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New Potassium Recommendations for North Dakota Crops (08/31/17)

During the past 3 years my graduate students and I have worked on the yield response of corn to fertilizer potassium (K).

New Potassium Recommendations for North Dakota Crops

During the past 3 years my graduate students and I have worked on the yield response of corn to fertilizer potassium (K). What I thought would be an easy task quickly revealed that our understanding of K in this state relative to corn was lacking. The K soil test only predicted whether a site responded or not about half the time. We began to investigate what other people had found in different parts of the US and the world, and found that clay type, potassium bearing minerals, soil moisture and other factors influenced response of crops to K fertilizer. In North Dakota, our soils have between 2 and 10% of the total mineral material as potassium feldspar (Figure 1). This modifies our K response, because opposed to what textbooks try to tell us, there is a rapid equilibrium between potassium feldspar and the soil solution that can be measured in hours and days, rather than in lifetimes as some used to suggest.

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More importantly, the clay type makes a difference in K availability. We have three dominant clay types in North Dakota; smectite (shrinking-swelling 2:1 clays), illite (not-so shrinking-swelling 2:1 clays), and kaolinite (non-swelling 1:1 clays), with a very small amount of chlorite (2:1:1 non-swelling clays). The K availability of kaolinite is totally dependent on CEC, but K availability of smectites and illites have nothing to do with CEC. In illites, the K is released from surface charge and interlayer K whether the soil is wet or dry. In smectites, K is released from surface charge and interlayer K only if the soil is moist. When the soil dries, in our area typically in late June, July, usually August, K is drawn back into the interlayer and becomes temporarily retained and plant-unavailable. Therefore, a soil with a large dominance of smectite requires a greater K availability initially than a soil with significant illite.

                In our work, the sites we worked at - about 30 sites from Cass, Richland, Sargent and Barnes counties- were a mix of soils with smectite and illite. The results of the study were that sites with a smectite/illite ratio greater than 3.5 required 200 ppm K in the soil test before there was no response to K in dry years. Soils with less than 3.5 required only 150 ppm K in the soil in wet or dry years.

Because a recommendation to the grower is based on clay type without any indication what are the clay types within their neighborhoods, it would be very confusing, and very expensive for growers to determine their smectite/illite ratios, a survey of the state was conducted during this past spring. In each county not sufficiently sampled during the K rate study, soils within two to three major soil groups in each county were sampled at the 0-6 inch depth in spring 2017. The soils have only recently been completely analyzed for potassium feldspar content and clay species in the clay fraction of the soils, along with other minerals. The map in Figure 2 provides the areas within North Dakota that correspond to those recommendation critical levels. Fields near the boundaries of the two classes should error on the side of higher ratios given our summer tendency for dryness in the state.

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The map in Figure 2 will be used to revise current K recommendations for corn, sugar beet and alfalfa, with the new recommendations officially printed and circulated in their respective Extension Circular revisions within the next 60 days. For now, this article should be a helpful guide as fall fertilizer plans for 2018 crops are being developed.

In addition, we found that K fertilizer applications greater than 200 pounds 0-0-60 per acre in a given season resulted in lower corn yields than the 150 or 200 pounds 0-0-60 rate, so 0-0-60 rates should be capped at 200 pounds per acre 0-0-60 for a single application. If a grower chooses to build soil test levels, application to soybean or other crops to obtain the higher total rotational rate would be advised, rather than apply large amounts of potash before corn or any other crop. We do not know why the yield response tails off with rate, but this phenomenon has been seen in other states as well.

Finally, soils that are sandy loam or coarser, with less than 2.5% organic matter will not be able to be built to higher levels than about 100 ppm K, if that. It is better to fertilize these low organic matter sandy soils every year, rather than apply buildup K rates.

Dave Franzen

NDSU Extension Soil Specialist

701-799-2565

 

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Corn Kernels with Red Streaking (08/31/17)

Earlier this week I received a question about the cause of red streaking in developing corn kernels.

