Beet crops continue to make good progress and the warm temperatures at the end of May have brought many crops on in leaps and bounds. Even crops which have been severely grazed by birds are recovering well, with more plants than expected having survived in many cases. Most of these fields are now clearly green down the rows. The most forward crops will be just about holding hands between the rows by the end of this week, although the majority will probably need another fortnight or so.
The warmer weather has also brought with it an influx of winged aphids. No reports of wingless aphids yet, indicating that seed treatments are holding up at present, although we have put measures in place should that situation alter over the coming weeks - see note below.
Beet leaf miner grubs co ntinue to be active on crops with no insecticide seed treatments but levels are low and crops appear to be growing away from any damage.
Weed control to date has been good, with many fields now having been tractor hoed as well. Many crops will receive a final application of residual herbicide to control any late flushes of fat hen where tractor hoeing has disturbed the existing layer of residual herbicide.
Peach-potato aphid control in Sugar beet
The cold, wet weather throughout April and May has caused a number of issues that appear to have affected the availability and uptake of the neonicotinoid seed treatments by the sugar beet plants. These products should give adequate protection of the seedlings for up to 14 weeks. However, since drilling many crops have received at least 200 mm of rain with some experiencing over 350 mm; leaching of these products away from the root zone appears to have occurred leaving plants unprotected in some cases. This, in combination with the cold weather, has led to the 2012 crop being at a much smaller growth stage than recent years and potentially vulnerable to attack from virus-carrying aphids through the June and possibly July, until it reaches mature plant resistance at the 12 leaf stage.
To this end, BBRO has secured an extension authorisation relating to the use of 'Biscaya' (M15014) for the control of aphids, principally peach potato aphid (Myzus persicae). This authorisation has been granted for the 2012 season in exceptional circumstances due to the unseasonal weather conditions which have affected crop development early in the season, and the developing high numbers of aphids including MACE resistant populations. Applications should be made via horizon tal boom sprayer in a minimum water volume of 200 litres per hectare. No more than two sprays of Biscaya may be made to sugar beet crops, and no later than then end of July.
Current BBRO aphid monitoring data shows that M. persicae numbers are increasing in all factory areas, but no reports of green wingless aphids yet have been received. ONLY IF green wingless aphids are observed at threshold levels should Biscaya be applied. The threshold for using Biscaya is one green wingless aphid per four plants below the 12 leaf stage, and one green wingless aphid per plant after this growth stage.
Please remember that this Emergency Use is time limited and it will expire on the 31st July 2012.
Bolting prospects - update
The figure above updates this year's intensities of vernalization at Bracebridge (Lincolnshire). The graph shows that the seasonal progression since the beginning of March is continuing to run ahead of the average for cold springs of the past 25 years. Accumulated intensities at the end of March, April and May for various drilling dates are also given in the table below.
Bearing in mind that the bolting threshold is 140 vernalizing hours, our view remains that, despite some warmer weather towards the end of May, we are likely to see significant bolting in early-sown bolting-susceptible varieties, and more than in recent years in early-sown bolting resistant ones.
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 Jill at BASIS registration on Jill@basis-reg.co.uk
For technical queries contact the BBRO helplines:
Pam Chambers , firstname.lastname@example.org 07887 628357
Colin Walters email@example.com 01733 422088
Caution : this information is based on results of experiments and experience but cannot constitute a recommendation.
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