It’s a “murder hornet”! Or is it?

Don’t reach for the shotgun yet.  There are many wasps that look similar to the Asian giant hornets you’ve seen on TV. Images courtesy Hanna Royals (USDA APHIS PPQ ITP), specimens provided by Colorado State University’s C.P. Gillette Museum.

If you’ve never heard of “murder hornets,” more accurately called Asian giant hornets, Vespa mandarinia, you’ve probably been living on the space station for the past month.  And at the risk of stirring up a hornet’s nest, I thought it worthwhile to remind us all June is the month of the cicada killer wasp.  This is another common large wasp likely to be mistaken for the Asian giant hornet haunting news feeds this spring.

Actually, both Asian giant hornet workers and cicada killer wasps vary in size based on their diets and environmental factors; so some cicada killer individuals may equal or exceed the AGH in length.

So, if you look in your backyard and see the biggest flying monster wasp you’ve ever seen in your life, and if you’re ready to grab your kids and leave town, calm down.  It’s probably the cicada killer wasp or one of the many native wasps that you’ve blissfully ignored in the past. By all accounts the Asian giant hornet will take years, if ever, to reach Texas.  And if it gets here, there’s a good chance it won’t like our treeless plains and hot summer temperatures.

For more information about cicada killer wasps, check out my earlier post.  Also, for a beautiful gallery of royalty free images of the Asian giant hornet and hornet look-alikes, check out the USDA/APHIS image gallery or, the very informative interactive ID guide for AGH put out by North Carolina State.


Emerald ash borer in Denton

map of EAB risk areas for the Dallas and Fort Worth area in May 2020

High risk zones for emerald ash borer based on known locations where the borers are established. May 2020.  Circles show the areas within 15 miles of known EAB infestations; any ash trees of value within these circles should be treated this year to ensure protection from attack.


When Denton urban forester Haywood Morgan moved to Texas from Milwaukee, Wisconsin six years ago he thought he was leaving the devastating emerald ash borer behind.  Instead the ash borer found him again.

EAB adult captured in Denton, TX. Photo by Haywood Morgan.

Morgan became reacquainted with EAB this month during a trip to look at some sick ash trees along a Denton, Texas street. After inspecting ash borer-like damage on the 11 year old ash, his experienced eye caught a glimpse of shiny green.  A quick grab and he had it–what appears to be the first emerald ash borer to be found in Denton county.

According to Morgan the insects appear to have been in this neighborhood for several years, based on extensive damage seen to a half dozen or so ash trees.

Arborist Scott Geer with Tree Shepherds also visited the site.  In addition to the landscape trees around the house Morgan inspected, Geer reported other neighbors with damage, as well as damaged native green ash in an adjacent forest.

“Ash are not the predominant tree in Denton County,” said Geer.  “Green ash are found in pockets, mostly along the creeks; but Denton county is dominated by post oak, blackjack oak and cedar elm with some ash scattered in pockets.”

The emerald ash borer attacks ash trees almost exclusively*, so non-ash tree species will be safe.

EAB damaged tree in Denton, TX. 2020. Photo by Haywood Morgan.

The insect Morgan collected has been sent to USDA experts for official verification, but everyone who saw the insect was convinced.

This makes the second active EAB site in the Dallas/Fort Worth metroplex, but the first in an urban neighborhood in Texas.

Most tree experts agree that emerald ash borer may be the most important exotic tree pest to enter the country since chestnut blight, which caused the near-extinction of wild chestnut trees in the U.S.  This beetle may be nearly as devastating, with some experts worrying that die-back of natural populations could threaten extinction for the 15-plus species of native ash in the U.S.

Damage to trees is not immediately visible as the beetles typically start their attack at the top of the tree. Symptoms to look for include canopy thinning in the upper tree, bark splitting, and sprouting or vigorous new growth from the ground and lower portions of the tree. Only later will the 1/8 inch, D-shaped emergence holes of the beetle be visible.

If you suspect your ash tree has symptoms of the borer you will need to either treat it, if damage is not severe, or cut it down.  Borer damaged trees quickly dry out and become brittle, making them hazardous to people and property. Local tree care companies have treatments that will provide 2-3 years of protection against the borer.  Do-it-yourself treatments are also available from garden centers.  They involve drenches with insecticides containing imidacloprid, azadirachtin or dinotefuran.  Home treatments must be reapplied annually.

