Success Factors in Controlling FHB

NDSU crop scientists recommend the following to optimize the success of a fungicide application for Fusarium head blight (FHB, scab) control:

Treatment Timing: Accurate timing of fungicide application is critical for success. In the field, multiple infections may occur if weather is favorable for infection. However, producers most often look for a single application timing to provide good control.  NDSU field studies indicate that if only a single application of the recommended rate of fungicide is going to be applied, the best timing for maximum reduction of scab severity is at early heading for barley (Feekes 10.3- 10.5) and early flowering for spring wheat and durum  (Feekes 10.51). Under weather conditions favoring infection, single fungicide applications that are too early (head half emerged) or too late (kernel watery ripe) are not effective.

Two Split Rate Vs. One Full Rate Treatment: NDSU studies with Munich durum in 2001 indicated that multiple applications do not significantly improve control over a single application at flowering.  Multiple applications with split rates of Folicur (2 fl oz + 2 fl oz) provided slightly greater reduction in percent FHB than did a single application (4 fl oz) at flowering, but differences among the treatments that included any treatment at early flowering were non-significant. In greenhouse studies at NDSU on Munich durum, Grandin hard red spring wheat, and Robust barley, one treatment at the full label rate at the optimum timing consistently gave better reduction in FHB than split applications with reduced rates, notes Marcia McMullen, NDSU extension small grains pathologist. A late application, when the kernel is watery ripe, always gave poor control.  Thus, one treatment at the recommended label rate is sufficient for FHB suppression, if the application is timely.

Adjuvants: NDSU research indicates that Folicur and Tilt perform much better with a non-ionic surfactant than without. Use an appropriate adjuvant and rate recommended by the fungicide label to get optimum performance against scab.

Nozzle orientation for ground application: Field and greenhouse studies have reaffirmed that angled spray nozzles directed forward and backward toward the grain head consistently result in the lowest scab severity when fungicides are applied with conventional-type ground sprayers. Leaf diseases are also reduced more with the forward/backward orientation of nozzles than forward or backward alone.

Spray volume, pressure: Most fungicide labels require a minimum of 10-15 gallons per acre by ground, 5 gpa by air.  NDSU research indicates that nine gallons of water applied by ground was consistently adequate to provide control of FHB in hard red spring wheat. 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. Use the upper end of recommended spray volume for durum and barley, as NDSU research indicates that increased water volume appears to improve FHB control on durum and barley. Whether using aerial or ground applications, spray in evening or early morning to capture dew as extra water volume, and use a small droplet size.

Insecticide-fungicide applications: Limited studies conducted by NDSU have indicated that Lorsban and Folicur can be applied together without antagonism for control of FHB, 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: Research is inconclusive in whether one method is more effective than the other.   Some crop experts recommend a ground application, since it can employ a larger spray volume.  An aerial application is preferable when field conditions are not conducive for ground spraying. 

Barley planting dates and DON: A past 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.

A visual scale to estimate severity of FHB in wheat, as well as other NDSU extension publications on managing FHB and other small grain diseases, can be found online at www.ext.nodak.edu/extpubs/smgrains.htm

The best timing for maximum reduction of scab severity is at early heading for barley (Feekes 10.3- 10.5) and early flowering for spring wheat and durum  (Feekes 10.51). Under weather conditions favoring infection, single fungicide applications that are too early (head half emerged) or too late (kernel watery ripe) are not effective. Photo: NDSU Extension Service.

Disease Forecasts Aid Treatment Decisions

To help decide whether a fungicide treatment is necessary or economically viable, follow general guidelines based on yield potential, crop price, and weather patterns, along with disease potential and presence, which can be determined through disease forecasting systems offered by NDSU and South Dakota State University.

NDSU’s disease forecasting system can be found on the web www.ag.ndsu.nodak.edu/cropdisease, the system’s information also is available via summarized, regularly updated, recorded toll-free telephone messages (1-888-248-7357).

The forecasting system, supported in part by the Minnesota wheat checkoff, tracks fungal spores, wheat growth development and weather conditions to pinpoint, in near real-time, the potential for FHB (scab), rust, tan spot and Septoria blotch disease infections in wheat.

