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Don’t let armyworms waylay your wheat or canola

By Tom Royer, Extension Entomologist

Heath Sanders could not have made a more prophetic statement for this Extension Entomologist than when he said: “we learn something new about canola every year”. I have learned something new every year that I have been working with canola, and this year is starting to confirm his “prophesy” once again.

This has been a banner year for fall armyworms. They built up populations early, and migrated into Oklahoma earlier than “normal”, attacking sorghum and pasture grasses. Now, they are ready to attack wheat (once it emerges) and possibly, are marching in to graze on newly emerged canola. Dr. Angela Post, OSU Extension Weeds specialist reported that there were caterpillars that appeared to be either beet armyworm or fall armyworms attacking canola. We are getting confirmation on their identity, but regardless, producers need to be vigilant and protect their fields.

I have already discussed their management in wheat http://entoplp.okstate.edu/pddl/pddl/2015/PA14-41.pdf, but now need to alert canola producers about them attacking seedling canola and eliminating stand.

Look for “window pane” damage in young canola plants and/or cut plants. At this time, with canola so small, armyworm and cutworm caterpillars cannot be allowed the chance to reduce stand. The suggested treatment threshold is 1 or more armyworms per row-foot.

Look for window pane damage in young canola plants. Treatment threshold is one or more worms per foot of row.

Look for window pane damage in young canola plants. Treatment threshold is one or more worms per foot of row.

Consult CR-7194 Management of Insect and Mite Pests of Small Grains and CR-7667 Management of Insect and Mite Pests in Canola for specific insecticides that are registered for control. Keep in mind that beet and fall armyworms can sometimes be difficult to control, so vigilance is needed by follow-up scouting following an application to make sure control is achieved.

Wheat head armyworms in Oklahoma wheat

Heath Sanders, Canola Field Specialist with Great Plains Canola, was scouting some wheat fields for armyworms in southern Oklahoma this past week and sent us some photos of damaged wheat heads that were being fed upon by wheat head armyworm. He stated that he had a hard time finding the worms because they blended in so well with the color of the wheat.

The insect causing the damage was Faronta diffusa, known as the wheat head armyworm. Unlike the armyworm, which was discussed last week, the wheat head armyworm is very capable of damaging wheat kernels. Adult moths lay eggs on plants in the spring, and the larva feed directly on the grain heads, mostly at night. The caterpillars range in color from gray to greenish with distinct yellow, white and brown stripes going lengthwise across the body. They typically have a larger head relative to their body. Because the larvae are so variable in color, the best way to identify them is to send in a sample to the Plant Disease and Insect Diagnostic Lab.

Wheat head armyworm

Wheat head armyworm

Wheat head army worm

Wheat head armyworm

Fields can be scouted with a sweep net to determine numbers of caterpillars. There is no established treatment threshold because it rarely causes economic damage and more often than not the damage is not noticed until the grain is harvested. If wheat is at soft dough, consider treating the field to reduce damage. This insect is often found along the margins of fields so if scouting shows that they are restricted to the field edges, consider spraying the field margins with a border spray. Pay careful attention to pre-harvest intervals when selecting an insecticide.

This insect rarely causes significant damage. The major issue with wheat head armyworm damage has to do with the grain grading which is classified as IDK (Insect Damaged Kernels). Grain elevators will dock wheat when samples contain 6-31 damaged kernels per 100 grams of seed. To coincide with the Food and Drug Administration’s defect action levels, the U.S. Standards for Wheat consider wheat containing 32 or more insect-damaged kernels per 100 grams as U.S. Sample Grade. This grain is unfit for human consumption and can only be sold as animal feed. It is important to note that although the wheat is damaged, it is not an indication of an on-going infestation of grain weevil or some other stored grain insect pest.

Wheat head army worm damage and a Suzuki 4-wheeler

Wheat head army worm damage

Kernel damage associated with wheat head armyworm

Kernel damage associated with wheat head armyworm

The best strategy to manage the problem at harvest is to combine wheat harvested from head rows with wheat harvested from the rest of the field to dilute IDK percentages. Treating a field with insecticide at harvest will be of little help because the damage is already done, most of the caterpillars have already pupated and remaining larvae can’t feed on the mature wheat grain.

If a load is docked or rejected, check on insurance options. Most crop insurance policies have a Quality Loss Adjustment clause that covers the damage up to 25% of the crop’s value, regardless of the yield. Work with your elevator to collect and store samples of the wheat that can be used as evidence of the in-field damage.

This link will access Subpart M for US Standards for Wheat which discusses grades and grade requirements for wheat: http://www.gipsa.usda.gov/fgis/standards/810wheat.pdf

For more information on this topic, contact Tom A. Royer, Extension Entomologist at tom.royer@okstate.edu or Edmond Bonjour, Extension Stored Grain Entomologist

Watch for armyworms in wheat

We have a late-maturing wheat crop that finally received some needed rain.   I received a report of armyworms infesting wheat in the Vernon, Texas area. Armyworm infestations typically occur in late April through the first two weeks of May, but the cooler spring we are experiencing this year may have delayed their development.

Armyworm infestations occur more frequently around waterways, areas of lush growth, or areas with lodged plants. These areas should be checked first to determine the size of the infestation. Armyworm 2 Royer 2007

Early signs of an infestation include leaves with ragged margins that have been chewed.  You may find “frass” i.e. the excrement from armyworm caterpillars, around the base of wheat stems.  They also tend to clip heads from developing wheat plants. The head clipping I have noticed over the years us usually restricted to secondary tillers with very small, green heads that would not likely contribute much to yield.

