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Businesses used to think of pest problems as seasonal. Ants in spring. Mosquitoes in summer. Rodents in fall. That calendar is not gone, but it is less reliable.

Warmer winters, longer warm seasons, heavier rain events, and sudden temperature swings are changing pest behavior in ways that directly affect commercial properties. For businesses, that shift creates more pressure on sanitation, customer experience, employee safety, compliance, and reputation. The CDC has noted that longer summers, milder winters, and extreme weather are helping mosquitoes, ticks, and rodents expand into new areas, and that the pathogens they carry are following.

Pest control can no longer be treated as a reaction after something shows up, which is why at Catseye the goal is to get in front of the issue. Climate shifts are making prevention more important, and businesses that ignore that reality are taking on more risk than they realize.

Why Climate Shifts Matter for Commercial Pest Control

Warmer Winters Help More Pests Survive

Hard freezes naturally reduce pest populations. When winters are milder, more insects and rodents survive into spring and do so with a head start. Businesses tend to see more overwintering pests, earlier spring activity, larger breeding populations, and more frequent sightings from employees and customers.

A mild winter may feel like a break for your heating bill. It can also be a head start for pests.

Longer Warm Seasons Create Longer Pest Seasons

Warmer average temperatures extend the active season for mosquitoes, ticks, flies, ants, cockroaches, and stored-product pests. Outdoor dining areas face longer mosquito and fly pressure. Warehouses and food facilities deal with more insect activity later into the year. Hotels and multifamily properties field more complaints. The EPA has tied warmer conditions specifically to longer seasons for disease vectors including mosquitoes, ticks, and fleas, pests that are now showing up in areas where they were historically rare.

The Biggest Climate-Driven Pest Pressures Businesses Are Facing

Rodents Moving Indoors After Weather Extremes

Heavy rain, flooding, drought, and sudden cold snaps can push rodents out of their normal nesting areas and toward commercial buildings. Restaurants, grocery stores, food processing facilities, warehouses, hospitals, schools, and multifamily properties are all at elevated risk. Rodents follow food, warmth, water, and shelter. Dumpster areas, loading docks, wall voids, and utility penetrations are common entry points, and small gaps become big liabilities fast.

A restaurant does not need a full-scale rodent infestation to lose customer trust. One mouse sighting near a dining area can turn into photos, reviews, and health department attention.

Mosquitoes Expanding Their Season and Range

Changing rainfall patterns create more standing water and more breeding opportunities. Outdoor seating becomes less comfortable. Employees working outside face more exposure. Hospitality, recreation, golf, property management, and event venues may see more complaints. Drainage inspections, stormwater management, and proactive monitoring around outdoor guest areas are all becoming more important, not just in summer, but across a longer window of the year.

Beyond Rodents and Mosquitoes

Climate-driven pressure is not limited to the obvious pests. Ticks have expanded well beyond wooded residential areas into landscaped commercial campuses, school grounds, golf courses, and healthcare properties. Cockroaches and flies thrive in heat and humidity, and for food facilities and restaurants, they are not just a nuisance but a direct threat to inspections, food safety, and trust. Shifts in rainfall patterns also drive moisture pests like ants, silverfish, centipedes, and earwigs indoors, particularly after heavy storms or extended drought. The common thread is unpredictability: pest activity is becoming harder to anticipate using old seasonal assumptions.

Why Reactive Pest Control Is No Longer Enough

Reactive pest control means waiting until the problem is visible. Climate-driven pressure makes that approach risky.

By the time pests are seen, they may already be established. A single sighting can damage customer confidence. Commercial properties have more entry points than homes, and constant foot traffic, deliveries, landscaping, and food sources create ongoing pressure. For regulated industries such as restaurants, food processing, healthcare, senior living, and schools, inspections and documentation matter as much as treatment, and in some cases disinfection services may be warranted before a facility can return to normal operations. Health and safety exposure, reputation damage, compliance violations, and operational disruptions are all downstream consequences of a pest plan that starts after something is spotted.

If your pest plan starts after someone sees a pest, your business is already behind.

What Businesses Should Do Differently Now

Start with an honest review of your property’s pest vulnerabilities under current conditions, not old assumptions. Entry points, moisture issues, drainage, landscaping edges, dumpster zones, loading docks, and storage areas should all be on that list.

Tighten Exclusion and Environmental Controls

Exclusion is one of the most important commercial prevention steps. Sealing gaps and cracks, installing door sweeps and dock seals, screening vents, and addressing roofline openings all reduce the opportunities pests have to get inside. Moisture control matters just as much. Fix leaks, improve drainage, clean gutters, address standing water, and watch condensation in food and storage areas. Climate shifts often mean more intense rain events followed by drought stress, and both conditions push pests toward buildings.

Build a Year-Round Commercial Pest Management Plan

Sanitation and pest management are not separate functions. Dumpster cleaning, trash pickup frequency, food debris control, spill response, and storage rotation all directly affect pest pressure. Pair strong sanitation with regular inspections, seasonal risk planning, monitoring devices, trend reporting, and fast response when activity is detected. The Global Food Safety Initiative has noted that rising temperatures and longer seasons create more favorable conditions for pests in food processing and storage, and that documentation and prevention planning are the appropriate response.

The Bottom Line

Climate shifts are not creating a brand-new pest problem. They are making the existing problem harder to predict, easier to miss, and more expensive to ignore. Businesses that treat pest control as a seasonal checklist will fall behind. Those that inspect, exclude, monitor, and plan year-round will be better protected.

If your property is seeing more pest activity, more customer complaints, or more pressure around your building, it may be time to rethink your approach. Catseye’s commercial pest control programs are built for exactly this kind of ongoing, prevention-first protection. Reach out to schedule a facility inspection and build a plan before pests become a public problem.

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Inertia is a property whereby objects in motion tend to stay in motion and objects at rest tend to stay at rest. One of the finest examples of inertia is the inexorable annual disappearance of evergreens down the gullets of bagworms. Bagworms are objects in motion. Sometimes, as I witnessed recently, property owners are too often objects at rest. Here’s why. Last week I stopped by my favorite coffee shop and as I sipped, I noticed a peculiar aberration in a lovely planting of arborvitaes lining the parking lot. Smack in the middle of the row of emerald beauties was one decidedly ugly brown rogue. Victim of too much mulch, too little water, or girdling plastic around the root ball, perhaps? Nah, a closer examination revealed hundreds of tiny bagworm caterpillars whose busy jaws were shredding foliage, transforming the evergreen to ever brown.  

