Crop & Pest Report - All
Weather Forecast: July 2 – July 8
Although the persistent smoke plume over the eastern part of North Dakota into much of Minnesota earlier this week suppressed the temperatures by several degrees and therefore, lowered the potential growing degree days (GDDs) by 10 to 20 degrees, the past week still finished with slightly above average temperatures in the east and well above average in western North Dakota. These warmer temperatures were associated with a strong ridge of high pressure that was centered over the northern Rocky Mountains over the past several days. That ridge is slowly shifting westward and by early next week it is projected to be centered over the Gulf of Alaska (Figure 1). That subtle shift west will mean that North Dakota and western Minnesota will transition into a cooler weather pattern after the Independence Day weekend.
That change will begin on Sunday (July 5) with a cold frontal passage. Although there will be other days with some thunderstorms (today, (Thursday) for example), that transition to cooler air on Sunday will be the day when much of the observed precipitation falls in the next week. Behind the front, Monday through Wednesday should record well below average temperatures, meaning fewer GDDs this week, plus, that cool air in combination with the Sunday precipitation, will likely mean low level relative humidity levels will be frequently high from Sunday through Wednesday (Figure 4).
Projected GDDs, base 34°, 44° and 50° for the period July 2 through July 8, 2015 are presented in Figure 3. With the cooler weather moving through the area at some point on Sunday, a higher percentage of these numbers will occur today through Independence Day than what is anticipated for early next week.
The rest of the month: The month of June finished with temperatures from 1 to 3 degrees above average. It may have seemed cool, but overall, it would be considered a mild month. The cool down next week may be a persistent pattern in July. Clearly not every week will be cooler than normal, but there are several indications that July as a whole may finish with slightly below average temperatures instead of the slightly above average temperatures recorded last month. Summer precipitation projections are always difficult because of the wide variations in rain totals in thunderstorms, but with a dominate flow from the northwest foreseen more often than not in July, near normal precipitation, overall, would be favored in that type of pattern.
Assistant State Climatologist/Meteorologist
(701-231-8209) Twitter: @darylritchison
With a break in the rain over the past week growers have finally been able to cut and bale hay. Peas and canola are flowering and small grains are heading. Crops are coming along well and corn in the area is looking good with recent warmer weather. Powdery mildew and downy mildew among other diseases have been reported and we are still at risk for scab. Wheat stem sawfly was found in the area as well.
We are gearing up for the field day next week at the Dickinson Research Extension Center on July 8th. The field day is split into a morning agronomy session from 8:30-12 ending with a lunch and an evening horticulture session from 4:30-7. Parking is available along Empire Rd/W 10th St or across the street from the grounds at the rec center parking lot. More information can be found through the following link. https://www.ag.ndsu.edu/news/newsreleases/2015/june-15-2015/dickinson-research-extension-center-field-day-set
Area Extension Specialist/Cropping Systems
The region’s NDAWN stations indicate rain received during June ranged from 1.5 inches (Robinson) to 5.6 inches (Linton). The region has adequate to excess soil moisture. Crops received various levels of hail injury during the past 10 days in the region’s northern counties: Wells, Eddy and Foster; and southern counties: Emmons, Logan and McIntosh.
Hay harvest continues to be a challenging task. First-half April seeded barley is in the soft dough stage while spring wheat is in the flowering to watery ripe stages. Current management decisions in spring wheat: Fungicide application at early flowering stage for control of leafspot disease and suppression of scab and DON; and foliar N application at post-flowering stage to increase grain protein. Corn growth has rapidly accelerated and crop planted in April and first week of May is in the 6- to 7-leaf stages. Based on NDAWN, accumulated corn growing degree day units from May 1 through June generally are similar to the long-term average for the period. Early May planted soybean is beginning to flower, and canola and flax are at full flower (see pictures). With pasmo disease presence, flax yield averaged over 10 NDSU trials with application of Headline fungicide at 6 fl oz/acre applied at late bloom increased yield by 6 bu/acre (17%) compared to untreated checks.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center
The past week was been newsworthy for disease and insect discoveries. Our Nelson County off-station spring wheat plot is striking with stripe rust infection, south of Pekin. The most susceptible varieties have up to 100% infection with over 70% of the leaf surface erupted in stripe rust. At the LREC, cereal leaf beetle was found and we are investigating other regional locations. Wheat and barley flag leaves will have a window-pane effect from the larva. They eat through the leaf in a linear fashion, just leaving the lower cuticle behind (see Figure 1).