Armyworm damaged wheat heads

Armyworm damaged wheat heads

Scout for armyworms, at 5 or more locations looking for “curled up worms”.  Armyworm caterpillars tend to feed at night, so a good strategy is to bring a flashlight and look at fields after dusk when they are feeding up on the plant stems.  The suggested treatment threshold for armyworms is 4-5 unparasitized caterpillars per linear foot of row.

Clipped heads from armyworm feeding

Clipped heads from armyworm feeding

Armyworms have a number of natural enemies that help keep populations in check, if given a chance.  In particular, parasitic wasps and flies attack them.  If you find small white cocoons littered on the ground that are about ¾ the size of a cue tip, the natural enemies have already taken care of the problem.

 

 

Parasitized armyworms

Parasitized armyworms

If wheat is past the soft dough stage, control is not warranted unless obvious head clipping can be seen and caterpillars are still present and feeding. Worms feeding on the awns when plants are past soft dough will not cause enough yield loss to justify the expense of an insecticide application that is solely intended for armyworm control. When choosing to spray, keep in mind that some insecticides require a 30 day waiting period for harvest.

Consult CR-7194 Management of Insect and Mite Pests of Small Grains for information on insecticides registered for control of armyworms.

For more information on this topic, contact Tom A. Royer, Extension Entomologist at tom.royer@okstate.edu

Fall armyworm on the march!

by: Tom Royer, OSU Extension Entomologist

Fall armyworms are active this fall. I checked a field of wheat this past weekend with significant damage from fall armyworms that averaged 6-7 fall armyworms per square foot. Scout for fall armyworms by examining plants in several (5 or more) locations in the field. Fall armyworms are most active in the morning or late afternoon. Look for “window paned” leaves and count all sizes of larvae.

Fall armyworm damage is characterized by window panning on wheat leaves. Injury can sometimes be greater in field margins as armyworms sometimes move in from adjacent road ditches or weedy areas.

Fall armyworm damage is characterized by window panning on wheat leaves. Injury can sometimes be greater in field margins as armyworms sometimes move in from adjacent road ditches or weedy areas.

Fall armyworms are generally most active early in the morning or late in the evening. Spray when 2-3 armyworms per linear foot of row are present.

Fall armyworms are generally most active early in the morning or late in the evening. Spray when 2-3 armyworms per linear foot of row are present.

Examine plants along the field margin as well as in the interior, because they sometimes move in from road ditches and weedy areas. The caterpillars were widely distributed in the field that I checked, suggesting that they were the result of a large egg lay from a recent adult moth flight. The suggested treatment threshold is 2-3 larvae per linear foot of row in wheat with active feeding. We won’t get relief from fall armyworms until we get a killing frost, since they do not overwinter in Oklahoma.

Consult the newly updated OSU Fact Sheet CR-7194 Management of Insect and Mite Pests of Small Grains for control suggestions.

Watch for armyworms in wheat

We have a late-maturing wheat crop that has fought its way through freezes, howling winds and it is now receiving some needed rain.  This cool weather is also helping slow the maturity of the wheat.  Right now, wheat is vulnerable to infestation from armyworms.  Armyworm infestations typically occur in late April through the first two weeks of May, but obviously, the cooler spring we have experienced this year has delayed their development.

Armyworm infestations occur more frequently around waterways, areas of lush growth, or areas with lodged plants. These areas should be checked first to determine the size of the infestation. Armyworm 2 Royer 2007

Early signs of an infestation include leaves with ragged margins that have been chewed.  You may find “frass” i.e. the excrement from armyworm caterpillars, around the base of wheat stems.  They also tend to clip heads from developing wheat plants. The head clipping I have noticed over the years us usually restricted to secondary tillers with very small, green heads that would not likely contribute much to yield.

Armyworm damaged wheat heads

Armyworm damaged wheat heads

Scout for armyworms, at 5 or more locations looking for “curled up worms”.  Armyworm caterpillars tend to feed at night, so a good strategy is to bring a flashlight and look at fields after dusk when they are feeding up on the plant stems.  The suggested treatment threshold for armyworms is 4-5 unparasitized caterpillars per linear foot of row.

Clipped heads from armyworm feeding

Clipped heads from armyworm feeding

Armyworms have a number of natural enemies that help keep populations in check, if given a chance.  In particular, parasitic wasps and flies attack them.  If you find small white cocoons littered on the ground that are about ¾ the size of a cue tip, the natural enemies have already taken care of the problem.

 

 

Parasitized armyworms

Parasitized armyworms

I have noticed that there has been some fungicides being applied during the past few weeks. If an insecticide was added to that spray, it is likely to have reduced any armyworm population already established in the field. Still, it is important to check the field.  Generally if wheat is past the soft dough stage, control is not warranted unless obvious head clipping can be seen, and caterpillars are still present and feeding.  Worms feeding on the awns when plants are past soft dough will not cause enough yield loss to justify the expense of an insecticide application.

Consult CR-7194 Management of Insect and Mite Pests of Small Grains for information on insecticides registered for control of armyworms.

For more information on this topic, contact Tom A. Royer, Extension Entomologist at tom.royer@okstate.edu