A prickly situation

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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 Opuntia.  Research 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

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Dobsonfly
Dobsonfly

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

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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

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”

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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?

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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 https://livestockvetento.tamu.edu/workshop-registration/ .

 

Texas/Oklahoma Pollinator Project

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bee on flower
bee on flower

Melissodes bimaculatus, two-spotted longhorned bee, on composite flower.

This summer Texas A&M AgriLife is conducting a citizen science project to document the preferred host plants of Texas & Oklahoma pollinators. In the process some energetic volunteers and I will be learning a lot more about how to plant a successful pollinator garden.

Last week I presented information about pollinators and how the project works to volunteers in the Dallas area.  If you are signed up as a volunteer, but missed the training, an edited version of the training is available here https://youtu.be/JfSpwlYcM3s  This training should prepare you to jump in and start recording data today.

If you are already an Extension volunteer (Master Gardener or Master Naturalist) and would like to be part of the research, you can still sign up by clicking on this link.

If you are not an Extension Master volunteer, but would like to learn more about our bees and other pollinators, you may find the first part of the video instructive.  Also, why not consider a longer term volunteer role with Extension? This is just one example of the many interesting projects our Texas Master Gardeners and Texas Master Naturalists get involved in every year.

Firefly Month (or it should be)

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firefly adult

Flickering lights, like so many Tinkerbells, dancing across lawns are one of the special memories of growing up in the South.

This time of year is your best chance to see fireflies, so this week I thought I would give a shout-out to Ben Pfeiffer, a firefly lover who has devoted himself to learning about the fireflies of Texas.

Ben has built an entertaining website, called Firefly.org. In it you can learn about the different kinds of fireflies (each has a unique flash pattern), where they live and what you can do to encourage fireflies to come live in your yard.  He’s got some great firefly pictures, and even tells us how to catch and keep (temporarily) fireflies.

So in celebration of firefly month (not really a thing, but it should be), get out of the house this week, walk around your neighborhood and look for fireflies. And if you have kids, bring a jar.

Areas of lawn next to dense vegetation, such as near a creek or fence line are good places to scan.  Even in suburban neighborhoods you may find some particular lawns blinking with fireflies. See if you can tell what is different about firefly yards.  Firefly larvae like taller grass, or deep thatch with good moisture. Here they are more likely to find the snails and tiny insects that they feed on.

Thanks to Ben for reminding us that getting away from the TV in the evening for a stroll can be an enlightening experience.

 

Multiplying millipedes

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Given the right conditions, millipedes can reach impressive numbers around homes and in the garden. Oxidus gracilis, or the greenhouse millipede, is a common species in Texas. This one appears to have over 30 pairs of legs. Photo: M. Merchant.

At first glance, millipedes are most remarkable for their ability to walk without tripping over their own feet.  The name millipede literally means “thousand feet” and though most don’t have that many legs, that’s still a lot of feet to keep track of. What’s even more remarkable about millipedes, once you get to know them, is their ability to reach astronomical numbers when weather conditions are prime.

Millipedes clinging to a clay pot, probably for moisture. Most millipedes are very sensitive to dry air.

That’s what’s happening right now, at least in parts of north and east Texas.  For the past month Extension offices have been getting dozens of calls about (sometimes) biblical numbers of millipedes.  One person today described finding millipedes throughout his home, “too many to count, entering through the house windows and doors,” like the hundred or so he found in his son’s second story windowsill.

Sometimes mistaken for caterpillars, such infestations begin outdoors with dozens or hundreds of millipedes swarming flower pots and crawling up the sides of buildings.

Millipedes aren’t all bad. Their role in nature is to serve as “decomposers,” feeders on dead plants and decaying wood.  Without critters like millipedes you wouldn’t be able to get new grass to grow through the layers of dead grass and leaves, and compost piles would take longer to produce compost. But this doesn’t stop them from sometimes becoming a royal nuisance.

Several years ago a brand new, local high school was invaded by millipedes. They stormed hallways and classrooms by the tens of thousands.  With no landscaping or mulch nearby, the only food source we could determine were buried heavy-duty cardboard boxes used by construction crews on the soil to support the floating slab foundation of the buildings.  Structural engineers figured the cardboard would decay innocently under the slab, but entomologists will tell you that burying paper under a building is asking for trouble in the form of termites and millipedes.

Some millipedes emit noxious defensive secretions when threatened. This child was playing with a millipede, rolling it in her hands. She soon had these itchy red stains. Photo courtesy Kim Benton.

Millipede mass migrations commonly occur in the fall, but can also happen in the spring. Above average rainfall is likely to blame for this year’s invasions. But such invasions don’t occur overnight, as it takes millipedes several months to develop.  It may be that waterlogged soils are forcing millipedes out of the soil in search of drier spots. Unfortunately for the millipedes that enter homes, indoor environments are too dry for their thin “skin”.  Though millipedes are relatively long-lived outdoors in the soil (up to 5-7 years), once indoors, millipedes desiccate and die within a matter of hours.

For this reason it’s usually unnecessary to spray insecticides indoors for millipedes. Instead use the vacuum indoors and focus your control actions outdoors. Make sure mulch is kept away from building foundations, and that weep holes and other entry points are screened or sealed.  In severe cases it may be helpful to apply a pyrethroid insecticide (in the form of granules or sprays) around the perimeter of the home and around windows and doorways.  Most of the time, however, millipede infestations go as quickly as they came, and insecticides are not needed.