The Canadian fires’ smoke haze has been present since Sunday. With a break in rainy June weather, hay was cut over the end of the last week through the weekend. The haze is slowing the drying time to a crawl in heavy alfalfa stands.
For canola, we are entering sclerotinia spray season. The latest from Dr. Luis Del Rio’s plant pathology program is: best spray timing varies according to a farmer’s fungicide selection. For Quadris, apply at 10-25% bloom and all other fungicides at 20-50% bloom The sclerotinia risk map is updated about every 3 days and can be found at https://www.ag.ndsu.edu/sclerotinia/. Most of northeast’s canola country remains at moderate risk for flowering canola.
Area Extension Specialist/Agronomy
Water Conditioning through an Injection Sprayer
Question: A grower has an injection sprayer and has treated the spray solution with a water conditioner. Since I am injecting glyphosate into the water stream and then is ejected out the nozzle a second later, is the water conditioner adjuvant actually doing anything?
Answer: The answer below is based on the assumption that all droplets will contain a minimum concentration of an effective water conditioner.
- The term “water conditioner” is broad. If this person is using any adjuvant containing ammonium sulfate (AMS) at the equivalent rate of 4 to 8.5 lb/100 gal water (dry AMS formulation) or 2.5% v/v (liquid AMS formulation) depending on water hardness then the reaction explained below will occur. Many liquid water conditioners do not contain AMS and are used at low use rates (0.5% v/v) and may not neutralize antagonistic minerals or optimize herbicides.
- Two reactions occur with AMS. First, is the reaction of the ammonium (from AMS) binding with glyphosate to form ammonium-glyphosate and second, the sulfate (from AMS) will bind with cationic minerals in the spray water forming Ca-sulfate, Mg-sulfate, Na-sulfate, etc. These two reactions occur in the spray droplet on the leaf. It can occur in the spray tank but Dr John Nalewaja and other weed scientists at NDSU has shown that binding effectively occurs in the spray droplets as water evaporates and is regulated by solubility. For example, as water in the spray droplet dries, sulfate will bind with Ca and precipitate out first because it is the least soluble. With the antagonistic mineral neutralized then the ammonium can bind with the weak acid herbicide (glyphosate) and will remain in solution because it is highly soluble. This ammonium-glyphosate molecule can pass through the cuticle with the aid of surfactant resulting in greater absorption and greater herbicide efficacy. Even in water with either no or low cationic salts the ammonium-herbicide binding will occur resulting in increased weed control.
- As stated earlier these two reactions will only occur in droplets containing AMS and glyphosate. I do not know the efficiency of getting glyphosate molecules into every droplet from an injection type sprayer system. If the grower used AMS as a water conditioner and the spray water was previously conditioned with AMS then AMS will remove/nullify the antagonistic salts from the water regardless if glyphosate is in the droplet or not.
Extension Weed Specialist
Equation Used to Calculate Rate of AMS
Question: Several of my growers have been using the formula listed in section #11 on page 72 in the 2015 ND Weed Control Guide to assess their water quality and AMS requirements: lbs AMS/100 gal = (0.002 X ppm K) + (0.005 X ppm Na) + (0.009 X ppm Ca) + (0.014 X ppm Mg) + (0.042 X ppm Fe).
Our good spray water quality has resulted in many cutting out or only using AMS at 0.5 lb/100 gallons of water for a water conditioner for Roundup. The 0.5 lb of AMS is much less than the 8.5 to 17 lbs/100 gallons of water that is recommended on the Roundup labels. How reliable is this formula? Is there a minimum amount of AMS recommended that we should be using? It seem like the growers are putting a lot of faith in this equation and I want to make sure that it works.
Short Answer: The information on page 72 in the 2015 ND Weed Control Guide does recommend using the equation listed above to calculate the amount the AMS need to condition spray water but there is additional information which is equally important, “Glyphosate labels suggest AMS at 8.5 to 17 lb/100 gallons of water. However, analysis of water across the U.S. shows AMS rates of 4 to 6 lbs/100 gal are adequate to overcome most hard water.” We recommend the 4 to 6 lb rate of AMS – See Long Answer.
