Crop notes June 2008

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.

Minimise problems later by eliminating infection sources now. You should:

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 who opt to use phenylamides 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’). If a phenylamide is used, do not exceed two sprays and switch to another product no later than 15 July

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.

A very dry April and May have has left most of the barley looking poor. Uneven germination and severe drought stress seems to be the norm across the country. This will cast its shadow at harvest, because barley that’s had a hard time soon after emergence rarely seems to yield. Although I would love to offer a quick fix for stressed spring crops, there is only one solution…rain and good growing conditions. Foliar feeds may help for a couple of days, but are no substitute for a few showers. Herbicides should generally be applied at an early stage of growth to maximize yield, but this year I would delay until the crop has lifted out of stress as a herbicide will only make things worse.

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 GS 39 – 49 (flag leaf emergence – first awns visible).

Mixtures of triazole and strobilurin, for example, Mobius or Fandango 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.

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.

Last year many of us were tempted not to apply protection at ear emergence as conditions were dry. However, this proved costly, as wet weather returned and caused a lot of damage with ear diseases. This final spray should always be applied before diseases are visible, the best timing is usually when the ear has just finished emerging and is starting to flower.