Corn growers have come to expect some rootworm damage, but University of Illinois entomologists say putting management plans in place now could help growers avoid major losses.
“Over the last few years, western corn rootworm populations with resistance to toxins present in common Bt corn hybrids have been documented in Illinois,” says Joseph Spencer, insect behaviorist at the Illinois Natural History Survey (INHS) at U of I.
“We’re specifically seeing resistance to Cry3Bb1 and mCry3A toxins, but we know that resistance to these toxins also confers resistance to the structurally similar eCry3.1Ab toxin,” he says. “Cross-resistance among these ‘Cry3’ Bt toxins should be expected for Illinois western corn rootworm populations.”
Resistance to pest-control practices in western corn rootworm is nothing new; the insect is notorious for developing resistance to control tactics such as insecticides and crop rotation. Part of the concern with these recent developments is that there are relatively few Bt toxins available to combat corn rootworm.
“All available hybrids with pyramided traits for corn rootworm use either Cry3Bb1 or mCry3A in combination with a second toxin, either Cry34/35Ab1 or eCry3.1Ab,” Spencer says. “This means where resistance is present in the population, there might be at best only one effective toxin at work.”
There are steps producers can take to manage corn rootworm and possibly slow further development of resistance. Nick Seiter, entomologist in the Department of Crop Sciences at U of I, says the best way to delay resistance to any control tactic is to reduce exposure of the target insect to that tactic in the environment. This can be accomplished using the following strategies.
Apply rootworm control, whether in the form of a Bt hybrid or a soil insecticide, only where it is economically justified. This determination should be based on sampling rootworm adults the previous year. According to surveys conducted by Kelly Estes, agricultural pest survey coordinator for Illinois Extension and INHS, densities of rootworm adults have been relatively low in recent years, although they did trend slightly upward in 2017.
“If you monitor using a yellow sticky trap, the economic threshold is two rootworm beetles per trap per day in corn following corn,” Spencer says. “For rotated corn, the economic threshold is 1.5 western corn rootworm beetles per trap per day in soybean.”
Rotating corn with soybean or another non-host crop remains an effective management strategy in the southern portion of the state. While crop rotation is no longer a reliable method to protect first-year corn from western corn rootworm damage in central and northern Illinois, Seiter notes, all larvae that hatch into soybean still die, and every acre planted to soybean is an acre where larvae are not being exposed to Bt toxins or soil insecticides.
Where monitoring indicates that control is justified in corn, rotate the control measures used from year to year. This means rotating Bt hybrids with different trait combinations and non-Bt hybrids treated with a soil insecticide.
“Follow all refuge requirements for any Bt corn hybrids you plant. In many cases, the ‘refuge in a bag’ or ‘RIB’ approach is now used, but check with your seed distributor on specific requirements for your hybrids,” Seiter says.
Finally, an important step is to monitor the performance of control methods. While lodging is often the cue growers look out for to identify rootworm damage, it’s important to remember that corn can take a lot of damage without lodging, and plenty of factors other than rootworm damage can lead plants to lodge.
“The best approach to evaluating rootworm damage is to dig a representative sample of roots in late July and evaluate them for feeding damage: unpleasant work, but necessary if we want to understand the true extent of the damage,” Seiter says.
Consider planting a small area or a portion of a row with a non-Bt/untreated hybrid as a check strip. Having an untreated patch in the field will allow growers to compare the efficacy of the management tactic vs. the background level of damage where no rootworm protection was used.
Finally, if you experience greater damage than expected in Bt corn hybrids in 2018, let Seiter know by emailing email@example.com. “Your reports will help us document the status of resistance in Illinois and provide updated information to producers,” he says.
For more information, read the full report on The Bulletin.
Source: University of Illinois
It is looking like at least some harvest surprises may be positive after an up-and-down 2017 season in Illinois. The September 1 yield predictions released by the USDA this week are for Illinois corn yield to average 189 bushels per acre, up a bushel from the August 1 estimate. The soybean yield estimate is unchanged at 58 bushels per acre. Both would be outstanding after the tough start to the year and dry weather at times over much of the state.
Many soybean fields in east central Illinois are dropping their leaves, and harvest is getting underway. While we don’t expect as many 80+ bushel yields this year as we had in 2016, pod numbers look better than many had expected after dry weather in August and September. Rain now might boost yields by a little, but only in fields planted late or with late-maturing varieties where plants are still green. Cool temperatures in recent weeks have lowered water use rates, though, and we aren’t seeing the premature leaf drop that sometimes signals an early end to seedfilling due to lack of water.
With high temperatures in the 80s now and expected for the next week or more, the process of shedding leaves and drying down will accelerate, and it will be important to try to harvest soybeans at seed moisture above 10 percent. While some rain would help lawns and still-green crops, it would be better for the pod integrity if it stayed dry until after harvest, especially if temperatures stay high.
With high temperatures, seeds and pods following maturity will dry within hours instead of days, and we need to be alert and ready to harvest as soon as plants can be cut and seed moisture is at 12 or 13 percent. If moisture drops to 10 percent or less during harvest, it might be worth stopping until pods and seeds take on some moisture in the evening or overnight. Breeding and the use of improved combine headers have reduced pod shatter, but seeds less than 10 to 11 percent moisture can crack more easily. This might be one of those years with frequent switching between soybeans and corn harvest.
The corn crop in many fields is also looking a little better than expected as the leaves dry down and ears start to drop. As of September 10, two percent of the state’s corn crop had been harvested, mostly in southern Illinois. Yield reported so far range from low to high, reflecting differences in planting (or replanting) time, ability of soil to hold water for the crop, and whether rain fell or didn’t fall at critical times.
