See No Weevil
Many people in Loudoun County have been noticing signs of something a little unusual lately: Some may have noticed some unusual damage to their trees, particularly on magnolias, or perhaps yellow poplars (also known as tulip trees), and sassafras. Others are alarmed to see large numbers of an unfamiliar insect.
While I have yet to see any declaration from an official source or noted authority, the Ashburn area seems to be experiencing what entomologists refer to as an outbreak of Odontopus calceatus, the Yellow Poplar Weevil.
Not Your Pantry Pest: Identifying the Yellow Poplar Weevil
First, let's clear up some confusion. Some may be familiar with weevil infestations that can occur inside a home, particularly in flour, rice, and other stored dry goods in the pantry. There are two other species of weevil known to cause such an infestation: Sitophilus granarius (granary weevil) and Sitophilus oryzae (rice weevil).
Pantry Weevils (e.g., Rice Weevil, Granary Weevil):
Typically found indoors, in kitchens and pantries.
Feed on stored grains, cereals, and other dried foods.
Small, reddish-brown to black, with a distinct snout and often a more elongated body.
The Yellow Poplar Weevil is different, and will not proliferate in your pantry.
Yellow Poplar Weevils (Odontopus calceatus):
Found outdoors, specifically on certain trees.
Small (about 2/16 to 1/8 inch long), oval-shaped, and can range in color from black to brownish-black to reddish-brown, with deeply grooved wing covers.
They have a snout, characteristic of weevils, but are distinctly different from the weevils you'd find in your food. They are often mistaken for "flying ticks" due to their size and shape.
When disturbed, they often "play dead" by folding their legs.
The Damage They Inflict: A Closer Look at Affected Plants
The Yellow Poplar Weevil has a specific taste for trees in the Magnoliaceae family, which includes the Yellow Poplar (Liriodendron tulipifera) and various Magnolia species. They also feed on Sassafras (Sassafras albidum), despite it belonging to a different plant family.
The damage you're observing is caused by both the adult weevils and their larvae:
Adult Feeding: Overwintered adult weevils emerge in the spring and begin feeding on emerging buds and young leaves. Their chewing creates characteristic crescent-shaped or "rice-grain-sized" holes in the leaves. As the leaves expand, these small holes can become larger and more ragged, sometimes giving the foliage a "swiss cheese" appearance. A second generation of adults emerges in mid-summer, often causing even more widespread damage. Heavy feeding can lead to leaves wilting, turning brown, and even dropping prematurely, making trees look "burned" or as if they've suffered from drought.
Larval Feeding (Leafminers): Female weevils lay their eggs in the midribs of leaves. Once hatched, the small, legless, grub-like larvae burrow inside the leaves, feeding between the upper and lower surfaces. This creates unsightly blotch mines, which are discolored, irregular patches on the leaves. While larval mines are noticeable, the more significant and widespread damage is typically from the adult weevils.
Risk Assessment for Your Trees
It's natural to be concerned when you see your trees suffering from an insect infestation. However, for most established trees in Northern Virginia, the Yellow Poplar Weevil is primarily an aesthetic nuisance rather than a fatal threat.
Established Trees: Older, healthy yellow poplars, magnolias, and sassafras trees are generally resilient. While a year or two of heavy feeding may make them look unsightly, they typically have enough energy reserves to withstand the defoliation and will put out new leaves. The damage is largely cosmetic and does not usually impact the tree's overall health or longevity.
Newly Planted Trees: This is where homeowners should be more vigilant. Young or recently planted magnolias, yellow poplars, and sassafras trees are more vulnerable to severe infestations. Their root systems are still developing, and heavy leaf damage can significantly stress them, potentially impacting their growth and establishment. If you have newly planted trees and notice extensive weevil activity, intervention may be warranted.
What to Do (and Not Do)
In most cases, the best course of action for established trees is to simply tolerate the damage. Here's why:
Natural Controls: Yellow Poplar Weevil populations tend to fluctuate. During outbreak years, natural predators and parasites often build up their numbers and help bring the weevil population back into balance in subsequent years. Applying broad-spectrum insecticides can harm these beneficial insects, disrupting the natural control cycle.
Aesthetic vs. Health: Remember, the damage is primarily cosmetic for mature trees. The trees will usually recover on their own.
However, if you have newly planted or particularly stressed trees, or if the infestation is exceptionally severe on an established tree you're particularly concerned about, here are some considerations:
Monitor: Keep a close eye on your susceptible trees, especially in spring when buds swell and new leaves emerge, and again in mid-summer when the second generation of adults appears.
Hand-picking: For smaller trees, you can hand-pick adult weevils and drop them into a bucket of soapy water.
Horticultural Oils or Insecticidal Soaps: These can be effective against adult weevils if applied thoroughly, but timing is crucial as they only work on contact. They need to be applied when the weevils are actively feeding.
Systemic Insecticides: For severe infestations on young, vulnerable trees, systemic insecticides (absorbed by the plant) can offer more long-lasting protection against both adults and larvae. These are typically applied in the spring. Always read and follow product labels carefully, and consider consulting with a certified arborist or your local Virginia Cooperative Extension office before applying any chemical treatments. They can provide guidance on appropriate products and application timing for your specific situation.
While the sight of weevil-damaged leaves can be disheartening, understanding the life cycle and impact of the Yellow Poplar Weevil can help Northern Virginia homeowners make informed decisions for their landscape. In most cases, a little patience and a healthy dose of natural control will see your trees through these periodic outbreaks.
