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Date: Mon 13 Jul 2009
Source: Farmers Weekly Interactive [edited]
<http://www.fwi.co.uk/Articles/2009/07/13/116603/control-rust-to-protect-foliage.html>

Control rust to protect foliage

Sugar beet growers who aim to lift their crops after the 1st week of November [2009] can help to reduce the risk of frost damage by ensuring their crop is free from rust. But action may be needed sooner than usual. Signs of the disease are already starting to show due to the warm and damp weather over the past couple of weeks, says Mark Stevens of Broom's Barn. "Rust usually appears in late August or early September, but recent weather has brought many foliar diseases forward," he says.

Trials conducted last year [2008] at Broom's Barn found that of all the foliar diseases, rust had the greatest effect on the susceptibility of beet to subsequent frost damage, while presence or absence of powdery mildew was shown to have little or no impact.

"The run of frosts we had between October and December in 2008 caused plants infected by rust to sustain high levels of defoliation; the higher the level of infection, the greater the damage became," says Dr Stevens. Once significant defoliation had occurred, the crown was exposed and the root was vulnerable to frost damage. Lessening the effects of frosts is therefore essential for any grower storing crops in the ground later in the season. "If beet is going to be lifted late, good rust control must be achieved," says Dr Stevens.

"Growers should also be looking out for powdery mildew, cercospora, and ramularia and adjusting their fungicide strategy to suit. It is important to keep a close eye on the crop and take appropriate action as diseases start to develop."

[Byline: James Andrews]

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[Sugar beet rust is caused by the fungus _Uromyces beticola_ (previously _Uromyces betae_). It affects _Beta vulgaris_ and subspecies including sugar beet, beetroot, spinach beet, mangolds, wild beet as well as some other species in the genus (_Beta_ species taxonomy remains to be clarified, see link below).

Symptoms include small brown pustules on leaves, petioles, and seed stalks which in susceptible varieties spread quickly. Older leaves wilt and die prematurely, younger leaves become crumpled, drooping, and yellow. The disease can quickly decimate green leaf area and thus photosynthetic potential, and badly rusted plants finally collapse.
There is little information on direct crop losses, but the secondary effect due to defoliation reported above is an important aspect.

The fungus overwinters on seed crops and beet plants left behind in the field. Spores are spread by wind, water, plant debris and mechanical means and may adhere to seed clusters. A spore viability of
2 years in store houses has been reported. Wide variation in rust resistance exists in sugar beet varieties, but some varieties widely used in Europe are amongst the more susceptible ones. Disease management relies usually on preventative fungicide applications.

The other sugar beet fungi referred to above are leaf spot diseases caused by _Ramularia beticola_ and _Cercospora beticola_, and powdery mildew caused by _Erysiphe betae_. For more information see previous ProMED-mail posts below.

Maps of UK
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif>  and <http://healthmap.org/r/008E>

Pictures
Rust symptoms on sugar beet leaf:
<http://www.inra.fr/hyp3/images/6037061.jpg>  and <http://www.inra.fr/hyp3/images/6037063.jpg>
_U. beticola_ teliospores, microscopy:
<http://www.inra.fr/hyp3/images/6037062.jpg>

Links
Information on sugar beet rust:
<http://www.inra.fr/hyp3/pathogene/6urobet.htm>  and <http://www.cababstractsplus.org/abstracts/Abstract.aspx?AcNo=20056400177>
_U. beticola_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=131936>
Broom's Barn Applied Crop Sciences:
<http://www.rothamsted.ac.uk/broom/sbrindex.php>
Species and taxonomy of genus _Beta_:
<http://www.plantnames.unimelb.edu.au/Sorting/Beta.html>.  - Mod.DHA]