This article was written by Tom Royer, Extension Entomologist and IPM Coordinator and Kelly Seuhs, Associate Extension Specialist.

Several people, including Lanie Hale, Rob Anderson, and Mike Rosen of Wheeler Brothers and Area Extension Agronomist Heath Sanders have reported possible army cutworm activity. These reports are based on direct observations and noticeable crow and blackbird “gatherings” in some wheat and alfalfa fields in areas of western Oklahoma. Infestation levels were at the “caution” stage at this time and caterpillars measured ¼ to ½ inches.

Army cutworms tolerate cold and feed throughout the winter months. Adult army cutworm moths migrate to Oklahoma each fall (August through October) from their grounds in the Rocky Mountains.  They seek bare or sparsely vegetated fields (like a newly prepared field ready for wheat planting, or a field that was “dusted in” and had not yet or just emerged, or a newly planted alfalfa stand). The eggs hatch soon after deposition.  A producer might see different sizes of larvae in a field due to the long migration period. Army cutworms feed throughout the winter and molt seven times before they turn into pupae in the soil.  Most larvae will have pupated by mid-late March. Adult moths begin emerging in April to fly back to the Rocky Mountains to spend the summer.

Army cutworms can severely damage wheat, canola, and newly planted stands of alfalfa if not controlled. Cutworm damage often goes unnoticed through much of the winter because the caterpillars grow slowly and don’t get big enough to cause noticeable damage until temperatures warm in the spring.  One early indication cutworm presence in a field is the gathering of blackbirds and or crows that seem to be actively feeding. It becomes important to check the fields for cutworms before they cause damage and stand loss.

Sample a field by stirring or digging the soil to a depth of two inches at five or more locations.  The cutworms will be “greenish grey”, and will probably curl up into a tight “C” when disturbed. 

It is better to control army cutworms when they are small (½ inch long or less). Army cutworms are very susceptible to pyrethroid insecticides. At this time of year, an insecticide application can be combined with a late winter top-dress nitrogen application.  Suggested treatment thresholds for army cutworms in wheat are 2-3 worms per row foot when conditions are dry and 4-5 per row foot if moisture is adequate. Current recommendations for army cutworm control in small grains are listed in CR-7194, Management of Insect and Mite Pests in Small Grains. 

It is better to control army cutworms when they are small (½ inch long or less). Army cutworms are very susceptible to pyrethroid insecticides. At this time of year, an insecticide application can be combined with a late winter top-dress nitrogen application.  Suggested treatment thresholds for army cutworms in wheat are 2-3 worms per row foot when conditions are dry and 4-5 per row foot if moisture is adequate. Current recommendations for army cutworm control in small grains are listed in CR-7194, Management of Insect and Mite Pests in Small Grains. 

The suggested treatment threshold for cutworms in canola is 1-2 per row-foot.  Current recommendations for control of army cutworms in canola are listed in CR-7667, Management of Insect and Mite Pests in Canola.

In newly seeded alfalfa, the threshold is 1-2 larvae per square foot. In established alfalfa fields, the threshold is 2-4 larvae per square foot and should be adjusted based on the size of the caterpillars (2-3 per square foot if caterpillars are more than ½ inches, 3-4 per square foot if less than ½ inches). Current recommendations for control of army cutworms in alfalfa are listed in CR-7150, Alfalfa Forage Insect Control.

This article was written by Bob Hunger, Extension Wheat Pathologist

This is an early season update to summarize a few items that have come up during this week. To start however, I need to repeat that this past fall and winter have been amazingly lacking in diseases. The Diagnostic Lab only received a few wheat samples during the fall, none of which were found to be associated with a pathogen/disease. Causes included low pH, nutrition, and/or environment. This lack of disease still seems to be the predominate scenario. Around Stillwater, I was not able to find any rust or powdery mildew in any of the trials I examined this week. Additionally, it appears as though foliar disease is absent in south Texas as well as indicated by Dr. Amir Ibrahim (Regents Professor, Small Grains Breeder/Geneticist, Texas A&M University, College Station, TX) who indicated to me that, “It has been really quiet here. We have not seen stripe or leaf rust so far. I doubt the former will be an issue this year since it has not established yet and it is already getting warmer. However, I expect to see heavier leaf rust in mid-April if it continues to be this warm.”

