Crop & Pest Report - All
Valor use in Dry Beans
Question: I heard yesterday Valor does not have a dry bean label for ND anymore but OK in MN though. What am I missing here Rich?
Answer: I can see why there is confusion. Valor and Spartan are related herbicides. They have the same mode of action and have a similar weed spectrum of control. Back in the late 90s early 2000s I worked with Valent to find a way to get adequate Valor safety on dry beans. Valent even tried reformulating the herbicide several ways to make it safer and nothing worked. The soils in this region for some reason make it too active and we gave up on it and Valor was never labeled on dry beans in the entire mid-west. Researchers out west did studies on dry beans and found better safety but still some risk of injury to dry beans. Valent developed a supplemental label allowing use only in CO, OR, and WA: http://www.cdms.net/LDat/ld3LL038.pdf
The herbicide for dry beans in ND and MN is sulfentrazone - the active ingredient in Spartan Charge/Spartan Elite…..and nary should they be confused with Valor.
To my knowledge, Valor is NOT labeled in MN on dry beans nor any other state in the mid-west.
Extension Weed Specialist
Contact Injury on Wheat
Question: Does this look like a contact herbicide on wheat leaves? There is damage on one side of field and less as you go farther out into field. The injury is greatest along the whole field edge. The adjacent field is soybeans and I think it was sprayed prior to beans emerging. So maybe a burn down product was used, do you know what may have been used as a contact burn down product?
Answer: This desiccated tissue showing localized spotting and speckling is classic paraquat (Gramoxone) symptomology. Sharpen can also cause similar symptoms but would require addition of an aggressive oil adjuvant like an MSO. When contact herbicide injury is observed, new growth will not have symptoms and there should be no yield loss.
Extension Weed Specialist
When to Spray after a Frost
The following is adapted from a phone call with Dr. Kirk Howatt, NDSU Weed Scientist.
Question: How soon can I make my herbicide application to my wheat and barley that have been injured by frost?
Answer: The short answer: After 3 or so days of growth and evidence of new green plant tissue produced. Plants require time to recover from the frost and resume normal metabolism necessary to breakdown applied pesticides. Small grain plants that only show minor frost injury, such as desiccated leaf tips, may only need a day to resume normal growth if day-time temperatures initiate growth after the frost. Those plants that show significant injury will require evidence of new growth before herbicide applications can be made. To determine viability of wheat and barley plants, cut the main stem with a knife and observe the growing point. If the growing point is white then the area is unaffected. A tan or brown tissue means the growing point has been injured and plants may not recover. Low areas of the field will likely be affected the most rather than the entire field. Weeds may not show much frost damage, but in cases where weed tissue is injured, herbicide efficacy may be reduced. Grass weeds beginning to tiller and broadleaf weeds that are 3 to 4 inches tall may require timely herbicide application to prevent yield loss from weed competition regardless of frost injury. Group 1 grass herbicides used in small grains contain a safener which increases crop safety to the herbicide. For wheat, many Group 2 herbicides also include a safener, but the level of safety has not been as high as with Group 1 herbicides. The risk of injury and yield loss with Group 2 grass herbicides increases substantially after the 5-leaf stage. When staging small grains remember to include leaves destroyed by frost. Group 2 broadleaf herbicides require active metabolism in wheat and barley plants for adequate crop safety and these herbicides can increase injury with Group 2 grass herbicides when applied together.
Extension Weed Specialist
No-Till Fields Planted
I have, or will have, 30 sites this year from Casselton to Beach to Bottineau in various studies. Of these, all of my long-term no-till sites (15) are planted. The ones that are not planted (2) are conventional till. ‘No-till means no farm’?
NDSU Extension Soil Specialist
Tillage- The ‘Gift’ that Keeps on Taking
We do not see the dust clouds in fields this first week of June as we did in April, but soil is moving just the same. Yesterday I spent most of the day splicing wires for moisture sensors in ‘minimum-till’ Valley soils within a few feet of the soil surface and the 20-30 mph winds resulted in residue movement and soil movement so that within an hour there was grit in my eyes, mouth, and all other uncovered areas. The material was black, so organic matter was being lost.
Rainfall on non-residue protected soil dislocates soil particles from each other and when they dry the small soil particles at the surface are at high risk for loss. The losses are small, but on-going, and they will keep on-going until the crop is tall enough to break the wind. Tillage is a ‘gift’ that keeps on taking.
NDSU Extension Soil Specialist
Patience on Yellow Corn, but React to Yellow Wheat Now
Most wheat fields are in the 3-5 leaf stage and have some yellow in them, especially in areas receiving near record May rains. Now is a good time to stream UAN and maybe a little ammonium thiosulfate or ammonium sulfate solution to avoid a large protein dockage and perhaps protect yield. Application of N/S would best be done sooner rather than later. Stream nozzles can also work, but greater wind speeds break up the stream pattern sooner with nozzles than stream bars. Adding ammonium thiosulfate to the mix increases the severity of any leaf splash under high wind conditions. Be sure the yellowing isn’t due to disease or another condition. This is another case where a crop consultant can be a great benefit and help confirm the probable causes of a poor crop.
