While not completely certain about the cause of the declines, Virginia Department of Forestry and Cooperative Extension officials believe they may be connected to an infestation of previously unnoticed insects.
Although the yellow, or tulip, poplar has very few insect and disease problems due to chemicals contained in its leaves, bark and wood, VDOF senior area forester Bill Miller said there are some exceptions.
“Two notable exceptions to this rule, however, are native insects known as the tulip tree scale and the poplar weevil,” Miller said. “The scale is a tiny sap-sucking insect that produces a brown, waxy covering that looks something like a tortoise shell. Populations of these insects can occasionally reach such high levels in the forest that they can damage and even kill poplar trees, although this is rarely seen in Southwest Virginia.”
The poplar weevil, Miller said, is a defoliating insect that is common to Southwest Virginia, Lee, Scott and Wise counties. The weevil is also found in adjacent counties in Kentucky and Tennessee.
In most of these counties, as many as six to eight poplar weevil outbreaks have been documented over the last 25 years by VDOF forest health personnel.
While spring feeding by individual weevils causes little damage to new leaves — other than a small brown patch — outbreaks involving millions of weevils can result in poplars being heavily defoliated.
These outbreaks are often patchy in nature but can span large areas, officials said.
Recently, some landowners across Lee, Wise and Scott counties have seen such poplar decline over the last few years and have expressed concerns to local foresters.
According to the Scott County Extension Office, isolated areas of decline can be found around the Natural Tunnel area in Scott County and from Ewing to Dryden in Lee County.
The areas of defoliation usually range anywhere from a half acre to several acres in size, although several locations have exhibited decline spanning 50 to 100 acres.
“There appears to be no obvious reason why these declines show up where they do, other than the fact that these areas were known to have several weevil outbreaks during past years,” VDOF forest health specialist Chris Asaro said. “Because tree decline is a gradual process that can take many years and be caused by multiple agents, it’s always difficult to pinpoint exact causes.
“But knowing that the weevil is a major presence in the region and one of the few insects that can feed on poplar, it seems very possible that it is playing a prominent role in these decline events.”
Because the trees are probably not dead, the wood could still be sound enough to be salvaged, officials said.
The yellow poplar is considered one of the most abundant and resilient hardwood trees in Virginia. It is also an important timber species in far Southwest Virginia due to its rapid growth, straight trunk and wood properties, VDOF officials said.
The tree also does particularly well in moist cove habitats and fertile soils common to the lower slopes and valleys of the southern Appalachians, officials said.
Forest landowners concerned about their poplar stands should consult their local Virginia Department of Forestry office for further information and advice.