Populations of bagworms seem to be on the rise again in the DMV. Whether it’s favorable weather, a dearth of natural enemies, climate change, or just bad luck, bagworms have returned in force to many places in our region. Bagworms have been reported to feed on more than 100 species of plants in our area. They are most damaging to evergreens such as juniper, spruce, arborvitae, pine, and Leyland cypress; however, they will consume a wide variety of deciduous trees and shrubs with equal gusto. Complete defoliation of an evergreen such as pine, arborvitae, or spruce can kill the tree in a single season. Deciduous trees such as sycamore or maple are much more tolerant of this abuse, as they may be able to produce new leaves if defoliation has not occurred too late in the season. If you have bagworms on your plants, especially evergreens, you may be in deep trouble as you read this story. But if your conifers are not yet knocking on heaven’s door, this is a good time to save them for years to come. 

Oh no, what’s up with this brown arborvitae? Hundreds of tiny bagworm caterpillars, that’s what. Some are dining on foliage, others are adding silk to their bag from silk glands on their mouth, others are relocating their shelter, and some are just hiding from the camera. In another month or so, tiny caterpillars will be more than an inch long, performing aerial acrobatics as they move about. Left unchecked, this is what bagworms will do to an evergreen tree, sorrow and death may await these evergreens.

The bagworm is named for its curious habit of carrying about its refuge, a bag woven of silk and plant parts. Back in May, eggs of bagworms completed their development inside overwintered bags dangling on trees. Tiny caterpillars hatched and emerged from the bottom of the bag. Some stayed put on their natal plant while others ballooned on silken threads to other plants nearby. Caterpillars construct and enlarge their bags as they grow. People sometimes confuse the bagworm’s bag with a plant part such as a pinecone. This makes detection a problem. However, a closer look at the bag, especially on a warm summer’s day, often reveals the head and legs of the caterpillar as it moves about eating leaves or needles. By late summer, larvae complete their development, securely attach their bags to twigs with silken threads, and pupate within the bags.

After a few weeks, the male bagworm, a black moth with clear wings, emerges from his bag and flies to find a mate. The female, a maggot-like wingless sack of eggs, releases a pheromone, a sex attractant, to lure the male to her bag. After attracting her mate, the female bagworm does not emerge to greet him. Instead, she remains in her bag, hidden from her mate during the conjugal visit. After mating, she lays from several hundred to more than 1,000 eggs in the bag, and then, like a tragic Greek heroine, she dies, leaving her eggs behind to hatch next spring.  

If bagworms are no longer actively feeding or moving, the damage is done and applying insect sprays is useless. So, don’t do that. However, if large bagworms are still active, it is not too late to nip next year’s incipient bagworm explosion in the bud. Removing bags by hand can be very effective in halting an outbreak, so put on a pair of gloves, grab a garbage bag, and start pickin’. As you remove the bagworms, be sure to collect them in a container or bag, seal it tightly, and dispose of them. Do not simply toss bagworms on the ground or in the driveway. Displaced bagworms are relentless and they will return, crawl up your tree, and resume their feast. If offending bagworms have completed development in late summer or early autumn, you can dramatically reduce the population next year by removing the egg-laden bags now. 

Returning to the present, what can be done now to reduce the carnage? Large numbers of tiny bagworms may be too numerous to be picked by hand. If the caterpillars are small, you may be able to control them with a thorough application of an insecticide such as biologically based, Bacillus thuringiensis (Bt). Some formulations of Bt are listed by the Organic Material Research Institute (OMRI) as safe to use in the production of organic foods you purchase in the market. Bt works well on small caterpillars. If caterpillars are larger, an insecticide containing the OMRI listed, reduced risk active ingredient called spinosad works well to control bagworms. 

Remember, as we approach the middle through the end of August in the DMV, bagworms will have completed their development and sprays on foliage will not kill pupae, adults, or eggs. Physical removal is your best alternative from late summer until May of next year. Sometimes natural enemies including birds, wasps, and voracious predatory bugs kill enough bagworms to quell an outbreak, but I would not count on it. Take stock of your bagworm situation, make a plan, and snap to it! 

Acknowledgements 

Information for this Bug of the Week came from “Managing Insects and Mites on Woody Landscape Plants: An IPM Approach” by J. A. Davidson and M. J. Raupp. For more information on bagworms check out the following website: https://extension.umd.edu/resource/bagworms-trees-and-shrubs/

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Commercial property owners are used to thinking about insurance in terms of storms, fires, water backup, or equipment failure. Pest damage is different. It can build quietly for months, stay hidden inside walls and ceiling voids, and surface at the worst possible time — during a sale, an inspection, or an active claim. When it does, it rarely arrives alone. Pest activity overlaps with moisture intrusion, structural deterioration, insulation loss, contaminated inventory, and electrical hazards, and that overlap is exactly what makes pest damage so difficult to resolve during the claims process.

This post is not legal or insurance advice. It is a practical look at why pest-related damage complicates commercial insurance claims and what property owners and managers can do to stay ahead of it.

Why Pest Damage Creates Problems During Insurance Claims

Most commercial property policies are built around sudden, accidental losses. Pest damage rarely fits that model. Termites work inside wall cavities for years before anyone notices. Rodents nest above ceiling tiles through an entire winter. Birds establish colonies in rooflines and HVAC equipment across multiple seasons. By the time damage is visible, the timeline is hard to establish, the cause of loss is hard to isolate, and the maintenance history becomes part of the conversation.

This creates three problems that adjusters and property owners regularly run into:

The damage is gradual, not sudden. Many commercial policies treat long-term deterioration differently from sudden accidental loss. Pest activity that developed over time may raise questions about whether the damage was preventable.

The cause is hard to isolate. Pest damage frequently overlaps with other issues. Carpenter ants excavate galleries in wood that has already been softened by moisture. Rodents enter through gaps created by settling or storm damage. Raccoons exploit rooflines that were already compromised. Separating pest damage from water intrusion, mold, or structural deterioration can require multiple inspections and competing assessments.

The maintenance record becomes relevant. Visible signs of long-term pest activity — droppings, rub marks, nesting material, gnaw marks, insect frass, recurring moisture — can raise questions about whether the property was maintained appropriately before the damage occurred.

Common Types of Pest Damage in Commercial Properties

Rodent Damage

Mice and rats gnaw through wiring, insulation, pipes, and stored materials. Droppings and urine contaminate food inventory and storage areas, and odors from nesting inside wall voids can affect health inspections and tenant relationships. For restaurants, warehouses, multifamily buildings, and healthcare facilities, rodent activity can trigger temporary closures well beyond what physical repairs alone require. Properties with active rodent pressure should disinfect surfaces as part of any remediation plan.

