Distinctive white marks on their heads give baldfaced hornets their name. Photo: Johnny N. Dell, Bugwood
It’s been a good year for baldfaced hornets. Many people have contacted me to report their grey papery nests in trees or hanging from the eaves of their homes.
So, are they good guys or bad guys? Do they need to be controlled? It’s a matter of making an informed choice. So here are the facts.
First, baldfaced hornets aren’t hornets at all. They’re black and white yellowjackets that nest in trees, shrubs, and on buildings. Since they kill many harmful pests, they are considered beneficial.
It’s only when their nests are nearby that they pose a potential threat from stinging. Left alone, they tend to be benign. They usually only sting to defend their nests. I’ve had several walk up and down my arm peaceably.
The white marks on their head earn them their “baldfaced” moniker. Workers measure about three-quarters of an inch long and queens are slightly larger.
In the spring, overwintering queens emerge from tree bark, stumps, logs, rock piles, and other protected spots. Each queen builds a small nest with a few brood cells, lays eggs, and gathers insects to feed the growing workers.
When those workers become adults, they take over the housekeeping duties, building and taking care of the nest, foraging for food, and tending to the growing family from eggs laid by the queen.
Baldfaced hornets’ football-shaped nest is an engineering marvel. To that first handful of paper cells, workers add layer upon layer of hexagonal combs similar to those of the honey bee.
It is a common misconception that all mosquitoes feed on blood. Unlike ticks, which require a bloodmeal to progress from one life stage to the next, mosquitoes largely rely on plants throughout their life cycle. Only adult female mosquitoes bloodfeed in order to acquire protein to lay eggs; otherwise, adult mosquitoes feed on plant sugars to gain energy for flying, mating, and metabolic demands. Once those eggs are laid in standing water, mosquitoes hatch as aquatic larvae that eat microbes supported by decaying organic matter, called detritus. This detritus often comprises plant parts like leaves, seeds, and fruits that fall from nearby vegetation into larval habitat. The next life stage before adulthood, the pupa, is non-feeding, so the amount and quality of detritus mosquitoes receive as larvae are crucial. Just like we tell children to drink their milk to grow up to be big and strong, mosquito larvae with plentiful and nutritious resources can reach adulthood faster, grow larger, live longer, and lay more eggs as adults. Yikes!
Leaves may vary drastically in their chemical composition, affecting which microbes they support, how quickly they decay, and what beneficial nutrients or toxic secondary metabolites they release as they decompose. Researchers are still working to identify important traits in a detritus resource base, but a trend has emerged: non-native plants seem to support non-native mosquito populations better than native plants do.
Native species, whether plant, animal, or microbe, are those that occur naturally in the region where they evolved. Over the course of time, these species have adapted to the local environment and developed relationships with other native species. Conversely, non-native species are those which evolved in a different region from that in which they can now be found. A small percent of non-native species establish and spread rapidly throughout their new home, with the potential to harm human well-being, environmental health, and/or economic prosperity. Some researchers speculate that non-native species share certain traits that make them successful invaders. The Asian tiger mosquito, Aedes albopictus, is one of the most successful invaders of the past century, arriving in Texas from Asia in 1985 and reaching us here in Maryland by 1987. The tiger mosquito is capable of spreading viruses such as dengue, West Nile, and zika; it is also a nuisance vector, driving people indoors with its aggressive daytime biting behavior.
An Asian tiger mosquito (Aedes albopictus) larva [left] and female adult [right]. Photo: Ary Farajollahi, Bugwood.org Continue reading →
The best kind of green thumb…a perch for a Luna Moth. Photo: M. Talabac
Q: I found a huge green moth on my front door! What is it, and do they visit flowers so I can attract more?
A: This beauty is one of my favorite insects…a Luna Moth, a native species and one of our largest North American moths. Their green color, rare among our local moths and butterflies, ranges from medium to pale celery-green or a pistachio ice cream hue. Their long hindwing tails and eyespots combine to give them a look resembling an elephant’s face. I imagine those eyes give foraging birds a moment’s pause, though the bigger predator for these moths is probably bats since they are night-flying.
Adults have vestigial mouthparts and cannot feed, so flowers won’t attract them. They rely on body fat stored from the caterpillar stage (which grows gleefully big) to fuel their brief search for mates and egg-laying sites. You can support breeding populations by caring for caterpillar host plants, which for Luna include hickory, walnut, sweet gum, and white oak, among other trees.