Nearly all of Illinois had below-normal rainfall in August, and little or no rain has fallen over most of Illinois during the first half of September. Dry soils during grainfill can decrease leaf photosynthesis, and when that happens, sugars are pulled out of the stalk into the ear to fill the grain. This leaves the stalks more susceptible to stalk-rotting fungi, and so more subject to lodging. So fields – especially those where leaves dried up earlier than expected – should be checked for stalk strength. Good growing conditions in July can increase the deposition of stalk-strengthening lignin, however, making stalks less likely to break even if sugars are pulled out. So as long as winds stay relatively calm, lodging is not expected to be much of a threat, especially in those parts of the state that received more rainfall in July and August.
Below-normal temperatures in recent weeks – most of central and northern Illinois are now about 150 GDD behind normal since May 1 – have slowed grainfilling rates and delayed maturity of the corn crop. The cooler temperatures have probably been positive for yields, by extending the water supply into mid-September. But the mid-August predictions that early-planted fields would mature by late August or early September didn’t happen. With GDD accumulation rates now above normal, a lot of fields will reach physiological maturity quickly, and grain will start to dry down. High temperatures mean rapid grain moisture loss; we’ve seen moisture loss as high one percent per day under high temperatures, especially if it’s breezy.
Dry conditions over the past month have limited the spread of ear rots. Most kernels now have the bright yellow color we like to see at harvest, and if the grain reaches maturity and can be harvested without an extended period of wet weather, we can expect grain quality to be good. Harvesting at high moisture and drying at high temperatures, or storing grain without proper care, can all compromise quality, however, and can mean getting a lower price for the crop.
One issue that often comes up for discussion during corn harvest is that of corn test weight. If test weight turns out to be lower than the standard of 56 pounds per bushel, many people consider that a sign that something went wrong during grainfill, leaving yield less than it could have been. And, test weights in the high 50s or above are often taken as a sign that kernels filed extraordinarily well, and that yield was maximized. Neither of these is very accurate –high yields often have test weights less than 56 pounds, and grain from lower-yielding fields can have high test weights.
Test weight is bulk density – it measures the weight of grain in 1.24 cubic feet, which is the volume of a bushel. Kernel density is the weight of a kernel divided by its volume, so does not include air like bulk density does. Kernel density is a more useful measure of soundness and quality than is test weight, but is harder to measure. A typical kernel density might be 91 pounds per 1.24 cubic feet of actual kernel volume. So a bushel of corn grain is about 56/91 = 62 percent kernel weight; the other 38 percent of the volume is air. Kernels with higher density tend to produce higher test weights, but only if they fit together without a lot of air space. Popcorn, as an example, has small, high-density kernels that fit together well, and a typical test weight of 65 pounds per bushel.
Hybrid genetics, growing conditions, and grain moisture at which test weight is measured can all affect test weight. If kernels appear to be well-filled, without a shrunken base that can signal that grainfill ended prematurely, it’s likely that they filled to their capacity and that yield was not compromised even if test weight is less than 56 pounds per bushel. For reasons that go back to an earlier time, though, corn needs to have a test weight of at least 54 pounds per bushel in order to be sold as U.S. No. 2 corn, which is the most common market class. Corn with a test weight of 52 or 53 might not be docked in price if it can be blended with higher test weight corn to reach the minimum. That’s much easier to do in a year when test weights are generally good. We expect that 2017 might be such a year.
Source: Emerson Nafziger, University of Illinois
This is the first in a series of iGrow articles that will be dedicated to the issues and questions we receive related to establishing, re-establishing, and maintaining grass-based plantings for grazing, hay, wildlife, and recreation. This series will attempt to address the issues related to grasslands in a systematic process that helps the reader to understand key concepts of grassland management, and thus better prepare the reader to set specific goals and objectives to achieve desired results.
What do I want my grassland to provide?
Of primary importance is to ask a few key questions: “what is it that I want my grassland to provide?”, “what am I willing to invest?”, and similarly, “what is the time frame that I expect results?”.
For starters, we will consider the first question, “What do I want my grassland to provide?”. There are major differences in what can be achieved in grassland projects based on the history of the land and its management. Native (unbroken) sod in the form of grazing pastures or prairie areas has certain characteristics and potentials that planted or tame grasslands do not. However, there is great variability within the native sod category regarding historical use and management, which may include various grazing, haying, chemical, fire, or other management techniques.
Past Management Considerations
Past management often drives the direction of the plant community itself, impacting plant health and variety depending on the action.
What native sod can provide in relation to desired goals, such as annual production or plant diversity, can sometimes be achieved, sometimes not, and is often dependent on whether the plant community has been ‘simplified’ through invasion of exotic species, past management, or both. In general, native sod that is not performing to its potential should be regarded as something to be healed through well-timed actions that focus on the plant community rather than something to be ‘fixed’ through mechanical soil manipulations.
If the grassland is not native sod and is currently tame species or ‘go-back’ grass that has revegetated on its own, one still must consider past management. The potential of what the grassland can provide will be based largely on the species (native and non-native) that are now established. In these areas, there is often more opportunity to actively change the plant community through various manipulations than on native sod, though one must be realistic in expectations and timelines.
If the area of concern is currently managed for row crops, cover crops, hay, CRP or some other cover, the opportunity to quickly establish or re-establish a desirable community is possible. However, past management in relation to soil conditions and residual chemicals can have a dramatic impact on establishment of new vegetation.
