ISSUE 6 June 11, 1998
SMALL GRAIN DISEASE UPDATE
Diseases in small grains did not progress much the past week due to the cold temperatures across the state and relatively dry conditions. Reports from the area agronomists and crop protection specialists in the north central and northeast districts indicated little evidence of disease. However, surveys of spring wheat in counties in the southeast, east central, central and south central districts the past week showed that leaf rust, tan spot, and Septoria were common, but primarily still confined to the bottom tier of leaves in crops from the tillering to early jointing stages. Surveys in these counties were done by crop scouts Carrie Buttke, Sarah Gehlar, and Extension crop protection specialist Jim Harbour.
Wheat leaf rust was detected in 75% of these spring wheat fields surveyed, with incidence of infected tillers within fields ranging from 2 to 58% and severities ranging from a trace level to 4% on bottom leaves. These levels are still low but bear watching, because leaf rust can develop readily under warm, moist conditions. Most spring wheats and durums have resistance to prevalent races of leaf rust, but last year, detection of another race group occurred in some fields in North Dakota. This race group may have accounted for increased leaf rust severities in some fields of 2375 and AcBarrie in 1997. Leaf rust ratings at Fargo, Carrington, and Langdon in 1997, done by pathologists Jack Rasmussen and Jim Miller, indicated Russ, Sharp and Gunner had lower leaf rust ratings than AcBarrie, 2371, and 2375.
Tan spot was detected in 83% of the above mentioned wheat fields surveyed this past week. Incidence of infected tillers within fields ranged from 8 to 94% and severities on lower leaves ranged from 1 to 68%. Septoria-like fruiting bodies in leaf lesions also were detected at low levels on bottom leaves of many spring wheat fields. Confirmation of Septoria tritici was made for one of these fields, with other species identification yet to be made. Further tan spot and Septoria development will require more moisture and warmer temperatures.
Barley fields were surveyed in northeast and north central counties on June 4-5 by Jeremy Pederson, Extension barley technician, and Mike Peel, Extension small grains agronomist. They found very little evidence of barley diseases in these northern areas. Jim Harbour did detect low levels of net blotch, spot blotch, and barley leaf rust in barley trials at the Carrington Research and Extension Center.
Barley yellow dwarf virus (BYDV) infections were evident in a field of Russ spring wheat, 6-7 leaf stage, at Fargo. This virus disease is vectored by several cereal aphids, a few of which were also found in this field. The infected plants showed the characteristic symptoms of golden yellow to slightly purple discoloration of the leaf, from the leaf tip downward, plus the symptomatic plants showed various degrees of stunting. The plants most infected were along the field edge, or isolated in patches in parts of the field where poorer stands occurred. The aphid vectors often land, feed, and transmit the virus along field edges or in patches. Some similar symptoms have been reported around the area in wheat and in barley, but BYDV has not yet been confirmed for these fields. Aphids are carried into North Dakota on prevailing winds from states to our south. The degree of BYDV infection depends on aphid populations and how early the infection in a field occurs. Late season infection is seldom damaging.
The occurrence and severity of the above mentioned small grain diseases are still low, but with a possible shift to warmer and wetter conditions, most of the diseases could develop rapidly along with the crops. Producers, crop consultants, and field scouts need to be monitoring these crops regularly, to avoid any unpleasant surprises. As flag leaf and heading nears in spring grains, decisions on foliar fungicides to protect against leaf and/or head diseases also is nearing. More on fungicide use will follow in upcoming pest reports.
Extension Plant Pathologist
CANOLA PESTICIDE SUMMIT
A canola pesticide summit was held in Fargo on June 4, sponsored by the Minnesota Canola Council, the Northern Canola Growers Association and the U.S. Canola Association. It was a joint meeting of canola growers, canola industry personnel and regulators from both the U.S. and Canada. One of the main thrusts was harmonization of pesticides registered in the two countries: there are 40 pesticides registered on canola in Canada and 8 in the U.S. Currently, 85% of canola oil consumed in the U.S. is imported from Canada, and the U.S. market is expected to grow. This growing demand provides opportunities for U.S. producers, as Canada does not believe it can meet all of the demand. Consequently, all participants felt that harmonization was important.
Stephen Johnson, Deputy Director, Office of Pesticide Programs, U.S. Environmental Protection Agency (EPA) discussed priorities for registration. Each manufacturer is allowed five priorities for registration, which EPA works on. When EPA nears completion of these priorities for all manufacturers, they call for the next five priorities. EPA also has certain priorities: 1) methyl bromide, 2) reduced risk pesticides, 3) new uses as determined by USDA analysis of needs, 4) tolerance petitions for minor uses, 5) registrants' other priorities, and 6) trade irritants.
EPA is working with Canada's Pest Management Regulatory Agency (PMRA) and California EPA on joint or parallel registrations of new products. Each agency evaluates selected studies, thereby sharing work loads and increasing efficiency for all three agencies. This approach has certain limitations, however, as Canada requires efficacy data and the U.S. does not; the U.S. requires certain other studies that Canada does not require. Taking registration data that PMRA analyzed several years ago results in "data gaps" when EPA examines the data package under current U.S. laws and EPA guidelines.
The regulatory community understands the pressing need for more registered products for U.S. canola and is striving to meet this need, but progress is slow and frustrating for the producer.
Is There Progress Toward a Section 18 and Ultimately Full Registration of Benlate for Sclerotinia Stem Rot? The IR-4 minor use residue study is completed and a label request should be written, ready for submission to EPA by the end of the year. There were no detectable residues in the oil. In addition, duPont has completed a risk assessment of Benlate. Both the residue data and the risk assessment were submitted with a section 18 request for both North Dakota and Minnesota. Currently, the fate of this section 18 is uncertain, but we are hoping for the best. We also hope that the new risk assessment and the residue data will lead to full registration in a year or two. There are several hurdles that must be crossed, however, so stay tuned.
Extension Plant Pathologist