[et_pb_section fb_built=”1″ admin_label=”section” module_id=”1″ _builder_version=”4.17.4″ 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” 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=”4.27.4″ _module_preset=”default” header_font=”||||||||” header_text_align=”left” header_font_size=”22px” width=”100%” module_alignment=”center” custom_margin=”3%||22px||false|false” custom_padding=”||||false|false” global_module=”23371″ saved_tabs=”all” locked=”off” global_colors_info=”{}”]<\/p>\n
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Order: Diptera
Family: Agromyzidae<\/p>\n
Amauromyza karli<\/span><\/i>\u00a0is an emerging stem-boring pest of quinoa, recently <\/span>identified in Colorado, Oregon, and Idaho and confirmed in Canada. Although quinoa has been cultivated in Colorado since 1982, the discovery of <\/span>A. karli<\/span><\/i> marked a significant shift. From 2021 to 2025, <\/span>A. karli<\/span><\/i> infested all quinoa crops in Colorado, leading to a dramatic decline in acreage from approximately 3,000 acres in 2021 to just 160 acres by 2025. To date, there are no published reports of <\/span>A. karli<\/span><\/i> colonizing other food crops in the U.S. or internationally. As a result of the devastating outbreaks, this invasive pest poses an immediate threat to quinoa production, a niche crop valued for its high nutritional content and drought tolerance. Given quinoa\u2019s potential to support climate-resilient agriculture, its continued cultivation remains important, making effective management of <\/span>A. karli<\/span><\/i> a pressing concern.<\/span>\u00a0<\/span><\/p>\n \u00a0All agromyzid flies are herbivorous. While most species feed by mining leaves, some\u2014such as <\/span>Amauromyza karli<\/span><\/i>\u2014attack stems instead. In quinoa, <\/span>A. karli<\/span><\/i> females deposit eggs inside stems, and the emerging larvae tunnel through the pith. This extensive feeding disrupts nutrient transport, weakens structural integrity, and often leads to lodging, reduced yield, and plant death. Before pupating in the soil, larvae create distinctive exit holes on the stem surface. In Colorado, this type of injury has caused severe declines in quinoa production.<\/span>\u00a0<\/span><\/p>\n [\/et_pb_text][\/et_pb_column][et_pb_column type=”1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_blurb title=”Quick Facts” use_icon=”on” font_icon=”||fa||900″ icon_color=”#F15625″ image_icon_width=”36px” _builder_version=”4.27.4″ _module_preset=”default” header_level=”h3″ header_font=”|||on|||||” header_text_align=”center” header_font_size=”26px” background_color=”#FEBD3B” custom_padding=”4%|4%|4%|4%|true|true” global_colors_info=”{}”]<\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/10\/Exit-hole-in-quinoa-stem.jpg” alt=”Exit hole in quinoa stem” _builder_version=”4.27.4″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Exit hole in quinoa stem caused by larvae of A. karli. <\/em>Image credit: Adrianna Szczepaniec, Colorado State University<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_2,1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2025\/10\/quinoa-pith-lab.png” alt=”Damaged inner stem of quinoa” _builder_version=”4.27.4″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Quinoa pith destroyed by <\/span>A. karli <\/span><\/i>feeding<\/span>. <\/span>Top: healthy stem with intact pith. Bottom: infested stem showing pith with frass due to larval feeding; larvae are often found in these galleries.<\/span> Image credit: Neha Panwar, Colorado State University<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][et_pb_column type=”1_2″ _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2025\/10\/quinoa-pith.png” alt=”Damaged inner stem of quinoa” _builder_version=”4.27.4″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Quinoa pith <\/span>destroyed<\/span> by <\/span><\/span>feeding of <\/span><\/span>A. <\/span>karli<\/span><\/span>. <\/span><\/span><\/em>Image credit: Patrick O\u2019Neil, San Luis Valley, Colorado<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.17.4″ _module_preset=”default” background_color=”#F1F1F1″ global_colors_info=”{}”][et_pb_row column_structure=”1_2,1_2″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”1_2″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_text admin_label=”Squiggle” _builder_version=”4.17.4″ _module_preset=”default” header_font=”||||||||” header_text_align=”left” header_font_size=”22px” custom_padding=”||||false|false” saved_tabs=”all” global_colors_info=”{}”]\t\t Adults of <\/span>Amauromyza karli<\/span><\/i> are about 3 mm long, with a dark brown thorax and abdomen and a distinct yellow head. They also have light yellow halteres (small knob-like structures that are a modified version of hindwings) and dark brown legs with narrow yellow ends near the joints. Larvae are white and grow to about 4.5 mm, while pupae are brown and roughly 2.5 mm long. The eggs of <\/span>A. karli<\/span><\/i> have not yet been observed, but eggs of closely related species are typically white, oval-shaped, and laid in clusters.