The Bottom Line
How much one should invest to change a grassland plant community can be a challenging question. Input costs for soil preparation, seeding, and maintenance can be highly variable. One must first consider a strategy to ensure the soil is ready to receive the new plants. Profit potential can also be highly variable and is directly related to initial and ongoing input expenses.
This article just scratches the surface of considerations related to maintaining and establishing grasslands. We will continue to explore the vast variety of questions posed by landowners seeking to improve their grassland resources.
Source: Pete Bauman, iGrow
Herbicide-resistant weeds such as Palmer amaranth, waterhemp and horseweed (marestail) are spreading, increasing weed control costs and yield losses in soybeans. Because of this, producers need to take action to prevent or reduce the spread of these weeds. Combines, tractors and tillage equipment have been identified as some of the main culprits in spreading weed seed from field-to-field.
The first step is to scout all of your soybean fields prior to harvest and determine if herbicide-resistant weeds are present. Most marestail is considered resistant to glyphosate and many populations are also resistant to the ALS-inhibiting (Group 2) herbicides. Palmer amaranth and waterhemp are commonly resistant to glyphosate and the ALS inhibitors and can be easily distinguished from other pigweed species by their smooth and hairless stems. Additional information on identifying and managing herbicide-resistant weeds is available at Michigan State University Weed Science.
One of the most practical and effective methods of reducing field-to-field spread of weed seed is to harvest fields or areas of fields infested with herbicide-resistant weeds after harvesting all of your clean fields.
When infested fields must be harvested before clean fields, a thorough top-to-bottom and front-to- back cleaning of the combine is recommended. However, this may take 4 to 5 hours, so it is probably not possible when moving from field-to-field. When a thorough cleaning is not possible, Iowa State University Extension agricultural engineer Mark Hanna recommends investing 15 to 30 minutes to remove at least some of the plant material before leaving the field. The steps to this procedure are listed below.
- Remove the combine head and open the doors at the bottom of the rock trap, clean grain elevator and the unloading auger sump.
- Clear the area around the combine to avoid injury from flying debris.
- Allow the combine to “self-clean” by starting it up and running it with the thresher and separator at full speed, the concave clearance and cleaning shoe sieves fully open and the cleaning fan set to the maximum speed. Drive the combine over the end rows or other rough ground to dislodge biomaterial.
- Shut the combine off and use an air compressor or leaf blower to clean the feederhouse, rock trap and head. Using a two-strap dust mask and eye protection is highly recommended when using an air compressor or leaf blower.
- Close the doors on the rock trap, elevator and unloading auger sump when finished.
While the procedure outlined above will help reduce the quantity of weed seed moved from field-to-field by the combine, it is not as effective for removing small seeds as a complete top-to-bottom cleanout. Therefore, consider thoroughly cleaning the combine on rainy days and again at the end of the season. Information regarding a complete and thorough combine cleanout is available at “Recommended Procedures for a Complete, Top-to-Bottom and Front-to-Back Combine Cleanout” by Iowa State University and MSU Extension.
Weed seeds also travel on tractor tires and tillage implements, so tilling your weed-infested fields after your clean fields is the best way to prevent spreading weed seeds during tillage operations. When this is not possible, remove as much soil as you can from all tires and the ground-working parts of tillage implements before entering a new field.
The steps you take this fall to reduce the spread of herbicide-resistant weeds will also help prevent the spread of soil-borne pathogens such as sudden death syndrome, white mold and soybean cyst nematodes.
Average soybean harvest losses range from one to two bushels per acre under normal conditions. However, harvest losses can increase significantly when harvesting tall, lodged plants or short, drought-stressed plants. Due to the variable distribution of precipitation across the state this summer, some producers will harvest fields with significant lodging and others will harvest short plants with brittle pods. The recommendations provided in this article will help soybean producers reduce their losses under either scenario.
Properly timing your harvest operations is critical to reducing harvest losses. Harvest operations can begin any time after the beans have initially dried to 14 to 15 percent moisture. Depending on weather conditions, this is usually about five to 10 days after 95 percent of the pods have reached their mature color. Try to harvest as much of your crop as possible before the moisture level falls below 12 percent to reduce splits and cracked seed coats. Shatter losses have been shown to increase significantly when seed moisture falls below 11 percent and when mature beans undergo multiple wetting and drying cycles. Shatter losses can be reduced by harvesting in the morning or the evening when relative humidity is higher.
Before harvest operations begin, inspect and repair the cutting parts on the header. Make sure that all knife sections are sharp and tight and all guards are properly aligned. Check the hold-down clips to ensure that they hold the knife within 0.03125 inch (thickness of a business card) of the guards. Adjust the wear plates to the point that they lightly touch the back of the knife.
Equipment adjustment and operation when plants are tall and lodged
The main problem when harvesting lodged soybeans is the cutter bar will ride over uncut plants. The following recommendations will reduce this important source of harvest loss.
- Decrease your ground speed to 2.5 to 3 miles per hour.
- Increase the reel speed in relation to the ground speed incrementally to the point that the lodged plants are being cut and gathered into the combine without beating the beans out of the pods.
- Position the cutter bar as close to the ground as possible.
- Angle the pickup fingers on the reel back slightly to more aggressively pull the lodged plants to the cutter bar. Reduce the angle of the fingers if the plants are riding over the top of the reel.
- Run the reel axle 9 inches to 12 inches ahead of the cutter bar.
- Contact the manufacturer for specific recommendations if using an air-assisted reel.