For more information on EAB, it’s ID, biology and control, go to Also, reports of suspected EAB may be submitted through the Sentinel Pest reporting function of the Texas Invasives website. Experts from USDA there are ready to evaluate samples, but keep in mind some simple guidelines for sending in pictures.  For more information about how to recognize EAB damage, check out this guide.

Insect Updates will keep you informed about continued spread of EAB through the Dallas/Fort Worth area.

* Cases of EAB attacking Chionanthus virginicus (white fringetree) have also been documented.


Giant hornets genuinely frightening

face of Asian giant hornet

face of Asian giant hornet

The Asian giant hornet has recently been spotted close to the Canadian border in Washington state. Photo courtesy Washington State Department of Agriculture.


Last year’s quiet arrival of a foreign wasp known as the Asian giant hornet is no longer a secret outside of Washington state.  Within the past few days, all the major TV networks have broadcast stories of the arrival of the wasp to the Pacific Northwest.  Known to entomologists as Vespa mandarinia, it has been named by the press the ‘murder hornet’.

It’s hard to argue with the name ‘murder hornet’ given that this wasp causes 30-50 human deaths a year in Japan. And the threat is serious enough that the Washington State Department of Agriculture has devoted a website to the pest and assigned public engagement officer, Karla Salp, to handle public concerns.  “Our hope is to eradicate it before it can get established in Washington,” she said. “Barring that, containing it is our second goal.”

Let’s face it, the thought of giant stinging wasps touches our deepest fears. If proof was needed of how scary wasps are to most people, look no further than the Hunger Games and its “tracker jacker” wasps. Even Hollywood knows the idea of being attacked by a swarm of wasps or bees is horrifying in the most primal way (and therefore sells tickets).

How bad?

Given the fact that lots of other stinging wasps and bees are already a part of the landscape in Texas, why the fuss?  After all, it’s just another wasp.  One of the reasons the Asian giant wasp generates so much attention is its size.  At 1 1/2 inches long (queens up to 2 inches) it is reportedly the largest wasp in the world. Its sting is excruciating and, unlike the honey bee, it can sting repeatedly.

dorsal view Asian giant hornet

The Asian giant hornet has a distinctive yellow-orange head and heavier body than those of our largest native wasps. Photo courtesy Washington State Department of Agriculture.

And while we’re talking bees, a gang of 30 Asian giant hornets can take out a hive of 30,000 honey bees in a few hours. The European honey bee–the predominant species used by beekeepers–lacks the behavioral defenses that Japanese honey bees use against this wasp.  With its giant jaws capable of decapitating honey bee defenders, and a exoskeleton impervious to bee stings, the giant hornet makes a formidable foe. To make matters worse, beekeepers who encounter these wasps face 1/4-inch-long stingers that penetrate standard beekeeper garb.

Impact on Texas

The bottom-line is that the chance of Asian giant hornets invading Texas soon is slim, given that at the moment only a few wasps have been found in only one county in the far northwest corner of the U.S.  Also, hornets are less likely to be transported by humans than many other exotic insects, like fire ants or emerald ash borers.

As with any social insect, hornets live and survive in colonies, not as individuals. So an individual worker wasp that accidentally flies into a vehicle, for example, will not be able to survive away from its colony.  The only way to spread the wasp is by transporting an entire subterranean nest (highly unlikely), or to transport a  previously mated queen, capable of starting a new nest on her own. The chance of the latter happening is greatest if a mated queen going to bed for the winter (they like to do this in loose plant debris or soil) happens to bury herself in the loose soil of a potted plant, and the plant shipped elsewhere. This is currently the leading theory for how the hornet got to North America.

Natural spread on the ground could certainly also occur, but it should take much longer.  In China the wasps seem to favor forested areas and avoids high altitudes and open grasslands.  Texas does not seem to be ideal habitat for this wasp. Nevertheless, it’s hard to feel completely safe from an insect that just successfully hopped an ocean.  And according to Salp there is genetic evidence that the Asian giant hornet (against the odds) slipped into British Columbia not once, but twice in the past year.


cicada killer wasp on ground

The cicada killer wasp, Sphecius speciosus, is another large wasp, approaching the length of the Asian giant wasp, common in Texas.

