ISSUE 5   June 1, 2006

NDSU IPM SURVEY BEGINS

NDSU IPM’s summer survey program began last week with training of field scouts at the Carrington Research Extension Center on May 24th. Field scouts will be scouting for insects and diseases of wheat, barley, soybean, canola, and sunflower, with some additional insect trapping for corn. Scouts will be looking at fields in each county, and will be operating in their regions under the direction of: Roger Ashley, Area Extension Specialist at the Dickinson Research Extension Center; Greg Endres, Area Extension Specialist at the Carrington Research Extension Center; Terry Gregoire, Area Extension Specialist at the Devils Lake Area Extension Office; Denise Markle, Area Extension Specialist at the North Central Research Extension Center, Minot; and Jan Knodel and Marcia McMullen, Extension Entomologist and Plant Pathologist, Fargo.

IPM scouting reports will be summarized weekly, with timely reports of pest problems provided on the web, through ag alerts, and the NDSU Crop and Pest Report. Initial scouting indicated few insect or disease problems in crops across the state, but tan spot in wheat was detected in the wetter regions in young spring wheat and was common in some winter wheat fields.

 

NDSU’s WHEAT LEAF DISEASE FORECASTING

The NDSU Small Grain Disease Forecasting Model web site is up and running for the 2006 growing season. The web address of the site is:

http://www.ag.ndsu.nodak.edu/cropdisease/cropdisease.htm

This web site provides information on the risk of infection by certain fungal leaf diseases on wheat, including tan spot, leaf rust and Septoria blotch. The information provided tells you whether infection by the fungi that cause these leaf diseases was likely over the past 13 days. The information is calculated based on the rain accumulation, relative humidity, temperature and duration of wet period over these days at the NDAWN remote weather stations located across the region.

An individual user must pick the appropriate location of the nearest weather station and the closest growth stage of the crop to get the forecast. A separate table on average weather conditions for each day at that location also is provided.

A sample chart with data from the Cando, ND weather station on May 30th indicated the following days had weather favorable for some leaf spot infection:

Disease

5/29

5/28

5/27

5/26

5/25

5/24

Tan spot

Yes

Yes

Yes

Yes

Yes

Yes

Septoria

Yes

Yes

Yes

No

No

No

Leaf rust

Yes

Yes

No

No

Yes

No

The Cando area had substantial rain over the Memorial Day weekend. Other NDAWN stations reported fewer days of leaf disease risk.

 

CHANGES IN FUSARIUM HEAD BLIGHT (FHB) FORECASTING MODEL

Plant Pathology researchers from Penn State University provide the model formula for predicting Fusarium head blight (FHB) for spring wheat and winter wheat regions of the US. They have modified the model for 2006 to allow incorporation of information about the susceptibility of the spring wheat variety to this disease. Now producers and other users of the FHB disease forecasting web site will get different risk maps based on the susceptibility of the variety, with varieties separated according to: very susceptible, susceptible, moderately susceptible, and moderately resistant. The FHB disease forecasting web site also is found at the same web site as the leaf spot predictions, at:

http://www.ag.ndsu.nodak.edu/cropdisease/cropdisease.htm

A user of this web site must chose the nearest NDAWN weather location, the flowering growth stage, and then will get the forecast of risk of FHB.

The variety ratings are based on information provided by NDSU, and are available in the Hard Red Spring Wheat Variety Bulletin A574, which can also be found at the following web address:

http://www.ag.ndsu.nodak.edu/aginfo/variety/A574.pdf

Information on FHB risk is provided as a color code: red = high risk, yellow equals moderate risk, and green = low risk of FHB infection. Although crops are not yet flowering, the following two maps are provided from the Cando location from May 30th, as examples of maps for a susceptible variety and for a moderately resistant variety, to indicate the variation of risk of the disease depending on variety choice.

Susceptible variety risk of FHB map
Susceptible variety risk of FHB on May 30

Moderately resistant variety risk of FHB map
Moderately resistant variety risk of FHB on May 30

These maps reflect the heavy rains in the Cando area over the Memorial Day weekend, and indicate a high risk to susceptible varieties, if that crop would be flowering at this time. Fortunately it is a ways away before that risk of FHB is determined for our spring wheat cultivars.

Marcia McMullen
NDSU Ext. Plant Pathologist
marcia.mcmullen@ndsu.edu

 

BLACKLEG OF CANOLA: TO SPRAY OR NOT TO SPRAY?