- Operate the reel as low as necessary to pick up lodged plants without causing them to ride over the top of the reel. Raise the reel if this happens.
- Consider installing vine lifters on the cutter bar if the plants are severely lodged.
- If the plants are badly lodged in one direction, try adding vine lifters to the cutter bar and harvesting at a 30 to 45 degree angle to the direction of the lodging. If this doesn’t work, harvest all of the lodged plants in the direction opposite to way they are leaning.
Equipment adjustment and operation when plants are short and drought-stressed
The main problems that occur when harvesting short beans are gathering short plants into the combine after they have been cut and excessive shatter losses due to brittle pods. The following recommendations will help producers reduce these important sources of harvest loss.
- Position the cutter bar as close to the ground as possible.
- Consider purchasing an air-assisted reel as the air stream produced by this equipment effectively moves short plants and loose beans and pods to the auger or belt.
- Consider removing the rock guard on the cutter bar if it is preventing short plants, loose beans and pods from moving to the auger or belt and you do not have an air-assisted reel.
- Harvest on an angle in fields planted in 15 inch or 30 inch rows. This will help the short plants feed into the combine more unformly.
- Of all the combine adjustments, improper reel speed and reel position cause the most shatter losses so pay close attention to these in drought-stressed fields. Set the reel to run 10 to 20 percent faster than the travel speed and lower the reel so that it contacts the top a third of the plants. Reduce the reel speed and/or raise the reel if beans are being flailed out of the pods.
- Shatter losses can be reduced by harvesting in the morning or the evening when relative humidity is higher.
Source: Michigan State University
Now is the time of year to be looking for palmer.
Palmer amaranth is in the pigweed family and has a lot of close relatives that can be confused with it. Common waterhemp is the one that is most commonly confused with palmer. We also have spiny pigweed, tumble pigweed, smooth pigweed, and redroot pigweed that can be confused with palmer.
Scouting & Identification
A few keys to look for on palmer are that some of the petioles (the short stem from the main stem to the leaf) will be a lot longer than the leaf length. Also, the area where the stem connects to the petioles will have spines on it. On palmer the leaf is more cordate (heart shaped) than waterhemp which is more elliptic (oblong). Lastly the head will be long and if female will also be spiny. There is no one thing to look for that is a sure sign in all cases that the plant is palmer. It seems like we are more likely to find it in areas that have stress periods. So far we have found it mainly in the central part of the state, and usually we will find it in sunflower or soybean fields.
If you suspect you have palmer amaranth start by taking pictures to have it identified. Take pictures of the whole plant, the leaf and petiole area, the stem and petiole area, and a picture of the seed head. Email the pictures to Paul O. Johnson and make sure to send the highest resolution picture as possible it will help with the identification. Please include the best contact information to return the identification or ask more questions. For more information, contact Paul O. Johnson.
Source: Paul O. Johnson, iGrow
Although Midwestern soybean growers have yet to experience the brunt of soybean rust, growers in the southern United States are very familiar with the disease. Every year, the fungus slowly moves northward from its winter home in southern Florida and the Gulf Coast states, and eventually reaches Illinois soybean fields—often just before harvest.
Research shows there is a possibility the disease could jump much longer distances and reach the Midwestern soybean crop earlier in the growing season. Studies suggest that air masses moving from the south could sweep up rust spores from infected plants (kudzu or soybean) and transport them hundreds of miles north earlier in the season, potentially endangering the Midwestern soybean crop.
This could be happening right now as the storm system that created Hurricane Harvey moves north, according to Glen Hartman, a USDA Agricultural Research Service plant pathologist and professor in the Department of Crop Sciences at the University of Illinois. After all, hurricanes have been responsible for long-distance movement of rust spores in the past; scientists think Hurricane Ivan brought soybean rust to the United States from Colombia in 2004.
Although long-distance movement can and does happen, short-distance spore movement has been responsible for most of the annual northward spread of the disease since 2005. Hartman thinks this short-distance movement has been occurring as usual this season and, barring any unusual fallout from Hurricane Harvey, he expects to see rust showing up in Illinois soybean fields late in the 2017 season.
It is this short-distance movement that intrigues Hartman; he says predictions of long-distance spread haven’t taken real-world spore movement into account. Without knowing the number of rust spores that actually escape from the canopy and the conditions that favor spore dispersal, long-distance spread models could be inaccurate. So, in a recent study, Hartman and his colleagues placed two kinds of spore-collecting traps in, around, and above rust-infected soybean fields in Alabama, Georgia, and Florida. The team also measured environmental data, including air temperature, relative humidity, wind speed and direction, precipitation, and leaf wetness.
The majority of spores stayed within the canopy, but a proportion (one-third to one-half) floated above. Spores moved laterally away from the field, too, but most stayed within 50 feet, with about half as many moving out to 200 feet.
These numbers explain how short-distance spread of this disease typically works. Rust might spread within a field, then jump to a nearby patch of its alternative host, kudzu. Considering how much kudzu is spread around the south, it’s a good bet another soybean field is within a couple hundred feet. From there, it jumps again, moving incrementally to the north. In an average summer, Hartman says, soybean rust rolls up from the south at a rate of about 30 miles a day.
Hartman’s study also identifies environmental factors that favor or impede short-distance movement of rust spores. Using a statistical approach known as machine learning, the team found that spores went farther in hot and windy conditions, and stayed closer to the canopy in humid, wet conditions.
“What really drives local infection is humidity and moisture,” Hartman says. “Those are good conditions for fungal infection and production of spores. When it rains, it washes the spores out of the leaf lesions, so they’re not available for long-distance transport. But then the fungus just forms new spores that are ready for transport on a dry and windy day.”
