Infestation on Ninebark (Diablo)

Asked September 12, 2017, 10:13 AM EDT

I discovered massive amounts of bugs on the bottom of the leaves about 8 weeks ago. A horticulturalist at Bachman's thinks they are thrips and whiteflies. I have been spraying "Eight" once every seven to ten days, getting under the plants and spraying the infected bottoms as well as the tops. There are 3 shrubs totaling about 20 feet wide and 6 feet tall. Some new growth is white and the plant looks very stressed. Do you have any suggestions? Also, is there a way to submit a sample? I did originally show a sample to the Master Gardeners at the Richfield Farmers Market. They were not sure what the infestation was and suggested organic treatment (mint oil and something else) which did not help at all.

Hennepin County Minnesota pest control

3 Responses

Can you catch some of the bugs and take closeup photos?
http://www.kiwicare.co.nz/help/problem/?sid=thrips
Thrips can cause leaf silvering. White flies can cause leaf curling. Both are serious and hard to control pests.
http://cottonbugs.tamu.edu/seedling-pests/thrips/
Be sure to follow the directions on the label carefully and do not exceed the application rate. More than is directed is not better and it is often toxic to the plant.

Your answer provided links to an Australian product (KiwiCare Plant Health "Spectrum") that, according to their website is not available here. And a link to thrips and cotton manangement. Neither help me. Can I submit a sample to verify the insects are correctly identified? I can't include any photos.

I am very aware that overspraying is not beneficial. That is why I am reaching out to the extension service, as using "Eight" does not seem to be helping.

A sample of the insects can be sent to https://www.extension.umn.edu/garden/insects/team/ Contact person Jeff Hahn Make sure the sample is in a crush proof container so it is not damaged in the mail. Another option is to contact Mr. Hahn and ask if a sample may be dropped off and arrange a time.