It’s not unusual when a scary new pest gets reported in the news for everyone to start seeing them in their backyard (it’s a natural human response to believe that if something bad is going to happen, it will happen to us personally first).  But in this case, there are much better explanations for big hornets in your backyard.  In Texas one of our largest stinging insects is the cicada killer wasp.  Cicada killers range in size from 1 to 1 1/2 inches-long, approaching the Asian giant wasp in length.  Although the bodies of cicada killers are more slender, and heads not as distinctively orange, they are still easily mistaken for the more sinister giant hornet.

Washington state officials are also responding to a worried public.  “We have created a chart to show people the size differences in native bees and wasps compared to the Asian giant wasp,” said Salp. “Its common to see other wasps and mistake them for the giant wasp.”

In Texas, it is highly unlikely that the Asian giant hornet will be spotted for many years, if ever. But if you see something unusual, a good picture is usually sufficient to roughly identify a bee or wasp.  Send the image to your county Extension office with a description of the city and county and date where it was taken. Also, as accurately as possible estimate the length of the insect.  The better the picture and description, the more likely you are to get an answer.

And, as for now, don’t watch the Hunger Games if you want to sleep well tonight.



Kudzu bug in Texas

kudzu bug adult
kudzu bug adult

Kudzu bugs are beetle-like in appearance, but like all true bugs have sucking mouthparts. Photo by Dan Suiter.

Last week Texas became the fourteenth state with verified populations of kudzu bug.  An alert county Extension agent, Kim Benton, reported kudzu bugs from a home garden in Rusk, TX, south of Tyler. The bugs were clustered on eggplant and other vegetables before being transplanted into the garden.

The kudzu bug saga in the U.S. began in October 2009 when millions of small, pill-like bugs startled homeowners across nine counties in northeast Georgia. The never-before-seen insects covered the sides of homes by the thousands, and concerned citizens began calling county Extension offices daily, including the office of urban entomologist Dr. Dan Suiter. Though puzzled at first, Suiter eventually identified the insect as “kudzu bug”, an exotic insect never before seen in the U.S.

The kudzu bugMegacopta cribraria, is native to Asia, where it is widely distributed. As its name implies, its preferred host plant is the invasive weed, kudzu.  No one knows how it got here, but like many invasive pests it made itself at home quickly.  Highly mobile, within a year the kudzu bug had spread to 60 north and central Georgia counties.  Two years later every county in the state was infested.


It is hard to mistake kudzu bug for anything else.  It is beetle-like in appearance with a unique, four-sided, ovoid shape.  It is greenish-brown and shiny, up to 1/4 inch-long (3.5-6 mm).  Like other true bugs in the order Hemiptera, it uses its piercing/sucking mouthparts to feed on sap.  It is found mostly on kudzu but will feed and reproduce on other legumes.

kudzu bug on soybean

Kudzu bugs feeding on the stems of soybeans in a Georgia farm field. Photo by Phillip Rogers via

The kudzu bug’s second favorite food is soybean, into which the bugs move during mid-summer. The first generation of bugs emerge during April when the bugs may cluster on non-food plants before moving to kudzu. The second generation may move from kudzu into soybeans or other legumes such as edamame, sweet peas, snap beans, cowpeas, lima beans and wisteria, where they are available.

Is it a good bug?


Kudzu is also known as the foot-a-day plant because of its fast growth.

Anyone familiar with the weed kudzu will be excused for thinking that having kudzu bug might be a good thing.  After all, one of the reasons kudzu is such a horrible weed is that few things eat it.  Wouldn’t it be good to have an insect to keep kudzu in its place?

That’s what the good folks in Georgia hoped.  But according to Georgia extension entomologist Phillip Roberts, their optimism didn’t last.  “The first years we saw what we thought was a lessening of the kudzu problem.  Other weeds seemed to be competing more effectively with the kudzu.”  But after a year, he said, the kudzu seemed unfazed.  “We cannot see any noticeable decline in kudzu growth since the beetle moved in.”

Household pest

Kudzu bug is one of a few agricultural pests that can become an household pests. In Georgia kudzu bugs invade homes especially homes near kudzu patches.  According to Suiter, unlike the multicolored Asian lady beetle, kudzu bugs are attracted to buildings but rarely come indoors. “We never really see them getting inside,” he said.

Nevertheless, if it’s your home, you will doubtless be unhappy to see thousands of bugs clustering on any white-painted parts of your house such as gutters, siding and around windows. Attempting to pick up the bugs with your hands is also not a good idea because the bugs have an odor and secrete an irritating, yellow-fluid that stains skin.