Termite and Wood-Destroying Insect Damage

Termite damage is often concealed until it is severe. Subterranean termites can damage structural framing and support members over years without visible surface signs, making the timeline of infestation difficult to prove after the fact — a direct problem during claims.

Carpenter Ant Damage

Carpenter ants do not consume wood like termites, but they excavate galleries in wood softened by moisture. In commercial buildings with roof leaks, plumbing issues, or condensation problems, carpenter ant activity can compound structural damage and complicate efforts to determine which problem came first.

Bird, Bat, and Wildlife Damage

Bird and bat droppings cause façade staining, vent blockages, slip hazards, and contamination. Squirrels and raccoons damage rooflines, soffits, and attic insulation, and create entry holes that allow water intrusion. What starts as a nuisance wildlife problem can quickly become expensive repairs if entry points go uncorrected.

How Pest Damage Affects the Claims Process

Beyond the physical damage itself, pest activity creates friction at each stage of a commercial insurance claim.

Adjusters may need more time and documentation when damage involves hidden pest activity. Walls, attics, crawl spaces, mechanical rooms, and rooflines may require additional inspection before the scope of loss is clear, which delays assessment and extends the timeline.

Policy language varies, and many commercial property policies treat pest, vermin, insect, and maintenance-related damage differently from sudden accidental losses. Property owners should speak with their insurance professional about how their specific policy handles these situations — this post does not offer legal or coverage advice.

For restaurants, food processors, hospitality properties, healthcare facilities, and multifamily buildings, pest activity can affect operations even when physical damage appears limited. Temporary closures, discarded inventory, failed inspections, tenant complaints, and sanitation work can all factor into business interruption considerations.

Insurance carriers may also request pest inspection reports, service history, maintenance records, photos, repair invoices, moisture assessments, and proof that corrective action was taken.

Warning Signs Commercial Properties Should Document

Catching pest activity early — and documenting it — matters both for remediation and for claims readiness. Property managers should record:

• Gnaw marks on wiring, pipes, framing, or stored goods
• Droppings in storage rooms, utility spaces, kitchens, or ceiling voids
• Damaged insulation or nesting material
• Insect frass, wings, sawdust-like material, or mud tubes
• Soft, hollow-sounding, or blistered wood
• Grease marks along walls or baseboards
• Damaged roof vents, soffits, fascia, or exterior penetrations
• Bird nesting near HVAC units, loading docks, signage, or roof edges
• Unexplained odors
• Recurring moisture, leaks, or standing water

Early documentation helps establish when activity was first observed, separates new damage from pre-existing conditions, and demonstrates that the property owner responded responsibly.

What Commercial Property Owners Can Do Now

When pest-related damage is discovered, the immediate priorities are documentation, notification, and professional assessment. Photograph and video the damage before any cleanup or repairs begin. Notify your insurance carrier or broker promptly. Schedule a professional pest inspection to identify the pest, likely entry points, and extent of activity. Keep all reports, invoices, and service records in a claim-ready file.

Longer term, prevention is best. Routine pest inspections create a documented timeline of activity and corrective action. Exclusion work — sealing or correcting access points — reduces repeat entry for rodents, wildlife, and birds. Paired with sanitation improvements, moisture correction, and structural repairs, ongoing pest management gives commercial property owners a defensible record that the building was actively maintained.

How Catseye Supports Commercial Properties

Catseye provides commercial pest inspections, rodent control and exclusion, wildlife exclusion, bird pressure assessments, termite and wood-destroying insect inspections, disinfection services, and ongoing pest management programs for commercial properties across New England.

Professional inspection and documentation will not guarantee claim approval, but they give property owners a clearer picture of the damage, documented corrective action, and better records before a claim ever becomes necessary.

Concerned about pest activity at your commercial property? Schedule a Catseye commercial pest inspection to identify activity, entry points, and prevention steps before small problems become expensive claims.

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Every now and then, for reasons known or unknown, some of our native insects go wild and reach astounding numbers, creating some concerns and damage. Earlier this year we met an outbreak of native caterpillars defoliating hundreds of acres of native hardwood trees in Western Maryland. In June of 2021, you may recall a report of thousands of periodical cicadas that appeared on the beaches of the Chesapeake Bay. Well, earlier this month an avid beach comber reported “billions” of robust tiny beetles lining the western shore of the Chesapeake for more than a mile near Calvert Cliffs, MD. Some were dead but many were alive, clinging to beach wrack and each other along the shoreline. These waterlogged insects were Yellow Poplar Weevils (YPW), a native insect that reached outbreak levels in 2025 in nurseries and landscapes here in the DMV. To learn a bit more about this strange event, we spoke to Professor Paula Shrewsbury of the University of Maryland, an expert in the management of pests of ornamental plants. Her comments are excerpts from weekly reports prepared for the Green Industries of the Mid-Atlantic region in 2025 and 2026.

“These types of “wash ups” are often related to winds and water currents, and the weevil’s (YPW) ability to float. Environmental conditions came together this week that resulted in so many weevils on the shoreline. In looking into this, there have been other reports of similar wash up phenomena of YPW in MD and VA over the years.”

Piles of small black beetles are composed of thousands of Yellow Poplar Weevils that washed up on the shores of Chesapeake Bay in June. Tiny jaws on the snout of the beetle damage leaves on several kinds of ornamental plants. Watch as one of these tiny terrors moves along stems and leaves of a yellow poplar, a.k.a. tulip tree, and a closeup of the small beetle on a magnolia leaf. Recently, it has been raising havoc in commercial nurseries and landscapes in the DMV. Images by Katherine Nelson, Michael Raupp, and Paula Shrewsbury, video by Marie Rojas and Michael Raupp.

“Monday, June 9th, [2025] I was contacted by two nurseries in Frederick County, MD describing extremely high numbers of native yellow poplar weevil (YPW) adults, Odontopus calceatus (Coleoptera: Curculionidae), on magnolias and they were causing significant damage to the newer foliage. This is a new pest to me and as I searched for information, I found reports of YPW in recent days from VA, DC, and OH. This weevil is known to sporadically outbreak. In an article from Penn State Extension on YPW published in 2015, they reported extremely high densities of YPW in PA and the mid-Atlantic and stated that the level of outbreak then had not been seen since 1968.

Host plants of YPW include magnolias, sassafras, tulip tree (yellow poplar) and sweet bay.  YPW’s life cycle consists of one generation per year and YPW activity is reported to occur from mid-late May through mid-July. YPW overwinter as adult weevils in the leaf litter under their host plants. In the spring / early summer as the weather warms, adult weevils emerge and feed on the buds and newer foliage of their hosts with their chewing mouthparts, mate, and lay eggs in the mid-vein on the lower leaf surface. Newly hatched larvae chew into the leaf tissue and feed as leaf miners. Multiple leaf miners can be found in a single leaf. Larvae pupate within the leaf mine.

