[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: Acari
Family: Eriophyidae<\/p>\n
Like all eriophyid mites, adult leaf blister mites have cylindrical bodies that taper at both the head and rear.<\/span> <\/span>They have two pairs of legs near the head<\/span> <\/span><\/span>and are extremely small, measuring <\/span>roughly <\/span>0.2<\/span> mm<\/span> in length<\/span> as adults<\/span>. These mites<\/span> cannot <\/span>be seen<\/span> without a hand lens or microscope capable of <\/span>10x-<\/span>20x or greater magnification. <\/span>Eggs of the <\/span>pearleaf<\/span> blister mite <\/span>are about \u00bc the size of adults, oval shaped, and translucent to white. <\/span>The first stage nymphs are about half the size of adults, while the second stage nymphs are about the same size as adults. <\/span>Given their extremely small size, the presence of feeding injuries <\/span>is often used<\/span> <\/span>to indicate that an<\/span> infestation<\/span> is present<\/span>.<\/span><\/span>\u00a0<\/span><\/p>\n [\/et_pb_text][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/09\/pear-leaf-injury.jpg” alt=”pear leaf injury” _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 Pear leaf injury caused by feeding of pearleaf blister mites. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org<\/em><\/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\/agbio\/wp-content\/uploads\/sites\/127\/2022\/08\/single-eriphyid-mite.jpg” alt=”Single eriophyid mite” _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_color_all=”#F15625″ global_colors_info=”{}”]<\/p>\n Eriophyid mite adult. All leaf blister mites are eriophyid mites. Leaf blister mites cause blistering on leaves and fruit. In Colorado, leaf blister mites can attack apple and pear trees in orchards or home gardens. These mites are not usually considered a major pest in orchards and can be managed using integrated pest management practices. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org<\/em><\/p>\n [\/et_pb_blurb][et_pb_blurb image=”https:\/\/agsci.colostate.edu\/agbio\/wp-content\/uploads\/sites\/127\/2022\/09\/close-up-of-leaf-blisters.jpg” alt=”close up of leaf blisters” _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 Close up of leaf blisters caused by feeding of\u00a0P. mali<\/em>, commonly referred to as the appleleaf blister mite. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org<\/em><\/p>\n [\/et_pb_blurb][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”4.27.4″ _module_preset=”default” global_colors_info=”{}”][et_pb_column type=”4_4″ _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” content_max_width=”984px” _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” height=”414px” custom_padding=”4%|4%|4%|4%|true|true” hover_enabled=”0″ global_colors_info=”{}” sticky_enabled=”0″]<\/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 _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 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 Adult leafblister mites overwinter in colonies under the fruit scales and leaf buds host trees. They tend to be most abundant in terminal buds.<\/span> In the spring, females begin feeding and laying eggs in buds when the buds start to swell. <\/span>A single female can lay as many as two dozen eggs throughout her life.<\/span> The nymphs develop within blisters and exit the natal blister through a small hole in the center after reaching adulthood. The adults migrate to form new blisters on the host plant, and mites only survive for several days outside of leaf blisters.<\/span> Both mite species can attack other trees as well as small shrubs such as mountain ash (<\/span>Sorbus americana<\/span><\/i>), snowberry (<\/span>Symphoricarpos albus<\/span><\/i>), serviceberry (<\/span>Amelanchier arborea<\/span><\/i>), hawthorn (<\/span>Crataegus monogyna<\/span><\/i>), <\/span>Cotoneaster <\/span><\/i>spp<\/span>., and quince (<\/span>Cydonia oblonga<\/span><\/i>).<\/span>\u00a0<\/span><\/p>\n The average development time from egg to adult takes 20-30 days in the spring, but only 10 to 12 days in the summer when temperatures are more favorable for mite development. Leaf blister mites can migrate to growing terminals of the plant in response to overcrowding or when leaves sustain heavy damage and<\/span> migrate to overwintering sites before leaves drop in the fall.<\/span> At least two generations are produced each year in Colorado.<\/span>\u00a0<\/span>\u00a0<\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section][et_pb_section fb_built=”1″ _builder_version=”4.17.4″ _module_preset=”default” 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 _builder_version=”4.27.4″ _module_preset=”default” header_3_font_size=”26px” global_colors_info=”{}”]<\/p>\n Feeding by leaf blister mites causes several symptoms on apple and pear trees including blistering on leaves, leaf discoloration, deformation and scarring of fruit which makes them unmarketable. Blistering occurs when plant cells die and separate in the center of the forming blister. At the same time surrounding cells enlarge and create a hole, which provides mites with access to plant tissue deeper in the leaf for feeding. <\/span>Mites that reside within blisters are protected from natural enemies and pesticides. Therefore, the timing of applications is important.