Eriophyes rhois

Aculops toxicophagus

Eriophyidae

Aculops

Rhus aromatica

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Toxicodendron diversilobum

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An Illustrated Guide to Plant Abnormalities Caused by Eriophyid Mites in North America

Aculops rhois

Infestation is common and typical of the leaf galls. It consists of puckered, irregular, rounded, or wartlike pouches affecting both upper and lower surfaces of the leaves. The galls are usually scattered about indiscriminately on the leaf blade. They range from green to pinkish, to red brown. Poison oak leaves are often so heavily attacked that they become visibly crinkled and distorted. 

Specimens were collected on poison oak in Oregon and California and on poison ivy in Ohio and Maryland. It has also been found on poison sumac (Rhus vernix L.) in Ohio. The mite is probably present throughout its host range.

Aculops rhois

Eriophyes sp.

Hosts: Toxicodendron radicans ssp. radicans, diversilobum, vernix

Relationship: "Corrugations (galls) on upper and lower surfaces of leaf with numerous, whitish hairs or erinea"; leaf deformation; stunting of plant? Flowers of large vines sometimes become deformed producing numerous long narrow filaments that are narrow rolled leaves; mites develop in large numbers within the rolls; in some cases the filaments are somewhat more leaflike (West Virginia: Monongalia, Nicholas, Preston and Tucker counties; Maryland: near mouth of Susquehanna River). Are these a different species?

Range: MA, CA, FL, GA, IN, MD, OH, PA, SD, WV

Notes:

Amrine & Stasny, 1994, erroneously listed this mite as nomen nudum. The mite described by Stebbins meets all code requirements for an older description: "a name, a mention of the animal and a description of the work of the animal"; thus her name is valid and has priority over Ewing's toxicophagus. We hereby elevate her name, Eriophyes rhois Stebbins 1909 to the accepted name for the poison ivy ( Toxicodendron radicans) gall mite. Ewing's Phyllocoptes toxicophagus is valid and occurs on Toxicodendron diversilobum. The deutogyne of rhois was photographed by Briones & McDaniel, 1976, 41, f. 88 and was observed by J. Amrine, 2 Sep. 1998 on specimens collected from Monongalia Co. WV, Cobun Creek Trail, by pasture, south of Cobun Creek Rd, 1 Sep, 1998, ex poison ivy (Toxicodendron radicans); they need to be described. The name rhois is a modified form of Rhus. Mites, if they occur on Toxicodendron pubescens Mill. (Atlantic Poison Ivy) and T. rydberghi (Small ex Rydb.) Greene (Western Poison Ivy) may all be separate, distinct species.  

Nalepa 1929 listed on p. 124, under Rhus radicans, Eriophyes rhois Stebbins 1909, and under Rhus diversilobus, Phyllocoptes toxicophagus Ewing, 1922; it may be that galls on each species of Rhus is caused by a different mite. Very careful morphological studies should be done, with rearing experiments and DNA studies. Probably, Aculops toxicophagus (Ewing) will be the name for the mite causing galls on Rhus diversilobus, and Aculops rhois (Stebbins, 1909) for the mite causing erineum galls on Rhus radicans.

NOTE: Inflorescences of Rhus radicans often have flowers & fruits formed into long foliar filaments, with the edges curled in toward the upper midrib, containing numerous mites and a few hairs. Much of this dries up during the season and becomes brown or black and brittle, resembling Spanish Moss on poison ivy. But, many deformations continue to have parts of the deformity growing, tender and green containing mites eggs and offspring even into November. Deutogynes in August were more common in older filaments; protogynes and developing mites in the tender growth. Deformed fruiting bodies have been found at cliffs at Blackwater Falls St. Park (Tucker Co., WV),at the Summersville Library on several large plants on three large trees (Nicholas Co.), at I-79 Rest Area N. Bound, north of Clarksburg, Harrison Co., WV, at Cheat Lake south of Mont Chateau (WV Geological Survey), at Cheat Lake, Morgan's Run Park and Trail, at Monongahela River, just south of the Morgantown Dam, east side along bike path, and at 24 Pinnacle Lane, Monongalia Co., WV. Originally, the foliated fruit was thought to be injury from glyphosate (A.I. of Roundup herbicide), but, symptoms have been found where pesticides have never been used. These mites are very similar to Aculops rhois and careful descriptions should be made to determine if one and the same species causes both kinds of deformities. It is not known if this symptom occurs on Poison Oak, Poison Sumac or other species of Rhus in North America. Examination of large hedgerows of poison ivy in New Orleans failed to find any of this new symptom. So far, it has only been found in several locations in West Virginia, in Bridgeport, Morgantown, Cooper's Rock State Forest, and Black Water St. Park in Tucker Co. 

Amrine Catalog

Rhus aromatica is confirmed as a host based on Ron Russo's Plant Galls of the Western United States (2021). In addition, Charley Eiseman reports at https://bugguide.net/node/view/296654 that Raymond Gagne said the same. 

Gallformers ID Notes