Hence, it appears that early season stripe rust and leaf rust should not be a major concern in Oklahoma. In contrast, leaf spot diseases (especially tan spot) should be watched for if you have wheat planted into wheat residue. Josh Anderson (Senior Research Associate, Noble Research Institute, Ardmore, OK) found tan spot in no-till wheat plots planted into wheat residue near Burneyville in far south-central OK (Figure 1). Tan spot can be damaging to seedling wheat especially when it occurs in emerging spring wheat in northern states. However, tan spot also can be damaging to winter wheat if infection is severe in the spring as plants are coming out of winter dormancy. Often an early season fungicide application is used to control not only tan spot but also early season stripe rust and powdery mildew. Such an early season application (late February/March) will not provide protection from leaf rust later in the season (April/early May). If you do have wheat planted into wheat residue, I highly recommend scouting for the presence of not only tan spot, but other early season foliar diseases such as Septoria and Stagonospora leaf spots, powdery mildew, and early season stripe rust. If any of these diseases are seen as severe in late February or March, applying an early application of a fungicide may be beneficial. Keep in mind however, that the timing for an early season fungicide application does not coincide with the optimum timing for top-dressing with fertilizer. If it is likely that two applications will be used, I recommend making the first application with a lower cost generic and reserve the second application for a higher priced premium fungicide. For a photo guide to wheat diseases, go to: http://dasnr22.dasnr.okstate.edu/docushare/dsweb/Get/Document-11682/E1024%20Wheat%20Disease%20Identification.pdf

For more information on fungicide applications, see: CR-7668 (Foliar Fungicides and Wheat Production in Oklahoma) and PSS-2138 (Split versus Single applications of Fungicide to Control Foliar Wheat Diseases)

First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of stem below the developing grain head (full explanation). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

The latest FHS results from our forage trials in Chickasha (Table 1) and Stillwater (Table 2) are listed below. Few wheat varieties at Chickasha and Stillwater have reached or passed the 1.5 cm threshold.

The Mesonet First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis. 

Table 1. First hollow stem (FHS) results for each variety collected at Chickasha. Plots were planted on 09/19/19. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

Table 2. First hollow stem (FHS) results for each variety collected at Stillwater. Plots were planted on 09/18/19. The threshold target for FHS is 1.5 cm (5/8″ or the diameter of a dime). The value of hollow stem for each variety represents the average of ten measurements from non-grazed plots. Varieties that have reached FHS are highlighted in red.

• Additional resources available:
• PSS-2147 First Hollow Stem: A Critical Wheat Growth Stage for Dual-Purpose Producers.
• CR-2141 Fall forage production and first hollow stem date in small grain varieties during the 2018-2019 crop year
•  Mesonet First Hollow Stem Advisor

First hollow stem (FHS) is the optimal time to remove cattle from wheat pasture. This occurs when there is 1.5 cm (5/8” or the diameter of dime) of hollow stem below the developing grain head (Fig.1). To give you a point of reference, the average FHS date over the past 20 years at Stillwater is March 6.

Several factors influence the onset of FHS. These include the wheat variety, location, temperature, available moisture, level of grazing, and planting date (later sown wheat will typically reach FHS later). Varieties can differ by as much as three weeks in onset of first hollow stem, and later maturity varieties generally reach first hollow stem later. Dual-purpose producers are encouraged to select varieties that are characterized as medium, late or very late in occurrence of FHS.

The latest FHS results for each variety planted in our forage trial at Chickasha are listed below (Table 1). None of the varieties are at FHS (all values are below 1.5 cm), but values are likely to change with current soil moisture conditions and warmer temperature predicted for the next couple days.