<\/span>\u00a0<\/span><\/p>\n In Colorado, adult activity begins in May and extends through August with peak activity occurring in early July. During this period, adults mate and females lay eggs on quinoa. Like other agromyzid flies, females likely deposit eggs by repeatedly thrusting an egg-laying structure, called an ovipositor, into plant tissue until the eggs are laid. After hatching, <\/span>A. karli<\/span><\/i> larvae feed within quinoa stems from early June to late July. When development is complete, larvae exit the stems and pupate in the soil from late June through August. The flies overwinter in the soil as pupae from August through May, and adults emerge the following spring to begin the cycle again.<\/span>\u00a0<\/span><\/p>\n [\/et_pb_text][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/10\/A.-karli-in-quinoa.jpg” alt=”A. karli fly” _builder_version=”4.27.4″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” custom_padding=”4%|4%|4%|4%|true|true” border_width_all=”4px” border_color_all=”#F15625″ global_colors_info=”{}”]<\/p>\n Adult A. karli<\/em> collected from quinoa grown in Alamosa, Colorado. Distinguishing features include a yellow head and dark brown body with light-yellow halteres\u00a0(small knob-like structures that are a modified version of hindwings)<\/span>. The legs are dark brown with yellow ends of the femur and tibia. Image credit: Tim McNary, Colorado State University<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][et_pb_column type=”1_2″ _builder_version=”4.16″ _module_preset=”default” global_colors_info=”{}”][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/10\/A.-karli-larva.jpg” alt=”A. karli larva” _builder_version=”4.27.4″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]<\/p>\n Larva of A. karli<\/em> collected from quinoa stems grown in Colorado. These larvae feed within the plant stem of quinoa and cause plant death or severe yield losses. Image credit: Tim McNary, Colorado State University<\/em><\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/10\/A.-karli-pupa.jpg” alt=”A. karli pupa” _builder_version=”4.21.0″ _module_preset=”default” body_line_height=”1.4em” image_icon_custom_margin=”||-22px||false|false” global_colors_info=”{}”]Ventral view of an A. karli<\/em> pupa. Most other stem-boring agromyzids pupate outside of the stems, and while pupation habits have not yet been observed in A. karli<\/em> it is likely that the larvae exit the stems before pupating in the soil as well. Image credit: Tim McNary, Colorado State University<\/em> Monitoring<\/span> <\/span>of<\/span> <\/span><\/span>A. <\/span>karli<\/span><\/span> in <\/span>quinoa<\/span> <\/span>is<\/span> <\/span>effectively<\/span> <\/span>accomplished<\/span> <\/span>through<\/span> <\/span>several<\/span> <\/span>techniques<\/span> <\/span>that<\/span> <\/span>help<\/span> <\/span>determine<\/span> <\/span>the<\/span> <\/span>onset<\/span> <\/span>of<\/span> <\/span>an<\/span> <\/span>infestation<\/span> and <\/span>the<\/span> <\/span>extent<\/span> <\/span>of<\/span> <\/span>an<\/span> <\/span>infestation<\/span> after <\/span><\/span>A. <\/span>karli<\/span><\/span> <\/span>presence<\/span> <\/span>is<\/span> <\/span>confirmed<\/span>. <\/span>To<\/span> <\/span>monitor<\/span> <\/span>adults<\/span>, <\/span>sticky<\/span> <\/span>traps<\/span> can be <\/span>used<\/span> <\/span>to<\/span> capture <\/span>flies<\/span>;<\/span> <\/span>flies<\/span> can<\/span> <\/span>then<\/span> be<\/span> <\/span>identif<\/span>ied<\/span> and <\/span>count<\/span>ed<\/span> <\/span>using<\/span> a <\/span>hand<\/span> <\/span>lens<\/span> <\/span>or<\/span> a <\/span>dissecting<\/span> <\/span>microscope<\/span>. Blue <\/span>sticky<\/span> <\/span>traps<\/span> <\/span>make<\/span> <\/span>identification<\/span> <\/span>of<\/span> <\/span>the<\/span> <\/span>flies<\/span> <\/span>easier<\/span>, <\/span>allowing<\/span> <\/span>for<\/span> <\/span>the<\/span> <\/span>bright<\/span> <\/span>yellow<\/span> <\/span>heads<\/span> <\/span>to<\/span> be <\/span>discernable<\/span>.<\/span><\/span>\u00a0<\/span>Fields<\/span> can <\/span>also<\/span> be <\/span>surveyed<\/span> <\/span>using<\/span> a <\/span>sweep<\/span> net. Once <\/span><\/span>A. <\/span>karli<\/span><\/span> <\/span>adults<\/span> are <\/span>\n
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\n[\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” header_2_font_size=”36px” header_3_font_size=”26px” global_colors_info=”{}”]<\/p>\nDescription and life history<\/h2>\n
\n[\/et_pb_blurb][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.18.0″ _module_preset=”default” background_color=”#F1F1F1″ global_colors_info=”{}”][et_pb_row _builder_version=”4.17.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _builder_version=”4.17.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_text admin_label=”Squiggle” _builder_version=”4.17.4″ _module_preset=”default” header_font=”||||||||” header_text_align=”left” header_font_size=”22px” custom_padding=”||||false|false” saved_tabs=”all” locked=”off” global_colors_info=”{}”]\t\t
\n[\/et_pb_text][et_pb_text _builder_version=”4.27.4″ _module_preset=”default” header_3_font_size=”26px” global_colors_info=”{}”]<\/p>\nMonitoring<\/h3>\n