ISSUE 8 June 25, 1998
SMALL GRAIN DISEASE UPDATE
Spore tracking of disease organisms in Fargo the past week have given some indication of recent rain effects on spore development. Tim Friesen and Eric DeWolf of Dr. Len Francls lab have indicated the following from the past weeks trap: Many spores of Gibberella zeae, the sexual stage of the scab fungus, were collected on Wednesday, June 17. After the heavy rains of June 18, only a few to scattered spores of the scab fungus were collected up through Sunday, June 21. The rains most likely "scrubbed" these spores from the air. However, spore numbers of Septoria (Stagonospora) nodorum have been consistently high, except for the period immediately during the rains. Eric reports that a very favorable infection period occurred on the evening of June 22 at Fargo, Langdon and Minot. So lots of spores are out there now of Septoria, and a flush of scab spores could be expected soon, based on environmental conditions of June 22. The spore tape will be recollected today, Wednesday, June 24th, for further observation of spore numbers since Monday.
The most recent surveys of wheat this week indicated that Septoria infections in SE and EC counties are increasing, found on the middle leaves now of spring wheat, and on flag leaves of winter wheat. Severities on middle leaves ranges from 5 to 30%. Leaf rust also advanced to the middle leaves with severities ranging from 1 to 30%. A 20% severity of leaf rust on middle leaves was recorded in a winter wheat field in Cass Co. Loose smut levels in headed wheats in these counties ranged from 0 to 30%.
As stated in previous Crop and Pest Reports, the optimum timing of fungicide application for suppression of scab in wheat is at the flowering period. In NDSU sponsored tests at various locations in 1995, applications at different growth staging showed that applications prior to flowering, at early heading, or applications afterward, at early milk, did not rate as well in reducing scab or increasing yield as applications at early to mid-anthesis. Applications to barley should be made soon after the main stem heads have fully emerged. Last year, fungicide applications to reduce scab also significantly reduced leaf diseases in both barley and wheat.
Questions about tank mixing fungicides with insecticides or nitrogen have come in to me the past week. Representatives from fungicide manufacturers have indicated tank mix compatibility with most insecticides for small grains. However, I would check the labels for any tank mix restrictions, plus check with company representatives for further guidelines.
I have no information on tank mixing fungicides for scab suppression with nitrogen for protein enhancement. With fungicide application targeted at the flowering period, and nitrogen targeted at early kernel development for protein boost, it is apparent that the timing of application for scab suppression versus timing for protein enhancement do not coincide.
APPLICATION OF FUNGICIDE FOR SUPPRESSION OF SCAB - NEW PUBLICATION AVAILABLE
A new publication on application of fungicides for suppression of Fusarium Head Blight (Scab) has just become available through NDSU Extension. The publication (AE-1148) is available in hard-copy form through the Agricultural Communication Distribution Center (701-231-7882) and also can be viewed via the internet at the NDSU Extension website:
or the North Dakota Small Grains website:
Extension Plant Pathologist
SCLEROTINIA WORKSHOP PROCEEDINGS POSTED ON WORLD WIDE WEB
On January 21 an 8-hour in-service training on Sclerotinia was held in Fargo for county and area educators in North Dakota and Minnesota. This workshop provided basic information on the biology of Sclerotinia; disease losses in dry bean, soybean, canola, and sunflower; resistance to Sclerotinia in dry bean, soybean and sunflower; effect of calcium on enhancing plant resistance; fungicides (or lack of fungicides) and application methods for dry beans, soybeans, canola and sunflower; selected references and selected Web sites. The proceedings of this symposium were recently published on the World Wide Web under the home page of the NDSU Department of Plant Pathology. This page is located at: http://www.ndsu.nodak.edu/plantpath/
It is listed as "Proceedings of the Sclerotinia Extension Workshop, January 21, 1998". It appears near the bottom of the home page under "Departmental News and Special Events".
The departmental home page also provides information on potato late blight, Fusarium head blight, the International Sclerotinia workshop to be held in Fargo in September, the Potato Association of America Workshop to be held in Fargo in July, a list of extension plant pathology publications (with links to those posted on the Web), and general information on the Department.
BIOLOGICAL ACTIVITY OF SECTION 18 FUNGICIDES FOR POTATO LATE BLIGHT
The section 18 fungicides include Acrobat MZ, Curzate 60DF, Manex C-8 and Tattoo C. Acrobat MZ contains dimethomorph + mancozeb, Curzate 60DF contains cymoxanil and is to be tank-mixed with a protectant fungicide, Manex C-8 contains cymoxanil + mancozeb and Tattoo C contains propamocarb + chlorothalonil. Mancozeb and chlorothalonil are non-systemic protectants that are included in prepack mixes with their respective section 18 active ingredients. Dimethomorph (Acrobat) and cymoxanil (Curzate and Manex C-8) are locally systemic: they are taken up by the leaf and move within the leaf, but do not move out of the leaf into other parts of the plant. Propamocarb (Tattoo) is taken up by the leaf and is translocated upward in the water-conducting tissues of the plant, moving into new plant growth. None of the products moves downward, and so none provides direct tuber protection as Ridomil did in the past.
Dimethomorph (Acrobat) requires 2-3 hours for uptake, cymoxanil (Curzate and Manex C-8) require 1 hour and propamocarb (Tattoo) requires ½ hour. Dimethomorph (Acrobat) has antisporulant activity. Cymoxanil (Curzate and Manex C-8) has 2 days post-infection (curative) activity and persists 2 days after infection; it also has antisporulant action. Tattoo also has antisporulant activity.
Cymoxanil (Curzate and Manex C-8) prevents infection from direct germination of sporangia, which occurs at warmer temperatures, but does not prevent infection from zoospores, which are produced in cooler weather. Dimethomorph (Acrobat) and cymoxanil (Curzate and Manex C-8) are effective against the formation of the sexual spores, called oospores.
Extension Plant Pathologist
PLANT DIAGNOSTIC LAB REPORT - MUSHROOMS IN THE LAWN
There have been several questions regarding mushrooms in lawns this past week. Mushrooms are the fruiting body, the spore producing part, of a group of fungi called basidiomycetes. These fungi are one of natures recycling mechanisms, they utilize dead and dying matter as a food source. In the lawn, mushrooms are generally living on decaying wood in the soil under the grass. The wet weather that we have been experiencing provides an ideal environment for prolific growth of mushrooms, they flourish in a moist environment. There is no control for mushrooms in the lawn. They can be picked out of the lawn or mowed over when the grass is cut but there is no other way to remove them. Fortunately as the weather warms up and drys out a bit, the mushrooms will also dry up.
The number of chemical injury samples continues to increase, on sugarbeet, wheat, sunflower, home garden vegetables, and ash and lilac. Barley Yellow Dwarf Virus (BYDV) was confirmed on barley. The first soybean sample came in last week and was diagnosed with Rhizoctonia root rot. There were two new insect identifications - chinch bug and bird mite. Plant samples were identified as quack grass, western salsify, and black henbane.
The acute problem of ash anthracnose has abated but ash tree samples continue to come in with various disorders. Ash plant bug, Tropidosteptes amoenus, is still active, but it wont usually cause leaf drop. Orthene and Isotox, diazinon, Sevin, or malathion are all effective compounds for ash plant bug. Another pest on ash, the ash bud flower gall mite, has been observed. This mite causes a rosetting of leaves at the base of a stem. Malathion, Sevin, Kelthane, and dormant oils are all effective treatments for gall mites. Iron chlorosis has also been diagnosed on some green ash. This can be remedied with a foliar application of iron, or a soil or root application of a chelated iron.
Plant Pest Diagnostician