals:
<https://fwi-wp-assets-live.s3-eu-west-1.amazonaws.com/sites/1/2012/07/5237802-barley-yellow-dwarf-virus.jpg>,
<http://bulletin.ipm.illinois.edu/wp-content/uploads/2013/05/BYDV3.jpg>
(wheat),
<https://image.slidesharecdn.com/r-180626054804/95/barley-yellow-dwarf-disease-15-638.jpg>
(barley),
<https://oatnews.org/sites/default/files/BarleyYellowDwarf04.jpg>
(oats),
<http://www.ent.iastate.edu/imagegal/plantpath/wheat/ydwarf/0093.04ydwarfmv.html>
(compared with healthy),
<https://img.yumpu.com/46899655/1/358x269/barley-yellow-dwarf-symptomspdf.jpg?quality=85>
and
<http://www.ent.iastate.edu/images/plantpath/wheat/ydwarf/0093.10ydwarfwheat.jpg>
(affected field)
Aphids:
<https://d1o50x50snmhul.cloudfront.net/wp-content/uploads/2013/11/dn24513-1_800.jpg>
and
<https://ohioline.osu.edu/sites/ohioline/files/imce/Plant_Pathology/PLPTH-CER-01_wheat-aphid-infestation.png>
Links
BYD disease information:
<https://cereals.ahdb.org.uk/cereal-disease-encyclopedia/diseases/barley-yellow-dwarf-virus-(bydv).aspx>,
<http://www.usask.ca/agriculture/plantsci/winter_cereals/winter-wheat-production-manual/chapter-22/viruses.php#barley>,
<https://ohioline.osu.edu/factsheet/plpath-cer-01>,
<http://www.grdc.com.au/GRDC-FS-BYDV>,
<https://cropwatch.unl.edu/plantdisease/wheat/barley-yellow-dwarf>
and
<http://www.croppro.com.au/crop_disease_manual/ch10s09.php>
BYD disease cycle:
<https://cereals.ahdb.org.uk/media/14884/BYDV-life-cycle.jpg>
Virus taxonomy via:
<https://talk.ictvonline.org/taxonomy/>
Information on aphid vectors via:
<http://www.cals.ncsu.edu/course/ent425/text18/plantvectors.html>
Neonicotinoid and glyphosate status in the European Union via:
<https://ec.europa.eu/food/plant/pesticides/approval_active_substances/approval_renewal/neonicotinoids_en>
and
<https://ec.europa.eu/food/plant/pesticides/glyphosate_en>
- Mod.DHA]
[See Also:
2018
----
Barley virus G - Australia: 1st rep (VI)
http://promedmail.org/post/20181126.6166030
2017
----
Barley yellow dwarf, cereals - UK, Canada
http://promedmail.org/post/20170818.5257933
Barley yellow dwarf - Ireland: (WX)
http://promedmail.org/post/20170609.5094454
2016
----
Barley yellow dwarf, cereals - UK
http://promedmail.org/post/20161011.4550142
2015
----
Barley yellow dwarf, wheat - Denmark
http://promedmail.org/post/20150622.3455679
Barley yellow dwarf, cereals - USA: (ID) alert
http://promedmail.org/post/20150404.3276394
2014
----
Barley yellow dwarf virus-PAS, wheat - Turkey
http://promedmail.org/post/20140616.2543025
2010
----
Wheat streak mosaic & barley yellow dwarf, wheat - USA
http://promedmail.org/post/20100511.1529
2009
----
Wheat viruses - New Zealand: 1st reports
http://promedmail.org/post/20090412.1402
and older items in the archives]
Topics
Species
