Knockout rose bush problems

Asked July 2, 2018, 2:47 PM EDT

I have roughly 2 dozen knockout rose bushes that I planted around 3 sides of my house. The first 2 seasons they grew like weeds and looked great. This year they look terrible ( see photo). What I find especially remarkable is that every single one of them on all 3 sides of my house looks bad, not just a handful. What’s the problem?

Wayne County Michigan

1 Response

Hello,

The large holes in the leaves are caused by beetles, perhaps Japanese beetles or Rose chafers. The tiny white-ish spots are signs of leafhopper feeding. The tan areas that look lacy are from rose slug feeding. If the brown wilted petals on your flowers are not just old blooms, but got that way before the blooms faded and you have been watering the shrubs, then it is probably rose thrips. Here are references for you-

https://hgic.clemson.edu/factsheet/rose-insects-related-pests/

( note: in the above link, milky spore is recommended for Japanese beetles. It has not been found to be effective in Michigan due to our severe winters).

http://msue.anr.msu.edu/news/rose_chafers_a_punctual_and_pesky_insect

http://www.canr.msu.edu/resources/slug_sawflies

The link below lists some organic options-

http://ipm.ucanr.edu/PMG/PESTNOTES/pn7466.html

The brand names in the references are examples only. MSU Extension does not endorse or recommend any brands or retailers. Products with the same active ingredient (for example pymethrin or Bt) can be considered. Please remeber to,follow,all,label,cautions,when using chemicals. The good news is I don’t see any fungal diseases! If you have more questions, please write again. Thank you for using our service.