ISSUE 2 May 14, 1998
CURZATE 60DF REGISTERED FOR POTATOES
On May 6 duPont received full section 3 federal registration for Curzate 60DF for use on potatoes. This followed shortly after the granting of a section 18 for Acrobat MZ, Curzate 60DF, Manex C-8 and Tattoo C. Originally, a section 18 was requested for North Dakota and many other states because none of these products was expected to have full federal registration by the cropping season. The section 18 remains in effect, but Curzate 60DF now will be shipped with the full federal label rather than the section 18 label.
Curzate 60DF is registered for application by ground, air or chemigation. It is registered only for commercial farm plantings; it is not registered for use in home plantings, nor for U-Pick or Pick Your Own operations. The Curzate 60DF label recommends use of an Integrated Pest Management Program that includes planting healthy seed, use of a late blight forecasting model or scouting, elimination of volunteer potatoes and potato cull piles, adequate hilling to prevent spores reaching the tubers, use of a protectant program early, vine kill infected fields at least 14 days before harvest and minimizing tuber damage at harvest.
Curzate 60DF is to be used at 3 a oz per acre. It is to be used only in combination with a protectant fungicide such as mancozeb, chlorothalonil triphenyltin hydroxide or metiram. Curzate 60DF should not be used alone. There is a limit of no more than 7 applications per season, and a 14 day PHI.
Curzate 60 DF is locally systemic with rapid uptake. It is rainfast within 2 hours of application.
ROOT ROTS CAUSED BY WATER MOLDS
Recent rains in many parts of the state have been good news. However, areas in the southeastern part of the state may have waterlogged surface soils; these areas are at risk from seedling diseases and root rots caused by water molds. These are fungi that produce a swimming spore, including the causal fungi of Pythium seedling disease, Phytophthora seedling disease and root rot of soybean and Aphanomyces seedling disease and root rot of sugarbeet. Pythium can cause seeds to rot in the ground and seedlings of many crops to turn brown and mushy, often rotting near the soil surface and falling over shortly after emergence. Since many soybeans have not been planted yet, Phytophthora may not be much of a threat to most soybeans. However, soybeans that were planted before the rains could be at risk if they do not have Phytophthora resistance. The risk is greatest if soil temperatures are warm following the rains. Most sugarbeets have been planted, and could be at risk from Aphanomyces if the soil temperatures are warm after the rains. Soil temperatures above 70ºF are the most favorable for Aphanomyces. Another water mold, downy mildew of sunflower, is not likely to be a problem at this time since most sunflowers had not been planted before the rains.
Apron seed treatment is highly effective against Pythium, Phytophthora and sunflower downy mildew infections of the young seedling. Sugarbeet and sunflower seed is normally sold treated with Apron. Apron is not effective against Aphanomyces; Tachigaren seed pelleting of sugarbeet provides protection of seedlings against Aphanomyces for 3-4 weeks, depending on the rate used.
EXTENSION PUBLICATION ON SUGARBEET ROOT DISEASES AVAILABLE
An extension publication entitled Identification and Control of Seedling Diseases. Root Rot, and Rhizomania on Sugarbeet is now available. It was prepared by Dr. Carol Windels, plant pathologist at the University of Minnesota Northwest Experiment Station, Crookston, and myself. It was partially funded by the Sugarbeet Research and Education Board and is available from the Distribution Centers at North Dakota State University, Box 5655, Fargo, ND 58105 and the University of Minnesota Extension Service, 20 Coffey Hall, 1420 Eckles Ave., St. Paul, MN 55108-6069. Sugarbeet growers who do not already have this publication should contact their agriculturist.
Extension Plant Pathologist
STATEWIDE RAINS WILL BRING ON TAN SPOT OF WHEAT
Recent rains across the state will favor development of the tan spot fungus. Infested residue from last years crops will release spores that will infect any wheat planted into last years wheat or durum stubble. Dwain Barondeau, Hettinger Co. Agent, and Greg Endres and Jim Harbour, Area Agents at Carrington, have already reported tan spot infections on 2-3 leaf wheat planted into last years wheat residue.
Recent rains have also favored large scale development of weed populations. As growers prepare to spray wheat for weeds they should keep in mind the possible use of a tank mix with fungicides for early season suppression of tan spot. A recommendation for early season fungicide use on wheat is based on meeting all of the following criteria:
1) wheat or durum is planted into wheat or durum stubble
2) a leaf spot susceptible variety is planted
3) rainfall and/or wet soils occur which favor high humidities and dew formation on the young crop
4) leaf spots are showing on the older leaves of a 3-5 leaf crop
Fungicides available for early season use on wheat for leaf spot control include the protectant mancozebs (several trade names and formulations) or the systemic propiconazole (Tilt). Mancozebs should be applied at this stage at the rate of one lb/acre or 0.8 quart/acre, at a cost of about $3.00-$3.15/acre. If Tilt is used, it should be applied at the 2 fl. oz/acre rate at a cost of about $4.65/acre. If an early season application of Tilt is used, a grower cannot come back with a full label rate later on to protect against later leaf spots or head diseases.
Some herbicides have label restrictions against tank mixing with fungicides. The ND Weed Control Guide has summarized herbicide/fungicide tank mixing restrictions in a table on p. 64. The fungicide label also may have directions for tank mixing, as well.
Response to use of early season fungicides has been variable, depending on early season moisture and variety grown. Response has ranged from 0 bushels in a dry year on a leaf spot tolerant variety, to as much as 11 bushels on a susceptible wheat grown in wheat residue in a wet spring. Average response in hard red spring wheats during wet springs has been around 3-4.5 bushels/acre.
REVISED LEAF RUST CIRCULAR
The Wheat Leaf Rust circular, NDSU Extension Publication PP589, was revised this past winter, with Dr. Jack Rasmussen, NDSU Plant Pathologist, as coauthor. The revised circular updates information of resistance and fungicide use. Copies of the revised circular are available from local county extension offices or from the NDSU Agricultural Communication Dept.