Welcome to CAM Crops!
CAMCrops is a new resource from CSU Extension to bring Colorado producers the most up to date, timely, and accessible resources. A partnership between statewide and campus Extension Specialists, CAMCrops is the first stop for CO’s production agriculture’s questions.
June 2nd, 2023 Updates
Southwest
Southwestern Colorado had some moisture in the past two weeks and cooler temperatures that have slowed snow melt in higher elevations. Temperatures have started warming up but more thunderstorms are in the forecast. Rivers have peaked so flooding concerns are decreasing.
Irrigators are now getting more serious about turning on water as temperatures warm and plant water needs begin to increase.
In rangelands we’re seeing a diversity of plants that have responded to the winter moisture. Globemallow is experiencing a great year! There is also good grass growth, while slightly delayed, this summer should have good forage production for livestock this summer.
Northeast
Periodic rainfall continues on the Front Range and in isolated patches eastward. Wheat disease and fungal pressure is being observed above I-70, refer to the Wheat Disease Newsletter for more information.
Some areas of Weld County have taken the first cutting of alfalfa. Corn emergence is beginning in areas of earlier planting.
Cheatgrass and mustard species have quickly emerged and are rapidly moving towards maturity. If pre-emergent herbicides were not applied in crop fields, but sure to begin scouting now to ensure a timely post-emergence application in high value crop fields.
With the excessive rainfall, consider performing in-season N soil testing to ensure adequate N.
Contributors: Kat Caswell, Weld and Washington Agronomist and Emily Lockard, Montezuma County Director
Michaela Mattes, Southeast Area Agronomist
Let’s consider the following scenario: The producer inspects his or her wheat field and decides that the stand is poor. He or she will ask themselves: Should I plow it under, plant something else, leave it fallow, wait and see, or abandon the field?
Dr. Robyn Roberts, Field Crop Pathologist and CSU Assistant Professor
Root rot has been identified in eastern counties. Changing weather patterns may alter the fungal disease outlook for the summer. To continue reading, scroll down into the “Wheat Update” Section.
To read the 5/23/23 Wheat Disease Newsletter, continue here
May 19th, 2023 Updates
Areas of the eastern plains have received over 2 inches of rainfall. Areas of heavy rainfall have left standing water or have delayed summer crop planting with wet soil conditions. Some wheat fields in the southeast part of the state have been abandoned and will be replanted with a summer crop.
Similar conditions persist on the Western slope as earlier in the month. If current conditions are maintained, it will be a good year for forage production.
Drought ratings have been lowered across the state, with the worst conditions persisting in the southeast corner.
Contributors: Ron Myer, Golden Plains Agronomist and Retta Bruegger, Western Slope Rangeland Specialist
Kat Caswell, Washington and Weld Agronomist
Rain is great, but too much rain in too short a period of time can leave fields with standing water. Unplanted fields should be left until water has drained and dried out before planted a summer crop.
Dr. Robyn Roberts, Field Crop Pathologist and CSU Assistant Professor
Root rot has been identified in eastern counties. Changing weather patterns may alter the fungal disease outlook for the summer. To continue reading, scroll down into the “Wheat Update” Section.
To read the 4/25/23 Wheat Disease Newsletter, continue here
May 5th, 2023 Updates
Ron Myer, Golden Plains Area Agronomist
Soil temperatures below the optimum 50 degrees for corn can slow germination and put corn seeds at risk of damage for pests and insects.
Kat Caswell, Washington and Weld Agronomist
Chilly soil temperatures have delayed the germination of early emerging weeds. Later weed emergence means later herbicide application.
Todd Gaines, CSU Associate Professor of Weed Science
We conducted a survey of eastern Colorado for winter annual grass weeds in wheat. We found no resistance in the samples to quizalofop (Aggressor herbicide in CoAXium) as expected since CoAXium wheat hadn’t yet been introduced, and we found that mostly all the samples were sensitive to imazamox (Clearfield wheat and Beyond herbicide), except for a couple of samples in Weld county.