<\/span>\u00a0<\/span><\/p>\n Beginning in early spring, blisters are formed on <\/span>leaves along the midvein<\/span> and can reach sizes up to 3 mm (1\/8 inch) <\/span>in diameter. Initially the blisters are pale, green, pink, or red, but graduate darken to black or brown.<\/span> The blisters may be less visible earlier in the season, but young leaves infested with leaf blister mites will have noticeable rough areas that are light green to light red in color. Leaf drop and lower shoot growth may occur when damage to foliage is severe. Unlike leaf blisters, mites do not live in blisters on fruit. For examples of blistering damage on fruit, see the <\/span>Washington State University webpage<\/span><\/a>. <\/span>These mites can also feed on fruit blossoms, which kills them are reduces fruit yield. Fruits that do develop are often abnormally shaped with brown scabs and scarring on the skin. However, certain pear varieties naturally produce fruit with russeted surfaces, such as Bosc, Hardy, Nelis, and Winter, and do not show scabbing.<\/span>\u00a0<\/span><\/p>\n [\/et_pb_text][\/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 _builder_version=”4.27.4″ _module_preset=”default” header_3_font_size=”26px” global_colors_info=”{}”]<\/p>\n Natural enemie<\/span>s of leaf blister mites include <\/span>predatory mites (Acari: <\/span>Phytoseiidae<\/span>), <\/span>predatory thrips (Thysanoptera: <\/span>Aelothripidae<\/span>)<\/span>, and <\/span>certain <\/span>lady beetles (Coleoptera: Coccinellidae<\/span>) such as the spider mite destroyer, <\/span><\/span>Stethorus<\/span> punctum <\/span>picipes<\/span><\/span>.<\/span><\/span> <\/span>Leaf<\/span> blister mites are not usually a problem in orchards with good integrated pest management practices where natural enemies <\/span>are conserved<\/span> and <\/span>provide protection against mites in residential trees. To protect natural enemies, broad spectrum insecticide applications should <\/span>be avoided<\/span>, ant populations should be controlled, and young trees should be hosed off periodically<\/span> to remove dust.<\/span><\/span>\u00a0<\/span><\/p>\n Leaf blister mites more commonly attack trees in neglected or abandoned orchards. When an infestation is present, there are many options for chemical management since blister mites are not resistant to pesticides. Leaf blister mites are most susceptible to chemical treatments when on fruit and terminal buds prior to bud swell in the spring. Therefore, pesticides should be applied before bloom or after harvest to prevent fruit damage. Summer applications of fuming or systemic pesticides can provide some control, however they will not prevent fruit damage.<\/span>\u00a0<\/span><\/p>\n Post-harvest applications of horticultural oils or neem oils can be effective when mite damage is persistent and intolerable. It is recommended that plants be irrigated before oil applications during periods of low rainfall. In addition, spray applications of micronized or wettable sulfur can be effective when plants are treated after buds swell but before most buds have opened. However, to prevent inadvertent toxicity toward plants, sulfur should not be applied to plants within one month before or after applications of oil, or vice versa. It is worth noting that feeding injuries cannot be reversed after fruits have set, although treating infested trees can help reduce feeding injuries the following season.<\/span>\u00a0<\/span><\/p>\n [\/et_pb_text][\/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=”#FFFFFF” 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 _builder_version=”4.27.4″ _module_preset=”default” header_3_font_size=”26px” global_colors_info=”{}”]<\/p>\n Amrine, J. 2013.<\/strong> Eriophyid mites. Washington State University. Available here<\/a>.<\/strong><\/p>\n Claudia, D., C. Linder, and E. Wyss. 2007. <\/span><\/span><\/strong>Autumn acaricide applications as a new strategy to control the pear leaf blister mite\u202f<\/span><\/span><\/a>Eriophyes<\/span>pyri<\/span><\/a>. <\/span>Crop Protection. <\/span><\/span>26(10): 1532\u20131537.<\/span><\/span><\/p>\n Colorado State University. 2022.<\/strong> Eriophyid Mites. Colorado State University: Extension \u2013 Plant Talk Colorado. Available here<\/a>.<\/p>\n Davis, R. 2011.<\/strong> Eriophyid Mites: bud, bluster, gall and rust mites. Utah State University \u2013 Cooperative Extension. Available here<\/a>.<\/p>\n UCIPM. 2021.<\/span><\/span><\/strong> Pearleaf<\/span><\/span> blister mite \u2013 <\/span><\/span>Eriop<\/span><\/span>h<\/span><\/span>yes<\/span><\/span> (<\/span><\/span>= <\/span>Phytoptus<\/span><\/span>) <\/span><\/span>pyri<\/span><\/span>. <\/span>University of California \u2013 Agriculture and Natural Resources. Available here<\/a>.<\/span><\/span><\/p>\n Utah State University. (n.d.).<\/strong> Blister Mites (Appleleaf & Pearleaf Blister Mites). Utah State University Extension. Available here<\/a>.<\/p>\n\n
\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>\nLife history and habits<\/h2>\n
Injury<\/h3>\n
Biological control<\/h3>\n
Chemical control<\/h3>\n
References<\/h3>\n