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ISSUE 8  June 21, 2001

 

SMALL GRAIN DISEASE UPDATE, JUNE 21

Tan spot continues to be the wheat disease most commonly observed by field scouts, with incidences highest where wheat is planted into wheat stubble. (See figure with most recent tan spot observations by NDSU IPM scouts). Many of these fields have a definite yellow cast to them, from the symptoms caused by the tan spot fungus.

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Barley yellow dwarf virus (BYDV) symptoms were observed in barley by Jerry Schneider in Logan and Barnes counties, and I observed symptoms in my barley plots in Fargo. Incidences were low, but the characteristic golden yellow tips of flag leaves were observed. Aphid populations detected in the canopy in these fields were almost nil, however.

Net blotch of barley is being observed in fields in the southcentral, northcentral and southeast areas. Net blotch causes a dark lesion running parallel to the leaf vein with small dark brown to black lesions running perpendicular to these long lesions. The net blotch fungus is much like the tan spot fungus, favored by wet weather and surviving in residue.

No observations of leaf or stripe rust have been confirmed in North Dakota yet. Some hot spots have been seen in South Dakota, as reported by Dr. Marty Draper, but the disease has not become apparent in North Dakota. Dr. Draper reports that Dr. Yue Jin at SDSU suspects that Oxen, Forge and Ingot may be susceptible to stripe rust. I donít have information on response to stripe rust for other commonly grown cultivars in this region.

 

FUNGICIDES FOR SMALL GRAINS

Some of the small grain crops are now in the flag leaf stage, and the earliest are even showing a few awns. With all the wet weather recently, fungicides for small grains are on many growerís minds. The need for fungicides may be high this year, since we are sitting in an incubation chamber, but timing of application will be critical, and growers should also make their decisions based on: 1) yield potential; 2) variety response to leaf spot diseases, rust and scab; disease presence as determined by field scouting; and indications of infection periods as described by the NDSU Disease Forecasting Model (most sites in the forecaster have shown very favorable conditions for tan spot the last 10-12 days, surprise, surprise).

As crops are now generally beyond the 4-5 leaf stage, and are getting closer to heading, I would recommend holding off with fungicide spray until heading or flowering, unless tan spot or net blotch are very severe on the flag leaf minus one. Leaf rust hasnít been detected yet, so if it does develop, it may only be a factor on later seeded grain.

Fungicides registered for small grains in ND as of June, 2001

Product*

Chemistry

Company

Growth stage limitation or PHI

Benlate

Benomyl

DuPont

21 days

Champ,
Kocide

Copper

Agtrol,
Griffin

early heading
10 dys later

Dithane,
Manex II
Manzate
Penncozeb

Mancozeb

Various

26 day PHI
(often applied 2x)

Tilt;
Tilt 24(c)

Propiconazole

Syngenta

Feekes 8; Feekes 10.5 or 40 day PHI

Quadris

Azoxystrobin

Syngenta

46 day PHI

Flint

Trifloxystrobin

Bayer

35 day PHI

Stratego;
Stratego 24(c)

Flint + Tilt

Bayer

35 day PHI; Feekes 10.5 or 40 day PHI

Folicur Sec. 18

Tebuconazole

Bayer

30 day PHI

PropiMax

Propiconazole

Dow

Feekes 8

*All products should be applied according to label rates and with appropriate use of adjuvants (we have seen adjuvants improve performance of these products). Prices are variable, but prices for Tilt, Folicur, Stratego, and Propimax are ranging around $9.00-$9.50/acre for full label rate. Mancozeb costs are around $2.30-$2.50/lb, and a full labe rate is 2 lbs/acre.

 

POTATO LATE BLIGHT HOTLINE

Potato late blight severity values jumped dramatically since the last pest report. Although the disease has not been observed yet in the state, the potato plant pathologists are recommending fungicide applications in the irrigated areas, and that non-irrigation growers should apply at least one fungicide application prior to row closure.

Marcia McMullen
Extension Plant Pathologist

mmcmulle@ndsuext.nodak.edu

 

SCLEROTINIA RISK MAP FOR CANOLA

The first Sclerotinia risk map for canola was posted on Tuesday, June 19. This is the same type of risk map that the Canola Council of Canada has posted on their web site for the prairie provinces of Canada for some time. The risk maps will be posted on the Northern Canola Growers website:  http://www.northerncanola.com , the NDSU Agriculture website:  http://www.ag.ndsu.nodak.edu/cropprod.htm and the Rock and Roll Agronomy website:  http://www.rockandrollagronomy.com . The second risk map will be issued late on Thursday. Additional risk maps will appear late on Mondays and Thursdays through the canola flowering season.

The Sclerotinia Disease Forecasting System is a regional guide to sclerotinia of canola disease risk. It is meant to be a management tool that canola producers can use in making a decision on the necessity of applying a fungicide to their canola crop for control of sclerotinia stem rot. It is not meant to be a field_specific recommendation for the application of fungicides for the control of sclerotinia. Other factors such as local weather conditions, seeding date, previous cropping history, and yield potential should be considered as well as the risk maps in making the final decision. The forecast maps show regions of North Dakota and Minnesota where the environmental conditions are favorable for the germination of sclerotinia sclerotia, development of apothecia and release of spores. The degree of risk is shown as low, moderate and high coded green, yellow and red. Maps are also produced showing top zone soil moisture and canola growth stage based on average seeding dates for canola crops in the vicinity of North Dakota Agricultural Weather Network (NDAWN) weather stations.