The study explains short-distance transport, but how do the results inform predictions of long-distance movement?
“I think the study gives a good idea of rust spore counts in the atmosphere in and above the soybean canopy and a distance away from an infected field. There is a lot of variation in the number of spores in that air space,” Hartman says. “If you think of the airspace beyond the field, the dilution factor is huge.”
In other words, the chances of spores making it out of the canopy and picked up by updrafts for long-distance movement might be lower than assumed. And the chances are lower still if you consider what it’s like for spores to survive in high-elevation air currents.
“Spores in these high-elevation air masses are exposed to temperature extremes and to UV radiation. Not many spores survive that, although those that are darkly pigmented may have a better chance. Soybean rust spores have very little pigment, and lightly pigmented spores are very susceptible to UV,” Hartman says.
New models will need to incorporate Hartman’s findings to better predict the chances of long-distance movement of soybean rust throughout the U.S. and other parts of the world.
For further information regarding soybean rust, Hartman suggests the soybean rust website, http://sbr.ipmpipe.org. He also encourages Midwestern soybean growers to contact their local Extension office if they see symptoms of rust developing earlier than usual.
The article, “Prediction of short-distance aerial movement of Phakopsora pachyrhizi urediniospores using machine learning,” is published in Phytopathology. Hartman’s co-authors, Liwei Wen and Roger Bowen are also from the University of Illinois.
Source: University of Illinois
The end of season corn stalk nitrate test is one of the few diagnostic tools available to determine if excess nitrogen was applied to corn. The methodology and interpretation of this test were highlighted in previous Michigan State University Extension articles: “End of season corn stalk nitrate test” and “End of season cornstalk nitrate test in a drought year.”
Here are some tips to the correct sampling procedure that is critical to getting reliable data from this test.
- The time for stalk sampling is critical. It is two to three weeks after physiological maturity or when black layers have formed on about 80-90 percent of the kernels. At this stage, any further mobilization of nitrogen from the plant to the kernels has ceased. Typically, most leaves and stalks have turned brown at this stage.
- The portion sampled is the 8-inch segment of stalk between 6 and 14 inches above the soil.
- Collect 12-15 segments within an area no larger than 10 acres.
- Remove all the leaf sheaths from the segment.
- The sample needs to be taken at random, but any plant with stalk rot should be discarded. The rot destroys the pith area of the stalk, rendering it dark brown to black. Notice the color of healthy stalks in the photo.
- Plants adjoining a skip should be avoided.
- Areas with different soil types or management histories (manure practices and previous legume crops such as alfalfa and clover) should be sampled separately.
- Hybrids with different maturities and widely different planting dates may require different sampling dates.
- Place samples in paper (not plastic) bags to allow some drying and minimize mold growth. Send to a laboratory as soon as possible. Refrigerate samples (do not freeze) if stored for more than a day before mailing.
Most soil testing labs in your area will offer this test, such as A&L Great Lakes Laboratories, 3505 Conestoga Dr. Fort Wayne, IN 46808. For questions regarding shipping, cost and the test, contact your local soil testing lab or A&L Great Lakes Laboratories at 260-483-4759.
Although this test does not provide any remedy for the current year, familiarity with the data over a number of years including wet and drought years should assist producers in fine-tuning their nitrogen fertilizer practices.
Source: George Silva, Michigan State University Extension
Without advanced sensing technology, humans see only a small portion of the entire electromagnetic spectrum. Satellites see the full range—from high-energy gamma rays, to visible, infrared, and low-energy microwaves. The images and data they collect can be used to solve complex problems. For example, satellite data is being harnessed by researchers at the University of Illinois for a more complete picture of cropland and to estimate crop yield in the U.S. Corn Belt.
“In places where we may see just the color green in crops, electromagnetic imaging from satellites reveals much more information about what’s actually happening in the leaves of plants and even inside the canopy. How to leverage this information is the challenge,” says Kaiyu Guan, an environmental scientist at the U of I and the lead author on the research. “Using various spectral bands and looking at them in an integrated way, reveals rich information for improving crop yield.”
Guan says this work is the first time that so many spectral bands, including visible, infrared, thermal, and passive and active microwave, and canopy fluorescence measurements have been brought together to look at crops.
“We used an integrated framework called Partial Least-Square Regression to analyze all of the data together. This specific approach can identify commonly shared information across the different data sets. When we pull the shared information out from each data set, what’s left is the unique information relevant to vegetation conditions and crop yield.”
The study uncovers that the many satellite data sets share common information related to crop biomass grown aboveground. However, the researchers also discover that different satellite data can reveal environmental stresses that crops experience related to drought and heat. Guan says the challenging aspect of crop observation is that the grain, which is what crop yield is all about, grows inside the canopy, where it isn’t visible from above. “Visible or near-infrared bands typically used for crop monitoring are mainly sensitive to the upper canopy, but provide little information about deeper vegetation and soil conditions affecting crop water status and yield,” says John Kimball from University of Montana, a long-term collaborator with Guan and a coauthor of the paper.
“Our study suggests that the microwave radar data at the Ku-band contains uniquely useful information on crop growth,” Guan says. “Besides the biomass information, it also contains additional information associated with crop water stress because of the higher microwave sensitivity to canopy water content, and microwave can also penetrate the canopy and see through part or all the canopy. We also find that thermal bands provide water and heat stress information,” Guan says. “This information tells us when leaves open or close their pores to breathe and absorb carbon for growth.”
