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ISSUE 16  August 22, 2002

 

FUNGICIDE CONTROL OF WHITE MOLD IN SOYBEAN

Soybean, like most other broadleaf crops, is susceptible to white mold or Sclerotinia stem rot. Although thiophanate-methyl (Topsin, T-methyl) has a label for control of white mold in soybean, spraying may not always be economical. Field trials conducted at several locations in Illinois, Ohio, and Wisconsin revealed that when white mold disease incidence was greater than 25% no consistent control was observed with fungicides. Since soybeans are often solid-seeded in North Dakota, it is very difficult for the fungicide to penetrate the canopy and cover the blossoms. If a spraying system was used that was capable of penetrating the canopy, and disease incidence was less than 25%, then the use of fungicides reduced the amount of disease. In conclusion, the data developed at these states suggest that for a fungicide to significantly reduce white mold in soybean, two things must occur:

  1. Disease incidence must be less than 25%.
  2. The fungicide must penetrate the canopy and cover the blossoms.

 

WEBSITES ON SOYBEAN RUST

Soybean rust is a disease of soybean that has not been found in the continental United States. It occurs in Africa, Asia, Australia, and most recently South America. Information about the disease is available on the web at:

http://www.aphis.usda.gov/ppq/emergencyprograms/pestdetection/soybean_rust/soybeanrust.html

AND

http://www.planthealth.info/rust/rust.htm

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

 

THANKS TO NDSU IPM FIELD SCOUTS

The NDSU IPM field scouts have completed their survey efforts this past week and are headed either back to school or to new jobs. Many thanks to the following for their outstanding job this year: Patrick Metzger, Sheri Trumbull, Christen Laventure, Matthew Gregoire, Holly Semler, Kelly Novak, Chris Rylander, Brooke Klein, and Lorilie Atkinson.

The scouts surveyed for insects and diseases of six crops - wheat, barley, canola, sunflower, soybean, and flax, and also collected soil samples for Dr. Luis Del Rio, NDSU dry bean pathologist and soil samples for Dr. Tom Guyla, USDA sunflower pathologist.

Details of the survey results have yet to be compiled and summarized, but reports will be available in the upcoming months. The barley survey was a cooperative effort with Dr. Stephen Neate, NDSU barley plant pathologist; the canola survey was a cooperative effort with Dr. Art Lamey, NDSU professor emeritus; and the flax survey was a cooperative effort with Dr. Carl Bradley, NDSU extension plant pathologist.

 

WHEAT AND BARLEY SURVEY SUMMARY

The NDSU IPM field scouts surveyed 921 wheat fields and 275 barley fields from May 20 through August 16. The majority of small grain fields were surveyed between June 17 and July 22, but 313 of the 921 wheat fields were surveyed in early to mid-dough stages.

The field severity of scab during the last week of survey is indicated in the following figure.

wheatz71scabindexupdated8_19.jpg (51447 bytes)

As the figure indicates, the majority of fields in the north central and northwest regions had low levels of scab, but one field had a field severity in the 1-25% range. Over all fields surveyed in the dough stages, the field severity of scab in wheat ranged from 0 to 24.4%, but the average was only 1.2%, indicating a much lower level of scab in wheat in 2002 than in 2001. Field severities of scab in barley also were quite low, overall.

Summaries of wheat and barley survey data will become available in the upcoming months, indicating incidence and severity of diseases per district and averages. Maps of the occurrence of some of the major diseases are available now on the web, at the following site:

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

A big thanks also goes to Jerry Schneider for working with Phil Glogoza and I to compile the data from the field scouts and put that data into the maps, found at the above web site. Jerry was field scout for three years at Carrington, and currently is a business teacher and assistant football coach at North High in Fargo. His computer expertise was very valuable.

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


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