Blackleg, a fungal disease of canola caused by Leptosphaeria maculans, overwinters on canola stubble. In the spring, airborne spores of the blackleg fungus are released from the canola stubble and land on cotyledons and early leaves of spring-planted canola plants. These spores infect and cause circular lesions, gray to white in color with tiny fruiting bodies (pycnidia) in the center of the lesions (see figure). Quadris fungicide is registered for control of blackleg on canola for application at the 2 to 4 leaf stage; however, data from NDSU indicate that growing a resistant variety is the most economical and effective way to control this disease (see table). In addition to planting a resistant variety, crop rotation (two years out of canola) plays an important role in reducing inoculum levels within fields. For more information about blackleg, refer to the NDSU Extension Service Circular PP-1024, "Blackleg of Canola: Biology and Management".

Effect of Quadris fungicide (15.4 fl oz/A) on canola varieties differing in blackleg susceptibility at Langdon in 2004.

Variety

Fungicide

Yield (lb/A)

Mod Susc

None

1124

Mod Susc

Quadris

1300

Mod Res

None

1290

Mod Res

Quadris

1556

Res

None

1985

Res

Quadris

2048

 

LSD 0.05

320

Blackleg lesion on canola
Blackleg lesion on canola leaf

Carl A. Bradley
Extension Plant Pathologist
carl.bradley@ndsu.edu

 

PLANT DIAGNOSTIC LAB SAMPLE SUMMARY

A turfgrass sample with suspected Pythium infection turned out to be more likely infected by the disease known as take-all, based on appearance of dark, runner hyphae and hypopodia on bentgrass roots (the annual poa in the mix was not affected, but the bentgrass was completely annihilated in the sample). Pea seed destined for certain countries with import restrictions continues to be screened for stem nematode (Ditylenchus dipsaci), and to date, this nematode has not yet been detected in any pea seed lot grown in North Dakota. A brief synopsis of some other samples processed by the lab in the past week: another winter wheat sample tested positive for Wheat Streak Mosaic Virus; ash leaves infected with ash anthracnose were submitted; oak anthracnose was diagnosed on a bur oak sample; winter injury was determined to be the ultimate cause of pith injury on a strawberry sample submitted (recovered fungi were identified as saprophytes, and not plant pathogens); several plants were submitted for identification, including a leafy spurge, a perennial sowthistle, a sweet clover, and a probable motherwort.

No insect/arthropod pests were received by the lab last week for identification, but a digital image of a viburnum plant that appeared to be infected with an eriophyid mite was submitted. The symptoms of the eriophyid mite on viburnum can be initially confused with downy mildew, but the symptoms occur predominantly on the upper leaf surface (unlike downy mildew diseases, which are predominantly on the lower leaf surface). On closer examination under a dissecting microscope, the tiny mites can be seen moving among the hair-like ‘galls’ that are formed by the plant as a result of some kind of inducement by the mites. The symptoms start out cream-colored and felt-like, and as the symptoms progress, the tiny hair-like galls attain a pinkish-rose color, and the leaves can become deformed in a way that resembles growth regulator herbicide injury. Miticides are not thought to be very effective against this pest, since they are well-protected by the hair-like galls. Usually, eriophyid mites (which are usually highly host-specific) cause little lasting damage on their respective hosts. The extent of injury that may be caused by the mite that is specific to viburnum is not understood at this time, since this particular mite has only fairly recently been recognized as a previously undescribed mite and it has not yet been extensively studied.

Kasia Kinzer
NDSU Plant Diagnostic Lab
Website: www.ag.ndsu.nodak.edu/diaglab
e-mail: diaglab@ndsuext.nodak.edu
Telephone: 701-231-7854
206 Waldron Hall, PO Box 5012
Fargo, North Dakota 58105

 

SUGARBEET – CONTROLLING RHIZOCTONIA ROOT ROT

Rhizoctonia root and crown rot of sugarbeet is caused by the fungus Rhizoctonia solani. The fungus may cause infection in dry conditions but prefers wet fields at soil temperatures above 68 F. Characteristic symptoms of Rhizoctonia include sudden wilting of leaves and blackening of petioles at the point of attachment to the crown. Rhizoctonia root and crown rot generally occur in patches. Over time, the disease spreads, and entire fields may be lost. Fields with a history of severe Rhizoctonia root and crown rot should be planted with tolerant varieties. Unfortunately, there are only a few tolerant varieties available.

Growers may use azoxystrobin to control Rhizoctonia root and crown rot. Timing of fungicide application is critical. Azoxystrobin should be applied when the bare soil temperature at the 4 inch depth is about 65 to 70 F. Soil temperature from a weather station near to your farm may be accessed at ndawn.ndsu.nodak.edu. At this soil temperature, plants are usually at the 4 to 6 leaf stage. The fungicide should be applied in a 7 inch, or narrower band, if possible. Azoxystrobin is available as Quadris and Amistar. Quadris should be used at 9.5 fluid oz/acre and Amistar at 4.5 oz/acre. Do not apply azoxystrobin with a herbicide since serious phytotoxicity may result.

Mohamed Khan
Extension Sugarbeet Specialist
701-231-8596
mkhan@ndsuext.nodak.edu


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