Spiny Rose Leaf Gall from Japan

Subject: eggs on roses leaves
Location: Japan
June 4, 2016 6:08 pm
I found these on the leaves of one of my roses in Japan.
Tried to google it, but couldn’t find them on the net….
It would be great to know !
Thank you!
Signature: Dasha

Spiny Rose Leaf Gall
Spiny Rose Leaf Gall

Dear Dasha,
These are not really eggs.  The are Galls, growths on plants that are usually caused by insects.  According to the University of Minnesota:  “Galls are abnormal plant growths caused by various organisms (insects, mites, nematodes, fungi, bacteria, and viruses). This publication will deal with galls caused by the feeding or egg- laying activity of insects and mites. Because of their unusual forms and colors, galls often cause homeowners to become concerned. However, galls seldom threaten plant health and their numbers are highly variable from season to season. For those reasons, control is generally not suggested. How are galls formed?  Galls are formed by insect/mite feeding or egg-laying activity. Either mechanical damage or salivary secretions (introduced by insects and/or mites) initiate increased production of normal plant growth hormones. These plant hormones cause localized plant growth that can result in increases in cell size (hypertrophy) and/or cell number (hyperplasia). The outcome is an abnormal plant structure called a gall.
Gall formation generally occurs during the accelerated growth period (late spring) of new leaves, shoots, flowers, etc. Mature plant tissues are usually unaffected by gall-inducing organisms. The gall-making organism develops inside the gall and the gall continues to grow as the insect/mite feeds and matures. Once gall formation is initiated, many galls will continue to form even if the insect dies. In addition, most galls are usually not noticed until they are fully formed and remain on plants for extended periods of time (more than a season).”  We believe your Galls are Spiny Rose Leaf Calls that are caused by the Gall Wasp,
Diplolepis polita, thanks to a matching image on Ereimer.net.  We verified the identification on BugGuide.  We will be postdating your wonderful submission to go live during our absence from the office next week.

Spiny Rose Leaf Gall
Spiny Rose Leaf Gall

Thank you Daniel for your quick and thorough response!
Wish you a lovely Sunday!

1 thought on “Spiny Rose Leaf Gall from Japan”

  1. This was very helpful! I found similar galls on a rose here in Washington state. I had never seen anything like them before. From what I read here, I don’t think the wasps will hatch and eat my rose leaves, so I will probably leave them alone.


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