Long Answer: Two reactions occur with AMS. First reaction: sulfate (from AMS) will bind with cationic minerals in the spray water to form Ca-sulfate, Mg-sulfate, Fe-sulfate, etc. Second reaction: ammonium (from AMS) binds with glyphosate to form glyphosate-ammonium. After antagonistic minerals are neutralized by the sulfate then the ammonium can bind with most postemergence herbicides and form the optimum ammonium-herbicide salt (glyphosate-NH4, dicamba-NH4, Poast-NH4, 2,4-D-NH4, etc.). This ammonium-herbicide molecule can more effectively pass through the cuticle resulting in greater absorption and greater herbicide efficacy. The equation listed above can be used to calculate the amount of sulfate in AMS that is needed to overcome antagonistic minerals in the spray water. Some water in this region may have low mineral content and when using the equation only a small amount of AMS will be calculated to nullify the hard water. Section #11 on page 72 contains another important fact: “The formula does not account for cationic minerals (Ca) on leaf surfaces (lambsquarters, sunflower, velvetleaf, others) that can antagonize glyphosate.” Some plants contain Ca on the leaf surface and additional sulfate is needed to nullify that mineral source. It is not practical to calculate the amount of Ca on weed leaf surfaces and will require increasing the amount of AMS needed just for that mineral source.
It is important to remember that the function of ammonium is just as important as role of sulfate. The equation in section #11 does not address the amount of ammonium in AMS needed to enhance/optimize the herbicide. **Important point: Even in water with no or low antagonistic cationic salt content where no sulfate is needed, a generous amount of ammonium is required to form ammonium-herbicide for optimum herbicide activity. All weak-acid herbicides are enhanced by ammonium. Always add a nitrogen source if allowed and not restricted by the label!
Water conditioning trials have been conducted at NDSU for well over 30 years and researchers have repeatedly found that AMS is the most economical and effective water conditioner for glyphosate and many other herbicides. It is from this research and also from an extensive water quality testing campaign conducted by Winfield with thousands of water samples tested across the U.S that we have concluded with a general recommendation to “Always add AMS at 4 to 6 lbs/100 gal of water”.
Water quality in the mid-west and west is notoriously bad. Mineral level in water increases to over 1,600 ppm in western ND. ND water often contains a combination of sodium, calcium, magnesium, and iron and these cations are generally additive in the antagonism of herbicides. Water in ND, SD, and MT is often high in sodium bicarbonate which does not normally occur in other areas of the U.S. Calcium levels above 150 ppm and sodium bicarbonate levels above 300 ppm in spray water can reduce weed control in all situations. Water with 1600 ppm sodium bicarbonate may occur in ND, but total hardness levels can exceed 2,500 ppm. Water quality must be known to adjust AMS rate. Growers using the equation and adding AMS only at 0.5 lbs/100 gal may overcome herbicide antagonism from low mineral content in water but the low amount of AMS will not provide sufficient ammonium to optimize herbicide activity – the 0.5 lbs of AMS may have enough sulfate to bind minerals but it does not contain enough ammonium to enhance the herbicide.
Last thought – A great scientist (Dr. John Nalewaja) once said the following, “The best adjuvant for Roundup is more Roundup”. Most growers (should) use full glyphosate rates to delay resistance in weeds. When using high glyphosate rates the requirement for AMS diminishes and complete control may occur on susceptible weeds if AMS is used or not used. The value of AMS will be clearly evident not only when spray water contains antagonistic levels of minerals, but also on those weeds that are less susceptible, weeds larger than recommended, weeds hardened by drought, weeds stressed by environment or previous herbicide applications, or when using herbicide rates that are lower than required for complete kill.
Extension Weed Specialist
Iron Deficiency Chlorosis Refresher
Growers and crop consultants in the Valley are well acquainted with iron deficiency chlorosis (IDC) through years of experience. Not everyone in the Valley (few, really) follow the best advice in dealing with it, but many growers have made great strides in the past 20 years in being able to live with it. A fully explained narrative of the causes of IDC in soybean is available in the soybean fertility circular available at https://www.ndsu.edu/fileadmin/soils/pdfs/sf1164.pdf
In brief form the following is what is happening to fields of soybeans:
For IDC to be a hazard, the soil must be calcareous. This means that soil pH will be greater than 7, and if a calcium carbonate equivalent test is performed, free carbonates are greater than zero; sometimes greater than 20% by weight in just the surface six inches of soil. Carbonates themselves in a dry to a little moist soil will not result in serious IDC. However, if the soil is wet enough to dissolve some of the carbonate and form the anion bicarbonate, IDC will appear. Soybean roots exude acids, which acidify their root system. There are probably many reasons for them to do this, and most plants do this for many reasons. A particularly important reason for soybean roots to do this is that the iron (Fe) exists in soil as the oxidized ion Fe+3, which is extremely insoluble. Reduced Fe (Fe+2) is extremely soluble, as evidenced by the iron removers in many rural homes. Most people also understand that without an iron removal system, sinks, tubs, shirts, nearly everything ground water touches turns orange. This is because the reduced iron (you can find as much reduced iron in water as a 2 penny carpenter nail per quart) immediately becomes one trillion times less soluble when exposed to oxygen and falls out as Fe+3 oxide.