Flooding, cool temperatures, and varying grass growth will determine management in the approaching summer season.
Agriculture plays a large role in the economy and environment of Colorado. The goal of CAMCrops is provide the most timely information, resources, and solutions for those working in Colorado’s crop production.
Our job is the determine the unique issues, concerns, and needs of each Colorado community and to help offer effective solutions.
Wheat Updates - 2023 Crop
Total planted winter wheat acres in the US were up a modest amount of the 2022 year. Winter wheat stands in areas that were most heavily impacted by drought in Colorado are being evaluated as temperatures warm and plants break dormancy.
The Wheat Disease Newsletter is written by Dr. Robyn Roberts, Field Crop Pathologist and CSU Assistant Professor. Email her at Robyn.Roberts@colostate.edu
Summary
The recent rain across much of Colorado has favored development of fungal diseases. Additionally, the first report of plants testing positive for Wheat streak mosic virus and Triticum mosaic virus was collected from ARDEC.
The Plant Disease Diagnostic Clinic is offering free, no-cost diagnostic testing to farmers in Colorado! Contact the Plant Diagnostic Clinic for sample submission or send an email.
Disease Observations
Flag Smut
Flag smut was reported in Lincoln County (Figure 1). Flag smut is caused by a fungus (Urocystis tritici), and infected plants have twisted leaves with long, gray-black lesions that run parallel to leaf veins. Lesions will erupt and release large numbers of powdery, black fungal spores. Tillers may become infected, causing poor head development and little to no grain. Some countries have import restrictions on grain infected with flag smut. The fungus survives as spores in the soil for up to four years, and can also survive on the surfaces of seed. Infection occurs shortly after fall planting before the seedlings emerge, and the risk of infection is greatest when winter wheat is planted into warm, moist soil (~50-70°F). The fungus invades the growing plant and remains dormant in the winter, becoming active again in the spring where it grows throughout the entire plant.
Figure 1 – Symptoms of flag smut on winter wheat found in Lincoln County.
Management and Prevention
Fungicide seed treatments are the most effective at managing flag smut, and many seed treatments are labeled and marketed for control of this disease. Crop rotations with non-hosts, such as soybean, sorghum, or corn, can help decrease spore levels in the soil. There are no fungicides that are effective against flag smut once symptoms develop.
Figure 2. WSMV/TriMV symptomatic wheat from ARDEC.
Wheat streak mosaic virus/Triticum mosaic virus
Plants testing positive for Wheat streak mosaic virus and Triticum mosaic virus were collected from ARDEC (Figure 2). Importantly, viruses typically exist in a complex in Colorado, including Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and sometimes High Plains Wheat Mosaic Virus (HPWMoV). WSMV and TriMV are transmitted by the wheat curl mite, and typically occur together. Symptoms appear as yellow streaks and mosaic, yellow and green patterns on leaves.
Management and prevention
There is no treatment for virus-infected plants, and no miticides are effective against the vector (the wheat curl mite). Controlling volunteer wheat and planting WSMV- and mite-resistant varieties are the best control measures. However, there is no resistance against TriMV available, so controlling volunteer wheat between harvest and planting is critical.
Figure 3. Tan Spot symptoms on wheat. Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org
Tan Spot
Tan spot was observed in Baca, Otero, and Adams counties (Figure 3). Tan spot appears as necrotic (dead, brown) diamond-shaped spots surrounded by yellow halos or borders. It is often found along with Stagonospora leaf blotch (Figure 5).
Management and Prevention
Typically, as the weather warms tan spot does not continue to be a problem in Colorado, so fungicide applications are not usually recommended. Fungicides are recommended for tan spot only if the flag leaf is at risk of infection. When scouting for tan spot, take note of the growth stage of wheat, the severity of the infection, and whether the flag leaf is at risk of disease, and monitor disease development closely.
