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Issue 30 |
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Prairie Grains is the official publication of the Minnesota Association of Wheat Growers, North Dakota Grain Growers Association, South Dakota Wheat, Inc. and the Minnesota Barley Growers Association. |
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NDSU research reinforces fungicide application recommendations to control scab in wheat and barley
By Tracy Sayler Research over the past year
at North Dakota State University reinforces recommendations in applying fungicides effectively on wheat and barley to suppress scab.General conclusions from ground application trials and greenhouse tests indicate that
across all crops and nozzle arrangements, an angled spray toward the grain heads outperformed a vertical orientation, for head coverage and disease control. However, optimum spray pressures and water volume varied
among crops. Hard red spring wheat:
Nine gallons of water applied by ground was consistently adequate to provide control of scab for hard red spring wheat (Most fungicide labels require a minimum of 10-15 gpa by ground, 5 gpa by air). A range of 40-90 psi gave good control. Lower spray pressures reduce the risk of spray drift, but under calm conditions, the 90 psi gave good control as well. XR8001 flat fan nozzles oriented both forward and backward generally provided slightly better disease control or spray coverage than TwinJets, Hollow Cone, or XR11001 nozzles. The optimum timing of application for scab control in spring wheat is early flowering, at Feekes growth stage 10.51 (Table 1).
Durum: Water volume is important for disease control in durum, because the grain heads are very difficult to wet. Eighteen gallons of water gave better disease control than 9 gpa. With XR8001
nozzles and 18 gpa, 90 psi gave slightly better disease control than 40 psi, under calm field or greenhouse conditions. Optimum timing of application for FHB control in durum is early flowering, Feekes 10.51
(Table 1). Barley:
Increased water volume also results in improved scab control in barley, with 18 gpa providing better disease control than 9 gpa. At 18 gpa, the 90 psi with the XR8001 flat fan nozzles has resulted in improved control in barley, under calm conditions. In barley, the optimum timing of application is at early, full head emergence (Table 1).
Fungicide rate: A full label rate of Folicur (4 fl oz) provided better control of scab than lower use rates, both in the field and in the greenhouse. (Table 2). Surfactants: Surfactants such
as Induce or Silwet added to fungicides at very low volumes (0.03 to 0.06% v/v) improved fungicide performance for scab control. General recommendations
• For ground application, angle spray towards grain head, using forward and backward mounted XR8001 nozzles, or nozzles that have a two directional spray, such as
Twinjet nozzles. To help decide whether a fungicide treatment is necessary or economically viable, follow general guidelines based on yield potential,
price of crop, disease presence, past week's weather and two-week weather forecast. If conditions warrant treatment for scab suppression, these recommendations have also resulted in good control of leaf spot
diseases and leaf rust, notes NDSU extension plant pathologist Marcia McMullen. Five products are currently labeled for heading application for wheat, via full federal registration, a Section 18 Emergency Exemption,
or a 24C state label. Benlate, various mancozebs, and Quadris have full registration for heading application to wheat. The mancozebs also are registered for barley. Folicur has a Section 18 emergency
exemption for use on wheat and barley for scab suppression. Tilt has a 24C state label for use on wheat at heading for scab suppression. NDSU will release application recommendations in a bulletin, "Application
of Fungicides For Suppression of Fusarium Head Blight (Scab)" in June. The bulletin, referred to categorically as AE-1148 (revised), will be available through the NDSU Distribution Center, Morrill Hall, Box 5655,
Fargo, ND, 58105, ph. 701-231-7883. It may also be posted on the NDSU Plant Pathology Department home page, Other NDSU Wheat and Barley fungicide research highlights, 1999 Experimental fungicides—In various wheat and barley trials, two experimental products, BASF 500 and Stratego, compared well with leading fungicide products that are currently available
in controlling scab and leaf diseases. Insecticide-fungicide applications—Limited studies conducted in Ward and Benson Counties (Minot) last year indicated that Lorsban and Folicur can be applied together
without antagonism for control of scab, leaf diseases, and orange wheat blossom midge. However, adequate economic thresholds for both the insect and diseases must be present for a dual application to be
warranted. Timing is also key for the combination to be effective in controlling midge and disease. Aerial vs. ground—Two studies conducted last year near Erie and Casselton in ND compared the effects of
aerial versus ground fungicide applications for controlling scab in wheat. Scab levels were very low in both fields, and thus no conclusions may be drawn yet from the limited data. More studies will be
conducted this summer. Barley planting dates and DON — A study of barley planting dates (April 27, May 18, May 27, June 8) at the Langdon Research Extension Center indicated that while DON levels
(deoxynivalenol, or vomitoxin) decreased with later planting, there was a definite trade-off in yield. Yield was 113, 100.9, 99.3, and 55.6 for respective planting dates from earliest to latest, with corresponding
DON levels (in parts per million) of 3.9, 2.9, 1.3, and 0.7 from earliest to latest planting dates. For a more detailed report of field results from NDSU fungicide studies in 1999, supported in part by the
Minnesota Wheat Research and Promotion Council, contact extension plant pathologist Marcia McMullen, ph. 701-231-7627, or email: |
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