Crop scouting is going to be essential to determine which small grain fields will warrant foliar fungicide use this year, according to Marcia McMullen, extension plant pathologist at NDS U.

Uneven emergence, drought, and extrelme temperature stresses are all going to result in reduced yield potentials in many fields, and good yield potentials generally are required for economic use of foliar fungicides, she says. Thiis means 40 to 45 bushels per acre yield potential in wheat and 65 bushels or greater potential in barley.

Dry weather also has delayed disease development in most areas, but rainfall or high humidities could still result in sub stantial disease pressure. Leaf rust was detected at low levels on May 31 in both winter and spring wheats in Cass and Richland counties, McMullen says. Various leaf spots diseases also were present at low levels in these fields, and also have been reported from western North Dakota counties.

Foliar fungicides are used to protect the flag leaf and the head above from infections. Many small grain fields in southern North Dakota are already approaching the flag leaf stage, while winter wheats are beyond. On some small grain fields the decision to use fungicides needs to be made soon, says McMullen.

The uneven development of a single crop in a field is a1so going to make the decision on when to apply a fungicide more difficult, because these fungicides are registered to be applied at specific leaf stages.

Tilt fungicide is a systemic compound and it is registered to be applied at early flag leaf emergence (Feekes growth stage B). Tilt has good activity against leaf rust, leaf spots, glume blotch, and powdery mildew of wheat and barlev.

The mancozeb fungicides (Dithanes, Manzates, Penncozeb, Manex II) are protectant fungicides and are recommended to be applied at boot stage, when the flag leaf is fully out Feekes growth stage 10), followed by a second application ahout 10 days later. The mancozebs have good activity against leaf rusts and common leaf spot diseases of wheat and barley.

Foliar fungicides are used on fields that have good yield potential, diseases present in the lower canopy, and where high humidities and rainfall are likely or predicted. This information will have to be gathered on a field-by-field basis by careful scouting if the producer is going to benefit from fungicide use, McMullen says.

The approximate cost of foliar fungicide application, including aerial application costs, is $12 per acre, a cost high enough to warrant wise use of the fungicides in a year that has already seen economic loss to small grain farmers, she says.