Avoiding pesticide use in home landscapes is of critical importance, though communities that are subjected to aerial forest sprays for Spongy Moth or other pests may, unfortunately, experience population declines, even though such treatments are relatively targeted. Gardeners attempting to rid a tree of nuisance aphids, Spotted Lanternfly, scale, and other insects could inadvertently affect harmless species like these moths in the process. Remember that any tree roots infiltrating a lawn that is treated with a systemic insecticide (like for grubs) might absorb some of those chemicals and transport them into the canopy.
Light pollution is another big detriment to these and many night-active insects (like fireflies), with home landscape accent lighting, porch lights, street lights, and other sources of illumination interfering with their ability to navigate at night.
For anyone curious about moths, I encourage you to participate in or follow National Moth Week, a citizen science project taking place the last full week of July each year. Check out what visits your porch lights, flowers (there are some day-flying nectar-feeding moths), and see if you can ID the caterpillars that wander the landscape or chew holes in tree, shrub, or perennial leaves. So few are truly pests so you won’t need to worry about managing them; leave them to fulfill their part in the food web of our local ecosystem.
You can also sign up to learn about nighttime pollinators and how to support them in the upcoming free webinar: “Working the Night Shift: Pollination After Dark,” taking place on August 3 from noon to 1:30 pm.
By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.
Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round.
In this month’s episode of The Garden Thyme Podcast, we are talking about two common household pests: ants and termites. We often get questions about these two pests. While both live in colonies and can enter our homes, they have very different lifecycles and social structures. Some of them are nuisance pests, while others can cause damage to our homes.
We also have our:
Native Plant of the Month – Wild mint (Mentha arvensis)– ~ 24:25
Bug of the Month – Golden-backed snipe fly ~ ~28:30
The Garden Thyme Podcast is brought to you by the University of Maryland Extension. Hosts are Mikaela Boley, Senior Agent Associate (Talbot County) for Horticulture; Rachel Rhodes, Agent Associate for Horticulture (Queen Anne’s County); and Emily Zobel, Senior Agent Associate for Agriculture (Dorchester County).
Asian Tiger Mosquito. Photo: Ary Farajollahi, Bugwood.jpg
Mosquito season is (slap) upon us. Fortunately, there are (slap) many things you can do to minimize their (slap) nuisance.
Only females bite, so that’s the good news. Only half of them are out to get you.
Mosquitoes need water. They have four stages of development – egg, larva, pupa & adult – (complete metamorphosis for you geeks) and spend their larval and pupal stages in water.
Mosquito larvae hang upside down in the water and get air from a siphon tube. They wiggle when disturbed, mildly entertaining. Pupae look like commas and are called “tumblers” for the way they move.
After a snack (cue ominous Dracula music,) adult females lay their eggs on water. They can do this in as little as a teaspoon of water. Yes, a teaspoon. So eliminating standing water is crucial to control.
Water collects in obvious places like ponds and marshy areas. But it also pools in birdbaths, rain barrels, wading pools, pot saucers, gutters, and downspouts.
You also find mosquito-attracting water in used tires, plastic toys, recycling bins, tarps, grill covers, tree stumps, wading pools, pet dishes, and more.
So, eliminate water traps such as used tires. Screen rain barrels. Twice a week add fresh water to birdbaths and pet dishes and remove any water you find any of the other hiding spots above.
Clear debris from gutters and downspouts and cover the opening to corrugated drain pipe on downspouts with pantyhose held with a rubber band. Very sexy.
If you have a pond or rain barrel, use mosquito dunks, donut-shaped disks containing Bti, an organic biological control. Getting goldfish or mosquito fish (Gambusia) that eat mosquito larvae also is helpful.
Part two of mosquito control – after managing standing water – is personal protection. Mosquitoes find us very tasty so we need to know how to keep them at bay.
Most mosquitoes are active from dusk to dawn, so avoiding activity then is helpful. If you’re having a party or just want to sit on your deck, hook up a fan. The breeze is a serious deterrent.
For more protection, use repellants with DEET, picaridin, Icaridin, or oil of lemon eucalyptus. Wear long pants and sleeves since mosquitoes can bite through clothing. Clothing treated with the insecticide permethrin also deters mosquitoes.
Citronella candles, mosquito lamps, and butane-powered repellers aren’t very effective. Bug zappers kill few mosquitoes but many beneficial insects. And mosquito traps actually attract more mosquitoes.
Everyone’s instinct is to spray, spray, spray, but sprays kill predators and pollinators. You’re killing the good guys that help control many harmful pests.
