Knowledgebase
Emerald Ash Borer and Ash Flower Gall Mites #866307
Asked April 29, 2024, 1:40 PM EDT
I am looking for information on controlling Ash Flower Gall Mites if necessary or possible. They infested the whole tree last year. I know they are not usually a health issue for the tree but it seems they have gotten quite bad.
I would also like to know if I should be treating my mature (57" trunk) Autumn Purple Ash to prevent Emerald Ash Borer? The tree is at 44th Ave and Ward Road in NW Wheat Ridge. I am on a limited income and hoping for an economical alternative to the trunk injections. How effective would a soil treatment like "Bayer Advanced 12 month Tree Protect and Feed" Active ingredient Imidacloprid and some have Clothianidin. I have seen the infestation map for Jefferson county before but could not locate it today.
Jefferson County Colorado
Expert Response
Thanks for contacting the Jefferson County Extension Plant Diagnostic Help Desk.
The ash flower distortion is caused by an eriophyid mite (Eriophyes fraxiniflora) on the male ash flowers. Although unsightly, this damage is not considered to affect tree health.
CSU's "Insects and Diseases of Woody Plants in Colorado" (publication 506a) describes the life cycle: "the ash flower gall mites survive winters in the adult female stage under bud scales and other protected sites on the ash tree. As temperatures warm in spring, overwintering females commence feeding, initiate gall formation and begin egg laying on the newly expanding buds. The tissues of the flower become disorganized and form numerous small pouches in which the mites continue to develop. In midsummer as the galls dry, the mites move to the bud scales for overwinter shelter."
The attached CSU Fact Sheet discusses chemical controls for various gall-making insects and mites. Because this mite overwinters, winter application of dormant oil on the trunk can minimize mite survival. The Fact Sheet also mentions that Sevin and permethrin are also possible controls, but be careful not to apply them in spring when bees may be visiting the flowers.
https://extension.colostate.edu/topic-areas/insects/insect-and-mite-galls-5-577/
As for Emerald Ash Borer control, see the attached Fact sheet: https://extension.colostate.edu/docs/pubs/insect/05626.pdf
It includes the concentration and timing for imidacloprid as a soil drench, noting that the soil around the tree must remain moist for 2-3 weeks so the tree can take up the chemical. Imidacloprid is the only EAB treatment available to home gardeners, though must be applied annually and therefore is not considered as effective as other chemicals that are applied by arborists and can persist for 2-3 years.
If you have further questions, you can e mail the Plant Diagnostic Help Desk at: <personal data hidden>. Please note that your query relates to "Ask Extension" question # 0136228.
Pat B
