Crops Notes June 2009

Up to a week ago this year’s spring crop had been looking really well, with much of it benefiting from early drilling in favourable conditions. However, cool temperatures and excessive rainfall have started to take their toll, causing areas of compaction and “wet spots” in many fields to turn yellow as plants are stressed. There is little point in losing sleep over yellowed barley, as the situation will improve with the weather. Foliar feeds rarely do much good unless a specific trace element deficiency can be confirmed and treated within a day or two.

There is little point in discussing specific products as modern herbicides are broad spectrum and work under a range of conditions. However, there are a few simple points to remember when deciding on your weed control strategy:

For spring barley crops with high yield potential, a two-spray fungicide programme should be used. This is based on the use of reduced rate fungicide applications. The first application should be applied from late tillering to the start of stem extension. The second fungicide application should be made three to four weeks after the first at around flag leaf emergence – first awns visible (GS 39 – 49). Mixtures of triazole and strobilurin, for example, Proline and Comet at a reduced rate, are appropriate for both first and second treatments. The inclusion of Bravo at the later treatment will significantly help disease control and reduce abiotic leaf spotting which has been an increasing problem in the last few years.

For growers adopting a single fungicide approach this single application should be made at the earlier timing as this usually gives the best financial return.

It is time to plan this year’s blight control programme. Key elements to any programme are the removal of infection sources and a spray programme timed to have maximum impact.

Two types of systemic fungicides are approved for blight control, phenylamides (for example, metalaxyl-M in ‘Epok’, ‘Fubol Gold’) and propamocarb (in ‘Merlin’, ‘Tattoo’). Systemics are most useful early in the season when crops are growing rapidly.

Strains of blight resistant to phenylamides (but not propamocarb) occur in Northern Ireland and reduce the benefit of using phenylamide products. To help limit the incidence of phenylamide resistance, growers should apply no more than two phenylamide-based sprays and avoid their use after mid-July. Start the fungicide spray programme as soon as a blight warning is issued or when the crop meets within the drills (whichever is earlier). Start with a product containing a systemic, either propamocarb (for example, ‘Merlin’ or ‘Tattoo’) or a phenylamide (for example, ‘Epok’, ‘Fubol Gold’). Continue with either a protectant (for example, ‘Electis’, ‘Ranman’, ‘Shirlan’) or translaminar (for example, ‘Curzate’, ‘Invader’, ‘Infinito’, ‘Revus’). Complete the programme with at least three sprays of a protectant such as ‘Shirlan’, or ‘Ranman’ to help prevent tuber infection.

Ensure protection is maintained by regular spraying until the haulm is dead.

Appropriate spray intervals and complete coverage of the crop are the key to successful blight control. In humid, wet weather favourable to blight, use shorter intervals as recommended on the product label for high risk conditions. Nozzle selection can influence the efficiency of application and the volume of water used. Angled jets give better canopy cover at all stages of growth but particularly up to and including full canopy cover.

At the end of the season, if there is blight in the crop, destroy the haulm as soon as possible to reduce the risk of tuber blight and wait at least three weeks before lifting.