Barberry Defoliation Alert –

Help Needed Collecting Data

While hiking in the Sourland Mountains of central New Jersey a few weeks ago, I noticed that all the Japanese barberry plants had suffered heavy defoliation, something I had never seen in years of studying this invasive species.  In particular, all of this year’s growth – the new shoots that grew up vertically from the older stems – had lost most or all of their leaves (see pictures).  With some additional observations, I discovered that the agent is a night-feeding caterpillar, the “barberry geometer,” which is a native moth species that is rarely found here but is best known from areas in the mid-west that have a native, American, species of barberry.  To my knowledge, no one has previously seen such large-scale defoliation of Japanese barberry growing in natural areas by this native insect or by any insect.

I would like to find out how extensive this defoliation is in the region, and I invite the hiking community to help collect data for me.  If you are hiking and see barberry in the woods, take a look at the new shoots (anything sticking straight up) and note whether the leaves are all intact (no defoliation), are partially chewed (light to moderate defoliation), or completely missing (heavy defoliation).  Let me know 1) what trail you are on, where (park name or TC map number) and your approximate location on the trail, 2) the level of defoliation (none, light-moderate, heavy), and 3) how extensive the barberry is (scattered plants, dense thicket).  If you own a GPS unit, it would be great if you could send me UTM coordinates of your observation point(s).  Also, if you own a small digital camera, take a few pictures and send them along, so that I can compare your observations and mine.  The data will be used to create a map of the extent and intensity of defoliation in the New Jersey-New York area.

Please go to rci.rutgers.edu/~trails/barberry/barberry.htm to record your information.

If you participated in the Rutgers-Trail Conference Invasive Plant Monitoring Project, please let us know your volunteer code number or check the box on the form.

Thanks!!
Joan Ehrenfeld
Rutgers University