Corn is yellow mostly because the soil is still cold (put your hand in the soil- it feels like an icebox), the wind is beating the young plants up, and the lingering effect of frost(s) still takes a toll. Growers should be patient with the corn until it approaches V-5, then assess whether N/S is a problem and take remedial action. Until then, patience should be the rule.
In both conditions, it makes no difference to the plant what form of N is used as long as the plant can get to it. Avoid low-rate slow-release products on wheat, not because the products are not effective if used at similar N rates to UAN or urea, but because they are no more efficient in wheat uptake than UAN or urea and can be as much as 8 times higher in cost. The smart money is on more traditional products for yield and protein increases.
NDSU Extension Soil Specialist
Stripe Rust Detected in North Dakota
On Monday, we received a wheat leaf sample collected by Dr. Janet Knodel and Sam Haugen (Plant Pathology graduate student) that was confirmed as stripe rust. On Tuesday, the IPM scouts in central (Kyle Aasand) and northeast (Jaime Lundquist) North Dakota also documented the presence of stripe rust. This information combined with the early development of the disease in states to the south, we can expect that stripe rust is probably widespread on susceptible varieties on the eastern half of the state. I have not received any reports from western side of the state, but now is a good time to start scouting for the prevalence of this disease.
How common is stripe rust?
Stripe rust is often considered to be the least common wheat rust in ND. The last widespread stripe rust event in the state occurred in 2012 and several fields had high levels of stripe rust that required a fungicide application.
What are the ideal conditions for disease development?
The sporadic occurrence of stripe rust is largely explained by the environment. Stripe rust development is favored by cool nighttime (50-60˚F) and daytime (below 80˚F) temperatures with frequent moisture events such as heavy dews and rain; conditions that were readily observed during May.
Where does stripe rust come from?
Like all other wheat rusts, the stripe rust pathogen survives on living plants in the south and produces spores that are carried by winds north along the Puccinia Pathway. The route of spore travel is similar to the Central Flyway used by migrating waterfowl. This year Kansas and Nebraska reported several fields of high stripe rust incidence and severity producing an ample spore source for the neighbors to the North. This spore source combined with the cool wet weather experienced in May has contributed to the early documentation of stripe rust in ND.
How do you differentiate between stripe rust, leaf rust and stem rust?
Both color and rust pustule shape can help differentiate between the wheat rusts. Mature stripe rust pustules are yellow to orange and appear in an elongated stripe on the leaf. In early stages of stripe rust development, the typical elongating stripe lesion is not common and color must be used to identify stripe rust (Figure 1). Leaf rust has oval shaped pustules that are reddish-brown on the leaf blade (Figure 2). Stem rust primarily occurs on the stems of susceptible plants, but can also be observed on the leaf blades as dark red-brown irregularly shaped pustules.
Most of the rust breeding efforts on spring wheat have been dedicated to leaf and stem rust, yet susceptibility differences to stripe rust were observed in 2012. For example, Prosper, Faller and Vantage were documented in having high stripe rust severities. Greenhouse screening of winter wheat varieties listed Ideal, WB Grainfield and Art as being resistant to stripe rust. Screening efforts are underway evaluating germplasm for resistance to all three wheat rusts.
Fungicides in the triazole and strobilurin classes offer very good to excellent management of stripe rust. These same classes of fungicides have similar efficacy against other fungal leaf spots as depicted in the 2015 NCERA-184 Wheat Fungicide Efficacy Table (Click on the Link and select 2015 Wheat Fungicide Efficacy Table). The timing of an application is the most critical and trickiest part in fungicide management of stripe rust. The key leaf to protect from stripe rust is the flag leaf. Remember that fungicides do not cure infected leaves and should be used in a protective manner. When deciding to make a fungicide application, consider the growth stage, level of rust incidence in a field and future weather conditions.
No need to hit the panic button yet, but scout and pay attention to the weather. When it comes to scouting, if you don’t see stripe rust now, this does not necessarily mean the stripe rust pathogen is not in your field. Once a spore lands on a leaf, a new pustule will not be produced for about two weeks under ideal weather conditions. Therefore, frequent scouting is needed to document any changes in disease incidence. If nighttime temperatures stabilize in the upper 60s and several daytime highs are above 80˚F, the pathogen will go dormant. However, if ideal conditions continue in the next two weeks, the decision to make a flag leaf fungicide will come into question.
Evaluating Emergence Uniformity in Corn
Last week I wrote about evaluating corn stands to determine if replanting would be profitable. This week I will discuss the issue of stand uniformity. Corn is less flexible than wheat and soybeans in filling in gaps in the row after emergence and it also does not compete well with other nearby plants early in the season. Therefore, stand uniformity is a much more important goal with corn than with many other crops. The optimum scenario for corn is that every seed that is planted emerges on the same day with no skips or doubles. Achieving perfect uniformity of emergence is unlikely, even with the best of conditions and equipment. Nevertheless, better uniformity means higher yields so striving for improved uniformity will help improve productivity and profitability. Though there is no management practice that can ameliorate uneven stands at this point, evaluating the uniformity of stands can be a useful learning exercise for future years.