Adults emerge and use their chewing mouthparts on the end of their long “snout” to feed on leaves (usually newer, tender leaf tissue), stems, and flowers resulting in crescent-shaped (more or less) brown etching in the tissue. Feeding results in leaf curling and distortion, and premature leaf drop. YPW are reported to cause the most damage during this time. Around mid-July or so YPW adults enter a period of aestivation (summer inactivity) and enter the leaf litter, where they overwinter. Areas that are under drought conditions seem to suffer from YPW more.

What else do we know? As of now, I have only seen and had reports of adult weevils being active and causing damage, and only on Magnolia in two nurseries. There are high populations of adults, and they are causing lots of damage, and the damage happens quickly. Monitor hosts of YPW now! Magnolia species / cultivars appear to vary in the amount of YPW adult activity and damage they are receiving. It appears that varieties that still have tender newer foliage are getting hit worse than those with foliage more hardened off. Weevil adults are being seen on non-plant structures (ex. plant poles / signs) and other plants (ex. dogwoods near the magnolias – but I did not see damage on the dogwoods as of Monday).”

Scientists report that following years of outbreaks, YPW populations decline dramatically. Upticks of predators and several species of parasitic wasps and late spring frosts are implicated in these population collapses.

Of the many comments that have appeared in response to the appearance of YPW, people have wondered if YPW is “the lesser of two weevils” and noted that these weevils are now “all washed up.”

Acknowledgements

Sincere thanks to Dr. Shrewsbury for allowing us to reprint information from her reports and for sharing images of the YPW. Thanks also to Marie Rojas for contributing her images and videos of the weevil. Thanks to Katherine Nelson for providing the inspiration for this episode and sharing wonderful images of waterlogged weevils she spotted on the shores of the Chesapeake.

For more information about the Yellow Poplar Weevil life cycle, ecology, damage, and management, please click the following links:

https://www.psu.edu/news/agricultural-sciences/story/yellow-poplar-weevil-makes-presence-known-pennsylvania-mid-atlantic

https://bygl.osu.edu/node/2486

https://content.ces.ncsu.edu/yellow-poplar-weevil

https://www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/odontopus-calceatus  

https://www.fs.usda.gov/foresthealth/docs/fidls/FIDL-125-YellowPoplarWeevil.pdf

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Last week while tidying up a basement walkout, a colleague discovered a gorgeous and very pregnant black widow spider attempting to escape her broom. Fortunately, my colleague did not freak out and punish the spider. After glamming for the camera for a while, the widow casually strolled into a capture jar held by the dauntless homeowner. This beauty, named Lola, enjoyed a photo shoot and will soon be joining her cousins as a full-fledged member of the Insect Petting Zoo at the University of Maryland. Another name for these creepily beautiful arachnids is ‘hourglass spiders’ due to the bright red hourglass-shaped mark on the underside of the abdomen of some species.

What a surprise! A gorgeous female black widow spider making a basement walkout her home. After glamming for the camera for a few moments, she readily investigated a capture jar held in the steady hands of stout-hearted Dr. Shrewsbury. This beautiful spider, now christened Lola, will join more than a hundred of her arthropod kin in the insect petting zoo at the University of Maryland, College Park.

The black widow is arguably one of the most interesting characters in Marvel Comics pantheon of heroes and one of the most dangerous groups of spiders in the United States. The widow’s venom contains a very potent neurotoxin, alpha-latrotoxin. A measure of the toxicity of alpha-latrotoxin, an LD50 of 20 – 40 micrograms per kilogram of body weight, puts it right up with some very deadly snakes. Fortunately, widows do not always inject venom when they bite and even if they do, the quantity is exceedingly tiny. There are five species of widows in the United States, three native species and two non-native species, and they are found in every state except Alaska, but mostly in southern and western states. Widows spin loose webs in protected places such as under logs, stones, or boards, and in angles of windows and shutters. They are commonly found in dumps and in rural areas such as farms and plant nurseries where they frequent barns, sheds, outhouses, and equipment storage areas.

Like most spiders, the fangs of the black widow are used to capture prey and the venom injected through the fangs helps subdue the victim. Also like most spiders, black widows are not aggressive and bite humans only when harassed or accidentally pinched or grabbed. The bite of the widow is usually painless or felt as a pinprick. The more serious symptoms of the bite first appear within 30 minutes to two hours after the bite. These include back pain and muscle cramps that can be severe, rigid muscles in the abdomen, nausea, vomiting, sweating, restlessness and, in some cases, elevated blood pressure. These symptoms are most severe after 3 hours but may persist for many days.

A previous member of the Insect Petting Zoo at the University of Maryland, a gorgeous black widow named Scarlett, glides back to protect her unhatched brood in the egg case after carefully inspecting her gossamer web.

Black widows do not discriminate among their human victims, and envenomation can occur in people of any age. In the U.S., between 2,000 and 2,500 bites are reported each year with the greatest number of bites in children. Lethal bites are exceedingly rare and only three deaths have been reported worldwide in medical literature. Complications associated with black widow bites are greatest for the very young, the very old, and people with cardiovascular disease. The death rate from documented bites occurs in far less than 1% of reported cases. Rapid treatment with antivenin and other medications can greatly reduce the severity and duration of symptoms associated with a black widow bite. Unlike other spider bites, such as those from the brown recluse, there is no terrifying necrotic skin lesion at the site of the bite.

To avoid bites of black widows and other spiders, wear gloves and long-sleeved shirts when you work in areas that might house spiders. Try to reduce clutter such as brush piles, vegetation, trash, and rubbish where spiders might hide outdoors. Do the same for furniture, sports equipment, and clothes indoors. Carefully inspect these items before moving them and store them in containers or sealed bags whenever possible. If you are bitten by a spider, try to collect the spider whether alive and intact or dead and pulverized. This will help a trained arachnologist identify the offending arthropod and help direct the course of therapy. If you or your child is bitten by a black widow spider, seek medical attention immediately. Finally, despite its name, the black widow does not always eat her mate. In fact, in some species of widows the male brings food to his mate. What a guy!

References

Special thanks to courageous Dr. Shrewsbury who discovered and captured Lola, the gorgeous black widow spider featured in this episode. The great spider books ‘Biology of Spiders’ by Rainer Foelix, “Black widow spider” by Steve Jacobs, and the fact filled article “The Treatment of Black Widow Spider Envenomation with Antivenin Latrodectus mactans: A Case Series” by Steven R. Offerman, G. Patrick Daubert, and Richard F. Clark served as references for this episode.