Corn Kernels with Red Streaking

Earlier this week I received a question about the cause of red streaking in developing corn kernels. This phenomenon is quite common in North Dakota and is caused by the plant’s reaction to the feeding of the wheat curl mite on the pericarp of the corn kernel. The wheat curl mite is the same pest that vectors the wheat streak mosaic virus in wheat. Corn is a host of the wheat curl mite, though it is unaffected by the wheat streak mosaic virus it may carry. This tiny mite moves from wheat and other grassy weeds to corn as they mature and dry. When these mites feed on developing corn kernels, the feeding can induce red pigments to form. Just as hybrids differ in amount of red coloring in their tassels, leaves, and cobs, hybrids differ in their response to producing red pigmentation when fed on by the wheat curl mite. This discoloration is the result of the plant reacting to something in the saliva of the wheat curl mite, it is not the remnant of a toxin injected by it. Therefore, these kernels do not contain any harmful chemicals, just some additional pigmentation.

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Joel Ransom

Extension Agronomist for Cereal Crops

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Cover Crop Tour - NDSU Campus Fargo September 26 (08/31/17)

Showing various cover crop species in the field and learning about the benefits of cover crops, will be the focus of a North Dakota State University Extension Service field day on Tuesday, September 26.

Cover Crop Tour - NDSU Campus Fargo September 26

Showing various cover crop species in the field and learning about the benefits of cover crops, will be the focus of a North Dakota State University Extension Service field day on Tuesday, September 26.

The half day of educational sessions and field visit will be at the NDSU campus research site, 0.4 miles west on 15th Ave. N from the 15th Ave. N and 18th St. N corner, Fargo, ND, beginning at 8:00 a.m. and ending at 1:30 p.m.

Sessions at the Fargo research site will feature information about 32 different cover crop species and how they can fit into the farming operation. In addition, a research plot with cover crops interseeded into soybean will be showcased. At a third station, the effect of cover crops on soil health will be discussed. The planter used to interseed cover crops in corn will be available at the site.

Participants will also visit, by bus, the field research and demonstration plots near Hickson. Stops include cover crops interseeded corn, and a research site investigating the effect of cover crops on soil health and fertility when interseeded in corn.

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Participants in the field day will have the opportunity to learn about cover crop research findings as well as Interact with other participants who already have experience with incorporating cover crops into their farm operations.

To register online go to https://goo.gl/forms/dM3lVdsUsO0s2rd52. Lunch is provided; however, registration is required.

This field day is part of the outreach effort associated with a professional development grant from the North Central SARE (Sustainable Agriculture and Research and Education) and a grant the U.S. Department of Agriculture awarded to North Dakota Agricultural Experiment Station scientists. Research is conducted to study how cover crops can increase the resilience and productivity of crops such as corn and soybeans and improve soil health and land use efficiency. Information about this research can be found at http://www.cropsyscap.org/               

Hans Kandel

Extension Agronomist Broadleaf Crops

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Wheat Stem Sawfly Lodging (08/31/17)

Lodging from wheat stem sawfly was observed this past week near Grenora in Divide County, northwest North Dakota (Source: Clair Keene, Area Extension Specialist/Cropping Systems, Williston REC).

Wheat Stem Sawfly Lodging

Lodging from wheat stem sawfly was observed this past knodel.2week near Grenora in Divide County, northwest North Dakota (Source: Clair Keene, Area Extension Specialist/Cropping Systems, Williston REC). The wheat producer commented that “It has been a long time since he had such widespread and severe damage due to wheat stem sawfly.” See photos. Dr. Keene found that the lodging was most severe along the field edges; however, there are many areas well inside of fields that have substantial lodging. In the worst affected areas, 50-80% of the crop is down. Wheat stem sawfly lodging also was reported in Mountrail County near Makoti-Plaza, north central North Dakota (Source: T.J. Prochaska, Area Extension Specialist/Crop Protection, NCREC). Last week, Minnesota reported that wheat stem sawfly was causing lodging problems in wheat in Polk County and around Crookston and East Grand Forks (Source: MN Crop News, August 14, 2017).