What are the yield loses associated with variable stands? For the past two years, with initial funding from the North Dakota Corn Growers and under the leadership of Lindsey Novak, a graduate student in Plant Sciences, a number of Area and County Extension Agents have assessed plant stand uniformity and measured its impact on yield. Averaged over all field locations, they found that within a planter width, the most variable row yielded 9 bu/A less than the least variable row (Table 1). The most common problem causing the variability was variability in emergence date and not skips and doubles. In fact, doubles were not a common problem in most fields, suggesting that most planters used in the fields sampled were very good at ensuring singulation.
When measuring the yield loss on a plant basis, skips were the most impactful, followed by plants emerging 11-17 days after early emerging seedlings (Table 2). Plants next to a skip could add 10% greater yield when compared to normal spacing, but this was much less than the 50% needed to totally compensate for the lost plant. Plants next to a late emergers were able to add 5% greater yield, but again, they could not completely compensate for the loss of production by plants emerging later.
There are a number of causes of poor emergence uniformity. Skips can be caused by non-viable seed and one should expect some skips as seed lots normally have germination percentages around 90 to 95. Doubles can be traced back to a planter problem. Though doubles generally do not result in a yield reduction (data not shown), they are not an efficient use of seed. Difference in the timing of emergence is caused by differences in access to soil moisture by the seeds, differences in soil temperature and/or seeding depth. Uniform moisture was a big issue for many fields earlier this spring. Determining the optimum seeding depth is not always easy and is a key decision impacting emergence in dry soils. Planting into moisture is recommended if no rain is forecast in the next 5 to 10 days. Planting too deep, prior to a heavy rain, on the other hand can slow emergence and in heavy soils that are prone to waterlogging, result in stand loss. The cool weather this spring accentuated emergence problems. Small differences in the temperature that the seed encounters can be caused by difference in depth of seeding and the amount of residue that is retained directly above the seed. Uniform seeding depth (planting speed impacts this) and uniform residue cover should be evaluated if you are disappointed in the uniformity of emergence timing this year.
Extension Agronomist for Cereal Crops
Counting Soybean Plants
Counting soybean plants just after plants are up and in the cotyledon or unifoliate growth stage is a good method to evaluate the crop stand. Based on various hail loss studies and other research, the minimum stand for soybean in North Dakota is suggested to be around 75,000 plants per acre, which is approximately 50% of the recommended stand. If you use the “hula hoop” method to estimate the number of plants in solid seeded fields, you would need a minimum of 1.75 plants per square foot.
The hula hoop method for solid seeded soybean stand counts depends on a circular hoop with a known diameter. The hoop should be tossed randomly at five different locations in the field and plants should be counted within the hoop. The area of a hoop can be calculated by the formula: Area = πr2, where r is the radius (or half the diameter of the hoop) and π (pi) is approximately 3.14. So with a hoop diameter of 24 inches the area is 3.14x122 = 452 square inch / 144 = 3.14 square feet. If the average number of plants in this hoop is 6, the population estimate can be calculated to be 6/3.14 (area of the hoop in square feet) x 43,560 (square feet per acre) = 83,236 plants per acre.
When you use 30, 14, or 7 inch row spacing, you need at least on average 4.3, 2, and 1 plants per foot of row, respectively, to equal 75,000 plants per acre. It is important to count several feet per row at various locations per field and average the numbers to estimate the stand. When you have a 50% reduced stand, yield reduction will be somewhere between 10-20% of the potential yield of a timely planted soybean field with 150,000 established plants. Soybean stands usually are not uniform throughout the field and there will be areas with higher or lower plant counts. With uneven emergence and gaps between plants, yields may be lower compared with an evenly distributed low stand of 75,000 plants per acre.
Soybeans have the ability to compensate for a low number of plants per acre by additional branching, more pod production per plant, more seeds per pod, and increased seed size. The plants in low population environments may have branches lower on the stem that break before or during harvest thus increasing the potential for greater harvest losses. Also some of the pods will develop lower on the plant.
Extension Agronomist Broadleaf Crops
Cereal Aphids Arrive
Our first cereal aphids were detected in McHenry County in the NC area of North Dakota at sub-economic level, 14% incidence, on durum wheat by the IPM Scout, Jacee Aaseth. Scouting over the next month will be important for the wheat (spring, durum and winter), oat and barley. Cereal aphids are blown into North Dakota from the south, and usually have several generations before dying off in the fall. Scouting should begin at stem elongation and continue up through the heading stage of wheat. For a scouting protocol, walk a Z or W pattern across the field and inspect 20 randomly selected stems at 5 sites for cereal aphids. Calculate the average number of aphids per stem or the percent of infested plants (incidence) with one or more aphids. The economic threshold is 12-15 aphids per stem or 85% incidence prior to the completion of heading. Heavy infestations of cereal aphids can reduce grain quality (protein and test weight). In addition, cereal aphids are good vectors barley yellow dwarf (BYDV), which can stunt plants and reduce yield! Symptoms of BYDV are yellowing of leaves (often the flag leaf) and stunting of plants. After the onset of flowering, the negative impacts of cereal aphid feeding are reduced (no yield loss).