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The arrival of scorching temperatures in the DMV provides an excellent reason to head for the hills for a cool hike. Forays to the Appalachian Trail and Catoctin Mountain Park in Maryland provide the perfect locations to escape summer’s heat and provide an opportunity to visit some of Mother Nature’s most interesting recyclers of organic compounds. Millipedes are detritivores, creatures that consume organic matter including mosses, algae, and decaying vegetation carpeting the forest floor. Millipedes belong to the subphylum of the arthropods called Myriapoda, those with “many feet”.

 Do they really have a thousand feet? Nah, they don’t really have feet, but they do have legs and the record number of legs for a millipede is somewhere around 750. However, most millipedes have fewer than 400 legs. Young millipedes have only a few body segments, each of which bears a single pair of legs. As millipedes molt and grow, body segments with two pairs of legs each are added. Millipedes live two to seven years and can produce hundreds of offspring during their lifetime. Millipedes do not bite or sting, but several species secrete noxious chemicals from glands lining the margins of their body.

On a stony forest trail, we happened upon two remarkable members of the millipede clan. The first was Narceus americanus-annularis, one of the true giants of the millipede world in North America. Its otherwise dull brown body was accented with beet-red legs and red bands encircling the body at each segment. These colors might serve as a warning of noxious defenses ready to be unleashed by the millipede. Unable to resist handling Narceus earned me an acrid reward of benzoquinones, foul smelling droplets of the millipede’s chemical defense.

The many legs of the millipede work in a wavelike fashion to propel these timid grazers as they search for organic matter to eat. Watch as it munches moss on the surface of a boulder. Nearby, another millipede dashes across a forest trail. Bright contrasting colors may warn predators not to mess with these chemically defended detritivores. Defensive compounds released by this millipede smell like almond extract. You might not want to handle this one.

 A bit further down a trail, we encountered one of the flat-backed millipedes, perhaps Apheloria virginiensis. Blending in with the forest floor was clearly not this creature’s game as it sported lemon-yellow legs, alternating bands of yellow and black along the back, and pink-hewed margins. When plucked from ground, the smell of almonds filled the air and brought me back to my days of organic chemistry when benzaldehyde was the unknown compound on the lab practical. Benzaldehyde is the compound found in bitter almonds and is used as a flavoring in almond extract. Ah, but benzaldehyde is not the only compound found in Apheloria’s defensive secretion. The other more lethal moiety released by the millipede is hydrogen cyanide. Glad no one sniffed this millipede too deeply.

 Millipedes, important recyclers of organic matter, are well-protected by potent toxins and irritants that could make a bird, lizard, or toad think twice about messing around with these denizens of the forest floor. As temperatures soar into the 90s, consider taking a hike on one of the beautiful shady forests in the DMV and be on the lookout for busy millipedes, recyclers of organic materials. 

 Acknowledgements

 We thank the intrepid hikers of Maryland’s highlands, Erin, Ellie, Abby, Maggie, Jo, Paula, Laurie, and Kevin for providing inspiration for this episode. Thomas Eisner’s books “The Love of Insects” and “Secret Weapons” were used as resources for this story.

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On a recent visit to one of my favorite relatives, while enjoying the fragrances and beauty of roses in their garden, I noticed some unnerving injury to the foliage of several plants. The injury took the form of a type of herbivore mischief known as etching. Etching results when small insects use their jaws to remove soft tissues between the vascular bundles that crisscross leaves, leaving behind veins and a layer of epidermal tissue. This produces a windowpane, or skeletonized, effect, and these withered leaves often appear like someone took a blowtorch to them. A wide variety of beetles and caterpillars are the usual suspects when skeletonization is afoot. However, in this bed of roses, sawflies larvae were the culprits.

 Sawflies are unusual insects, an ancient branch of the bee and wasp clan. Unlike the larvae of bees and wasps that make their living consuming nectar and pollen or the flesh and blood of insects, the larvae of most sawflies are plant feeders. At first glance, sawfly larvae look like small caterpillars with slender bodies and distinct heads. Upon microscopic inspection, you can see that the posterior segments of the sawfly’s body bear small sucker-like appendages called prolegs. Prolegs adorn the abdominal segments of plant-eating moth and butterfly larvae as well. But moth and butterfly caterpillars never bear more than five pairs of prolegs. Most sawfly larvae have six or more pairs. Another difference between these look-alikes is the presence or absence of small fishhook-like structures called crochets on the prolegs. Caterpillars have them, sawfly larvae do not. Crochets help caterpillars hold onto the smooth surface of a plant leaf.

Dappled in sunshine, a pair of roseslug sawfly larvae strip nutritious tissue from a leaf blade, leaving only veins and a thin layer of epidermis behind. Through the lens of the microscope, you can get up close and personal with a bristly roselug as it gobbles leaf tissue. As leaves desiccate later in summer, they crinkle and turn brown as if toasted by a blowtorch.

 After spending the winter as juveniles in the soil beneath rose plants, in spring when foliage returns the roseslug sawfly completes its development, and small wasp-like adults fly to leaves where they deposit eggs with an egg-laying appendage called an ovipositor. The ovipositor has teeth like a saw’s blade, hence the name sawfly. Eggs hatch and the larvae proceed to pillage rose leaves through May and June. Fortunately, only one generation of these scalawags occurs each year, but in some years, they may be abundant enough that by the end of June they can make roses look like they have been assaulted by a flame thrower.

 In addition to skeletonization, several leaves had large chunks of leaf tissue missing from the edges of the blade. This defoliation was the handiwork of the curled rose sawfly, an insidious leaf-munching machine that is beautifully camouflaged. When not actively feeding along the margin of a rose leaf, it is curled on the underside of a leaf or on a bud where it blends in cryptically with plant. After several days of hide-and-go-eat, the entire leaf may be reduced to nothing but a mid-vein. When its development is complete, the larva bores into the twig, where it pupates. Later a small wasp will emerge, mate, lay eggs and initiate a second seasonal generation.

 In May and June, I regularly inspect my roses for the telltale signs of skeletonization and defoliation. If sawflies are common enough to create problems for my roses, I simply squish the little buggers between my fingers or pluck them off and toss them in the lawn to become a feast for the ground beetles or lightning bug larvae lurking in the thatch. Several environmentally friendly insecticides listed by the Organic Materials Review Institute (OMRI) with active ingredients including insecticidal soap and spinosad work well against these sawflies. OMRI listed products are used for production of fruits and vegetables marketed as organic, and when insecticide applications are necessary, I try to select from the OMRI list whenever possible. As with all insecticides, always read the label carefully and follow precautions, including those safeguarding bees and other pollinators that might be on your roses. Strong directed streams of water are also reported to dislodge sawfly larvae from plants. If you have roses, be on the lookout for these rose-eating rascals. 

