ISSUE 13 July 23, 2003
NDSU IPM DISEASE SURVEY RESULTS, 7/1-7/18
NDSU field scouts looked at 112 wheat fields and 104 barley fields during the week of July 14-18. Both crops are fast maturing in many regions of the state.
As crops approach grain ripening stage, leaf diseases such as Septoria and leaf rust in wheat and net blotch and Septoria in barley are common and occasionally severe on flag leaves (see following figures). Leaf rust is still a threat to late seeded wheat in the northeast counties. In the southwestern counties, tan spot and spot blotch were more commonly observed on wheat than was Septoria. Barley leaf rust was observed in 4 of the 104 barley fields surveyed, with three observations in the southwest.
Loose smut was observed in 26 of 39 wheat fields surveyed in the northeast counties, with average incidence of 5.5%, but one field with 18% incidence.
Bacterial leaf blight and barley yellow dwarf symptoms were primarily observed just in the northeast counties. Bacterial leaf blight was observed in some varieties at the Grand Forks county wheat plots on July 21.
Fusarium head blight (scab) was observed in 28 of 58 wheat fields surveyed past milk stage. Less than 1% field severity was observed in 68% of these fields showing some symptoms. The majority of the others had severities between 1 and 5%. Of the 85 barley fields in post-milk stage of kernel development, only 5 had some symptoms of scab. Three of these had severity < 1% and 2 had severity between 1-5%.
Additional information on the field scoutís observations can be found at the web site:
BACTERIAL LEAF BLIGHT AND BLACK CHAFF
Bacterial leaf blight has been observed in some fields in the Red River Valley and in spring wheat plots in Fargo and Grand Forks. The symptoms are a dark brown streaking on the leaves, often with a shiny appearance due to dried bacteria. If symptoms occur on the grain head, they appear as dark brown to purple streaks running the length of the glume. Bacterial infections occur during storms with high winds and rain. Moving soil particles create tiny wounds that allow bacterial entrance into the plant.
Last year I recorded differences among spring wheat varieties in response to bacterial blight at the Grand Forks County Extension plots. The response observed then is listed below. Similar responses were seen on July 21, 2003 at the Grand Forks plot tour, with Orion also showing considerable bacterial infection.
HRSW Response to bacterial infection, Grand Forks Co. plots, 2002
Fungicides will not control bacterial blight, so some fields with fungicide application may be showing the leaf browning due to bacterial infection. Bacterial infections often occur in patches or along field edges.
Extension Plant Pathologist
FUSARIUM WILT OF CANOLA
Canola growers close to the Canadian border should be on the lookout for Fusarium wilt. Fusarium wilt is a soilborne disease of canola that was found very frequently in Manitoba last year. This disease has not been verified as being in North Dakota or Minnesota. Symptoms of the disease include wilted branches, discoloration of one side of the plant, and discoloration of the vascular tissue. Unlike blackleg, no pycnidia (black spots) are associated with Fusarium wilt. The disease may be more severe under droughty conditions.
Fusarium wilt of canola
(Courtesy David Kaminski,
Manitoba Agriculture and Food)
Extension Plant Pathologist
ANTHRACNOSE IN DRY BEANS
Two dry edible bean samples came into the Plant Diagnostic Lab this week infected with the anthracnose pathogen, Colletotrichum lindemuthianum. It is advisable to begin scouting for this disease. Symptoms to look for include dark brown to black stripping along the veins on the undersides of leaves, on leaf petioles, and on stems.
Anthracnose lesions on dry bean
I found two fungicides labeled for use against this pathogen, there may be others. Amistar, is labeled for use against anthracnose on dry beans at a rate of 2-5 oz. product/acre. Begin spraying before disease begins and continue on a 7-14 day schedule. Label recommendations indicate not more than 2 sequential applications before using a different chemistry, and not more than 6 applications/year. The fungicide Headline is also registered on dry beans for anthracnose. It should be used at 8 oz/acre, and not more than 2 applications/year.