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Aceria malherhae
Biological agent type
Bindweed gall mite
 
Plant species attacked
 
Aceria malherbae
Adult, nymphs, and eggs. 

Galled plant.

Images by Eric Coombs, Oregon Department of Agriculture.
Galled plant.
 
If images are downloaded from the ODA web site and used please be sure to credit the photographer.  

Impact on target plant
Adult and nymphal mites suck plant juices that deforms leaves and developing buds, which interferes with flowering, seed production, and reduces plant biomass. Plant density reductions have not yet been documented.
 
Collection and release
Handpick infested plant material in summer when mite attack is evident. Place or intertwine pieces of infested material onto uninfested plants. One sandwich bag of infested material should contain about 1000 mites to treat one site.
 
Distribution
The mite has been released in 25 counties and recovered in 8. It is most abundant in the Columbia Basin counties. Attempts to establish the mite west of the Cascades has been unsuccessful.
 
History and comments
The leaf gall mite Aceria malherbae was released in 1999 in Polk County, at the Baskett Slough National Wildlife Refuge, but failed to establish. Mites were recovered in Tygh Valley in Wasco County in 2006. The mites caused reductions in plant biomass, flowering, and cover by over 90% by 2007. Redistribution began in 2008. A population of this mite was also reported from the Hells Canyon area. A 2010 survey of the general Columbia River counties in central Oregon, revealed mites were present at 80% of the bindweed infestations. A cooperative research project is underway in conjunction with Dr. Ed Peachy (OSU) and his staff to establish the gall mite in western Oregon, especially in crop fields. The long cool, wet season in 2011 and 2012, allowed plants to generally out-grow damage from the mites, therefore redistribution efforts were sparse. Scanning electron microscopy images of the mite indicated that the correct genus for this mite might be Aculops.
 
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