ash bead gall mite

Ash bead gall mite occurs in eastern North America from New Brunswick to Minnesota south to Alabama and Nebraska. It is uncommon in the Midwest based on the number of reported sightings, but it is probably underreported.

Ash bead gall mite is robust, spindle-shaped, yellowish, and just 1⁄100″ (210 to 260 microns) in length. It is large enough to be seen by the naked eye without magnification. The identifying features are the shape of the claws, the texture on the back plate (dorsal shield), the presence or absence of microscopic bumps on the second body segment, and the flap covering the female genitalia. None of these features can be seen without a microscope. However, identification in the field is easily made by noting host species and the properties of the abnormal growths (galls) it produces.

The galls appear on the leaves of green ash and white ash. When present, there are usually several galls scattered randomly on the lateral veins of a single leaflet. Each gall is a small, kidney-shaped, greenish-yellow capsule.

Total length: 1⁄100″ (210 to 260 microns)

Green ash and white ash

The life cycle apparently requires alternation of generations. Adults emerge on the underside of the leaf in late summer.

Sources

24, 29, 30, 82, 83.

iNaturalist has a doubtful sigthting in Chisago County (light green on the map). GBIF repeats iNaturalist sightings, including that one, which, based on the accompanying photo, may be in error.

Order
Until recently, herbivorous mites in Superfamily Eriophyoidea were included in Order Trombidiformes. Morphological and molecular DNA analyses in 2017, 2020, and 2023 found that they are evolutionarily distinct, and they should now be included in Order Sarcoptiformes. However, disagreement remains about the correct ranking between Superfamily Eriophyoidea and Subclass Acari. The ranking on this page follows iNaturalist.

Species
Some sources, including GBIF, treat Aceria fraxini as a synonym of Aceria fraxinicola. Other sources (Gallformers) treat Aceria fraxinicola as a synonym of Aceria fraxini. Still other sources (NatureServe) use the name Aceria chondriphora, now considered by most a synonym of Aceria fraxini. According to Gallformers and iNaturalist, Aceria fraxinicola is a European species that does not occur in North America.

I have a green ash with leaves completely covered in the gall mite bumps. Not sure how to eradicate and not looking forward to the emergence.

Joy Mouch
6/15/2024

Location: 23941 Taurus St, Linwood MN 555079

I have a green ash with leaves completely covered in the gall mite bumps. Not sure how to eradicate and not looking forward to the emergence.