Coauthor David Lobell from Stanford University, who crafted the idea with Guan, says leveraging all of this satellite data together greatly increases the capacity to monitor crops and crop yield.
“This is an age of big data. How to make sense of all of the data available, to generate useful information for farmers, economists, and others who need to know the crop yield, is an important challenge,” Guan says. “This will be an important tool. And, although we started with the U.S. Corn Belt, this framework can be used to analyze cropland anywhere on the planet.”
The study, “The shared and unique values of optical, fluorescence, thermal and microwave satellite data for estimating large-scale crop yields,” is published in Remote Sensing of Environment. The work was initiated and designed by Kaiyu Guan from U of I and David Lobell from Stanford University. It is coauthored by a multi-institute team of Jin Wu (Brookhaven National Lab), John S. Kimball (University of Montana), Martha C. Anderson (USDA ARS), Steve Frolking (University of New Hampshire), Bo Li (University of Illinois), and Christopher R. Hain (NOAA).
Funding was provided by the NASA New Investigator Award (NNX16AI56G), U.S. National Science Foundation (NSF-SES-1048946), a Terman Fellowship from Stanford University, the University of Illinois, NSF grant NSF-EF1065074, and NASA (NNX14AI50G).
All the data used in this study are available by request (firstname.lastname@example.org).
In addition to being an assistant professor in ecohydrology and geoinformatics in the Department of Natural Resources and Environmental Sciences in the College of Agricultural, Consumer and Environmental Sciences at U of I, Guan has a joint appointment as a Blue Waters professor affiliated with the National Center for Supercomputing Applications (NCSA).
Source: University of Illinois
Lightning Strikes in Soybeans
What are the odds that a soybean plant can be killed by lightning? Very low! In a recent ten year period, eastern South Dakota had an average of one to two strikes per square kilometer, per year. While quite uncommon for lightning to damage row crops, it does happen. Thunderstorms can have lightning that can burn soybeans plants leading to their death. Plants that looked just fine before the thunderstorm may suddenly start to show wilting symptoms and eventually die. Before you blame dead plants on plant pathogens, check to see if this could be due to a lightning strike.
How can you determine if plants were killed by lightning?
- Determine when the symptoms were first noticed.
Soybean plants affected by lightning will start to show wilting symptoms 1-2 days after the thunderstorm. Plants affected by lightning have black to dark brown discolored stems and petioles. They may have a scorched or burnt appearance.
- Look for the pattern of affected plants.
Plants killed by lightning are aggregated in a circular or elliptical pattern.
- Rule out plant pathogens.
While other diseases such as Phytophthora root rot, charcoal rot can also kill plants in aggregated pattern, rarely are all plants in an area killed at once. Charcoal rot usually develops in plants that have other stresses mainly moisture stress.
According to a University of Nebraska publication, lightning strike happens in poorly drained areas in the field where a pool of water may collect. Plants affected by lightning may show ozone injury symptoms. Lightning discharges ozone after the strike. Plants that are not completely killed by lightning may have other pathogens develop such as stem canker. However, stem canker does not need lightning in order to develop in soybeans.
Source: Emmanuel Byamukama, iGrow
Bean Leaf Beetles
In June, we discussed how we were observing quite a few bean leaf beetles in the Southeast Region of the state. Now, as we enter August, we are again observing an uptick in bean leaf beetle numbers. Why might this be happening? It is because bean leaf beetles go through two generations in South Dakota. The overwintering generation, which was initially observed this spring, is actually made up of adults that survived the winter and feed on soybean plants after they emerge. The bean leaf beetle adults that we are seeing now are actually part of the first and possibly second generation that occur each year. The first-generation adults usually show up in July and August in South Dakota. In the same areas where the first generation adults were seen, a second generation is typically observed from August to the first hard frost or when soybeans senesce. The Northern areas of South Dakota don’t have a second generation of bean leaf beetles.
Some of the individuals that we are currently observing may make up the population of overwintering adults. These individuals will seek out leaf litter and cover in late fall. While these adults are in soybean, they can cause significant amounts of defoliation to the leaves. A reduction in available leaf area can lead to reduced levels of photosynthesis and lower yields.
Identification & Scouting
Bean leaf beetles avoid disturbances, which makes them one of the more difficult insects to scout for in soybeans. Scouting and identifying bean leaf beetles can be especially difficult in soybeans that have canopied. The best method for scouting is to use a sweep net and collect 20 pendulum swings from four locations within the field. The economic threshold for bean leaf beetles is 70-100 beetles per 20 sweeps. This is based on bean leaf beetle populations later in the season.
Adult bean leaf beetles can vary in color from brown, yellow, and orange to red. The distinguishing characteristics of bean leaf beetles are the black triangle located behind their thorax (segment behind black head capsule) and the four spots that are present on their hardened forewings (elytra).
An alternative to directly scouting for populations of bean leaf beetles is to look for the amount of defoliation occurring within the field. This method may be more effective because of the potential for multiple species of defoliators being present. To scout for defoliation, examine 10 plants from five locations spread throughout the field. For each of the plants, estimate the percentage of leaf area that is removed from all of the leaves (i.e., defoliation). Record this for each of the examined plants and calculate the field average. Since the majority of soybean are past the initial flowering stage, the economic threshold for defoliation is 20%. At and above this level of defoliation a 3-7% yield loss may occur.
