NDSU Crop and Pest Report
Plant Pathology


ISSUE 11  July 10, 2003

SECTION 18 FOR QUADRIS ON SAFFLOWER APPROVED

A section 18 emergency exemption request for the use of Quadris fungicide for control of Alternaria leaf spot on safflower was approved by the EPA on July 2. The exemption is effective from July 2 to August 15, 2003. One application may be made at a rate of 6.2 to 9.3 fluid ounces per acre. Application should occur at the onset of the first flower ray on the primary head on the first plant in the field. A copy of the section 18 emergency exemption label is available on the North Dakota Pesticide Program website at:

http://www.ag.ndsu.nodak.edu/aginfo/pesticid/sec18_2003.htm

 

WHITE MOLD ON DRY BEAN

A few dry bean fields are beginning to flower, which is the susceptible stage for infection by the white mold fungus, Sclerotinia sclerotiorum. Fields planted in rows less than 30 inches apart are more at risk for disease. Research conducted at the University of Minnesota to determine the potential for a fungicide to be profitable on dry bean when total water (rainfall and irrigation) from June 1 until 10 days into bloom was recorded shows that:

Although both iprodione (Rovral) and thiophanate methyl (Topsin M, T-methyl, Farmsaver.com Thiophanate methyl 85 WDG) are labeled for control of white mold on dry bean, studies conducted at NDSU have shown thiophanate methyl to provide better control.

Carl A. Bradley
Extension Plant Pathologist
cbradley@ndsuext.nodak.edu  

 

ND SMALL GRAIN DISEASE SURVEY UPDATE FOR 6/30-7/4

ND IPM field scouts surveyed 91 wheat fields and 23 barley fields the week of the 4th of July. Crops were most advanced in the southeast counties, in the flowering to milk stage, while crops in the rest of the state were in various vegetative to reproductive stages. Crop growth stages at the time of survey can be observed at the IPM web site:

http://www.ag.ndsu.nodak.edu/aginfo/ndipm

Wheat leaf rust observations have primarily been confined to southeast and south central counties. Average leaf rust severity on the flag leaf was 4.5% in fields scouted the week of June 30-July 4, with one winter wheat field having an average 20% severity of leaf rust and one spring wheat field a severity of 10%, both in Sargent Co. Six wheat fields in the southeast survey were observed to have low levels of stripe rust, too. One barley field in Richland County had a 1% severity of barley leaf rust.

Tan spot and Septoria leaf blotch were commonly observed in wheat fields, with severities between 1-15% on the top leaves. In barley, similar levels of net blotch or spot blotch were observed in many fields.

Loose smut was observed in 24% of the wheat fields surveyed, with most having 2-4% incidence, but a few wheat fields in the southwest had 20% incidence of loose smut! In barley, loose smut was observed in 39% of the barley fields surveyed, with average incidence between 2-4%.

Trace levels (< 1/ 1000 heads) of head scab have been observed in wheat fields in the milk stage in a few fields in the southeast. No surveyed fields in this area have showed an appreciable level of scab.

 

BARLEY YELLOW DWARF DETECTIONS AND LOSSES

Barley yellow dwarf virus (BYDV) has been discussed thoroughly in previous Crop and Pest Reports (#8 and # 10) by Dr. Phil Glogoza, NDSU Extension Entomologist. Cereal aphids that vector this virus disease have been abundant in many areas of the state this year. Scattered, mild symptoms of BYDV have been observed in headed grain along field edges and in field research plots. In these fields the top half of the flag leaf is generally a golden yellow.

In the 10th issue of this yearís NDSU Crop and Pest Report, page 1, Dr. Glogoza states that potential yield losses due to BYDV are low if infections occur during the reproductive stages, only 5-10% or less. However, infections in young plants can cause severe loss. The 1997 edition of the "Compendium of Barley Diseases", published by the American Phytopathological Society, provides potential yield loss data from the virus disease at various growth stage timings of infection:

 

SMALL GRAIN DISEASE FORECASTING

The Small Grain Disease Forecasting information is once again available at a toll free number, as well as on the web:

http://www.ag.ndsu.nodak.edu/cropdisease/

The toll free number is:

1-888-248-7382

Unfortunately, the toll free number had been out of operation until now.

Fusarium spore counts for the southeast area of North Dakota will end by July 11, because of the relative maturity of the crop in this area. Fusarium spore counting will continue for other regions until Aug. 1.

Marcia McMullen
Extension Plant Pathologist
mmcmulle@ndsuext.nodak.edu

 

PEST DIAGNOSTIC LAB UPDATE

A brief summary of some of the samples through the lab this week includes:

  • Rhizomania - sugarbeet
  • Pythium and Rhizoctonia - dry bean
  • BYDV - barley, wheat
  • Bent nodes - wheat, due to regrowth of lodged plants
  • Cheryl Biller
    Plant Diagnostician
    diaglab@ndsuext.nodak.edu


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