Kudzu bug activity around structures is most noticeable in the fall when the bugs begin to seek out protected overwintering sites.

The good news

The good news is that after a few rough years, kudzu bug problems in Georgia and other states seems to be declining. Also, because kudzu is less common as a weed in Texas bugs may never become a severe problem. Click here to see if kudzu has been reported from your county.

The improved kudzu bug situation in Georgia seems to be due partly to two egg parasitiods (wasps that  attack the egg stage of the bugs) and to a fungus called Beauveria bassiana.  Together these natural control agents have severely reduced the kudzu bug problem in Georgia and most southern states. After being overwhelmed with calls the first five year after the bug’s discovery, today Suiter says he “doesn’t see more than 20 bugs a year” brought into his office.

What to do

If kudzu bug comes calling in your garden or home there are a few things you can do:

  • Don’t worry if you see clusters of bugs on non-legume garden plants.  In the spring it’s not uncommon to see kudzu bugs aggregating on other plants.  Within a day they are usually moved on without doing any damage.
  • Most insecticides labeled for garden use should kill kudzu bugs, including pyrethroid insecticides and malathion.
kudzu crown

To kill kudzu you must remove the crown. The crown consists of meristem tissue from which new sprouts emerge. Roots lack this tissue and cannot regenerate once the crown is removed. Photo courtesy Matt Frye.

  • If kudzu is present around your home, get rid of it. Though control of kudzu on a large scale has been difficult (impossible?), removing small patches of kudzu is possible with diligence.
  • Crown removal. This is easiest in the spring when new growth is just emerging and before vines become inpenetrable.  Look for main nodules (crowns) from which new growth is emerging and hack out using a maddox or other strong digging tool.  According to Dr. Matt Frye of Cornell University in NY, pulling vines does  not work, but removing the crown at this time will kill the plant.  It is not necessary to dig out the entire root of kudzu (which can extend 1-15 feet deep!) to kill it. For an excellent explanation of crown removal and biology of kudzu, click here
  • Herbicides can also be used to kill kudzu, but may require re-treatment over several years to completely kill the plant.
  • Around the home in the fall treat underneath eaves and any cracks or crevices where bugs are aggregating. The pyrethroid insecticides bifenthrin and lambda-cyhalothrin are reported to be among effective insecticides.

If you find what you believe are kudzu bugs we would love to get samples or see a clear photo.  Save specimens to bring to your county Extension office for official confirmation, or send a digital photo.  In this way you can help us track the spread of kudzu bug within the state.  For more information on kudzu bug see

POSTSCRIPT:  According to the USDA/APHIS, kudzu bug has previously been reported from Rusk and Upshur counties in Texas, going back as far as 2016.  This is the first record, however, reported to Extension or to the entomology department at Texas A&M.  This indicates the insect has been here for several years and is likely well established in multiple counties. We are still interested in reports of the insects or its damage.

Disinfectants are pesticides–so use safely!

AgriLife Logo

What do “pest control” and public health campaigns against SARS Cov-2 have in common?  Both activities use pesticides.  In the eyes of the law, sanitizer and disinfectant products are considered pesticides.  And if you’re a little wary of using pesticides, you should exercise the same caution when choosing and using a disinfectant.

Let’s start with some basics. The term ‘pesticide’ refers to any substance or mixture of substances used to prevent, destroy, repel or mitigate a pest.  All pesticides are regulated by the U.S. Environmental Protection Agency (EPA), which gets to decide if, how and where they can be used.

antimicrobial products compared

Antimicrobials include several categories of products. To maintain virus-free surfaces use a disinfectant or a virucide.  Sterilants are generally more toxic and reserved for critical environments like hospitals. Infographic courtesy Enviroxyclean.

Pesticides that fight microbes are generally called antimicrobials.  Antimicrobials that fight germs affecting human health can be further classified as sanitizers, disinfectants, virucides and sterilants.  About 275 active ingredients are found in antimicrobials, most of which are considered pesticides and must have an EPA-approved label (a few sanitizer products–such as alcohol gels–for use on skin are considered drugs rather than pesticides, and are regulated as such by the Food and Drug Administration). Most of the effective products that fight the SARS-CoV-2 virus are considered disinfectants or virucides.

