Weather conditions

Septoria will have been favoured by the recent wet weather. Where a fungicide to protect the flag leaf has yet to be applied, a high rate of a triazole fungicide with good action on Septoria (for example, Opus, Folicur) should be included to try to limit infection.

Many spring cereal crops, and barley in particular are showing yellowing symptoms to varying degrees. This is largely due to waterlogging which has impeded root development and nutrient uptake, and from the leaching of nitrogen. It is very difficult to improve this condition consistently, and some crops may not justify a lot of expenditure. The application of nitrogen top-dressing may however help in certain circumstances, especially if growing conditions subsequently improve.

Some spring cereal crops have yet to receive herbicide and fungicide applications. Growers should check latest application timings for herbicides. Some broad spectrum sulfonylurea herbicides (for example, Ally, Harmony M and Quantum) can be applied until the flag leaf has emerged - GS 39 (check product labels for approved crops and specific latest timings). As weeds are likely to be more advanced at this stage there is less scope for herbicide rate reduction.

The wet weather will have favoured development of diseases such as Rhynchosporium in barley. Where crops have yet to be treated with fungicide, this should be carried out as soon as conditions allow to limit disease spread. Fungicide choice will depend on disease(s) present and the yield potential of the crop. A mixture of a triazole plus morpholine will be suitable for most spring barley crops. The addition of a strobilurin should be reserved for crops with higher yield potential.

Blight infection periods have been recorded on 7-8 June and 13-14 June, and two field outbreaks of blight have been reported. Growers should apply fungicides at the intervals recommended for high risk conditions. Systemic fungicides such as propamocarb (as Merlin or Tattoo) or a phenylamide (for example, Fubol Gold, Trustan) are appropriate for the first two sprays when haulm growth is rapid. Following this, growers should switch to a translaminar (for example, Curzate, Invader) or protectant product (for example, Shirlan, Ranman, Dithane, Electis).

Options for chemical weed control in emerged potato crops are limited. Metribuzin (for example, Sencorex, Lexone) may be applied to certain varieties post-emergence before the longest crop shoots reach 15cm. (Check product label for varietal suitability). Rimsulfuron (Titus) is an option which must be applied to emerged weeds but before the crop is 25cm tall. It cannot be used on seed crops for certification.

Following the unseasonable weather the aim of top fruit growers should be to maintain as many fruitlets as possible on trees though continuing a programme of Scab Control and where necessary supplementary nutrition with foliar feeds.

Scab must be controlled. A short-term eradicant scab control program should be used where a protectant programme has not been possible due to ground conditions. Once scab is under control growers can return to a protectant programme.

Where trees are showing noticeable signs of stress, foliar feeds containing the major elements of N, P and K can be applied.

If ground conditions continue to be poor sprayers should be half filled to improve load bearing capacity and the use of low ground pressure tyres will be beneficial.

Scab inspections should now be much more often. Check trees every 2-3 days for symptoms.

Post emergence herbicides will be necessary where there has been poor performance of "sealer"". Growers are reminded of the Horticulture Bulletin issued last month which gave a weed control table and can be used to help choose the most appropriate herbicide option.

Where chemical control is not possible, mechanical weeding, if appropriate, is recommended. In high value crops hand weeding may be necessary. Growers will have to assess the resources required to ‘clean’ the crop and balance this with economic return.

Diseases are present in crops earlier this year. Ringspot and White Blister are already apparent on brassica crops as is blight in celery. Where disease is evident an eradicant fungicide should be applied. Protectant programmes should be commenced where disease is not yet visible in the crop.

On most soils the heavy rainfall will have leached the basal nitrogen from the soil. Top dressings will be necessary for most crops to sustain growth. Because plants are under stress it is recommended that small regular treatments be applied. When soil temperatures rise and crop growth returns to normal then normal treatments can be applied.

These DARD Special Management Notes have been prepared by Greenmount Campus - Tel: 028 9442 6771.

For further information contact your local Greenmount Development Adviser. Greenmount Campus is an integral part of DARD's Agri-Food Development Service.