“What’s going on with the poplar trees this year?” is a common question I’ve been hearing lately around central West Virginia. “I’ve lived here 50 some years and have never seen the poplar trees look like this,” I had one fellow from Braxton County say to me a few weeks ago. I have to agree with him as I’ve never seen them look like this either.
After a closer examination and a little investigation I found the culprits. It seems as if the yellow poplar trees in central West Virginia are getting a double whammy this year. The first insect is the tuliptree scale and what is causing the sap or “honeydew” substance underneath the poplar trees. The tuliptree scale is one of the largest soft scale insects in the United States and is a key pest to the yellow poplar.
In heavy populations like this year, the scale is evident often covering the underside of the branches. They are oval shape and pinkish orange mottled with black in color and give the branches a warty appearance. They over winter as nymphs in the waxy covered scale and resume feeding in the spring.
During the growing season the scale feeds on the sap of the tree and then excretes a honeydew substance that coats anything underneath it including vegetation, roads and my truck. The first indication of an infestation is the nasty sticky honeydew in which acts as a substrate for a black sooty mold.
In May you may have noticed the road looking wet in places under the poplar trees which was the honeydew. I had always parked my truck in the same place under a couple of poplar trees for five years now and had never had a problem before. One day I woke up and it looked like someone had poured a layer of sap all over the top of my truck. It coated the windshield and everything. The black mold came along afterward. It took a degreaser and a couple of hours at the car wash to finally get it off of my truck.
The males emerge from the scale in June as tiny, two winged individuals. They mate with the females and then die. This explains why the honeydew dropping has calmed down a little bit but it’s still coming down. Females give birth in August to what are called the crawler stage of the life cycle. Each female may produce up to 3,000 crawlers that move around in the tree.
In this stage the crawler can be transferred to another tree by wind or catching a ride on songbirds. If they don’t find a suitable host, or poplar tree, they will usually die in three days. Once a poplar tree is found, the crawlers insert their piercing-sucking mouthparts into the vascular system underneath the bark and begin to feed.
They only feed for a short time during this stage of the life cycle before molting into the waxy covered scale to over winter and start the whole process over again next spring. It’s during the spring when they feed heavily that they cause stress to especially the younger, smaller trees since they’re removing crucial plant fluid. There are several enemies and other predators that attack this pest but are seldom capable of managing a heavy infestation.
Thankfully, everything in nature is cyclic and populations tend to go up and down. The other insect that’s doing damage to the foliage of the poplar trees is the yellow poplar weevil. Yellow poplar weevils are small black snout beetles that have also been called flying ticks because they are about the same size and color. The adults chew crescent shape shot holes in the leaves and how you can tell their presence. The weevils feed until mid-July and then they hide in the leaf litter and remain inactive until spring.
Oftentimes outbreaks of yellow poplar weevils are sporadic in that trees in one valley may be affected whereas trees in the next valley over aren’t. They can cause stress to the trees but the result of their damage is usually minimal. Frosts during the late spring help keep the population in check by killing the adult and larvae.
It will be interesting to keep an eye on the poplar trees into next year to see if there’s any mortality as a result of this year’s heavy outbreak since they are getting attacked by two insects. If you were wondering what was going on with the shabby looking poplar trees this year you can blame it on the tuliptree scale and yellow poplar weevils.