Stagonospora leaf blotch
Stagonospora leaf blotch was found in Adams county (Figure 4), and is caused by a fungus (Parastagonospora nodorum and/or P. avenae f. sp. triticae). Symptoms develop in the spring and display small, yellow spots on lower leaves that develop into elongated, dark leaves as the season
Figure 4. Stagonospora leaf blotch symptoms on wheat. Photo: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org
progresses. Wet, rainy weather, high humidity, and moderate temperatures (~68-75°F) favor disease development, and recent weather has been favorable for disease development in some areas. The fungus survives in infected residue. Typically, Stagonospora does not cause significant yield losses in Colorado, and is often found alongside tan spot disease (Figure 5).
Figure 5. Wheat from the Front Range area showing both Stagonospora leaf blotch and tan spot. The disease progressed quickly after rain last week. Photo: Dr. Ana Cristina Fulladolsa
Management and prevention
As long as the weather continues to get warmer, Stagonospora activity should decrease. Because the fungus survives in wheat residue, rotating crops will help reduce the number of spores in a field the following years. Fungicide seed treatments also help protect seedlings from infection.
Figure 6. Leaf rust found in Kit Carson County. Photo: Ron Meyer.
Leaf Rust
Leaf rust (caused by Puccinia triticina) was found in small amounts in Kit Carson county (Figure 6). While stripe rust and leaf rust are both ‘rust’ diseases, they are caused by two different fungal pathogens and cause different symptoms (Figure 7). Stripe rust spores are a brighter orange-yellow color, and symptoms appear in stripes that are limited by the leaf veins. Leaf rust spores are typically a darker orange-brown or orange-red color, and symptoms appear scattered across the leaf surface that are not in a particular pattern and are not limited by the veins. Both leaf and stripe rust require wet conditions, but leaf rust typically progresses at warmer temperatures compared to stripe rust. Leaf rust usually shows up a little later in Colorado and is not typically a major disease problem compared to stripe rust.
Management and Prevention
As the weather continues to get warmer, leaf rust should be controlled. Fungicides should only be used if the flag leaf is at risk of infection.
Disease Watch and Management
Stripe Rust
There are currently no reports of stripe rust in Colorado, but stripe rust was reported in Texas, Kansas, and Oklahoma at low incidence and severity, and the drought is suppressing the disease in these states (Figure 7). Stripe rust disease is dependent upon cool, wet weather, and while Colorado has been wet overall, the inoculum (spores) will be limited in Texas and Oklahoma and few spores are likely to make it to Colorado. Stripe rust should remain limited in Colorado in the near future.
Figure 7. Comparison of Leaf Rust vs. Stripe Rust. Stripe rust (top and bottom, black arrows) has bright orange-yellow spores that develop parallel to the veins. Leaf rust (bottom, red arrows) makes darker orange-brown or orange-red spores that do not follow veins and are scattered around the leaf.
Soil moisture levels are often correlated with stripe rust incidence and can be used as a predictive tool in determining if stripe rust will emerge. This time of year, we look at the temperatures and soil moisture levels in the south, particularly Texas and Oklahoma (Figures 8 and 9). Most of Texas and Oklahoma has been very dry since last fall, and is currently experiencing low soil moisture; however, recent weather conditions have been conducive for disease development. At this time, it seems that stripe rust spore levels will remain low, suggesting a low risk for an epidemic in Colorado. We will continue to monitor for rust and provide recommendations as we reach critical growth stages. Please help us protect our fungicides and prevent fungicide resistance by carefully timing applications, following the label, and applying only when the disease pressure is appropriate. If you think you see symptoms, please feel free to send photos.
Figure 8. Recent weather in states reporting stripe rust is conducive to disease development, though risk for Colorado remains low. The stripe rust pathogen requires both cooler temperatures and wet conditions to cause disease. States that have reported stripe rust (Texas, Kansas, and Oklahoma, at low incidence and severity) have increasingly warmer nighttime temperatures (left panel) and much less than normal moisture (right panel), which is not conducive to disease development. Nighttime temperatures in Colorado are increasing and the precipitation is low-normal, which does not support disease development. Data from the National Weather Service Climate Prediction Center,
Figure 9. Soil moisture levels as a predictive tool for stripe rust risk. Higher soil moisture levels are typically associated with higher risk. We closely watch the southern states (Texas, Oklahoma, Kansas) for soil moisture levels and the emergence of stripe rust as one tool to predict risk in Colorado. Low soil moisture levels support less stripe rust disease development. Data from the National Weather Service Climate Prediction Center,
Growers are strongly encouraged to regularly scout wheat fields for diseases. Particularly, scout for stripe rust and viruses in the coming weeks.