Wheat stem sawfly thrives in continuous wheat crop systems, and crop rotation is one of the best cultural strategies for reducing population levels. Spring wheat, winter wheat and durum wheat are the primary cereal crops attacked by wheat stem sawfly. The drought may have provided favorable conditions for wheat stem sawfly populations to increase in western North Dakota in 2017.

Swathing prior to wheat stem sawfly cutting the stem or using a stripper header are the only pest management practices that can be utilized in the current year of the infestation. Swathing sometimes is conducted on just the outer one or two swaths bordering the field, if the infestation is heavy in the field edges only. Early swathing prevents sawfly larvae from cutting the stems and reduces yield loss and harvest problems due to lodging.

To determine if producers need to swath fields, sample wheat crops and determine the percent of plants infested by sawflies before harvest. The presence of wheat stem sawfly can be verified by splitting stems and looking for the S-shaped larvae inside the stems. Another symptom of sawfly feeding is the presence of sawdust-like frass (insect droppings) inside the wheat stem. Infested wheat stems often have a darkened area on the stem just below the nodes because of the internal feeding from sawfly larvae. This can be used to detect a sawfly infestation without splitting the stems. However, splitting stems to confirm sawfly infested stems is best.

If more than 15 percent of stems are infested by sawflies, producers should swath or use a stripper header on the wheat crop. Producers should swath sawfly-infested wheat as soon as kernel moisture drops below 40 percent to prevent infested stems from lodging. Stripper headers may be used for straight cutting the crop. This header will pick most wheat stems off the ground. Stems that are not firmly attached will be brought into the combine while stems still firmly attached to the ground will have grain stripped from the stem. Usually the volume of straw run through the combine will be less using a stripper header than straw run through the combine when picking up a windrow. Also, stripper headers will leave the lower ⅔ of stem intact for improved parasitoid conservation.

Next year, producers in wheat stem sawfly infested areas may want to consider growing a solid-stemmed wheat variety like the NDSU release, Mott, which prevents wheat stem sawfly larvae from tunneling in the stem and eventually kills the larvae. Our research found that the newer solid-stemmed wheat varieties have little or no yield drag compared to the yield drag of old solid-stemmed varieties like Rescue. The newer solid-stemmed wheat varieties have yields comparable to the popular hollow-stemmed varieties like Reeder, and have had higher yields than any hollow-stemmed cultivars at test locations with heavy sawfly pressure. Protein content, milling traits and baking quality are excellent in Mott. The most up-to-date information on wheat variety characteristics and performance can be found in the NDSU wheat guide at www.ag.ndsu.edu/varietytrials/spring-wheat.

Solid-stemmed cultivars do not appear to adversely impact parasitism; parasitism levels often exceeded 50 percent in solid-stemmed cultivars. If 10 to 15 percent of the crop was cut by sawfly in the current growing season, a solid-stemmed variety of wheat is recommended for the following planting season.

For more information, please see our NDSU Extension publication E1479 (revised) IPM for Wheat Stem Sawfly in ND.

 

Janet J. Knodel

Extension Entomologist

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Late Season Soybean Aphids (08/31/17)

Soybean aphid infestations near the economic threshold (E.T.) of 250 aphids per plant and 80% incidence have been reported in some soybean fields in the R6 (full seed set, green seed that fills pod in one of four uppermost nodes) in southeast North Dakota.

Late Season Soybean Aphids

Soybean aphid infestations near the economic threshold (E.T.knodel.1) of 250 aphids per plant and 80% incidence have been reported in some soybean fields in the R6 (full seed set, green seed that fills pod in one of four uppermost nodes) in southeast North Dakota. However, most fields do not have increasing aphid populations now, a critical part of the E.T. With our shorter, cooler days, soybean aphids are migrating around more to find later planted soybean fields (with younger plants in R4 or R5) or starting their migration to their overwintering host, buckthorn. This is the sexual part of the reproduction cycle and usually starts in late August and continues into September. If you are seeing a lot of winged aphids or white dwarf aphids, I would definitely not recommend any treatment. Remember to count only healthy Mountain-dew colored aphids for the E.T (don’t count the white dwarf aphids). Lots of winged aphids indicate that they are ready to move out and will not feed much longer on your soybeans.