Use of the risk map may be partnered with the Sclerotinia stem rot checklist, which is specific to each field evaluated by the checklist. The checklist can be found in the NDSU publication on Sclerotinia Stem Rot of Canola, PP-1201, which is also on the web at http://www.ext.nodak.edu/extpubs/plntdise.htm

The Sclerotinia Risk in Canola Forecast Program is a new service of the Northern Canola Growers Association and the Minnesota Canola Council for North Dakota and Minnesota canola producers.

By it use, users agree to release the Northern Canola Growers Association and its employees and project collaborators from any and all claims, demands, actions or liability for material used or relied upon by users through this service. All results, statements, technical information or recommendations herein are believed to be reliable, but their accuracy or completeness is not guaranteed.

The project collaborators are Dr. Gary Platford, Plant Pathologist, Jennifer Lamb GIS Specialist P&D Agro Consulting Inc., Dr. Art Lamey, Plant Pathologist Emeritus, North Dakota State University and the Canola Council of Canada.

Sponsors are the Northern Canola Growers Association, the Minnesota Canola Council and BASF.

Weather data and technical assistance is supplied by: Environment Canada Meteorology Service Commercial Weather Services Division, North Dakota Agricultural Weather Network NDAWN and John Enz, North Dakota State Climatologist.

A personal thanks to Dr. John Enz for his help with the NDAWN data and to Dr. Bruce Sellig, who provided information on soil types for many of the NDAWN stations. Also a big thanks to county agents/educators, area specialists and experiment station personnel across North Dakota and northwestern Minnesota who provided information on soil moisture at the beginning of the season, and to the NDSU soil testing laboratory for providing soil moisture assessments.

 

SCLEROTINIA OUTLOOK

The first risk map shows a low risk of Sclerotinia. Some people may wonder about this in the light of all the rain we had recently. Dr. Platford states that it takes 10 days for apothecia (the tiny mushroom-like bodies that produce the Sclerotinia spores) to develop once the top 4 inches of soil are at moisture capacity. If you read the text associated with the map, you will note that he expects apothecia may appear next week. So far, no apothecia have been observed by the wheat scouts or others who are looking.

Note that there are three maps: the risk map, a map on crop development and a map on soil moisture. Note that the soil moisture map indicates that a lot of the state is at or near moisture capacity. In areas where we continue to have small showers that keep the soil surface wet, expect to see the risk change over time as conditions favor the production of apothecia.

Art Lamey
Plant Pathologist Emeritus
alamey@worldnet.att.net

 

PLANT DIAGNOSTIC LAB SAMPLE SUMMARY

This past week in the diagnostic lab, we have diagnosed: 2 sugarbeets with Aphanomyces, some cool weather stress on corn, uneven planting depths causing emergence problems on corn, and Rhizosphaera needlecast and spider mite injury on spruce. Herbicide diagnoses include: negative MCPA injury on vegetables, ALS-inhibitor injury on canola, PPO-inhibitor injury on wheat, RoundUp drift on barley, and a negative growth regulator herbicide injury on lilac. Pseudomonas blight was observed on a cotoneaster and necrotic ring spot was observed on some turf samples. Cottony scale insects were seen on a linden tree. A tick coming from the Lake Lida area was identified as Ixodes scapularis, the Blacklegged tick (formerly called deer tick). Plant identifications include: apricot (Prunus armeniaca), creeping charley or ground ivy, and white clover.

Cheryl Biller
Plant Diagnostician

diaglab@ndsuext.nodak.edu

 

CRISIS EXEMPTION FOR QUADRIS IN CHICKPEAS

The North Dakota Department of Agriculture has cleared a Crisis Exemption for the use of Quadris Flowable Fungicide for distribution and use on chickpea in the state of North Dakota.

Ascochyta blight was a serious problem in chickpeas last year. The wet weather the past two weeks has been perfect for the development of ascochyta. Growers should be looking for the disease. Symptoms include light brown lesions with darker margins on chickpea leaves and stems. With the use of a hand lens, small black spores (fruiting bodies) can be seen in the center of the lesion. Ascochyta blight has already been found at Hettinger,

Beach, Plaza, and Minot, North Dakota. This disease can be devastating and is showing up a lot earlier than last year.

The crisis exemption for Quadris was issued and became effective on June 19 and will expire August 15, 2001. Quadris can be applied twice between June 19 and August 15. The most common rate to be used if applying twice is 6.2 fl oz/acre. It is best to wait 10 to 14 days after the first application before the second application is made. If only one application is to be made then a higher rate of 9.2 fl oz/acre is recommended. Quadris should be

applied with 20 gallons of water per acre by ground or 5 gallons per acre by air. The label must be in the possession of the user at the time of application.

Managing this disease is difficult and all varieties and types of chickpeas should be monitored closely for the disease. If ascochyta blight is present, an application of either Bravo Ultrex, Bravo Weatherstick ZN, or Quadris should be applied as soon as possible. If stem lesions are present, prior to flowering, then an application of Quadris is recommended over either Bravo fungicide. If conditions warrant another application 10 to 14 days after the first application then an application of either Bravo fungicide is recommended followed by an application of Quadris 10 days later. Chickpea growers can contact me at 701-857-7682 for further questions of ascochyta management and fungicide use in chickpeas.

Kent McKay
NDSU Extension Area Agronomist


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