Do you have a disease that you would like diagnosed? Contact the Plant Diagnostic Clinic for sample submission: https://plantclinic.agsci.colostate.edu/ or plantlab@colostate.edu.
Many thanks to Ron Meyer, Dr. Esten Mason, and Dr. Ana Cristina Fulladolsa, who contributed to this report.
The Wheat Entomology Newsletter is produced by members of the CSU Ag Bio Dept.
Adam Osterholzer 970-222-9568
Dr. Punya Nachappa 785-383-4873
Introduction
We are excited to begin our third year conducting the Wheat Entomology Newsletter! Our team is led by Dr. Punya Nachappa, entomologist and Associate Professor in the Department of Agricultural Biology (www.nachappalab.com). Adam Osterholzer, our Research Associate in the CSU Wheat Entomology Program, will help provide content from the field throughout the season. If you suspect insect infestations in your fields, please don’t hesitate to reach out to us. Punya is also available on Twitter.
We are also pleased to announce our new CSU Wheat Entomology Program website! We will be making regular updates as our research progresses.
The Wheat Crop
As reported by Madison Andersen (Colorado Wheat) and Ron Meyer (CSU Extension) earlier this month, wheat crop conditions are proving variable across the state. Yield potential is expected to be low throughout much of Southeastern Colorado due to drought. Kevin Larson (CSU Extension) has reported both poor emergence and losses due to dust storms in this area, despite chiseling efforts to prevent further losses. Regions further to the north have received significantly more moisture, resulting in healthier wheat stands.
Our lab operates primarily in Orchard and New Raymer, CO. These areas had rainfall as recently as April 25th, and the wheat fields in these areas have almost full plant coverage. We expect to have no issues obtaining the samples for our projects. Hail damage was noted in fields at Orchard, but not to the extent that would prevent sample use in our studies.
Wheat Stem Sawfly
To ensure that we will capture the beginning of the sawfly flight cycle, we began scouting in the field twice per week on April 14th. We have not yet observed any adult sawfly emergence. We are dissecting infected stubble on a weekly basis to monitor larval status. By viewing the larvae within the stems, it’s possible to predict the date at which adults will emerge in the spring. As seen in Figure 1 below, once larvae begin pupation, they will start to develop wing nodes and legs. Adults typically emerge 3 weeks after pupation commences. A few of the sampled larvae in Orchard have undergone very early stages of pupation so we except adult emergence in couple of weeks.
Figure 1: Image depicting WSS at different stages of development. Photo by Dr. Erika Pierce.
Figure 2 shows larvae recently acquired from Orchard and New Raymer, CO. Larvae at Orchard seem to be noticeably larger and more developed than those at New Raymer. Photo by Adam Osterholzer.
WSS Research and Predictions
Henrique Vieira, a PhD student in the Nachappa lab is trying to predict sawfly emergence based on climatic variables. Analysis of temperature and precipitation data from New Raymer meteorological station combined with our lab survey data from the past years (2016 – current) revealed a positive relationship between sawfly emergence and precipitation (snow and rain).
We see that sawflies can emerge as early as the beginning of May in dry years, and for wet years around late May. Precipitation might potentially influence population density as well. Temperature did not have an effect on sawfly emergence. Given that we had good moisture this spring and last winter, we predict delayed sawfly emergence this year.
How to Sample for WSS
If you are curious to know what stage the sawflies are in your field, then sample for larvae at the edges of your fields, which will likely have the highest concentrations of sawfly larvae. Here are the steps we follow in our own studies:
- Dig up several clumps of stubble with a shovel, taking care to keep all plant material intact, including the roots.