More beneficial insects are present in soybean fields now. If you are seeing a lot of beneficial insects, this is another good reason not to spray. With the recent rains, it is easy to find fungal infected soybean aphids in soybean fields.

Research indicates that there is not a yield benefit for treating soybean aphid as the soybeans reach R6 and later crop stages.

 

 

 

 

 

Janet J. Knodel

Extension Entomologist

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SCN Sampling (08/31/17)

When to sample, where to sample, how to sample and more answered.

SCN Sampling

When to sample? Sample in the fall when SCN egg levels are highest, and consequently, the most likely time of year to detect SCN. Sampling can be done before or after harvest, but it should be done before any tillage is done in the field.

Where to sample? SCN moves with soil, so consider the most likely way SCN-infested soil might be brought into a field. Additionally, consider “suspicious” areas. The most important areas (Figure 1) to consider include:

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  • Field entrance: SCN-infested soil often moves into new fields on equipment. Movement on equipment is the most common way the pathogen transfers and is thought to be responsible for its expansion across the U.S.
  • Flood-prone areas and low spots: Cysts will move with water, so areas that are prone to flooding and water pooling are likely areas where SCN will be introduced. SCN can be moved by birds, on their bodies and in their digestive tracts, and birds frequently visit wet spots in fields.
  • Shelter belts: Cysts can move in dust storms or high winds and are deposited as the wind speed slows. In North Dakota, this usually means shelter belts.
  • Yellow spots showing up in August: The damage from high SCN levels usually begins to appear in August, especially if plants are water-stressed. Any lens-shaped areas of fields turning yellow in August are suspicious.
  • High pH: High pH soils are very favorable to SCN and, as a result, SCN damage often is noticed first in high pH spots in fields.

            How to sample?

  • Go where SCN is, and aim for the roots. Sampling is most effective when the samples are collected within a few inches of the soybean stem and 6 to 8 inches deep into the soil.
  • More samples are better. Take 10 to 20 soil cores or thin shovel slices in a suspicious area and bulk the sample.
  • Keep the sample relatively cool and get it to the lab quickly. SCN is a tough worm, but SCN will struggle if the sample sits on the dash of a pickup in the August sun.

            What do the results mean?        Lab results will be presented as eggs/100 cc soil, which is the number of eggs in approximately a 6-ounce can. “J2,” which refers to the second-stage juvenile worm, also may be included. Think of the egg level as your “risk” factor: the higher the number, the greater the risk. Very low levels (less than 100) could be false positives and should be viewed with some caution. We recommend resampling. Very high levels (greater than 10,000 egg/100 cc) likely will impact soybean production for years to come.

            What do you do if you have SCN?          We recommend beginning management strategies if you find any positive samples.

            What do you do if you don’t find SCN?  Be vigilant and sample again next year.

Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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2017 Soybean Cyst Nematode Sampling Program (08/31/17)

The NDSU Extension Service and the North Dakota Soybean Council are working together again to coordinate a soybean cyst nematode (SCN) soil testing program. A total of 2,000 SCN soil test bags will be available to growers on a first come first serve basis.

2017 Soybean Cyst Nematode Sampling Program

The NDSU Extension Service and the North Dakota Soybean Council are working together again to coordinate a soybean cyst nematode (SCN) soil testing program. A total of 2,000 SCN soil test bags will be available to growers on a first come first serve basis.

By the end of the first full week of September, each County Extension office should have pre-labeled SCN soil test bags. Participants can pick up to three bags each. Each bag is pre-marked with billing information that will be covered by the North Dakota Soybean Council. To submit a sample, fill the bag with soil, provide site information and send the bag to the partner lab (Agvise). Results will be mailed directly to the growers and the laboratory fees are covered by checkoff dollars to the North Dakota Soybean Council.

