Wednesday, July 6, 2011

Curled Leaf

I hate to see plants suffering from afflictions that result in abnormal growth or deformities of the leaves. It’s especially disturbing when the plant in question is generally uncommon. From a distance I noticed the pale yellow coloring of the new growth on a patch of Carolina Buckthorn, a southern species that just barely makes its way into Southern Ohio.

Then I found a few older leaves that were tightly curled and displaying a mottled coloration. Most of the leaves still looked perfectly healthy, but I know how quickly that can change. Besides being curled, the leaves contained holes and various sized spots of dead leaf. The leaf petiole and portions of the branch contained similar discolorations. It’s not normal for Carolina Buckthorn to be showing this type of damage.

Ants are always foraging on the plants of Blue Jay Barrens, so it’s not odd to find them on the buckthorn. Their behavior can often give clues as to the reason they are present. As you might imagine, ants displaying a defensive posture usually have something to defend. That means there must be something here that is of interest to them. There doesn’t appear to be anything of significance on the outside of the leaf, so maybe it’s hidden in the curl.

The ants would have been hovering over these aphids if they had not all exited stage right to attack my hand as it held the leaf open enough to take a picture. Aphids produce honeydew which is collected by the ants for food. There are several aphid species that cause curling of the leaf as a result of their feeding activities. These aphids worry me because they look like the Asian Soybean Aphid, which is one of the new invasive species rapidly infesting the Midwest. They have become quite a pest in Soybean fields. So what are they doing on buckthorn?

The Asian Soybean Aphid is one of those species that uses multiple hosts during the year. During the summer it feeds on Soybean plants. In the fall, it lays its eggs on the invasive European Buckthorn. The eggs hatch in the spring and feed on the buckthorn. When winged adults are produced, they fly off to develop colonies on Soybeans. Carolina Buckthorn is in the same genus Rhamnus as the European Buckthorn. Having invasive insects attacking invasive plants doesn’t bother me. When the invasive insect begins to utilize native plants, I become concerned. Will the aphids next find a native legume to use in place of the Soybean? This situation deserves a little more study.


  1. Hi Steven...seeing ants....hmmm good year for the black ant they are everywhere, and occasionally in the house which makes me grrrr!!!
    I have noticed that ants usually have a reason for there presents and aphids seen to be the reason...or my humming bird feeder... haha!!
    Lets hope we don't have another invasive bug!!
    I have had a red beetle,who loves lilies for about 5 years now that never had before ...story is that they possibly came from Asia with the bulbs...Japaneese beetles are out this week in full force ..gggrrrrr!!
    Good luck with that study!!

  2. I can't seem to get the ants out of my home this year, so it may be a good year for ants, generally. The fact that the Carolina buckthorn is at the extent of its range might also allow it to succumb to the invasion more easily. (just one more stress)

  3. Hi, grammie g. There always seems to be something new coming along to eat our plants. It can be aggravating.

    Hi, nellie. We've also had a lot of ants invading the house this year. Some are types we've never seen in here before. I'm not sure why it's happening.