Since January we’ve watched endless news clips of sanitary workers cleaning surfaces, and even entire buildings, with disinfectants. Shopping for groceries has become an adventure in disinfectant wipes and hand sanitizer.  And the empty shelves in the cleaning supply sections of stores attest to our new obsession with clean, clean, clean!

But how many of us stop to consider the health effects of disinfectants, or to read the labels on these products? If you find yourself using disinfectants, or touching disinfectant-treated surfaces, now’s an excellent time to brush up on disinfectant safety.  Specifically let’s review some of the important things we all need to know about reading and understanding disinfectant labels.

disinfectant precautionary statement

There is a lot of information on a disinfectant label. Not reading and following label instructions puts you at risk of breaking federal and state pesticide regulations-not to mention putting your health at risk.

Read the label

  • Unlike instructions on a box of mac and cheese, instructions on a disinfectant label are the law, not suggestions. Using even a little more disinfectant than the label allows in a cleaning solution, or failing to wear the proper safety gear specified on the label, to give two examples, is a violation of state and federal pesticide laws.
  • Look for an EPA registration number (see label to right). This is a unique number that tells you the product has been reviewed by the EPA and allows you to reference it.  For example, the EPA has developed a list of all disinfectants that are believed to be effective against the SARS-CoV-2 virus (List N).  If you want to know whether your disinfectant is likely to be effective against coronavirus, you can look it up in this table by its registration number.
  • Read the precautionary statements.  Precautionary statements include specific requirements on what you must wear when applying the product.  If you’re an employer or supervisor it’s critical you provide training to ensure employees know disinfectant instructions and have the proper safety equipment.  In a recent case, employees of a large company were told to switch from mild green-cleaning agents to a powerful disinfectant to deal with the coronavirus emergency.  Not used to the new product, janitorial staff became ill and suffered red- itchy skin and burning eyes.
  • Pay attention to contact times on the disinfectant label.  Many disinfectants must remain wet on surfaces for an extended time (usually 1 to 10 minutes) to effectively kill viruses and bacteria.  Don’t assume you can immediately wipe down a surface that you treat with a disinfectant.
  • When deciding on a safe disinfectant to use in your home or workplace, consider the signal word.  The signal word provides a quick reference to the relative hazard associated with using a product. One of three signal words–DANGER, WARNING, or CAUTION must be on the front panel of any disinfectant product.  DANGER signals the highest warning.  Such products may be highly toxic when ingested, or may induce irreversible eye or skin damage if used without proper protective gear.  WARNING labeled products are moderately toxic if ingested or may cause reversible skin or eye irritation.  CAUTION labeled products will be the least hazardous, and would be best for home environments, especially where children are present.
  • Pay attention to what surfaces the disinfectant is designed to be used on, and what kind of application methods are allowed by the label. If a product is labeled for use on hard, non-porous environmental surfaces, it shouldn’t be used on carpet or furniture. Something designed to be applied with a sponge should not be used in a fogger or sprayer.
  • Care should be taken with even with the simplest task of removing disinfectant wipes from their plastic tubs.  We have reports of people getting disinfectant in their eyes from tiny droplets erupting when towels are pulled too quickly from the container.

Treat all disinfectants with the same respect you would any pesticide.  Since coronavirus began its spread, the EPA has been receiving more health-related emergency calls about improper use of disinfectants. One common problem occurs when people use Clorox wipes to wipe their faces–not good.  One couple thought they could drink bleach to cure COVID-19.  And they are many more cases of people being hurt by mixing chlorine- and ammonia-containing products (resulting in production of the toxic gas, ammonium chloride). None of these are good ideas and none are recommended on the label.

Our office provides training throughout the year to folks in the pest control, public health and outdoor landscape maintenance industries.  One of the things we drill into our students is the importance of reading the label for safety and legal purposes.  All of us need to exercise the same caution when using disinfectant products.  They are, after all, pesticides.




