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ISSUE 1  May 7, 1998

 

TOPS MZ POTATO SEED-PIECE TREATMENT

    Tops MZ Potato Seed Piece Treatment was inadvertently omitted from the 1998 Field Crops Fungicide Guide. It contains thiophanate methyl (Topsin M) and mancozeb. It is to be used at the rate of 1 lb/cwt of seed. It provides good control of Fusarium and Rhizoctonia.

SECTION 18 GRANTED FOR POTATO LATE BLIGHT FUNGICIDES

    A section 18 was granted April 22 for the use of the following fungicides for control of potato late blight: Acrobat MZ, Curzate 60DF, Manex C-8 and Tattoo C.

    Acrobat MZ may be applied by ground, chemigation, or air at 2.25 lb product per acre, up to a maximum of 5 applications per season. There is a 14 day PHI. If the maximum applications of Acrobat MZ are made per season, a maximum of 6.75 lb mancozeb will be used.

    Curzate DF is to be used only in combination with a protectant fungicide, such as mancozeb, chlorothalonil, triphenyltin hydroxide or metiram. In combination with a protectant fungicide it may be applied by ground, chemigation or air at a maximum rate of 3 a oz product per acre, up to a maximum of 7 applications per season. There is a 14 day PHI.

    Manex C-8 may be applied by ground, chemigation or air at a maximum rate of 1.5 lb product per acre, up to a maximum of 7 applications per season. If the maximum applications of Manex C-8 are made per season, a maximum of 6.7 lb mancozeb will be used. There is a 14 day PHI.

    Tattoo C may be applied by ground, chemigation or air at a maximum rate of 2.3 pints product per acre. A maximum of 11.5 pints product may be applied per season. If the maximum applications of Tattoo C are made per season, a maximum of 4.5 lb of chlorothalonil will be used. There is a 14 day PHI.

 

POTATO CULL PILES AND LATE BLIGHT

    Losses from late blight in storage have been much less than in previous years. However, any culls from storage are a potential source of the late blight fungus. Although some of the culls may have been spread on the ground to freeze, or were disposed of by other means, including burying, chopping or burning, some piles may not be destroyed and could develop sprouts this spring. It is important to destroy all culls before the potato crop emerges in the spring. The piles could be tarped to prevent escape of spores and to allow the heat of sunlight to kill the fungus under the tarp. Piles that cannot be destroyed should be treated with a desiccant herbicide to kill sprouts.

    Check for hairy nightshade, which is a host of the late blight fungus. Eastern black nightshade and cutleaf nightshade are not hosts of the late blight fungus.

 

REDUCE EARLY SEASON SUNFLOWER RUST BY DESTROYING VOLUNTEERS

    Rust usually appears first on volunteer sunflower plants in late May. This year, however, it was observed by April 20. Rust first appears as the aecial stage, which results from sexual reproduction of the fungus. The aecial stage is recognized by yellow spots, 1/8-3/16 inch in diameter, on both the upper and lower surface of cotyledons and leaves. Up to a dozen tiny cup-like structures form inside each yellow spot. These cup-like structures are orange in color, and produce the aeciospores. The aeciospores as well as overwintering summer spores may produce early infections on commercial sunflower plants.

    After the initial infections occur the repeating or summer spore stage is responsible for most spread of rust in sunflower fields. The summer spore stage produces brown pustules with a brown powder, the summer spores.

    Control of sunflower volunteers and wild sunflower reduces early season infections from the aeciospores. This does not prevent rust from developing in commercial sunflower fields, but it does help delay its development and it helps minimize the development of new races of rust.

    Since we have no resistant hybrids or registered fungicides, control of volunteer sunflower and other management strategies are important in keeping rust levels as low as possible. Other management strategies to reduce rust development include planting early, avoiding excessive use of nitrogen fertilizer and avoiding excessive planting rates.

    Circular PP-998 on sunflower rust is available at county offices of the NDSU Extension Service.

Art Lamey
Extension Plant Pathologist

 

TILT® RECEIVES 24(c) SPECIAL LOCAL NEEDS LABEL

    The North Dakota Department of Agriculture has issued a Section 24(c) Special Local Needs Label for Tilt® fungicide for wheat. This label allows an extended application timing for Tilt fungicide use on wheat - up through Feekes growth stage 10.5, head fully emerged. Previously, Tilt could not be applied after Feekes growth stage 8, early flag leaf emergence. The Special Local Needs Label is for wheat only, and does not include barley.

    Earlier applications of Tilt at the 4-5 leaf stage or at Feekes growth stage 8, are still permitted if early evidence of leaf spots occur, BUT the maximum allowable use rate for Tilt is still 4 fl. oz./acre per season. If earlier season applications of 2 to 4 fl. oz. of Tilt are made, then a 4 fl. oz./acre at heading would not be permissible.