The soybean root also exudes an iron reducing substance, which takes F+3 and transforms it to F+2, making it a trillion times more soluble. This happens unless there is something in the soil to interfere with the reducing substance, which requires an acid pH environment to work. Bicarbonate neutralizes acidity around the soybean root, making it much, much harder for the soybean root to take up iron.
So the rainfall in the center and western part of the state this year has resulted in bicarbonate in the soil solution and caused IDC in regions previously unaffected.
The following are steps that growers should implement to reduce IDC in the future-
- The most important step is to choose an IDC tolerant variety-not Iowa tolerance, but North Dakota tolerance.
- Secondly- Choose fields carefully. Avoid fields with wetness issues, high carbonate levels and high salts (EC greater than 1.5 mmohs/cm). Also avoid fields with high residual nitrate.
- Third- Grow the soybean in wide rows- 15 inch to 30 inch rows. For some reason, when soybean plants are closer to each other IDC is greatly reduced.
- Fourth- Consider a companion crop of a bushel of oats or barley (barley is better on salty soils) to reduce soil moisture and residual nitrate. If conditions are dry, the companion crop can be killed out early; if a wetter season, wait until the 5th leaf stage to kill out.
- Fifth- If a tolerant variety is used, application of an ortho-ortho Iron EDDHA fertilizer with water in furrow at planting will usually reduce IDC.
NDSU Extension Soil Specialist
Scab Risk in North Dakota
The NDSU forecasting website indicates that most of the state is in low to moderate scab risk for susceptible varieties (Figure 1), whereas the national model has highlighted several pockets of high scab risk (Figure 2). Given that several areas of the state received significant rainfall over the weekend and other areas experienced high levels of humidity, I suggest that the scab risk is higher than the prediction given by the NDSU website. If warranted, a triazole fungicide application on early-flowering wheat should be considered in the areas experiencing warm and wet weather.
Extension Plant Pathology, Cereal Crops
Stripe Rust Being Found on Flag Leaves
The cool, wet weather in June provided ideal conditions for the development of great looking wheat crop. However, these same conditions also promoted the development of stripe rust (Figure 1). During the past ten days, there have been several reports of stripe rust lesions on flag leaves of spring wheat on the eastern half of the state. Several questions have been asked on how to manage this disease. I will provide some insight on some of the commonly asked questions.
What fungicides are effective on stripe rust?
Using data from the winter wheat belt in the southern Great Plains, strobilurin (ie: Headline, Quadris and Evito) and triazole (ie: Folicur (generics), Prosaro and Caramba) based products have very good to excellent activity on stripe rust. The more important issue is the timing of a fungicide application. Fungicides that were applied with a herbicide will help protect the leaves available at the time of the application, but as the wheat crop matured, newer leaves (especially the flag leaf) developed and were vulnerable to subsequent infection events.
I sprayed for scab and now I am seeing stripe rust lesions on the flag leaf?
The good news is fungicides that are effective in suppression scab and DON are also effective in managing stripe rust. The bad news is these fungicides will not cure infections that have already occurred. The amount of time it takes a spore landing on a leaf and causing a pustule is approximately 14 days. Therefore, when a fungicide application was sprayed at early-flowering, it will only protect the leaf tissue that has not been colonized by the pathogen. This is a perfect example of how rust diseases can appear to have increased after a fungicide application.
Are any of the spring wheat varieties resistant?
This past week Dr. Maricelis Acevedo and I rated a spring wheat variety by fungicide trial conducted by Dr. Joel Ransom in southeast ND. This trial had a natural epidemic of stripe rust and differences in susceptibility were observed amongst the spring wheat varieties. We found that a large majority of the spring wheat varieties were susceptible or moderately susceptible to stripe rust (Figure 2). Future evaluations will be conducted at other sites that are known to have stripe rust in them. We expect to gather more varietal information and include it in the Hard Red Spring Wheat Variety Selection guide for next year.
Continue to scout fields for the presence of stripe rust. If you have a later developing wheat crop, a flag leaf application may be needed if the weather remains cool and wet. If your area receives consecutive days of hot temperatures (close to 90˚F) and warm nights (above 60˚F) the stripe rust pathogen will “slow down” and may go into the overwintering spore stage (Figure 3).
Extension Plant Pathology, Cereal Crops
Extension Agronomist for Cereal Crops
NDSU, Rust Pathologist