SDSU will have its new forecasting system in place in the 2002 growing season
The model will use such factors as precipitation, temperature extremes and the period of leaf wetness or residue wetness to come up with a risk assessment. SDSU plans to gather information in the Britton and Aberdeen-Groton areas, and possibly in the Huron, Onida and Selby areas. For more information, see the web site http://plantsci.sdstate.edu/wheatpath or http://plantsci.sdstate.edu/planthealth

NDSU Survey Indicates Low Wheat Midge Risk
The threat of orange wheat blossom midge problems in wheat this year appears to be minimal, with estimated populations of overwintering midge as low as they have been in the last seven years, according to Phil Glogoza, NDSU extension entomologist. 

Based on results from the latest wheat midge survey, the overwintering population has decreased significantly in northwestern North Dakota, where problems with the insect have persisted for the past three seasons. Last year, the greatest numbers of midge were located in the northwest part of N.D., following a line from McLean County to Divide County.  It is assumed survival of midge larvae this year was low.  The populations continue to remain small in most of the eastern counties. The wheat midge soil survey, funded by the N.D. wheat checkoff managed by the North Dakota Wheat Commission, was based on soil samples taken last fall by county extension agents under the direction of NDSU entomologists.

None of the more than 300 fields sampled in the survey had overwintering populations of wheat midge larvae exceeding 1,200 larvae per square meter. This level of midge has been critical in the past. Midge management recommendations suggest when larval counts exceed 1,200, farmers should consider growing wheat only if they are prepared to monitor their fields for the adult midge, and only if they are prepared to budget for and make timely insecticide treatments where warranted.

In previous years, areas where population estimates are above 500 midge larvae per square meter still require close vigilance by wheat farmers, Glogoza says. These larval populations can lead to major infestations if the wheat crop is heading during adult midge emergence and environmental conditions are favorable for midge activity. Wheat is susceptible to midge infestation from the time the head emerges from the boot until 80% of the primary heads have anthers visible.

For more information on managing wheat midge or other crop pests, including a map of the latest midge survey and an update on degree day accumulations for keeping track of midge development, visit the NDSU web site: www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/index.htm

Other NDSU Insect Management Web Sites:

2002 N.D. Field Crop Insect Management Guide:  www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm

NDSU Crop Insect Publications:  www.ext.nodak.edu/extpubs/bugcrops.htm

Resources for Grasshopper Management
The USDA Agricultural Research Service has made a CD-ROM and web site available for grasshopper management. The web site:  www.sidney.ars.usda.gov/grasshopper/index.htm.The grasshopper management CD-ROM is available without charge by contacting the Northern Plains Agricultural Research Laboratory, 1500 North Central Ave., Sidney, MT 59270, phone (406) 433-5038, fax (406) 433-2020, hoppercd@sidney.ars.usda.gov

Grain temperature key to grain storability
Maximum recommended  moisture content for wheat is 14% (wet basis) for up to 9 months storage, and 13% for more than 9 months storage.  Barley moisture should be 13.5% and 12.5%, respectively, for the same storage periods.

Dry grain should be cooled to less than 60 degrees F as soon as possible after harvest, and to 20 or 30 degrees F for winter storage. A temperature gauge for stored grain:

80 degrees: The ideal temperature for insect and mold growth in stored grain.

70 degrees: Cooling grain below this temperature reduces insect reproduction,

50 degrees: Cooling grain below this temperature causes insects to become dormant.

40 degrees:  Mold growth is almost nil at temperatures below this.

20-25 degrees: Grain should be cooled to this range for winter storage.

Check the condition of stored grain about every two weeks while grain is cooling, then about monthly after grain has cooled. A check should include measurements of moisture content and temperature at several locations. Moisture measurement accuracy is dependant on the grain temperature, so it is best to collect a grain sample, let it warm to room temperature in a plastic bag or other sealed container, then check the moisture content. Also, be sure to cover fans and ducts after the grain has been cooled for winter storage to prevent snow from blowing into the bins.