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Perennial Weed Control in Dry Weather (8/03/17)

QUESTION: I am wondering about continuing to treat leafy spurge in the dry conditions we are experiencing this year. The leafy spurge plants I have treated with Tordon do not look like they are dying. Should I continue to treat, use a different chemical, or just stop until we get some rain?

Perennial Weed Control in Dry Weather

QUESTION: I am wondering about continuing to treat leafy spurge in the dry conditions we are experiencing this year. The leafy spurge plants I have treated with Tordon do not look like they are dying. Should I continue to treat, use a different chemical, or just stop until we get some rain?

ANSWER: While herbicides are typically not as effective when plants are under moisture stress, I think it is better to continue to treat leafy spurge rather than stop. My reasoning comes from the lessons learned during the drought in 1988 (that was the year Yellowstone burned). The entire state was very dry and temperatures were often in the 90’s and even over 100 with very little rain. No one really knew if they should continue to spray weeds or just stop and save the money. In my own research program, we stopped the field work in July and moved to lab and greenhouse research because the plants in the field did not appear to respond to any treatment. Some counties continued their treatment program and others stopped applications. What did we learn?

The following spring of 1989 the counties that quit treating leafy spurge had large increases in acres infested. Since the grass and most other species also stopped growing, it appeared the leafy spurge roots with no competition continued to spread. I remember leafy spurge was just about the only green plant in Badlands. The counties that continued to treat (using Tordon + 2,4-D) had less than average control, but the leafy spurge did not spread and infestations were similar in size to 1988. Tordon has fairly long soil residual, so even if the chemical is not absorbed or translocated immediately after application, the herbicide will still reduce regrowth following moisture. Based on this experience I recommend land managers continue to treat leafy spurge, but if possible, wait until the temperatures cool and perhaps rain lessens the drought. The lesson from 1988 is: Do not stop the treatment program!

Rod Lym

NDSU Weed Science, Perennial and Noxious Weeds

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Spotty Sugarbeets in NE ND, and NW MN (8/03/17)

I have had several questions regarding early yellowing of sugarbeet in NE North Dakota and NW Minnesota during the past couple weeks.

Spotty Sugarbeets in NE ND, and NW MN

I have had several questions regarding early yellowing of sugarbeet in NE North Dakota and NW Minnesota during the past couple weeks. Early in the season, I began noticing that this season would be different than last in regards to N release from soil mineralization. Last year was an amazing year, with greater check plot yields in several studies with low beginning soil nitrate levels. I estimated that 100-150 pounds N per acre were released during the season in some of my studies. In contrast, the check plots in low-residual N studies this year exhibited N deficiency early, and observations made me believe that soil mineralization rates were going to be very low. In the northeast part of the state, where the aftermath of last year’s extremely wet conditions lingered into late May, those persistently wet conditions also would not contribute to high N mineralization. Crops planted into those soils would likely have to contend with saturated subsoils for some time, which would restrict rooting depth. After a couple early season rains on sugarbeets following planting, conditions have become dry. Peak time for N mineralization is usually until the end of June, but this year it probably ended sooner than that.

Growers and consultants have all observed green beets and yellow beets at small spatial scales. That indicates to me that what is being seen is the effect of microenvironment in our ‘flat’ fields, where a little more moisture in one area has encouraged more N release, while drier conditions right next to that area have experienced less N release.

Earlier this season some growers side-dressed N to obviously N deficient beets. Studies conducted by John Lamb at U of MN and others in the drier years 30 years ago indicated that sidedressing about 6-leaf stage beets would sometimes effectively result in greater sugar, but sidedressing at later growth stages nearly always resulted in lower sugar yield and lower profits.

Dave Franzen

NDSU Extension Soil Specialist

701-799-2565

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Bacterial Blight Appearing in Soybeans (8/03/17)

I have been receiving some questions about foliar lesions in soybeans.

Bacterial Blight Appearing in Soybeans

I have been receiving some questions about foliar lesions in soybeans. What I have seen has primarily been bacterial blight. Symptoms often begin as small angular lesions often with a yellow halo (Figure 1), will eventually enlarge, turn black and tatter the leaves (Figure 2). The disease not usually of economic concern and fungicides do not manage the disease.