 References

 We thank Carole for providing the roses and sawflies that served as the inspiration for this episode. Two marvelous references, “Insects that feed on trees and shrubs” by W. T. Johnson and H. H. Lyon, and “Managing insects and mites on woody plants: An IPM approach” by J.A. Davidson and M. J. Raupp were consulted to prepare this episode.

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A home doesn’t need a gaping hole in the roof to have a serious pest problem. Many attic infestations begin with a gap no wider than your finger, hidden along a soffit edge, tucked behind a gutter line, or opened around an air conditioning line sealed years ago with foam that is now crumbling.

New England homes face freeze-thaw cycles, heavy snow loads, driving rain, and swings between summer humidity and winter cold. Fascia boards rot, soffits warp, vents loosen, and small gaps become highways for rodents, squirrels, bats, birds, and stinging insects.

Most homeowners never inspect the upper reaches of their homes until they hear scratching noises in the attic or watch wasps disappear into cracks under the roofline. By then, pests have been moving freely through the structure for weeks or maybe even months.

Why Aging Rooflines Become Pest Entry Points

Materials expand in summer heat, contract in winter cold, and endure snow, ice, rain, and wind over years. This cycle loosens fasteners, cracks sealants, warps boards, and opens gaps that pest can easily manipulate.

Fascia boards absorb moisture and soften. Soffits separate from mounting points. Flashing around chimneys pulls away. Trim boards crack. Sealants harden and fall out. Even well-maintained homes develop small separations along roof edges or vent openings that may be invisible from the ground.

Mice can squeeze through gaps the width of a dime, and bats can enter through cracks no thicker than a pencil. Squirrels investigate any opening and chew it wider if the wood is soft. These entry points sit high on the structure, often hidden behind gutters or tucked under roof overhangs, where homeowners rarely look.

Common Roofline Vulnerabilities That Attract Pests

Loose or Damaged Fascia Boards: Fascia boards support gutters along the roof edge. When they absorb water from clogged gutters or ice dams, the wood softens and boards separate from rafters. Gaps form where fascia meets soffit or where rotted sections remain unrepaired. Squirrels, mice, rats, wasps, and carpenter ants use these openings to their advantage.

Soffit Gaps and Vent Openings: Soffits close the underside of roof overhangs and include ventilation panels. Over time, panels warp, separate, or become damaged by wind or woodpeckers. If screening behind vented soffits is missing or damaged, pests pass can through easily. Even small displacement creates enough space for mice or bats to invade.

Chimney and Roof Intersections: Flashing pulls away from chimneys, mortar joints crack, and gaps form where brick meets wood framing. Squirrels and raccoons enter through flashing gaps or damaged mortar. Bats use cracks in masonry while birds nest in uncapped chimneys.

Dormers, Roof Valleys, and Additions: Each dormer introduces new roof edges, valleys, flashing, and trim. Roof valleys collect water and debris, which speeds up rot. Older additions may have mismatched materials and imperfect flashing.

Gutter Lines and Ice Damage: Clogged gutters hold water against fascia boards and roof edges, softening wood and attracting carpenter ants. Ice dams lift shingles, pull gutters away, and force water under roofing materials. When ice melts, it leaves warped boards and gaps.

How HVAC Penetrations Create Hidden Pest Access

HVAC systems, dryer vents, and utility lines all require holes through exterior walls or roofs. These penetrations get sealed during installation, but sealants break down faster than most homeowners realize. Sun exposure, temperature swings, and moisture cause foam to crumble, caulk to crack, and putty to fall out. What started as a proper seal five or ten years ago may now be a wide-open entry point ten feet off the ground where nobody ever looks.

Gaps Around Refrigerant Lines and Conduit: AC systems and mini-splits require refrigerant lines to pass through exterior walls. Penetrations get sealed with expanding foam, caulk, or putty that breaks down over time. Mice exploit these gaps, following lines into wall voids, basements, or attics.

Dryer Vents, Exhaust Vents, and Bathroom Fans: If vent covers are missing, damaged, or poorly fitted, pests can get inside. Birds build nests inside dryer vents, blocking airflow and creating fire hazards. Rodents use vent openings when screens break. Wasps build nests around exterior vent covers and may establish colonies inside if vents lead to wall voids.

Roof-Mounted HVAC Equipment and Vent Stacks: Larger homes and commercial buildings may have rooftop equipment requiring penetrations for ductwork, conduit, and vent stacks. Flashing and sealant around these penetrations loosen with age. On flat roofs, gaps around ductwork may go unnoticed for years.

Poorly Sealed Utility Chases: Electrical conduit, cable lines, and gas pipes often pass through walls or roof edges in groups. Sealant fails and gaps form. Once rodents or insects find their way into a utility chase, they move freely through wall voids and attic spaces to cause problems.

Which Pests Use Rooflines and HVAC Gaps?

Different pests target different vulnerabilities. Rodents prefer ground-level gaps but will climb to exploit roof openings if food and shelter are available. Squirrels go straight for roof edges and attic vents. Bats look for high, hidden cracks. Insects scout any cavity that offers shelter from weather and predators. Knowing which pests use which entry points helps you prioritize inspections and repairs.

Mice and Rats: Rodents enter through openings as small as a quarter-inch. They nest in insulation, chew on wiring, and contaminate areas with droppings. Scratching and scurrying sounds at night are common signs of these pests.

Squirrels: Squirrels enter through roof edges, soffits, and attic vents. They are active during the day and chew through softened wood to enlarge openings. Female squirrels seek attics to raise their young in the spring and fall.

Bats: Bats enter through very small gaps around dormers, vents, and chimneys. Bat exclusion requires careful timing and compliance with legal guidelines. Never seal suspected bat entry points without a professional inspection. For proper exclusion methods, see our guide on removing bats from your attic.

Birds: Birds nest in roof vents, soffits, and gutters. Nesting material blocks airflow and attracts secondary pests. Droppings damage roofing materials and create health concerns.

Wasps, Hornets, and Yellowjackets: These insects build nests in soffits, wall voids, and attic spaces. They enter through small gaps in trim or vent covers. Activity peaks in late summer and early fall when colonies reach their largest size.

Carpenter Ants and Moisture-Associated Insects: Aging rooflines create moisture problems. Water-damaged wood attracts carpenter ants that excavate wood to build nests. Their presence signals underlying moisture issues.

Why This Is Especially Common in New England

Many New England homes are older with complex rooflines, additions, dormers, and chimneys. Seasonal weather speeds up deterioration as materials expand in summer heat and contract in winter cold. Snow, ice, and spring rain drive moisture into joints and seams.