The First Hollow Stem Advisor and the updates we provide give an indication of the FHS stem conditions in a particular area. However, because of the number of factors that can influence when FHS occurs, it is extremely important to check for FHS on a field-by-field basis.

Table 1. First hollow stem results for each variety collected at Chickasha on 01/30/20. Plots were planted on 09/19/19. The threshold target for FHS is 1.5 cm. The value of hollow stem for each variety represents the average of ten measurements.

• Additional resources available:
• PSS-2147 First Hollow Stem: A Critical Wheat Growth Stage for Dual-Purpose Producers.
• CR-2141 Fall forage production and first hollow stem date in small grain varieties during the 2018-2019 crop year

Amanda de Oliveira Silva, Small Grains Extension Specialist and Misha Manuchehri, Weed Extension Specialist

November has been cooler than normal and that has limited wheat growth across the state. Most of fields where wheat was planted earlier have the crown roots slowly developing and top growth is lower than expected. Many of these fields have very thin stands and will probably not have enough forage to feed the cattle. In many areas, planting was delayed due to either lack or excess of moisture. Most of fields that were planted late are at 1-2 leaf stage with seminal roots developing. Plants are showing signs of cold injury but should grow out of it well.

Fall or Spring Herbicide Application for a slow-developing wheat?

Moisture has been plentiful in many areas in Oklahoma this fall. As a result, several winter annual weeds have emerged. These weeds are competing well with our wheat crop, which is behind in many areas due to cold temperatures. If you are investing in a herbicide application this year, you may be thinking “when should I apply”? The answer is not always simple but there are several things to consider before making this decision.

1. Is your wheat at an approved growth stage per the herbicide label?

Many postemergence herbicides labelled for use in wheat recommend the crop be at 2 or 3 leaves. Be sure to check these requirements to ensure crop safety.

2. What are your target weeds?

Many producers chose to apply a postemergence herbicide in the spring when top-dressing N to limit the number of passes made across their fields. This often makes sense for weeds that have multiple flushes, as two applications often are not financially feasible. For example, Italian ryegrass that is not managed with a delayed preemergence herbicide (Anthem Flex, Axiom, or Zidua) may be sprayed in the late winter vs. fall to target multiple flushes. On the other hand, early emerging, difficult-to-control grasses like rescuegrass, are best managed in the fall before entering “dormancy”.

3. What are daytime temperatures like? Are your wheat and weeds actively growing?

All postemergence herbicides labelled in wheat move in living tissue. Herbicide application will be most successful when your wheat AND your weeds are actively growing.

4. Have you applied this product before? Was it successful at that timing?

We can learn a lot from field history. If a product wasn’t successful in the past, we need to learn why so that we can make the necessary changes to increase its success or perhaps it is time to use a new weed management method. Finally, selection for herbicide resistant weed biotypes can occur quickly. If you are unsure if you have resistance, please send in a seed sample to the weed science lab.

By Amanda de Oliveira Silva, OSU Small Grains Extension Specialist and Tom Royer, Extension Entomologist

We are receiving reports of fall armyworms infestations and wanted to alert producers to check their wheat fields every day after seeding emergence. The worms can be very tiny and difficult to see it. Symptoms like “window pane” in the leaves indicate feeding from fall armyworm. Also, check under crop residue as they might try to hide from the heat.

Replanting decisions need to be made on field by field basis. Replanting might be best for producers taking the crop to a grain-only system. Also, allow some time to replant to avoid having infestations back again.

“We will not get relief from fall armyworms until we get a killing frost, so keep vigilant!” Tom Royer

Several helpful resources are available for producers. Contact your local county Extension office. For additional read refer to Pest e-alerts Reports of Seedling wheat Infested with Fall Armyworm 2019. Consult the newly updated OSU Fact Sheets CR-7193 Management of Insect Pests in Rangeland and Pasture and CR-7194 Management of Insect and Mite Pests of Small Grains for control suggestions.