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To help distinguish bacterial blight from Septoria brown spot I am reprinting a newsletter article from an NDSU graduate who became a faculty member at Purdue and is now the University of Kentucky (Dr. Kiersten Wise). Kiersten provides excellent diagnostic photos of both diseases (Figures 3-5) and a very nice 3 minute video comparing the diseases

https://www.youtube.com/watch?v=elVSfq_FFyI&index=6&list=PLnQq3T4QUKpZQyI3lcokex_DoIzqUR35N

Excerpt from - Kiersten Wise. Septoria brown spot vs. Bacterial blight in soybean. Purdue Pest and Crop Newsletter: Issue 16. July 16, 2015. Available at http://extension.entm.purdue.edu/pestcrop/2015/Issue16/

How do we distinguish between these two diseases? Leaves inmarkell.3fected by Pseudomonas sp. bacteria have brown angular lesions that are surrounded by a yellow ring or halo, and may have a water-soaked appearance. As lesions age, they turn dark brown and fall out of the leaf tissue, giving leaves a tattered appearance (Figure 3). Bacteria survive on soybean residue and in seed, and enter plants through stomates and wounds caused by equipment or other mechanical

damage, or from weather events such as heavy rains, wind, and hail. Long periods of leaf wetness and cool weather favor infection. Hot, dry weather will limit disease development. Yield loss may occur if disease is severe and plants defoliate. However, most fields in Indiana exhibiting symptoms of bacterial blight are only lightly to moderately affected by the disease and we would not expect to see yield loss due to this disease in these fields.

Symptoms of brown spot are typically observed in the lower canopy first, and are characterized by brown to black spots on upper and lower leaf surfaces (Figure 4). Lesions may or may not have the yellow halo of bacterial blight lesions, but leaves with lesions can turn yellow due to senescence (Figure 5). Research indicates yield reduction from this disease will be minimal if it stays confined to the lower 2/3 of the canopy.

Preventative management options for both diseases include crop rotation, tillage, and planting less susceptible varieties. These methods can lower the risk of disease developing in the subsequent soybean crop. Fungicides will not manage bacterial blight. Fungicide applications for brown spot are rarely warranted and may not be consistently profitable.

A past video comparing symptoms of bacterial blight and brown spot is available here: https://www.youtube.com/watch?v=elVSfq_FFyI&index=6&list=PLnQq3T4QUKpZQyI3lcokex_DoIzqUR35N

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Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

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Sunflower Seed Maggot In Sunflower Heads(8/03/17)

Field reports of a small, golden brown pupae in the face of sunflower heads, usually surrounded by a small number of damaged florets are being reported in south central, north central and northeast North Dakota.

Sunflower Seed Maggot In Sunflower Heads

Field reports of a small, golden brown pupae in the face of sunflower heads, usually surrounded by a small number of damaged florets are being reported in south central, north central and northeast North Dakota. This is the sunflower seed maggot (Neotephritis finalis). Larvae tunnel through the heads earlier in crop development and damage looks like a crease in the head during R5 stage. Planting date was evaluated as a cultural pest management strategy for control of N. finalis in several production regions of North Dakota during 2009 and 2010. Results from the nine site-year study revealed that late planting date (early to mid-June) reduced damage ratings and percentage of damaged heads for N. finalis compared to early planting dates (mid- to late May). Visual observations of adult N. finalis found that the majority of flies were found in the early planted sunflower (78.2 %) compared to the late planted sunflower (21.8%). Yield losses were reduced with late planting date when populations of N. finalis were high enoug to cause damage. In another field study, application timing of different insecticides were evaluated for control of N. finalis in four sunflower production regions of North Dakota during 2009 and 2010. Results of the eight site-year study revealed that different modes of actions and insecticide application timings (R1, R3 and R5)were not effective for controlling N. finalis, and consequently for mitigating yield losses.

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Janet J. Knodel

Extension Entomologist

 

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Weather Forecast: (07/27/17)

The July 27 through August 2, 2017 Weather Summary/Outlook

The July 27 through August 2, 2017 Weather Summary/Outlook

Clearly not everyone got a beneficial rain, but this past week was one of the wettest periods across the North Dakota Agricultural Weather Network (NDAWN) mesonet this growing season with all 91 stations recording measurable precipitation. The NDAWN stations in south central and southwestern North Dakota recorded around 50% or in some instances greater than 50% of their total rain since June 1 in the past week. It appears rainfall totals will be far less in in the next 7 days.

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As has been the case most of the past three months, western North Dakota recorded above average temperatures with much of eastern North Dakota and northwestern Minnesota recording temperatures closer to the current 30 year average.

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One of the principal reasons for the past two weeks being a bit wetter than other periods this year was a slight adjustment to the upper-level wind flow. The wind aloft was more from the west, rather than the northwest recently, but has now become more northwest dominate once again. A westerly flow allows storms more time to draw in moisture from the Gulf of Mexico in comparison to storms coming in from the northwest. This means that although there will likely be some rain in the next several days, it is expected to be spottier in coverage and produced lesser amount of rain. This of course is similar to the conditions much of the region has experienced in the past few months.

Temperatures are expected to be a bit above average for the time of year during this forecast period. The projected growing degree days (GDDs), base 32°, 44° and 50  for the period July 27 through August 2 is presented below.  Most of North Dakota and northwestern Minnesota will record about 20% more GDDs this period than this past week.