A prickly situation

Cactoblastis damage Texas 2019

Prickly pear cactus has its detractors.  Long hated for its long spines with a bite, and its clusters of barbed spines (glochids) that are heck to remove, it has been cursed, hacked, burned and sprayed. But prickly pear (Opuntia spp.) is also used by a variety of  wildlife and cattle, and is prized as a part of the Mexican-American diet.  There is even a small industry devoted to rearing insects, called cochineal scale, that feed exclusively on prickly pear (these scales produce a vivid red dye, called cochineal or carmine, sometimes used as a natural coloring agent in cosmetics and beverages–including some Starbucks frappucchinos).

rancher burning prickly pear in south Texas

A rancher in South Texas burns the spines off of prickly pear cactus to feed his cattle during a drought. Image courtesy Texas A&M AgriLife Extension. Photo by Omar Montemayor

There are over 100 species of Opuntia native to the Americas, and most are not considered pests. Though ranchers may curse prickly pears as “weeds”, they also rely on them to provide emergency food for cattle during times of drought. In addition, many insect and vertebrate species rely on different kinds of prickly pears for food and shelter. Despite our sometimes love/hate relationship, most Texans view the various prickly pear species as valuable native plants.

Unfortunately, a small moth called Cactoblastis cactorum poses a new threat to the ecological stability of Opuntia species in Texas. Cactoblastis is a predator of prickly pear in its native home of Argentina in South America. It was distributed by humans into the Caribbean in 1959. Since then it has expanded its territory slowly through Cuba and Florida, and most recently Louisiana.  The bad news is that Cactoblastis has now become established and is spreading in Texas, according to a recent post on the Facebook page of University of Texas biologist Larry Gilbert.

Cactoblastis damage Texas 2019

Initial point of entry by Cactoblastis, and hollowed-out pad, is evident in this backlighted photo of an Opuntia cactus. Photo courtesy Larry Gilbert.

According to reports, the moth appears to have leapfrogged over the Houston area into Brazoria County and is now established as far south as Mad Island, east of Victoria, TX.  According to Robert Vines’ book, Trees, Shrubs and Woody Vines of the Southwest, over 50 native species of Opuntia can be found in Texas and surrounding states.  It is not certain how many of these species will ultimately be affected by Cactoblastis.

The problem with invasive species is that natural control agents are often left behind in their country of origin.  When this occurs, the invading species is free of ecological restraints to reproduction.  This seems to be the case with Cactoblastis. Its impact on Opuntia is much worse here than in its native home.

Entomologists hope that an Argentinian wasp, Apanteles opuntiarum, might be enlisted in the struggle to preserve native OpuntiaResearch is being conducted to learn how to rear this tiny parasite wasp and learn whether it might be safe to release into Texas.

Ultimately, if Cactoblastis continues to spread, it could have an effect on ornamental cacti grown by Texas gardeners.  Of course as gardeners we have a variety of insecticides that can be sprayed on cacti–but who wants to have to do that?  Let’s hope that the Argentinian wasp can come to rescue, and tip the scales in the favor of the cactus.

Be sure to see Larry Gilbert’s post and excellent images showing Cactoblastis damage.




This Land of Insects


This four inch-long Dobsonfly is one of 29,000 species of insects to be found in Texas by those who know where to look.

Did you know that out of the 100,000 or so species of insects in the U.S., Texas is home to approximately 29,000 of them?  We live in a state that is gloriously full of six-legged creatures. From leafcutter ants to luna moths, Texas is a great place to see and learn about insects, spiders and many other arthropods.

As I was going through my 2019 calendar I was reminded of the Podcast on Natural Dallas (P.O.N.D.) that I did last year with Katharine Gulyamova, with the Dallas Public Library.  Katharine and I talked about insect life in Texas, and about local opportunities to learn more about the world of insects locally.  She came up with some really great questions, and the sound technicians at P.O.N.D. did their best to make me sound like I knew what I was talking about. So I figured at least a few of you readers of these Insect Updates might actually want to listen to me talking for 30 minutes about insects of Texas.

So here you go.  Click here to listen to the P.O.N.D.’s podcast on “This Land of Insects”.




Cleaning insect poop off trees

scrubbing crapemyrtle trees for sooty mold
Pandorus sphinx moth caterpillar

The Pandorus sphinx moth caterpillar can be difficult to see when it hides among green folilage.

Never estimate how low this blog can go in the search for article ideas. After listening to some internet chatter today on the subject of cleaning black mold off of trees, I thought someone else might be interested in the dark side of insect poop. Feel free to close your browser now if I was wrong.

Before anything else, let’s clear the air about insect poop.  Most insect poop is inconsequential, harmless and rarely noticed by the home gardener. The exception might be those caterpillars that leave poop big enough to be noticed.  In fact, one of the best ways to check your plants for caterpillar feeding is to look for the fluffy “poop pills” they leave behind. This scouting tip works because caterpillar poop is generally darker in color and sits mostly on tops of the leaves, compared to the devilishly camouflaged caterpillars themselves.

