[et_pb_section fb_built=”1″ admin_label=”section” _builder_version=”4.16″ global_colors_info=”{}”][et_pb_row column_structure=”1_2,1_2″ admin_label=”row” _builder_version=”4.16″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” width=”100%” global_colors_info=”{}”][et_pb_column type=”1_2″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_text admin_label=”squiggle-left” _builder_version=”4.24.1″ _module_preset=”default” header_font=”||||||||” header_text_align=”left” header_font_size=”22px” width=”75%” module_alignment=”left” custom_margin=”||||false|false” custom_padding=”||||false|false” global_module=”23371″ saved_tabs=”all” global_colors_info=”{}”]<\/p>\n
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Order: Lepidoptera<\/span> The armyworm is a globally distributed pest that attacks crops in North America, from southern Canada to the southern United States. In the United States, it is widely distributed east of the Rocky Mountains. The adults are approximately 3.8 cm (1.5 inches) and a dirty white color with black dots on their forewings. The mature larvae are hairless, smooth-bodied, 3.8 cm (1.5 inches) long, dark grey to green-black, and have five stripes running along the body. The two stripes on the sides are pale orange with white outlines, while the three stripes on the back vary in color. The markings on the head capsule resemble a honeycomb pattern.<\/p>\n [\/et_pb_text][et_pb_blurb title=”Quick Facts” use_icon=”on” font_icon=”||fa||900″ icon_color=”#F15625″ image_icon_width=”36px” _builder_version=”4.24.2″ _module_preset=”default” header_level=”h3″ header_font=”|||on|||||” header_text_align=”center” header_font_size=”26px” background_color=”#FEBD3B” custom_margin=”|4%||4%|false|true” custom_padding=”4%|4%|4%|4%|true|true” global_colors_info=”{}”]<\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/divi-agbio\/wp-content\/uploads\/sites\/127\/2022\/03\/true-army-worm.jpeg” alt=”True armyworm adult.” _builder_version=”4.21.0″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Armyworm adult. Image credit:<\/em> Natasha Wright, Braman Termite & Pest Elimination, Bugwood.org<\/i><\/p>\n [\/et_pb_blurb][\/et_pb_column][et_pb_column type=”1_2″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/divi-agbio\/wp-content\/uploads\/sites\/127\/2022\/03\/true-army-worm-3.jpeg” alt=”Masked chafer adults.” _builder_version=”4.21.0″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Armyworm caterpillar. Note the stripes running along the side. Image credit: Frank Peairs, Colorado State University, Bugwood.org<\/em><\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/divi-agbio\/wp-content\/uploads\/sites\/127\/2022\/03\/true-army-worm-2.jpeg” alt=”Japanese Beetle Larva.” _builder_version=”4.21.0″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Armyworm caterpillar on leaf. Image credit: Alton N. Sparks, Jr., University of Georgia, Bugwood.org<\/em><\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2024\/03\/armywom-caterpillar-parasitized-min.jpg” alt=”Armyworm caterpillar parasitized” _builder_version=”4.24.2″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Armyworm caterpillar parasitized by a tachinid fly. Note the presence of small white eggs (arrow) and the honeycomb pattern on the head capsule. Applying insecticides should be avoided when a high proportion of armyworm caterpillars are parasitized. Image credit: Robert J. Bauernfeind, Kansas State University, Bugwood.org<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.21.0″ _module_preset=”default” background_color=”#F1F1F1″ global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.24.2″ _module_preset=”default” hover_enabled=”0″ global_colors_info=”{}” sticky_enabled=”0″]<\/p>\n\t\t This species does not survive winter in Colorado or the northern part of its range in North America, and populations are reestablished annually as armyworm moths migrate north from subtropical and tropical regions. Armyworm adults lay their eggs in rows or clusters on the lower leaves of various grass crops. Over a one-week period, a single female can lay hundreds of eggs. Larvae primarily feed during cloudy days and at night, and often hide under crop debris during sunny weather. Larvae develop through six instars before pupating in a silken cell.<\/p>\n Populations do not usually reach economically significant levels and outbreaks tend to be sporadic and unpredictable. Once a particular food source has been consumed, the caterpillars migrate in large groups in search of new host plants. Cereal and forage crops such as oat (Avena sativa<\/em>), wheat (Triticum aestivum<\/em>), barley (Hordeum vulgare<\/em>), and corn (Zea mays<\/em>) are strongly preferred. In Colorado, this species occurs in most agricultural areas and is most often a pest of corn and spring grains but can also attack winter wheat. This species produces one or more generations per year in Colorado.