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With few rain events, more sunshine and an overall drier atmosphere, the number of hours with relative humidity (RH) values above 85% is expected to be less this week than what most locations experienced in the past seven days. The projected hours with high RH values for this period is presented below.

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Using May 10, 2017 as an average planting date, the number of corn growing degree days (Base 50°) accumulated through July 25 is depicted below. The exact numbers based on your actual planting date(s) can be found here: https://ndawn.ndsu.nodak.edu/corn-growing-degree-days.html

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Using a planting date of May 1, 2017, the number of wheat growing degree days (Base 32°) accumulated through July 25 is presented below. The exact numbers based on your actual planting date(s) can be found here: https://ndawn.ndsu.nodak.edu/wheat-growing-degree-days.html

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Daryl Ritchison

Meteorologist

Interim Director of the North Dakota Agricultural Weather Network

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Southwest ND (07/27/17)

Information from the Southwest region of North Dakota.

Scattered storms brought hail to parts of the region last week along with some rain. From July 19th to July 25th, NDAWN observed 0.74 inch of rain in Beach, 0.30 inch of rain in Dickinson and 1.13 inch of rain in Mott. Peas are continuing to be harvested with low yields.

Moisture is variable across small grain fields, especially with differences in soil type. Some have begun harvesting small grains like barley and some are starting spring wheat, but most in the region are still a little green. Small grain and canola harvest will begin in full swing soon.

Corn across the region is 1-5 feet tall, with most on the shorter end, and beginning to tassel. Sunflowers (below) are either in late bud or beginning to flower. Be sure to scout for seed weevils in sunflower. In the bud stage the weevils tend to feed and hide in the bracts. By spraying Deet on the face of the heads you can get the weevils to emerge.

With moisture differences throughout the field there is high variability in growth stage throughout many of the fields.

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Ryan Buetow

Area Extension Specialist/Cropping Systems

NDSU Dickinson Research Extension Center

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Northeast ND (07/27/17)

Information from the Northeast region of North Dakota.

Soybean aphids are being found across the northeast region. Numbers vary from a few aphids per plant up to the IPM threshold. Remember to refrain from spraying until aphids reach the IPM decision threshold of 250 aphids per plant in 80% of the field with aphids increasing. Soybeans are susceptible to soybean aphid injury through the R5 stage. Spraying aphids too early has several negative consequences: having to double your insect control cost by requiring a second spray, killing the natural aphid predators in the field that may be keeping aphids below the thershold, and promoting the risk of aphids developing pyrethroid insecticide resistance. Pyrethroid resistance has been found in Polk and Norman Counties in MN, so if you have ND fields where soybean aphids appear to be surviving after a pyrethroid application, Extension is interested in tracking this. Reach out to us.

Spring wheat is at the milk stages to soft dough. Grain aphids still present in wheat. While your field looks concerning, do not spray as we are past the recommended IPM threshold at heading crop stage. Pea aphids have been found at IPM threshold levels on early pod field peas in Cavalier County. On the disease side, scab has been found in wheat plots at the LREC station. We haven’t seen white mold infection develop in canola yet on station. Dry bean growers should scout for rust.

 

Lesley Lubenow

Area Extension Specialist/Agronomy

NDSU Langdon Research Extension Center

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Northwest ND (07/27/17)

Information from the Northwest region of North Dakota.

Some areas of Northwest ND caught a little rain last week. Portions of Divide, Burke, and eastern Mountrail Counties received about ½”. Scattered storms in McKenzie added up to about ½” in spots while nothing much fell in most of Williams. Though welcome, this rain likely isn’t enough to make a difference to most of the crops as they are maturing quickly with the hot and dry conditions. Long season crops like soybean, sunflower, and safflower could still make use of additional moisture, but most of our small grains and pulses are turning color.

Here at the Williston REC, we started cutting barley, spring wheat, and durum this week. Most of the small grains are ready to harvest and then we will move on to broadleaves. Our peas and lentils are ready or are very close while canola still has a way to go before it dries down.

Hot and dry conditions are predicted to continue in the coming week with highs in the 90’s expected most days. As you begin harvest, please use caution and be aware of the high potential for fires. Keep fire extinguishers and water tanks ready.

 

Clair Keene

Area Extension Specialist/Cropping Systems

NDSU Williston Research Extension Center

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North Central ND (07/27/17)

Information from the North Central region of North Dakota.

