Powdery mildew and rust

At Brooms Barn we are now finding rust and powdery mildew in the field and reports are coming in of disease being found in crops from all factory areas. Advice is to apply a full rate fungicide when disease is first found in the crop.

Some sugar beet crops were treated with a fungicide a few weeks ago, in conjunction with an insecticide to control silver y moth. Fungicides will normally be effective for 4 to 6 weeks depending on which actives were used so it will be necessary to re-check crops that were sprayed early on to assess the need for a second fungicide application.

It is possible in the majority of cases to tank mix a sugar beet fungicide with an insecticide, although if unsure, it is sensible to check with the manufacturer or your agronomist.

Cercospora
A leaf sample sent into the Plant Clinic today from Lincolnshire has just confirmed positive for Cercospora, a fungicide had not yet been applied to this crop. If you do find leaf spotting and are unsure of the diagnosis then we would be interested to receive samples.? The advice is to apply a fungicide that consists of a triazole plus strobilurin e.g. (Escolta, Opera, or Priori Xtra) or difenoconazole + fenpropidin (Spyrale) as soon as possible.

Black Aphid
Black aphid numbers have fallen since last week in crops which have not received an insecticide and high levels of natural predators are now being found. Recent rainfall has also reduced the pressure from black aphids. In fields that received a pyrethroid for silver y moth control, continue to monitor aphid and natural predator numbers and only where black aphid numbers are high (100+plant) should an insecticide be considered.

Silver Y Moth
Adult silver y moths can still be seen and in some cases they are present in crops that have not previously been damaged by this pest. We are expecting to receive reports of caterpillar activity any time now. The recent rainfall will have reduced the likelihood of potential damage from caterpillars though, due to them being washed off the plants and onto the soil. Continue to monitor all crops from now on for further signs of damage irrespective of previous damage levels or insecticide treatments applied.

The official spray threshold for treatment is 5 caterpillars per beet plant.

As silver y moth damage does not occur at high levels every year in the UK the above threshold should be treated with caution. Where caterpillar damage is reducing leaves to the veins then treatment is definitely advised, in other situations then frequent monitoring should be carried out and if required advice sought from your local British Sugar Area Manager/Agronomist or the Sugar Beet Advisory Assistance help line.

Weed beet
Continue to control weed beet and bolters, all beet plants that flower in July and August should be destroyed before they start to set seed.

If the plants have not started to set seed, pull them up, break the stems close to roots and drop in the field (ideally on top of the crop canopy to prevent re rooting occurring).

To check if seed has started to form, tap the flower stem and watch for the release of yellow pollen, if a small pollen 'cloud' is released it is generally safe to leave the plant in the field. If no, or a very small amount of pollen is observed then it is likely that seed is present, and if plants are left in the field there is a high risk that some of the seed will mature on the stem and fall in the field.

Where numbers are too high to hand pull then weed wiping or cutting should take place.

Weed wiping with glyphosate is the preferred option when there are between 1,000 and 10,000/ha. For best results treat approximately 14 days after flowering commences and then again 14 to 28 days later.

Cutting should be used when high populations (>10,000/ha) of weed beet are present. Control of around 94+% can be expected if three cuts are used, starting approximately 14 days after flowering commences and repeating at 14 day intervals. If cutting on two or more occasions, the first cut should be 20cm or so above the crop.
Clamps
Clamp sheets can still be ordered if you phone the Agricultural Help desk on 0870 240 2314, note the official offer date closed on 31 July but last minute orders are still being accepted.

If you plan to use large bales of OSR or cereal straw for clamping then ensure supplies are secured as soon as possible as straw will be short this season. Plan to store the beet no more than 2.5 m high and allow between 0.8 and 1.0sq m of base area for every tonne of beet to be stored.

BASIS and NRoSO points
Four BASIS points in total (not per bulletin) have been allocated for the period between 01/06/10 and 31/05/11 (2CP, 1E, 1PN), reference CP/16420/1011/h. In order to claim these points please contact Nick Smith at BASIS registration on nick@basis-reg.co.uk.

Caution : this information is based on results of experiments and experience but cannot constitute a recommendation.