Pandorus sphinx moth caterpillar feces are sometimes more easy to see than the camouflaged caterpillar.

Pandorus sphinx moth caterpillar feces are sometimes more easy to see than the camouflaged caterpillar.

Insect poop really only becomes a problem to a gardener (and the plant) when it’s in liquid form.  Liquid poop is called honeydew and it is excreted by insects feeding on the sugar-rich plant sap called phloem. Examples of sap-feeding insects that produce honeydew include aphids, some scale insects, mealybugs, whiteflies and some kinds of galls.


Honeydew is what remains of the processed plant sap that is expelled from the insect’s anus.  Far from being depleted of nutrition, honeydew retains up to 90% of the original plant sugars from the sap. For this reason, many kinds of ants, wasps, caterpillars, and flies are eager to feed on this energy-rich food. In fact, some ants go so far as to tend and protect scale insects and aphids from their natural enemies, like lady beetles, to maintain their free supply of “plant-juice Slurpee”.

Some sap-feeding insects produce lots of honeydew. Early instars of the willow aphid, for example, release more than their weight in honeydew every hour. That’s the human equivalent of drinking (and excreting) over 8 (24 can) cases of beer an hour for a 150 lb human.  That’s a lot of trips to the bathroom.

A leaf covered with sooty mold is an indication that a sap-feeding insect is nearby, usually on the same plant.

But insects aren’t the only things that like honeydew. A fungus mixture called “sooty mold” also feeds on honeydew deposits.  Sooty mold includes several species of fungi that thrive on honeydew sugars. The mold produces dark, threadlike mycelia that cover honeydew deposits and look like a layer of soot.  Sooty mold is commonly seen on the trunks and leaves of plants with honeydew producing insects; but it can also appear on sidewalks, walls, air conditioning units and even cars parked too long under a tree. In some cases, the aesthetic damage caused by the ugly black sooty mold is a bigger problem than any direct damage to the tree by the insects.

Managing sooty mold

Controlling sap-feeding insects is the first step in rehabilitating your sad, sooty-mold covered plants.  But even successful control of sap-feeding pests won’t result in a satisfying improvement in the way your plants look. Your plants will remain dingy as long as the mold remains.

Eventually sooty mold will slough off the plant, but it can be a slow process. Mold may remain several growing seasons, especially on bark. Cleaning your plants can hastening the process of restoring them to their intended glory.

scrubbing crapemyrtle trees for sooty mold

Scrubbing in combination with a systemic insecticide to control scale is the fastest way to rehabilitate a dingy crapemyrtle tree.

On waxy leaved plants Jody Fetzer, of Montgomery County Parks and Recreation in Maryland, recommends first spraying with  horticultural oil to help loosen the mold residue.  After 15 minutes or so, she washes the mold off with a hose using “pretty enthusiastic force”.  This has the added benefit of controlling some scale insects and other pest, she adds.

Just physical scrubbing with a sponge or a brush can be helpful both in removing mold and pests, like scale, on woody plants. We saw significant improvement in the appearance of scale-infested crapemyrtle trees by dipping a soft-bristle brush into a bucket of dish washing detergent and water, and scrubbing the trunk and branches.  A soft bristle, we found, was much better than stiff bristles for getting into the dips and crevices of the trees.  This also helps remove crapemyrtle bark scale. But don’t expect any significant reduction in scale infestation–just a nicer looking tree.

Similarly, student volunteers at the University of Kentucky were successful in reducing calico scale numbers just through scrubbing (dry or soapy water scrubs gave similar control) the branches of infested honey locust trees.

Smaller and more delicate woody plants are probably best cleaned with a bucket, sponge and soapy water or horticultural oil spray. Keep in mind that certain plants are sensitive to some soaps and detergents. It may be best to try cleaning a few leaves first and taking a few days to make sure the plant can handle the treatment. Commercial insecticide soap is formulated for use on plants and is less likely to damage plants. Gently wipe the soapy water over the blacked leaves with a sponge. For tough residues, let the soap sit for a few minutes before washing off.

So that’s the poop on sooty mold. I’d be interested in any success stories you have cleaning your trees and shrubs.