Pest pressure shifts with seasons. For homeowners throughout New England, rodents and squirrels become more noticeable in fall and winter as they seek shelter. Wasps, ants, bats, birds, and other pests become more active around rooflines in spring and summer during nesting seasons.

Signs Your Roofline or HVAC Opening Has a Pest Problem

Most pest problems start quietly. You might hear faint scratching one night and dismiss it. A few weeks later, the sounds get louder or happen during the day. By the time droppings appear in the attic or you spot a squirrel climbing into the soffit, pests have usually been active for a while. Catching the warning signs early prevents bigger problems and more expensive repairs.

• Scratching, scurrying, or chewing sounds in the attic or walls
• Droppings in attic insulation or basement areas
• Grease marks near openings
• Damaged soffits, fascia, or vent screens
• Chewed insulation or wiring
• Birds or squirrels repeatedly visiting the same roof area
• Wasps entering gaps under shingles or soffits
• Musty or ammonia-like odors
• Loose vent covers or failing sealant around HVAC lines
• Stains on ceilings near attic spaces

Why DIY Sealing Can Make Pest Problems Worse

Sealing gaps without understanding what’s using them can trap animals inside. Trapped pests create odor problems and chew new escape routes through walls or ceilings. Bat exclusion must follow legal timing guidelines. Expanding foam fails because rodents chew through it and squirrels pull it out. Professional rodent exclusion services use heavy-gauge mesh and reinforced barriers designed for roof pest control.

How Professional Pest Exclusion Works

Professional roof pest control starts with identifying all active and potential entry points around rooflines, soffits, vents, chimneys, and HVAC penetrations. After pest removal, technicians seal gaps with materials that withstand gnawing and weather, including reinforced screening, metal flashing, and pest-resistant barriers. Attic repair services handle contaminated insulation when needed. Year-round protection plans include seasonal inspections to catch new vulnerabilities early.

Prevention Tips for New England Homeowners

Inspect rooflines each spring and fall. Keep gutters clean. Replace rotted fascia or soffit boards promptly. Trim tree branches away from the roof. Check vent covers after storms. Look for gaps around AC lines and pipes. Never seal suspected bat openings without an inspection.

Schedule Your Roof Pest Control Inspection

Aging rooflines and HVAC penetrations create hidden entry points pests exploit year-round. If you’re hearing scratching in the attic, noticing damaged soffits or vent screens, or dealing with recurring pest activity, Catseye Pest Control can help. Schedule your roofline and attic pest inspection today.

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In last week’s episode, we met cankerworms pillaging hardwood forests on the western face of South Mountain in Maryland. A decade earlier, we witnessed a similar cankerworm outbreak further south on the mountain range at Weverton cliffs. During that eruption we arrived early enough in the predator – prey cycle to observe awesome Calosoma beetles putting a beat-down on cankerworm caterpillars, one of their favorite snacks. Let’s revisit that episode to learn about these fierce and marvelous predators. 

“While ogling fall cankerworms as they shredded leaves of maples and oaks, I was surprised to see many carabid ground beetles foraging in the canopies of trees. Now, as the name implies, ground beetles usually have their six tiny feet firmly planted on the ground where they provide great service hunting and eating a wide variety of soft-bodied pests, including rootworms, cutworms, and slugs, that plague our agricultural crops and backyard gardens. However, part of the clan, members of the genus Calosoma, are famous for their arboreal skills, ascending trees to deliver murder and mayhem to caterpillars.  

One of the largest members of Calosoma is a drop-dead gorgeous beetle that goes by the name the fiery searcher or caterpillar hunter. For an insect, it is big, often attaining a length of an inch and a half. My first encounter with the fiery searcher was disconcerting. Back in the days of Maryland’s gypsy moth plague, I lifted a burlap band on a tree to count gypsy moth caterpillars and out popped a fiery searcher that landed on my shirt. When I captured the assailant, it unleashed a potent chemical defense that lingered on my fingers for several hours. Calosoma beetles are notorious for producing potent defenses including methacrylic acid and salicylaldehyde.  

Despite their common name ground beetles, members of the genus Calosoma can be found hunting caterpillars in treetops. They are part of Mother Nature’s hit squad that helps to bring an end to important pests like cankerworms. There is murder and mayhem afoot in the tree canopy. Watch as this time-lapse video captures a Calosoma beetle using powerful jaws to crush and pulverize its cankerworm victim. This little cankerworm disappeared down the gullet of the beetle in less than five minutes. After finishing off one cankerworm, off it goes to find another. Arboreal ground beetles are awesome predators.

Although I did not see fiery searchers during my visit to cankerworm central, I was delighted to see scads of its smaller cousin Calosoma wilcoxi devouring cankerworms in the treetops and feasting on unlucky inchworms that had fallen on the ground. These beautiful hunters live two to three years or possibly longer. Romance happens in the month of June when mating pairs are active. Eggs are deposited in the soil in early summer, and they hatch in roughly a week. According to published accounts, larvae are ground dwellers where they consume a wide variety of prey, including gypsy moth and eastern tent caterpillars. Adult beetles hunt both day and night and in addition to fall cankerworms, on the menu are spring cankerworms, gypsy moth larvae, and eastern tent caterpillars.  

Several literature accounts associate the presence of Calosoma wilcoxi with the demise of cankerworms and the end of their devastating outbreaks in natural forest settings. One must wonder why some locations in Maryland, Virginia, and North Carolina have eruptions of cankerworms lasting years or even decades. One answer to this mystery may lie in the degradation of habitat that often accompanies the process of urbanization. In a recent review of responses of ground beetle communities to urbanization around the world, we discovered large forest dwelling ground beetles like our friend Calosoma wilcoxi to be the most severely impacted when forests become cities. Despite the presence of seemingly adequate prey for adults in some urban areas, other factors such as overwintering sites, food for larvae, cover for larvae and adults, and favorable thermal regimes may be inadequate or missing in developed areas. For our beleaguered oaks, maples, birches, and other hardwoods, let’s hope that Mother Nature’s hit squad of predators and parasites can bring the cankerworm catastrophe to a quick conclusion.” 

A quick conclusion to the cankerworm catastrophe is what we hope for. Unfortunately, history tells us that outbreaks of native caterpillars often last for several years in our natural forests. This year’s caterpillar outbreak, coupled with ongoing severe to extreme drought in parts of the DMV and extreme heat associated with El Niño this year, spell trouble for our native hardwoods. We will revisit South Mountain next spring to see how our oaks and maples fared. Fingers crossed the news will be good.      