Source: Adam J. Varenhorst, iGrow
The risks of hydrogen sulfide in swine operations have been known for years, but beef operators also need to be aware of the dangers this gas can pose. Increasing this awareness led Dan Andersen, assistant professor and agricultural engineering specialist with Iowa State University Extension and Outreach, to create a series of four publications that provide information and resources to help farmers stay safe when working with manure.hog confinement building
“One breath of hydrogen sulfide at 500 parts per million is enough to render someone unconscious almost immediately,” Andersen said. “Once you realize the gas is a problem it’s usually too late. Hydrogen sulfide gas smells at 1-2 ppm, but levels above that knocks out your ability to smell, so our natural detection system goes away.”
Information about the importance of monitoring for hydrogen sulfide and the types of monitors available for purchase is available in publication AE 3603, “Hydrogen Sulfide Safety – Monitoring.” Monitors are available from ISU Extension and Outreach agricultural engineering specialists who have several models for farmers to test.
“Personal protection meters are a low cost investment, usually around $200, that will notify you if gas is present,” he said. “These instruments can be taken anywhere and are always monitoring the air.”
The second publication in the series, “Hydrogen Sulfide Safety – Manure Agitation” (AE 3604), discusses how to stay safe when agitating manure.
“Manure that is stagnant and sitting around has minimal loss of hydrogen sulfide,” said Andersen. “These levels of hydrogen sulfide are typically not hazardous. But when the manure is agitated and the crust is disrupted, hydrogen sulfide levels can elevate quickly.”
The final two publications in the series focus on barn ventilation for both cattle and swine facilities. “Hydrogen Sulfide Safety – Barn Ventilation at Cattle Facilities” (AE 3605) and “Hydrogen Sulfide Safety – Swine Barn Ventilation” (AE 3606) discuss how to set up a ventilation strategy when working with manure.
“The most important thing to do is to try to maximize airflow,” Andersen said. “When agitating there should be at least a 10 mile per hour breeze and fans can be set up to bring in additional air.”
Proper positioning can also help minimize risks of exposure to gas.
“Think about where you are setting up,” Andersen said. “Don’t stand downwind from the barn if at all possible.”
Source: Iowa State University
Due to drier weather conditions small grain harvests are well ahead of average in some Regions of South Dakota. According to USDA- NASS report published on July 24th, 72% of winter wheat was harvested in the state, while spring wheat and oat harvest acres were 28% and 36% respectively.
Cover Crop Benefits
Interest in using cover crops after small grain is increasing in South Dakota. Cover crops provide diversity into the cropping system, reduce soil erosion, increase soil biological activity, and also help recycle nutrients in the soil. In addition, due to diverse growing habits of major crops and selected cover crop species, it helps to break disease and weed pressure in the field. Also, cover crops can be used as supplemental fall grazing, especially in the year like 2017 where forage shortage is widespread in the state due to prolonged moisture deficit conditions.
Even though cover crops can be grown as single species or in a mixture of variety of plant species, they are mostly marketed (and grown) as blends. Selecting fall cover crop mix is critical because in a cropping sequence, it should benefit your next cash crop, not hinder with any kind of yield or growth limiting factor. Rule of thumb is- cover crops should possess growth habit that is contrasting to the following cash crop. For example, if a field is going into corn as a next crop, then higher proportion of the cover crop blend should contain cool season broadleaf species because corn is a warm season grass species. Research data from studies conducted at SDSU Southeast Research farm near Beresford have shown yield advantage in corn when grown into cool season broadleaf cover crop mix residue following small grain cash crop.
Two major categories of broadleaves commonly used as cover crop species are non-legumes (i.e. turnip, radish, canola, rape, etc.) and legumes (i.e. vetch, clovers, pea, lentil, etc.). These cool season species have high tolerance to cool temperatures and rapid fall growth; however, these species are very low in fiber content and may not accumulate abundant residue cover in the spring. In some cases, volunteer small grain growth in the fall can compensate for cool season grass species which can add to some residue next spring. Species like radish and turnip have enhanced tap roots which will aid in breaking compaction in the ground. Legumes on the other hand will help fix atmospheric nitrogen which will contribute to the nitrogen need of other species in the mix such as radish, turnip, rate, etc. Legume species may also add to the soil nitrate content and would be readily available for next season’s crop. These species are generally winter killed. If the crop for next year is soybean, it is suggested to put a mixture high in cool season grasses (rye, oat, barley, triticale, annual ryegrass etc.). These will produce significant amount of biomass the next spring. Winter small grain species like triticale and rye are not generally winter killed in the S.D. environment and requires spring termination which adds extra management task in the spring. Also, producers that are growing wheat or oat grain for seed sale, it is recommended to avoid rye and/or triticale as it may act as significant seed contaminant in subsequent years. On the contrary, winter hardy species like rye can be successfully grown in corn-soybean system and be used as prolonged cover or fall and spring forage options.
Source: David Karki, iGrow
Factors that are likely to increase a return on a foliar fungicide investment include a history of disease, tight rotations, use of a susceptible hybrid, disease pressure at tasseling and weather conditions at tasseling and during grain fill.
Foliar disease management
Foliar fungal diseases of primary concern in Michigan are northern corn leaf blight and gray leaf spot. The fungal pathogens that cause these diseases survive on residue, so fields under minimum tillage and corn-on-corn rotations are at greatest risk. Spores from both of these pathogens can either be splashed up onto foliage or deposited by the wind.
Northern corn leaf blight can be identified by the distinctive lesions that form on the leaves. Lesions start out as light green, but develop into the tell-tale tan or gray “cigar”-shaped lesions. Gray leaf spot lesions typically appear two to three weeks prior to tasseling as narrow, long, rectangular (up to 2 inches) lesions and are light tan, typically delineated by the veins.