A few hit and miss rain showers arrived in the North Central (NC) region over the last week, though, probably not enough put a dent in the drought. However, some small chances of rain could bring relief to some areas over the next week. The NDSU small grain disease model continues to remain low across the area. On the insect side of things, a few English grain aphids have been found on small grains in parts of the area, though, I have not observed them at economic levels. However, scouting may be beneficial. Grasshoppers continue to be found along field edges through data observed through the IPM scouting program. Again, continue scouting protocols.

We have had some exciting events over the last few weeks with plot tours in Renville and Pierce counties and field day at the NCREC. Agronomy updates were provided along with information on UAV technology and pollinator information. We are not done yet as the NCREC will host one more field day on August 22nd at 9 am. For this event, we will play co-host with the NRCS with a focus on good bugs within an agricultural setting. Please note, registration is limited to the first 80 participants. Lunch will be provided. Early bird registration ends on August 1 ($30 cost). After this date, the registration cost will rise to $40. This will cover your educational materials and meal. A block of rooms has been set aside at the Astoria Hotel in Minot for those who would like to travel to this event. Registration and event information can be found on the NCREC website.

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TJ Prochaska

Area Extension Specialist/Crop Protection

NDSU North Central Research Extension Center

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Growth Regulator Symptoms on Soybeans (07/27/17)

The photo below was sent inquiring if the cause was from dicamba drift or the rapid response syndrome.

Growth Regulator Symptoms on Soybeans

The photo below was sent inquiring if the cause was from dicamba drift or the rapid response syndrome.

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Determining the difference between rapid growth syndrome and dicamba drift maybe difficult. I assume there may be confusion with growers also. As dry as it has been across the state I doubt symptoms from rapid growth syndrome will be expressed much. However, if an area received a rain event at this time of the season and soybeans undergo rapid growth then leaf blistering could be expressed. Last year I wrote a crop and pest report article on rapid growth syndrome and included a photo (see attached). The symptoms in the photo showing rapid growth syndrome are similar yet a little different than your photo above. Cupping is distinctive with dicamba but the blistering without cupping is distinctive with rapid growth syndrome.

To help determine similarities and difference between soybean symptoms from rapid growth syndrome and dicamba drift I reviewed photos recently taken from my research plots where dicamba had moved a few feet on Liberty link soybean (see below). The dicamba drift shows soybean leaf blistering without much cupping on some leaves.

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As soybean is most likely the most susceptible species to dicamba it is reasonable to assume that both events could manifest itself on soybean leaves but expression of rapid growth syndrome would only occur after adequate soil moisture and a conditions to support rapid growth.

The following is the article published in the 2016 Crop and Pest Report #14.

Question: Over the last 10 days or so, especially since we received the 6+ inches of rain, I’ve been coming across several soybean fields that are exhibiting substantial cupping and/or puckering of the leaves, primarily on the newest growth. Automatically the blame gets shed onto growth regulator (GR) herbicide drift/ volatilization since certain GR herbicides do indeed cause cupped soybean leaves. However I find this hard to believe since applications of dicamba on corn fields were applied 3+ weeks prior to these symptoms showing up on the soybeans. I didn’t believe it to be possible for dicamba to pick up, and move that long after applied, especially with after a heavy rain which should’ve moved dicamba farther into the soil.

Answer: Samples have come in showing classic growth regulator (GR) symptoms on soybean. In reviewing the field and chemical histories there was no indication of herbicide carryover, spray tank contamination, or droplet particle or vapor drift from the nearby area. This phenomenon has been seen certain years across the Midwest at this time of the year when soybean plants show accelerated growth. The leaf strapping and blistering from rapid soybean growth is classic symptoms that mimic growth regulator herbicides. Applied glyphosate which would normally not cause any expression of abnormal growth may also contribute to observed symptoms and may interact with environment and rapid plant growth to cause these GR type symptoms.

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There are a few factors that can differentiate this from actually GR herbicide/plant interactions. Leaf strapping and blistering from rapid soybean growth would be observed mainly on the leaves. GR herbicides can also cause these symptoms but in addition may cause epinasty (bending and curving) of leaf petioles. Soybean varieties may also show varying levels of symptoms expression – one variety may show prominent symptoms while another may show no abnormal growth.

A “loose” rule of thumb for soybean symptoms from GR herbicides is:

2,4-D = leaf strapping, blistering and leaf petiole epinasty. Stem cracking and callus growth may form on stems.

Dicamba = leaf blistering and upward cupping.

Clopyralid = Fiddlenecked leaves and growing points and some leaf strapping.

This year many have seen growth reduction/stunting in addition to the growth regulator symptoms on soybean plants. This does not fit the normal expression of rapid growth symptoms. There may not be a good explanation for this excessive symptomology except some varieties seem more susceptible than others. I have observed the same stunting and rapid growth symptoms on soybeans in my research plots with no evidence of carryover or drift from a growth regulator herbicide.

Rich Zollinger

Extension Weed Specialist

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