    The 24(c) label for heading application is specifically directed at the control of leaf blotch and glume blotch of wheat caused by several Septoria species. This application also may control tan spot or leaf rust fungi that are present, although the label is not specifically aimed at these organisms.

    Applications must follow all applicable directions and restrictions on the old EPA Tilt registration label. A 24(c) label applies only to the state where it was issued. A copy of the 24(c) label must be in possession of the applicator when this fungicide is applied past Feekes growth stage 8. As with the full label registration, Tilt applied at heading may be with a ground or aerial rig, and a spreader/sticker is not required.

FOLICUR SECTION 18 UPDATE

    A Section 18 Emergency Exemption request for the use of Folicur fungicide on wheat and barley was submitted by the North Dakota Department of Agriculture on February 2, 1998. This Section 18 requests permission to use Folicur fungicide for a heading application (Feekes 10.5) to wheat and barley for the suppression of Fusarium head blight (scab). As of today (May 5), North Dakota has not heard any word from EPA on the granting of this request. In the past week, Section 18's for Folicur on wheat have been granted to Texas, Arkansas, Oregon, Washington, and Idaho, so perhaps the EPA will be working their way through the Folicur Section 18 requests to North Dakota’s soon. I’ll keep you posted.

 

WHEAT DISEASES TO OUR SOUTH

    According to the Cereal Rust Bulletin Report # 1, as of April 8, wheat stem rust has not been found in the U. S. This bulletin also reports that leaf rust is lighter throughout the US and central plains than it was last year at this time, although some fields of susceptible winter wheats in Texas are showing 20% severities of leaf rust on lower leaves. Dr. Bob Bowden, Kansas State Extension Plant Pathologist, reports that, as of April 22, leaf rust infections in Kansas were still at light levels.

    We want to pay attention to leaf rust levels to our south, as these infections are the source of rust spores for our spring and winter wheat fields. In 1997, North Dakota spring and winter wheat fields saw varying levels of leaf rust infections. The average levels on the flag leaf were below 5% severity, but a few fields had an average leaf rust severity of 30% on the flag leaf. Some of the higher levels were seen on 2375 and ACBarrie spring wheats. Samples of rusted leaves were sent to the Cereal Rust Lab in St. Paul, MN. Results indicated that the great majority of leaf rust infections consisted of races commonly seen in North Dakota, but several of the samples sent to St. Paul had infections by a relatively new race of leaf rust that has shown up in Texas and Oklahoma recently. Therefore, we need to watch how leaf rust develops in southern plains states and monitor our own fields as the season progresses. Greater rust development in the south means more rust possible in North Dakota, if favorable weather conditions occur.

Marcia McMullen
Extension Plant Pathologist

 

DIAGNOSTIC SEASON OPENS

    As of April 1st the Plant Diagnostic Lab has been officially open and evaluating samples. The majority of the samples submitted are evergreen trees infected with Rhizosphaera Needlecast, spider mites, Cytospora canker, and Spruce Needle Scale. Other samples seen include seed potatoes for Late blight, nitrogen deficiency in Petunia, ethylene injury on various nursery plants and Blacknot on chokecherry.

    To submit a sample, collect as much of the plant as possible and reasonable to send or bring in to the lab. Plants for identification and those with foliar symptoms should be collected and placed in a paper bag, or a box with packing material so that it won’t slide around too much. Please DO NOT wrap in an airtight plastic bag or other container. This will facilitate growth of organisms that contribute to sample breakdown and will only complicate the diagnosis. If it is possible to send the entire plant or a root injury is suspected, put the root ball in a plastic bag and wrap it loosely around the stem of the plant. Insects for identification should be placed in a small, airtight container with a preservative such as rubbing alcohol, or if alive, place in a ventilated, sealed container. Include as much information as possible about the sample, such as soil type, chemicals applied, what may have been planted on the land previously, environmental conditions (weather and surrounding plantings), age of the plant, etc. Also be sure to include your name, address and phone number. Samples can be sent to Plant Diagnostic Lab, PO Box 5012, Fargo, ND 58105. If you would like to deliver the sample, we are located in Waldron Hall, room 206 on the campus of NDSU. Please feel free to call the lab if you have any questions about plant health or submission of a sample, 701.231.7854.

    Due to the increasing costs of operating the lab, both in supplies and technical help, the fee schedule for the lab has been revised. The new fee schedule is listed below.

 

Revised Plant Diagnostic Lab Fee Schedule

County agent samples

$10.00

ND Resident

15.00

Out of state resident

20.00

Culture or special test*
(this includes DED)

25.00

PCR for X-disease

25.00

* there will be a 20% discount for DED samples submitted
   in groups.

Cheryl Ruby
Plant Pest Diagnostician


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