Crop rotation will reduce the amount of inoculum of northern corn leaf blight and gray leaf spot present at the start of the season, and tillage can also help to break down corn residue. Scout fields before making a fungicide application. When scouting fields, walk into the field beyond the headland as disease is typically worse along the edge of the field, especially since that is where it is exposed to prevailing winds.
Common rust is another disease typically seen, but often not at economic levels. The rust fungi require a living host to survive. Urediniospores of common rust survive the winter on corn in the southern United States, and are then carried long distances by wind to reach the Midwest. Rust pustules typically appear in late June and are favored by high humidity and moderate temperatures. Most hybrids are fairly resistant and common rust severity is typically not severe enough to warrant selecting resistant hybrids. Crop rotation does not influence common rust disease as it does not survive on residue.
Ear mold management
Ear mold diseases of primary concern in Michigan are Gibberella and Fusarium ear mold. If you are considering making a fungicide application for ear mold suppression, it would be best to use a DMI group fungicide. Currently, Proline is the only fungicide labelled for ear mold suppression in Michigan. The application timing concept is similar to that for managing head scab in wheat. Application timing needs to coincide with silking, as this is the primary infection point for Gibberella ear mold. Studies out of Ontario have demonstrated that an application at full silking gives the best suppression.
Applications of the QoI or strobilurin group of fungicides during flowering have been demonstrated to increase DON levels (vomitoxin) in corn, just like it can in wheat, so caution should be used with this group of fungicides during this period if DON is of primary concern.
In collaboration with Michigan State University assistant professor of cropping systems agronomy Maninder Singh and supported by the Michigan Corn Marketing Program of Michigan, we are currently conducting trials across the state to examine the efficacy of Proline in reducing ear molds and mycotoxins.
MSU Extension suggests considering the following factors to determine if a foliar fungicide is warranted:
- Susceptibility level of corn hybrid. Corn hybrids that are susceptible to disease are more likely to benefit from a foliar fungicide.
- Previous crop. Corn following corn is more likely to develop disease as many of the pathogens survive on corn debris. High levels of corn residue on the surface can increase the severity of disease. Rotation can help to significantly reduce disease pressure.
- Weather. Rainy or humid weather conditions are generally favorable for most foliar diseases; hot, dry conditions typically arrest foliar disease development.
- Irrigation. Frequent irrigation provides moisture for disease development and can exacerbate disease.
- Field history. Planting corn in a field that has a history of foliar disease can increase the chances of disease development. Field location can also influence disease development such as low areas of a field or areas surrounded by trees.
- Disease presence. Is a fungal foliar disease present? The greatest chance of return on a foliar fungicide investment occurs when conditions favoring disease are present, and when fungal disease develops. Losses due to bacterial diseases such as bacterial leaf streak will not benefit from a fungicide application.
- Economics. Foliar fungicides can be used to manage northern corn leaf blight and gray leaf spot, but may not be profitable, especially given current corn prices. Damon Smith at University of Wisconsin-Madison has a nice article summarizing the economics of corn foliar fungicides, “In-Season Corn Disease Management Decisions – 2017.”
- Corn foliar fungicide efficacy chart from MSU Extension
- Arrested ear development, including use of non-ionic surfactants from Purdue University Extension
- Bacterial leaf streak from MSU Extension
Farm stressors can come from many directions including the agricultural system, farm and family finances, mental and physical health challenges, and relationship difficulties. A healthy response to these challenges involves paying attention to the stressors within all of these areas and determining coping strategies that are useful in each area.
5-Step Stress Management Process
To manage stress, it can be helpful to be reflective through a five-step process:
- Assess Needs and Impacts.
Any stressor can impact the individual, family, or farming operation. What is a need resulting from stress in your life? What is size of the impact (manageable or not manageable)? For example, a need in your life might be more or restful sleep.
- Identify and Access Resources.
What is needed to help manage the need you identified? Are the resources available to you? Resources can be tangible (knowledge, creativity, optimism) or material (money, land, equipment). For example, if the need is more or restful sleep, you might try to establish a sleep schedule, take a warm shower before bed, and turn off the TV.
- Pursue Good-Quality Decisions.
Decision-making involves assessing the options and determining how to respond. How should you use your resources? How can you be more open to change? In assessing your options, it can be helpful to become as informed as possible while thinking about the benefits vs. costs. Clarify your values and goals and discuss the options with those you trust (family, friends, professionals).
- Connect with Sources of Support.
An important aspect of decreasing stress is to engage in a support system. What type of support is most helpful for you to pursue quality decisions? Do you need to talk to someone at a bank regarding financial decisions, or would a more appropriate source be a counselor or pastor to discuss personal concerns? Find a support system that fits for you, whether the support is informal (close friends, neighbors, fellow farmers), within your family, or formal support (faith community leaders, medical providers, counselors).
- Use Effective Coping Strategies.
Think about the coping strategies that you use. Are they harmful (alcohol use, tobacco, unhealthy eating), or are they helpful (exercise, mindfulness, watching a movie, family conversations)? Think about matching a coping strategy with an identified need. It also does not hurt to learn new strategies to help alleviate stress.
With all of the factors that cannot be controlled in farming and ranching, using this five-step method for stress management may help farmers become better prepared for tough times. By identifying needs, resources, and sources of support, farmers can identify factors that can be controlled. Establishing a support system and using effective coping strategies are important in self-care and can help improve one’s overall health and well-being.
Source: Andrea Bjornestad, iGrow