Photo of the Week – March 17, 2016

You’ve probably seen them – funny-looking brown balls stuck to eastern red cedar trees.  Sometimes, the  balls have long gooey orange tentacles hanging from them.  Do you know the story behind them?


Cedar-apple rust is a fascinating organism that uses two different hosts to help it complete its life cycle.  Galls that form on eastern red cedar trees eventually release spores, some of which make their way to leaves of apple or crabapple trees.  On those leaves, they stimulate formation of yellow lesions that eventually mature and create more spores that then need to make their way back to another cedar tree to complete the cycle.  The lesions on the leaves can be harmful to the apple trees (including the one in my yard) but I’m not sure there’s any big impact on cedars.

You can read much more about this at the Missouri Botanical Garden’s website.

I found the above gall at our family prairie last month.  And yes, I did cut the cedar tree down after I photographed the gall (see photo evidence below).


Wild Rose Galls

We came across these galls on a wild rose plant last week, and Eliza insisted I do a blog post about them.  So here you go.

Insect galls on prairie wild rose - TNC's Platte River Prairies, Nebraska.

Insect galls on prairie wild rose – TNC’s Platte River Prairies, Nebraska.

Galls like this are formed when an insect lays an egg on or in a plant and the feeding of the recently hatched larva stimulates excess growth of plant tissue.  The result is that the plant creates a little structure that contains both food and protection for the young larva.  The most familiar example of this in prairies is the goldenrod gall, which can be seen in just about any prairie containing goldenrod plants.  In this case, a wasp laid eggs on this wild rose (Rosa arkansana) plant and inside each of the resulting galls is a tiny white larva.

More galls on the same plant.

More galls on the same plant.

For much more information on galls and the insects that create them on wild rose, click here.