This SCN sampling program began in 2013 and has been instrumental in understanding where SCN is located in the state. To date, over 2,200 samples have been submitted by North Dakota growers, and about 1/3 of those have had some level of nematode eggs. The egg levels and geospatial positions from previous years samples that were used to generate SCN distribution maps in North Dakota show ‘hot spots’ in much of the SE and movement west and north (Figures 1 and 2). In 2017, we will use egg level data and add to the map. Importantly, NDSU does not have access to any personal information – just the egg level and geospatial data to generate a map.

We encourage everyone to sample their soil for SCN and thank the North Dakota Soybean Council for funding the effort.

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Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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What is Soybean Cyst Nematode (SCN) and Why is it Important? (08/31/17)

Soybean cyst nematode (SCN) is a microscopic and parasitic worm (scientific name is Heterodera glycines). It is the most destructive pathogen of soybeans in North America and yield loss estimates from SCN have been measured between $100s of millions to over $1 billion annually.

What is Soybean Cyst Nematode (SCN) and Why is it Important?

Soybean cyst nematode (SCN) is a microscopic and parasitic worm (scientific name is Heterodera glycines). It is the most destructive pathogen of soybeans in North America and yield loss estimates from SCN have been measured between $100s of millions to over $1 billion annually. Additionally, SCN can make other diseases worse, particularly Brown Stem Rot and Sudden Death Syndrome (SDS has not been confirmed in ND but is prevalent in MN and SD).

Where is SCN in North Dakota? Soybean cyst nematode was first identified in the United States in 1954 in North Carolina. Over the next half century, the nematode spread throughout the country (Figure 1), and in 2003 was identified in North Dakota for the first time (Richland County). Currently, SCN has been observed in 19 counties in North Dakota (Figure 2). Even though SCN occurs in 19 ND counties, it is not distributed evenly in them; the nematode is common in Cass and Richland but likely rare in counties further north and west.

How does SCN move? SCN has been able to move across the country partly because of its biology. The nematode begins its life cycle as an egg, goes through several juvenile stages (infecting soybeans at the juvenile 2 [J2] stage) and eventually the impregnated female worms enlarge and their body wall becomes a ‘cyst’. The cyst is a very tough structure that can protect the eggs for many years. The cyst will move with soil on equipment, wind, water, birds, etc., and is the reason that SCN continues to spread in North America.

What does SCN look like? The most common symptom of soybeans infected with SCN is healthy looking soybeans. In fact, a 15-30% yield loss can occur (in spots in fields) before you see any symptoms at all. Once you do see symptoms, they typically show up as general stunting or yellowing spots that often become visible in August (Figure 3). Sometimes it is possible to see the white females (cysts) on the soybeans in late July or August. You need to carefully dig up a plant with a shovel, gently remove the soil from the roots, and you may need a hand lens to see them clearly. The females appear as cream-colored lemon-shaped objects on the roots (Figure 4). Towards the end of the season the white females turn into brown cysts, and are nearly impossible to see (Figure 5).

Why is soil sampling for SCN important? If you find SCN, you can manage SCN. Soil sampling is the most reliable way to identify SCN. To help make sampling easier, the North Dakota Soybean Council is sponsoring an SCN sampling program in North Dakota (see next article).

How do you manage SCN? Determining if you have SCN is the first step (soil sample). If you have SCN, then you must manage it or its population can explode quickly. The objective is to keep the egg levels low. To do this, we recommend; 1) Crop rotation: soybeans and dry beans are susceptible, every other crop is a good choice for reducing egg levels, 2) Resistant varieties: the sources of resistance used in soybean varieties are generally effective in North Dakota, and 3) Rotate varieties or resistance (if possible) – this helps preserve the host resistance. Additionally, in some situations a seed treatment may be considered. Nematicide seed treatments are not meant to replace genetic resistance or crop rotation, but may be helpful in some situations (for example, very high egg levels or when genetic resistance is not available). markell.1

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Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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Soybean Seed Quality from Dicmaba(08/17/17)

Most phone calls and emails received are about how much yield loss may occur from dicamba affected soybean.