<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.21.0″ _module_preset=”default” background_color=”#FFFFFF” global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.24.2″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n\t\t In Colorado, this species is mostly a pest of corn and spring grains, with only occasional infestations occurring in winter wheat. The severity of feeding injuries varies greatly from year to year. Armyworm feeding is limited mostly to grasses, although this insect will feed on several other plants as well. Caterpillars consume awns, tender kernels, and often cut the stem below the head, and young corn plants can be completely defoliated. Feeding is most notable on leaves of plants, but crowns can be chewed, and heads can be clipped as well.<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.24.2″ _module_preset=”default” background_color=”#F1F1F1″ global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.24.2″ _module_preset=”default” hover_enabled=”0″ global_colors_info=”{}” sticky_enabled=”0″]<\/p>\n\t\t <\/p>\n Field margins with lodged plants can be scouted for armyworm caterpillars, and the base of plants can be inspected for feeding injuries or frass (excrement). Fallen plant matter and the heads of barley or wheat can also be inspected. Another approach involves scouting for caterpillars by digging and sifting soil in a 0.09 m2 (12 foot) area for larvae. Five larvae per square foot is the action threshold when defoliation in the lower leaves is noted, and two larvae per square foot when head clipping is noted.<\/p>\n Insecticide treatments may be necessary when the lower third of field corn leaves are consumed, five larvae per square foot are observed in small grains prior to the heading stage, or two larvae per square foot are observed feeding in the head of small grains. Furthermore, insecticides should only be applied when most of the caterpillars are between 1.9-3.2 cm (0.75-1.25 inches) long, are free of small white parasite eggs or brown cocoons behind the head, and there is clear leaf feeding or head clipping on plants.<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.24.2″ _module_preset=”default” background_color=”#FFFFFF” global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_text _builder_version=”4.24.2″ _module_preset=”default” hover_enabled=”0″ global_colors_info=”{}” sticky_enabled=”0″]<\/p>\n\t\t <\/p>\n Many natural enemies exist for armyworm and help suppress populations below economically significant levels. Avoiding the application of broad-spectrum insecticides will help conserve resident populations of these beneficial insects.<\/p>\n Given the nocturnal feeding behaviors of armyworm caterpillars, applying insecticides in the afternoon when caterpillars are between 6.5-19 mm (0.25-0.75 inches) long can help maximize their efficacy.<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.24.2″ _module_preset=”default” background_color=”#F1F1F1″ global_colors_info=”{}”][et_pb_row _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_blurb title=”CSU Extension Fact Sheet” url=”https:\/\/extension.colostate.edu\/docs\/pubs\/insect\/05503.pdf” use_icon=”on” font_icon=”||fa||900″ icon_color=”#F15625″ image_icon_width=”36px” _builder_version=”4.21.0″ _module_preset=”default” header_level=”h2″ header_font_size=”36px” global_colors_info=”{}”]<\/p>\n Download or view the CSU Extension’s PDF fact sheet for your reference.<\/p>\n [\/et_pb_blurb][et_pb_text _builder_version=”4.24.2″ _module_preset=”default” global_colors_info=”{}”]<\/p>\n\t\t Carscallen, G., S. Kher, and M. Evenden. 2018.<\/strong> Efficacy of Chlorantraniliprole Seed Treatments Against Armyworm (Mythimna unipuncta<\/em> [Lepidoptera: Noctuidae]) Larvae on Corn (Zea mays<\/em>). Journal of Economic Entomology. 112(1): 188-195. Available https:\/\/academic.oup.com\/jee\/article\/112\/1\/188\/5156298?login=true<\/a><\/p>\n Kaur, N., A. Willette, and L. Van Slambrook. 2023.<\/strong> Pacific Northwest Handbooks: Field and Silage Corn Pests. pp 5-6. Available https:\/\/pnwhandbooks.org\/sites\/pnwhandbooks\/files\/insect\/chapterpdf\/agronomic.pdf<\/a><\/p>\n
Family: Noctuidae<\/span><\/p>\nDescription<\/h2>\n
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Life history and habits<\/h2>\n
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Injury<\/h2>\n
Monitoring<\/h2>\n
Biological control<\/h2>\n
Chemical control<\/h2>\n
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References<\/h2>\n