Birds, bats, frogs, lizards, and dragonflies eat mosquitoes. So create good habitat for them by planting native plants, adding birdhouses and birdbaths, and avoiding chemicals.
To keep mosquitoes from invading your home, use tight-fitting screens on windows and doors and replace tears quickly.
The newest bad actor is the tiger mosquito which is active throughout the day. Bigger, badder, and with striped legs, it is a brute.
Be a skeeter beater. Seek out and eliminate standing water. Dress for protection. And practice active avoidance. Combine multiple controls for less slapping and more smiling.
By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension. This article was previously published by Herald-Mail Media. Read more by Annette.
Imagine the perfect summer day. What are you doing? For most people reading this blog, I’m guessing it involves being outside in your yard—maybe working in the garden, reading in a hammock, or sharing an al fresco lunch with family and friends. Sounds idyllic! But, then, the dreaded whine, the too-slow slap, and the ensuing itchy bite left behind by a mosquito. On repeat. It’s enough to drive many of us indoors, even on the perfect summer day.
More mature readers may think to themselves “I don’t remember it being this bad when I was younger!” and you’re probably right. You are almost certainly being bitten by a relatively new invader called the Asian tiger mosquito (scientific name: Aedes albopictus) that was first observed in Maryland in 1987 and has adapted to thrive in urban and suburban areas. Named for its striped legs, the tiger mosquito is capable of spreading viruses such as dengue, West Nile, and zika. It is aggressive, and, unlike most other mosquito species that feed at dawn and dusk, it seeks its blood meals during the day.
An Asian tiger mosquito (Aedes albopictus) larva [left] and female adult [right]. Photo credit: Ary Farajollahi, Bugwood.org
One survey found that the tiger mosquito’s biting rate is 10 times higher than what Virginia residents were able to tolerate. In another, 61% of residents surveyed in the Washington, DC area reported that being bothered by mosquitoes caused them to change their behavior to avoid taking walks, gardening, or participating in other outdoor activities. So, if you’re hiding inside on a sunny day, you’re not alone.
What to do? Avoid them? Deter them with citronella candles? Swat them one by one?
The most effective action you can take to reduce the mosquito population in your yard is to cut them off at the source—their larval habitat. After a protein-packed blood meal, female mosquitoes lay their eggs in water-holding containers. Once flooded, the eggs hatch into an aquatic larval stage; after roughly a week of feeding on microbes in the water, the larvae develop into pupae and then emerge in a couple of days as the adults you know and hate.
If you’re committed and persistent in eradicating places for mosquitoes to breed, a practice known as source reduction, you can reduce the number of mosquitoes in your yard. For successful source reduction, follow the four “E”s:
Eliminate
The first step is to eliminate every water-holding container from your yard that you can. Throw away pieces of trash. Drill holes in the bottom of the tire swing. Store kids’ toys, wheelbarrows, watering cans, etc. in a shed or garage, under a deck, or on a covered porch. The tiger mosquito can breed in as little as one teaspoon of water, so be thorough in your search!
Exchange
Next, consider exchanging containers that cannot be eliminated. Swap an open rain barrel for one with a lid. Substitute corrugated extension spouts with splash guards, open chutes, or flat extensions at a downward angle. Trade lawn chairs with solid seats that allow water to pool with slatted chairs that do not.
Empty
Be vigilant about regularly emptying any water-holding containers that cannot be eliminated or exchanged—ideally twice but at least once weekly. Replace the water in pet bowls. Dump out flower pot saucers. Shake out tarps.
Emaciate
This one sounds weird, but stay with me. There may be standing water on your property that would be undesirable or impossible to eliminate, exchange, or empty, such as a bird bath, pond, or structural element (a common one I see in urban environments is the remainder of metal fence posts that were sawed off rather than torn out after the removal of a chain-link fence). For these sources, you can emaciate mosquito larvae with Bacillus thuringiensis subspecies israelensis, or bti for short; when larvae eat this normally soil-dwelling bacterium, the toxins released by the bti paralyze their gut, causing them to starve to death. A brutal way to go for mosquito, black fly, or fungus gnat larvae but harmless to other insects, pets, and people. Bti can be purchased online or at most garden centers—a common brand to look for is Mosquito Dunk®.
Adhering to the four “E”s of source reduction can help prevent mosquito infestations on your property so you can enjoy those perfect summer days!
But what about mosquitoes on your neighbors’ properties?