- Sort through the stubble, gently tugging apart the clumps with your fingers.
- Separate any stubs that have been cut by sawfly from the rest of the stubble (see Figure 3). Sawfly stubs will be short, usually having 1-2 inches of stem visible above ground level. An important feature to look for is a clean, horizontal cut at the top of the stem. There will also be a frass plug at this location, which will have the appearance of compacted saw dust plugging up the opening to the stem interior.
- Using a sharp knife and a set of tweezers, split the stubs open lengthwise. Any larvae within will be visible once the halves of the stubs are separated.
- Compare any larvae you find to Figure 1 for an approximation of their development status.
Figure 3: Image contrasting several sawfly stubs (left), with a non-infested stem (far right). Photo by Adam Osterholzer.
Additional Pests
Brown Mites
Both Ron Meyer and Kat Caswell (CSU Extension) have noted reports of brown mites being observed in the field. They appear widespread, having been seen from Walsh through the
Figure 3: Image contrasting several sawfly stubs (left), with a non-infested stem (far right). Photo by Adam Osterholzer.
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Burlington area. According to Ron, populations have not yet become large enough to meet the economic treatment threshold. Brown mites typically do well in warm, dry environments. As such, there is the potential for them to become a more severe issue within Southern Colorado.
Insecticides remain the best option for managing outbreaks. Previous research has shown that dimethoate insecticides are the most effective of currently registered products. Products containing chlorpyrifos should be considered if Russian wheat aphids are also present (see here)
Cutworms
Ron Meyer has reported no signs of cutworm activity across the state at this time. We will note any changes in the situation in our next newsletter.
More information on caterpillars in small grains can be found here.
Pyrethroid insecticides are effective against both army cutworm and pale western cutworm
Acknowledgements
We would like to acknowledge the tireless work of CSU researchers and extension agents for reporting pest problems throughout the state. Special thanks to Kevin Larson, Brett Pettinger, Ron Meyer, Todd Ballard, Sally Jones-Diamond, Dennis Kaan, Kat Caswell, and Michaela Mattes.
Ron Meyer, Agronomy, Golden Plains Area Agent
Colorado State University agronomists visited wheat testing trials in mid-April. Visited sites began at Walsh, Colorado and continued north to sites near Lamar, Burlington, Prospect Valley, Sterling, Haxton, and Julesburg.
Wheat trials south of I-70 are experiencing severe drought. Wheat stands are poor and yield potential is low. Disease observations found no virus (wheat streak mosaic or barley yellow dwarf) or stripe rust activity. Insect issues found were brown wheat mite, but populations were below economic treatment thresholds. Cutworms were not found. Severe drought is continuing at these sites.
However, wheat trials north of I-70 are exhibiting better stands and wheat growth. As a result, wheat fields north of I-70 have average to good yield potential. While some fields were showing winter kill on field edges and borders, most wheat fields are fully covered with wheat plants and are continuing to grow. This situation is a direct result of adequate winter snows received last winter, which southern locations did not receive.
In addition, wheat trial observations did not show evidence of viral diseases such as wheat streak mosaic or barley yellow dwarf. No stripe rust was observed. Insect observations failed to find cutworm activity. However, brown wheat mite were found in some fields, but populations were below economic threshold levels. Therefore, pest issues such as insects and diseases were not found at this time.
These on-farm trials are testing new wheat varieties at various locations to determine yield potential and quality parameters. Results will be made available following harvest.
Photo credit to Michaela Mattes, Southeast Area Extension Agronomist
The idea of CAMCrops came out of discussions of how to better meet crop concerns around the state of Colorado. Crop production in the High-Plains region faces unique challenges and production decisions can change from year to year.
The long-term goal for CAMCrops is to develop a reputable resource for all Coloradans to utilize for the most cutting-edge knowledge around crop production. As we build CAMCrops, we welcome any comments, suggestions, or ideas from the communities we serve. Please reach out to Kat Caswell with any thoughts you have.
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