To learn more about caterpillar outbreaks in the DMV this year please visit this link: https://news.maryland.gov/mda/press-release/2026/05/18/public-notice-maryland-department-of-agriculture-monitoring-frost-damage-and-caterpillar-outbreaks-in-western-maryland-hardwood-trees/

References 

Interesting accounts including “The genus Calosoma including studies of seasonal histories, habits, and economic importance of American species north of Mexico of several introduced species” by A. F. Burgess and C. W. Collins, “A meta-analysis of the effects of urbanization on ground beetle communities” by H. Martinson and M. Raupp, “Calosoma wilcoxi, A ground beetle” by T. Erwin, and “Defensive Secretions in Three Ground-Beetle Species (Insecta: Coleoptera: Carabidae)” by Sonja LečićSrećko, ĆurčićSrećko, and ĆurčićLjubodragVujisić,  were used to prepare this episode.

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Last week while driving eastbound on Route 70 from western Maryland, I was amazed to see a broad swath of leafless trees stretching for miles on the western face of South Mountain. A quick hike up the side of the mountain confirmed the handiwork of thousands of caterpillars whose hungry jaws completely stripped oaks, hickories, maples, birch, and assorted other trees and shrubs of their foliage. A recent post at the Maryland Department of Agriculture’s website implicated a late season frost as one cause of woes for trees here in the DMV, however the real culprits of severe defoliation in Allegany, Garrett, and Washington counties were several species of native caterpillars collectively known as cankerworms and loopers. A decade ago, in a previous episode we visited fall cankerworms as they laid waste to oak trees along the Appalachian Trail near Weverton, Maryland. By the time I scaled the slopes of South Mountain last week, denuded trees were all that remained of the caterpillar onslaught save a few shredded leaves of small saplings and a few tall trees. Cankerworm caterpillars had finished feeding and moved to the soil to continue their metamorphosis.

So, what are these culprits called cankerworms? The name cankerworm derives from the shredded, cankered mess caterpillars make of plant leaves as they feed. Another name for cankerworms is inchworms. Here’s why.  Fall cankerworms have multiple legs on their front and rear ends. By alternating their grasp between front and rear legs and arching their body into a loop, they move along twigs and leaves as if measuring the world an inch at a time. They belong to a family called Geometridae, literally “land measurer” in Greek.

Cankerworms move by alternating the positions of front legs and hind legs called prolegs. It’s easy to see why another name for cankerworm is inchworm.  Early in the season cankerworms make holes in leaves and nibble at the margins. Later in the defoliation cycle only shredded leaves, leaf veins, or no leaves may remain.

This season of evil began in early spring when eggs deposited on branches last fall and winter hatched near the time that buds of hardwood trees sprang to life, creating a new crop of tender leaves. Tiny caterpillars fed on young leaves, creating a type of damage called shot hole damage. Shot hole damage is so named because infested leaves appear to have been blasted with a shotgun. As the caterpillars grow and develop, they remove ever–increasing amounts of leaf tissue. These green or brown caterpillars dangle from leaves on a strand of silk when disturbed. Their larvae reach phenomenal numbers in some locations and years, and devastate many shade trees such as oaks, maples, elms, and lindens. The Maryland Department of Agriculture has reported periodic outbreaks in Anne Arundel, Calvert, Charles, and St. Mary’s counties, in addition to the ones in Frederick and Washington counties in 2015 and again in 2020. After pillaging trees in spring, caterpillars move to protected locations on the forest floor to pupate. Later in the season as autumn turns to winter, fall cankerworms complete their development and adults emerge from the earth.

These strange moths are remarkable in that the females have lost their ability to fly. Many entomologists believe that the cankerworm has found a clever way to leave more offspring behind. By shifting bodily resources from equipment needed for flight, such as wings and muscles to flap them, and redirecting these resources to the production of eggs, the female cankerworm may be able to lay more eggs, thereby bringing more little caterpillars into the world and ultimately enhancing her lineage’s odds for survival. Wingless females move from the soil and climb vertical structures such as trees and buildings. Shortly after sunset, on milder winter nights, female moths release a chemical signal called a sex pheromone to attract a mate. Fall cankerworm males have functional wings and are good fliers. The male moths track the pheromone to its source and the chilly moths mate. After this interlude, females climb high into the trees and place eggs on the bark of twigs and branches. Females do not live to see their offspring. Unlike other species of moths that have tubular mouthparts used to sip nectar, the female fall cankerworm lacks functional mouthparts. She cannot feed and shortly after depositing her eggs, she dies.

In addition to the fall cankerworm, other members of their clan, such as the spring cankerworm, half-winged geometer, and linden looper have flightless females. A close relative of the fall cankerworm called the winter moth has been making most unwelcome appearances in New England where it is wreaking havoc on many deciduous trees. Members of the nefarious cankerworms clan make their presence known up and down the east coast where communities and individual homeowners scramble to deal with this problem. Many insecticides are available to thwart this pest, including the microbial insecticide Bacillus thuriengienses (Bt) and reduced risk products containing spinosad, as well as many more potent insecticides. However, the sheer magnitude of the outbreaks makes control difficult and widespread applications of insecticides may harm non-target organisms. Some citizens believe they found relief by placing barrier bands around the trunks of trees. These bands snare female moths as they attempt to reach the treetops to lay eggs. In one published account on the use of barrier bands, the authors trapped thousands of moths but defoliation in the treetops was unaffected.

While short term eruptions of cankerworms are thought to have little lasting effects on trees, long term outbreaks of cankerworms in cities including Charlotte, North Carolina, have increased mortality of forest and shade trees. Trees in urban areas may face increased risk of death when cankerworms defoliate them due to inherent stress related to water deprivation, elevated temperatures, pollutants, and infestations of other debilitating insects and diseases. Fortunately, in natural settings Mother Nature’s checks and balances usually bring outbreaks of cankerworms to an end after a few years. Next week, we will meet two awesome predators that help put a beat-down on cankerworms and their kin.

References

The great references “Caterpillars of Eastern North America: A Guide to Identification and Natural History” by David L. Wagner, “The Effect of Sticky Bands on Cankerworm Abundance and Defoliation in Urban Trees” by Chanthammavong Noukoun, Gregory Bryant, and Steven D. Frank, and “Fall Cankerworm. Forest insect and disease leaflet 182. USDA Forest Service, Pacific Northwest Region (R6), Portland, OR” by W. M. Ciesla and C. Asaro were consulted to prepare this article. To learn more about caterpillar outbreaks in the DMV this year please visit this link:  https://news.maryland.gov/mda/press-release/2026/05/18/public-notice-maryland-department-of-agriculture-monitoring-frost-damage-and-caterpillar-outbreaks-in-western-maryland-hardwood-trees/

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