Bonus action: Encourage
Encourage your neighbors to practice source reduction as well! Devoted source reduction in your own yard may not protect you if your neighbors are harboring abundant larval habitat. Tiger mosquitoes don’t tend to fly far, especially when resources are plentiful, but depending on how close you live to your neighbors, they may cross into your yard. Local mosquito populations are best controlled when the entire community participates.
Bonus bonus action: Entice
Want to do even more? Perhaps you’re feeling a little vengeful from summers past? Entice mosquitoes into a larval habitat trap. You can purchase or DIY something called a Gravid Aedes Trap, or GAT for short, that targets species in the Aedes genus, like the tiger mosquito. Standing water inside the trap encourages gravid, or pregnant, female mosquitoes to lay their eggs, but a mesh cover above the water prevents any mosquitoes in the next generation from escaping. The clear sides around the dark funnel top confuse the females who enter, making it likely they’ll be stuck, too—especially if you add sticky paper or cover the inner walls with cooking spray or oil to coat their wings. This makes the GAT a double-kill trap, affecting two mosquito generations at once. Just be sure to check the trap regularly to ensure that water is present but below the netting. University Park, MD created a community-wide mosquito control program in their town and created a helpful PDF document for GAT deployment.
Gravid Aedes Traps. Image credit: Biogents
By eliminating, exchanging, and emptying water-holding containers in your yard and emaciating mosquitoes in remaining larval habitat (plus encouraging your neighbors and enticing egg-laying female mosquitoes!), you can once again enjoy your summer outside. Easy, brEEzy, bEautiful, mosquito sourE rEduction. Happy mosquito hunting!
By Sarah Rothman, PhD Candidate in the University of Maryland Department of Environmental Science and Technology. Sarah is studying the relationship between non-native mosquitoes and plants across socioeconomic gradients. Learn about the EcoHealth lab at www.leisnham.org. After graduating, she hopes to work in the public sector conducting ecological research and outreach on topics related to invasive species, restoration, and environmental justice.
Roseslug sawfly damage on rose. Photo: UME/Ask an Expert
Q: My rose leaves have white spots and holes in them. What causes this and how do I treat it? Is there a natural remedy that does not involve powerful chemicals?
Answer: It looks like your rose has symptoms of sawfly damage. Check the undersides of the leaves and look for tiny green larvae that look like little worms or caterpillars. These are the juvenile stage of an insect called roseslug sawfly.
Roseslug sawflies are neither slugs nor flies. They belong to the same order of insects as wasps, bees, and ants (Hymenoptera). Adult female sawflies use their unique ovipositor (egg-laying part) to saw a small slit in a leaf or stem where they lay their eggs. When the eggs hatch, the larvae feed on the leaf surfaces and cause an etched or scratched appearance. Some roseslug larvae chew through the leaves entirely. Damaged foliage turns brown and curls up as the season progresses.
In Maryland, there are three species of roseslug sawflies that cause damage to roses: the bristly roseslug sawfly, the roseslug sawfly, and the curled rose sawfly. Most of the feeding activity on roses in Maryland is seen in May and June, but some sawfly larvae can continue to be active until fall. Other insects, such as Japanese beetles, also cause chewing damage on rose foliage (typically in June-July).
Browning and leaf curling from rose slug sawfly damage. Photo: UME/ Ask an Expert
The best way to manage roseslug sawflies without chemicals is to monitor your plant(s) for damage symptoms early in the season (start looking in May) and manually remove any larvae (squish them or pick them off and discard them). A forceful spray of water from a garden hose targeted toward the leaf undersides can also get them off. Once dislodged, they cannot climb back up into the plant. Horticultural oil and Spinosad also work well against sawflies. Read and follow the product label instructions for the correct application procedures.
Two sawfly larvae are present on the undersides of rose leaves. Photo: C. Carignan
Predatory insects and birds help to manage sawfly populations naturally. Adding more flowering plant diversity to your landscape will provide food and habitat for beneficial animals that in turn help to reduce future pest problems.
Rose shrubs usually recover from sawfly damage eventually, as long as they are not struggling from other ailments or stressors such as drought.
Rosie Defoliators | Bug of the Week, University of Maryland, Department of Entomology
By Christa Carignan, Maryland Certified Professional Horticulturist, Coordinator, University of Maryland Extension Home & Garden Information Center. Read more by Christa.
Have a plant or insect question? University of Maryland Extension’s experts have answers! Send your questions and photos to Ask Extension.