Avoiding the “I-Got-the-Hotel-Bed-Bug Blues”

As the holiday season approaches and travel volume increases, the chance for traveler  encounters with blood-sucking bed bugs goes up. And while waking up with bed bugs in a hotel room is bad, waking up at home and finding that you’ve brought bed bugs home is even worse.  Bed bugs are one of the few insects that are adept at hitchhiking in personal belongings, so knowing how to minimize the risk of bringing unwanted guests home is an essential skill for the frequent traveler.

Fortunately it’s relatively easy to avoid bringing home bed bugs from a hotel.  We’ve put together a short video to explain how it’s done.  Check it out and avoid the “Hotel Bed Bug Blues”.

Where has West Nile virus gone?

bird bath with standing water

After last week’s rains, now’s a good time to walk your property and dump any standing water (gutters, flower pots, wheel barrows, bird baths, etc.). This year’s mosquito numbers are up, but disease incidence is low.

If it seems you’re hearing less about West Nile virus (WNV) this summer, you are not imagining it.  Although mosquitoes have been abundant this year, for some reason the virus has remained relatively quiet in 2019.

Where has WNV gone?

A paper written by epidemiologist Dr. Wendy Chung and colleagues in 2013 may offer some insights on the absence of the virus this summer. Those of us who lived in Dallas in 2012 may remember that summer as the worst human outbreak of WNV ever.  Nearly 400 cases were reported in Dallas County alone, and 19 people died of the disease. The epidemic was so bad that Dallas county resorted to spraying the entire county for mosquitoes by plane–something not seen in north Texas since an encephalitis outbreak in 1966.

Chung and colleagues charted the course of the disease during 2012 and saw high infection rates of mosquitoes early in the summer, followed by a rapid increase in human cases. Looking back over previous years and case numbers, the researchers concluded that an unusually mild winter followed by rainfall patterns ideal for mosquito breeding in the spring (and a very hot summer–West Nile virus multiplies quickly in mosquitoes at higher temperatures) created ideal conditions for an outbreak.

So what’s different about 2019? We had a relatively mild winter, with only three days at or below 28° F, and a wet spring–both conditions mosquitoes love. But the summer, at least by Dallas standards, has so far been cool.  Until this week, the DFW Airport weather station saw only two days over 100° F. By the end of July the area usually has experienced more than seven days over 100° F.

These graphs show 2019 mosquito abundance and Vector Index (V.I.) estimates compared to previous years. Although mosquito numbers are high this year, the V.I. has remained low for both Tarrant (Fort Worth-top) and Dallas counties (bottom). In 2012 the V.I. exceeded the danger level of 0.5 for multiple weeks. (Source: Tarrant County Public Health and Dallas County Health and Human Services)

Predicting WNV

One of the tools used by health departments to predict disease risk for WNV is the vector index (V.I.).  The V.I. is calculated weekly from mosquito trap data, and combines information on both average abundance of Culex quinquefasciatus (the main carrier of WNV) and disease incidence in the trapped mosquitoes.  A V.I. of 0.5 or higher for two or more weeks is considered a crisis indicator by health officials. Despite higher mosquito numbers this summer, the V.I. hasn’t ventured above 0.1 for either Dallas or Tarrant counties. Most of the summer the V.I. has been closer to zero. Hence fewer news reports about mosquito spraying or people getting sick. In Dallas county this year there have been no human cases of WNV. Tarrant County (Fort Worth) reports only one case this year with a very low V.I., near zero most weeks (top graph).

Looking Ahead

With this week’s string of 100° days will risk go up?  Certainly West Nile virus is a threat through the end of the summer and into the fall; but this late in the season the chance of a major outbreak is probably low. On the other hand, hot weather favors the virus. It’s no time to forget about mosquitoes. Indeed, I expect Aedes mosquitoes (yellow fever mosquito and Asian tiger mosquito) to become more abundant after last weekend’s rains.  This week is a good time to get out and dump standing water.  Although Aedes mosquitoes are not major disease risks, they cause most of the itchy mosquito bites we get during the day–and we don’t want that.

To learn more about mosquitoes, and best ways to manage and repel them, check out the Mosquito Safari website, where you can take a virtual tour of a field and backyard and learn important facts about mosquitoes.  For public health professionals and pest management professionals, Extension medical entomologist, Dr. Sonja Swiger, will be offering preparatory classes for pesticide applicators wanting their Public Health (Category 12) license, and a 3-day Master Vector Borne Disease Management Course.  To learn more, and to register, go to .