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 8 Feb 2022
Source: The News International [summ. Mod.DHA, edited]
https://www.thenews.com.pk/print/931720-premature-rust-attack-may-worsen-punjab-wheat-woes


Early occurrence of leaf and stripe rust has set off alarms as it may spread to threatening levels in the prevalent weather, which is conducive to these fungi, according to the Punjab Agriculture Department. Prospects for the current wheat crops are not bright. Rust attacks even on previously resistant wheat varieties are being witnessed in the Southern Punjab [see comment below].

The early occurrence of the rusts has been observed at the end of January 2022 at some locations in Southern Punjab. The weather in February is highly conducive to the spread to healthy crops. Maximum vigilance and correct management of the rusts is needed. Farmers should regularly inspect their crops and spray the appropriate fungicides as soon as infection appears to prevent further spread of the diseases.

[byline: Munawar Hasan]

--
communicated by:
ProMED

[Stripe rust (also called yellow rust) of cereals is caused by the fungus _Puccinia striiformis_. The disease affects wheat (_Triticum aestivum_), durum wheat (_T. turgidum_), some barley varieties, triticale (wheat/rye hybrids), and a number of wild grasses. It causes yellow stripes on leaves, which leads to loss of photosynthetic ability and plant vigour, as well as stunting of plants. Yield losses of 40-100% have been reported in wheat.

Leaf rust (also called brown rust) of wheat is caused by the fungus _P. recondita_. Related pathogens affect barley and rye. The disease reduces the photosynthetic potential of the plant and can cause yield losses of over 40% in individual fields. Symptoms include brick-red pustules on leaves, stems and, later, on heads. Epidemic severity increases exponentially over time and may appear to "explode" during favourable weather.

A third rust affecting wheat is stem rust (also called black rust), caused by the fungus _P. graminis_.

For more information on stem rust see ProMED post 20210408.8296894 and other items in the archives.

Rust spores are wind dispersed in several cycles during the cropping season and are also spread by mechanical means and with infected plant material (straw, grain). The fungi need living tissue to survive between seasons and cannot survive on seed or stubble or in soil. Volunteer cereal plants and some wild grasses may generate a "green bridge" providing inoculum to infect new crops. Disease management relies mainly on timely fungicide applications, choice of crop cultivars, and control of volunteer crop plants. Field monitoring for early discovery of infections is important so action can be taken to limit pathogen spread as well as build-up of inoculum.

New strains of cereal rusts with increased virulence are emerging worldwide. These include strains that show additional fungicide resistances and/or the ability to break down genetic resistance of specific host varieties (as is being reported above). Monitoring and resistance breeding programmes have been established in different regions for early detection of new rust strains and to attempt to stay ahead of pathogen evolution.

Development of crop varieties with stable resistance to multiple rusts (ProMED post 20120831.1274190) is particularly difficult since the pathogens can be expected to mutate independently, resulting in a range of changing combinations of strains. Furthermore, climate warming allows survival of wheat rusts on green bridges into higher latitudes as yet another example of pathogens extending their range due to climate change (see also ProMED posts 20141024.2895414, 20120809.1235745, 20090914.3230, 20110718.2172).

Maps
Pakistan:
https://www.nationsonline.org/maps/pakistan_map.jpg and
https://images.mapsofworld.com/pakistan/pakistan-political-map-1000px.jpg (provinces)
Punjab districts:
http://www.pakworkers.com/wp-content/uploads/2013/07/Map-of-Punjab-Province-district-wise-in-Pakistan.jpg

Pictures
Stripe rust symptoms on wheat:
https://www.realagriculture.com/wp-content/uploads/2014/07/stripe-rust-3-signature-small2.jpeg,
http://www.plantmanagementnetwork.org/pub/php/brief/2005/stripe/image/wheat3.jpg and
https://www.agric.wa.gov.au/sites/gateway/files/styles/original/public/Stripe%20rust%20infected%20glume.JPG
Wheat leaf rust symptoms:
http://www.forestryimages.org/images/768x512/5187012.jpg,
http://www.forestryimages.org/images/768x512/5154036.jpg and
http://www.forestryimages.org/images/768x512/1493026.jpg

Links
Additional news story:
https://www.thenews.com.pk/print/930954-experts-warn-of-disease-attack-on-wheat-crop
Information on stripe rust:
https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=45876,
https://www.agric.wa.gov.au/mycrop/diagnosing-stripe-rust-wheat,
http://www.ipm.ucdavis.edu/PMG/r730100511.html and
http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/158964/stripe-rust-in-wheat.pdf
Information on wheat leaf rust:
https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/leaf-rust-of-wheat,
https://doi.org/10.1111/j.1364-3703.2008.00487.x and
https://www.agric.wa.gov.au/mycrop/diagnosing-leaf-rust-wheat
Information on all 3 rusts via:
https://www.ars.usda.gov/midwest-area/stpaul/cereal-disease-lab/docs/cereal-rusts/
Wheat rusts overview, including epidemiology and spore types:
http://www.fao.org/3/y4011e/y4011e0g.htm
Fungal taxonomy and synonyms via:
http://www.indexfungorum.org/Names/Names.asp
Wheat rusts global tracking, current race analysis and distribution:
https://rusttracker.cimmyt.org/ and
https://agro.au.dk/forskning/internationale-platforme/wheatrust/
Global Rust Initiative:
https://bgri.cornell.edu/
- Mod.DHA]

See Also

2021
---
Stripe, stem & leaf rusts, wheat - Ethiopia 20210212.8186216
Stripe rust, wheat - India: (HR) 20210120.8121602
2020
---
Stripe rust, wheat - China 20200528.7391929
Stripe rust, wheat - UK: new strain susp. 20200410.7206768
Stripe rust & head blight, wheat - China 20200318.7104946
Stripe rust & karnal bunt, wheat - India: (HR) 20200204.6950281
2019
---
Stripe rust, wheat - China: alert 20191219.6849959
2017
---
Stem & stripe rusts, wheat - Europe, Asia, Africa: new races 20170206.4820305
2016
---
Stripe, stem & leaf rusts, wheat - Ethiopia 20161117.4637042
Leaf rust, wheat - UK: (eastern) 20160621.4299957
2015
---
Stripe rust, wheat - Europe: origin of strains 20150717.3517395
2014
---
Leaf rust, wheat - USA: races 20140411.2396698
2011
---
Leaf rust, wheat - UK: new strain 20110801.2315
and additional items on cereal rusts in the archives

Website: http://www.isid.org

Published: February 11, 2022