Soybean Seed Quality from Dicmaba

Most phone calls and emails received are about how much yield loss may occur from dicamba affected soybean. The boiler plate response has been to wait until harvest. I have wanted to do a literature search to see what previous research has been done to determine what to expect regarding soybean seed quality and quantity. The University of Arkansas researchers have conducted a literature search on this issue, and also included results from their research. The following information is a Fact Sheet FSA2181 – Dicamba in Arkansas – Frequently Asked Questions.

https://www.uaex.edu/publications/pdf/FSA-2181.pdf

Dicamba and soybean

University of Arkansas System Division of Agriculture researchers have conducted considerable field research involving control of resistant pigweed and herbicides containing dicamba.

 

Research has shown that yield reduction in non- traited soybean from dicamba injury depends on four factors:

•Growth stage of the plants

•Rate of dicamba exposure

•Number of times the plants come in contact with dicamba

•Environmental conditions following exposure

 

In testing soybean without the dicamba ­resistant trait, Division of Agriculture researchers found the following:

•Dicamba symptoms on soybean may be most visible during vegetative growth stages, but yield loss from one exposure will be minimal unless rate of exposure is ¹/64 X (1.8 ounces per acre or 8.75 grams acid equivalent per hectare) or higher.

 

•Yield loss from dicamba exposure is most likely to occur between late vegetative stages through R3.

 

•Application at ¹/64 X of the recommended rate on R1 soybean can cause greater than or equal to 20 percent yield loss. This rate contains ¹/8 ounce of dicamba spread over one acre.

 

•Application at ¹/1,000 of the recommended rate can cause 10 percent yield loss at the R1 growth stage – the appearance of first blooms. This rate contains 0.008 ounce of dicamba dispersed over one acre.

 

•Application at ¹/100,000 of the recommended rate can cause visible symptoms during vegetative growth but is unlikely to cause yield loss. This rate contains 0.00008 ounce of dicamba dispersed over one acre.

 

Consequences of dicamba drift on soybean without the dicamba­ resistant trait include:

•Lower seed weight (Wax et al. 1969; Kelley et al. 2005; Lyon and Wilson 1986)

•Lowered seed quality (Wax et al. 1969; McCown et al. 2016)

•Delayed maturity (Wax et al. 1969; Kelley et al.2005; Lyon and Wilson 1986)

•Pod malformation (Weidenhamer et al. 1989; Anderson et al. 2004; McCown et al. 2016)

•Reduced seed germination or lower rates of emergence of progeny from seed planted the following growing season (Wax et al. 1969; Thompson and Egli 1973; Auch and Arnold 1978; Lyon and Wilson 1986; McCown et al. 2016)

•Malformed seedlings from affected seed planted the next spring (Thompson and Egli 1973; McCown et al. 2016)

 

Based on these data, soybean seed production fields exposed to dicamba during later reproductive development would likely have dicamba­ like symp­toms on emerging seedlings after planting as well as reduced seed quality, vigor and germination.

Rich Zollinger

Extension Weed Specialist

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North Central ND (08/17/17)

Information from the North Central region of North Dakota.

Beneficial rainfall was finally observed throughout the area. Over the last couple weeks, small grain harvest, along with canola swathing has taken place in many areas of the North Central region. A few insect problems continue to be observed. Thistle caterpillar continues to be found in the region in soybean. More information can be found in the July 6th issue of the Crop & Pest Report and in this issue of the Crop & Pest Report. As of right now, economic thresholds have not been observed. Scouting practices should continue. Additionally, a field north of the Minot Air Force Base was detected with economic threshold levels of spider mites.  Mites can increase in population with dry, hot weather. Precipitation over the last few weeks may help keep population levels down. Again, scouting protocols may be important.

Upcoming events:

The good bugs workshop is fast approaching. The registration deadline has come and gone, but for those who have registered, the event will start at 9 am on Tuesday, August 22nd. The North Central Research Extension Center is the host of this event.

TJ Prochaska

Area Extension Specialist/Crop Protection

NDSU North Central Research Extension Center

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