BBRO Advisory Bulletin No 23

Powdery mildew and rust

Both powdery mildew and rust are active in unsprayed trials plots at Broom's Barn. Where the first fungicide was applied on the 29th of July, second sprays, where required, are planned for week commencing 29th August.
Two fungicide applications are recommended if:-

• there is a risk of rust developing
• beet is destined for later harvest
• fungicide applications after mid-September will be less effective.

Cercospora leaf spot

Currently there are no reports of any cercospora being found in the UK sugar beet crop. Researchers at Broom's Barn would welcome samples of suspected cercospora to use as part of a collaborative project with colleagues from the USA. The project is looking at the sensitivity of cercospora isolates to currently available fungicide actives. Cercospora can be confused with ramularia in the field (Photos 1 and 2), but under the microscope, the spores of the two fungi are easily distinguished.
Samples should be sent to the BBRO Plant Clinic, Broom's Barn Research Centre, Higham, Bury St Edmunds, Suffolk. IP28 6NP.

Rhizomania

To date there have been 16 confirmed cases of rhizomania, of which eight have been analysed in more detail. These results have confirmed the presence of the AYPR strain in rhizomania resistant varieties in two new fields in the Orford areas (Suffolk). Please contact your British Sugar Area Manager or Broom's Barn, if you suspect rhizomania on farm so that the necessary confirmatory tests can be performed. Symptoms can vary greatly, but usually a mass of fine hairy secondary roots is classic but chlorosis (pale yellowing) of foliage commonly occurs see Photo 3.

Beet cyst nematode (BCN)

One of the first indications of BCN damage to sugar beet can be pale yellowing of leaves and a higher number of weeds, as a result of reduced competitiveness of the beet plant. Plants that are infected are also more prone to wilting and heavy infestations will result in stunted growth. Root symptoms can sometimes be confused with rhizomania as they take on a bearded appearance. If confirmation of BCN is required then samples can be sent to into the BBRO Plant Clinic.

Yellow patches

Last autumn we received a number of enquires about sugar beet crops developing yellow foliage that was not caused by BCN, rhizomania, virus yellows or a nutritional disorder. It was most obvious in crops that had not received a fungicide spray or only one spray. In the latter case the old est and newest leaves often appear least affected (Photo 4). The phenomenon appeared to be variety related and the exact cause is still not clear. This week, the BBRO Plant Clinic at Broom's Barn received its first sample for 2011 showing these symptoms.

The advice is to check any crops that are showing yellowing, samples can be sent into the BBRO Plant Clinic if confirmation is required.

Weed beet and bolters  

• Do not weed wipe once roots are of a harvestable size - this can potentially lead to rotten roots entering clamps or the factory
• Where 'cutting' is being practiced continue with second and third cuts at three week intervals
• Where weed beet is a problem, look at the cropping rotation and extend the interval between beet crops where possible
• Plan forward to control weed beet in all crops in the rotation

Land preparation for the 2012 beet crop  

Conditions are ideal in most situations for ploughing in preparation for the 2012 beet crop, ploughing early in dry conditions should be a priority if time allows.

Key Dates 

For further details contact your local British Sugar Area Manager or call 0870 240 2314.

BASIS points

Two BASIS points in total (not per bulletin) have been allocated for the period between 01/06/11 and 31/05/12 reference CPD/20108/1112/a. In order to claim these points please contact Natalie at BASIS registration on Natalie@basis-reg.co.uk 

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