Late summer signals the time to consider disease control programmes in your fodder beet crops, having completed weed control and nitrogen (N) inputs.

Retaining fodder beet canopy through the application of registered fungicides helps reduce yield losses from foliar diseases and frost damage, while enhancing plant growth through physiological benefits.

Ideally, two fungicide applications should be made roughly three weeks apart. Apply the first at the initial signs of disease.

The main foliar diseases that affect beet crops are powdery mildew, rust, ramularia and Cercospora. The amount of disease present in a crop is often related to the drilling date, with earlier sown crops often presenting with higher amounts. The climate and variety of fodder beet are also drivers of disease occurrence.

Powdery mildew

» Presents – February to early autumn.

» Symptoms – Grey mould on the crop, starting on outer leaves.

» Risk – Mild winters, dry and warm conditions.

» Severity – Overseas data shows early infections can reduce yields by 20 percent.¹

Rust

» Presents – February onwards.

» Symptoms – Small orange/brown pustules on leaf surface, leading to defoliation.

» Risk – Damp conditions and temperature ranging from 15 to 22°C.

» Severity – Overseas data shows yield losses can be 10 to 14 percent.¹

Ramularia

» Presents – Mid to late autumn.

» Symptoms – Angular leaf spots with central silvery cells. At times, a dark outer margin on older leaves. Spots are larger than those of Cercospora.

» Risk – Temperatures from 17 to 20°C and wet conditions.

» Severity – Apply fungicide to control multiple foliar diseases including Ramularia.

Cercospora

» Presents – Late January to April.

» Symptoms – Circular spots 3 to 5 mm in diameter with necrotic, tan-grey coloured centres and reddish-brown boarder spots coalesce, leading to severe defoliation.

» Risk – Warm wet weather with temperatures above 25°C.

» Severity – Overseas, sugar beet crops yield losses can exceed 50 percent.¹ The disease can be exasperated in the presence of beet yellow virus.

» Resistance – Resistance to registered fungicides is a concern as it has been transported in seed from Europe. However, fungicide applications are still recommended.

Two products are currently registered for use on fodder beet, both using a mix of triazole and strobilurin. One product has a graze withholding period of 42 days while the other is 28 days. The differences in timings may influence your choice of product for the second application.

Prior to applying your first fungicide application, take a leaf tissue test to monitor the crop for any potential trace element deficiencies. If necessary, a trace element liquid can be applied with the first fungicide.

In the future, more accurate disease forecasting may be available using technologies such as Spore ID and local weather data. With the cost of inputs increasing and public awareness of food production becoming prevalent, these systems will prove helpful.

Your local PGG Wrightson Technical Field Representative can help formulate a disease control programme for your fodder beet crops.

1 British Beet Research Organisation. Retrieved from www.bbro.co.uk.