Millipede jaws are soft, restricting most species to feeding on soft, dead plant material.  Only a few, like the greenhouse millipede, can damage soft plant tissues such as found on emerging garden plant. Millipedes do not bite, but some species can emit noxious defensive secretions that can stain and even blister skin.

You have to respect millipedes. With only weak jaws, thin skins, and little more to their credit than lots of legs and incredible powers of reproduction, they manage to survive and thrive even in our urban landscapes.

 

Sunshine and wildflowers–its mosquito time again

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Texas wildflowers
Texas wildflowers

The arrival of wildflower season mean it’s time to start putting on the sun screen again. It’s also time to stock up on insect repellent.

Two weekends ago my wife and I went for a long bike ride. It was one of those rare, completely beautiful spring days, cool air and wildflowers lining the roads.  I knew it was going to be a long ride, and I knew the Texas sun was shining; but somehow the need for sunscreen never entered my mind (my wife had the good sense to lather up). It was a wonderful ride; but I’m still paying the price today, with the skin on my arms peeling like an onion.  What a dummy!

When spring arrives it’s easy to forget simple precautions like sunscreen.  It’s also easy to forget  the need for mosquito repellent.  But make no mistake, like the Texas sun mosquitoes are back, and with them the potential for West Nile virus.  Dallas County Health and Human Services announced the first catch of a mosquito positive for WNV last week.

West Nile virus remains the king of mosquito-borne diseases in Texas. This may be easy to forget in the wake of news stories about scary-sounding diseases like Zika and chikungunya.  These viruses caused surprisingly strong outbreaks in the Caribbean in 2014 and 2016 (remember the Zika scare during the Brazilian Olympics?); but for the most part Texas has escaped similar epidemics, likely due to both cooler weather and the way we retreat into air conditioned homes in the evening.

graph showing numbers of West Nile virus cases in Texas 2016-2018

July and August are the highest risk months for West Nile virus, though the season runs from May to December. Source: modified from Texas Department of State Health Services.

While most people who catch the WNV show no symptoms, 20% of victims get a disease known as West Nile fever. Think of a severe, month-long case of the summer flu.  Less than 1% of infected persons get a debilitating form of the disease known as the neuroinvasive form of West Nile virus. Nearly all who contract neuroinvasive WNV end up hospitalized, and face a long and uncertain recovery.  Neuroinvasive WNV mostly affects people over 50, but young healthy men and women and occasionally children have been struck down with the disease.

The worst epidemic of WNV occurred in 2012 in Dallas, when a very wet May was followed by drought and a hot summer from June to September. That year in Dallas County alone over 400 people got sick enough to go to the hospital and about 20 people died.

Late April or early May is when the first cases of WNV show up in Texas, though the season doesn’t get into full swing until mid-late June. Your highest risk of contracting the disease is July and August, with significant risks continuing into September until November.

West Nile virus is nothing to sniff at, so listen up.  Now is the time to survey your yard for potential mosquito breeding sites.  Any object that holds water is a potential mosquito maternity ward. Look for old buckets, children’s toys, leaf-choked gutters, potted plant drainage ditches, bird baths, even metal fence posts with the tops missing.  All these items can catch and hold water for the few weeks it takes mosquitoes to  breed.

Get in the habit now of putting repellent on when you spend time outdoors. I keep a can or squirt bottle of repellent on my patio to help remind me when I step outside.  When it comes to mosquito season, don’t be a dummy. Find a mosquito repellent you like, and use it.

To learn more about mosquitoes and how to combat them in your backyard, check out the Mosquito Safari website.

Dr. Don R. Read

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Don and Roberta Read
Don and Roberta Read

Dr. Don and Roberta Read April 2018 at the West Nile Virus Survivors’ Group.

The next best thing to being great, it’s been said, is walking next to someone great. I am grateful to have had the chance to meet and get to know the late Dr. Don R. Read, who passed away on March 21, 2019. He was one of our local colorectal surgeons in Dallas, and a great man in many ways.

Dr. Read made his (unfortunate) acquaintance with entomology in 2005 when he was bitten by a mosquito infected with the west Nile virus. He told his story of getting sick, and nearly dying, from the disease many times to the West Nile Virus Survivor’s group he organized and sponsored at the Dallas Medical Center.

In reading his obituary I was struck by how a man who led such an active and productive life could be slowed so dramatically by such a little insect.  Shortly after receiving his MD, Dr. Don served an externship with doctors in the bush in Zaire (Congo), bringing medical care to remote and primitive villages. As a young man he served as U.S. Navy surgeon in a forward M.A.S.H. unit in Vietnam, for which he received a Bronze Star. Besides bravery, he demonstrated a big heart for people in need. As president of the Dallas County Medical Society he helped organize Project Access to assist and serve the working poor, and was a local pioneer in programs to treat and rehabilitate medical professionals addicted to drugs or alcohol.  His life was marked by a remarkable willingness to serve and engage tirelessly with his profession and his community.

I learned a lot from Dr. Don about the human side of west Nile virus.  For me, he became the face of WNV survivors. He also showed me how it’s possible to turn illness and disability into something positive.  He talked about the long recovery for everyone who suffered from the neuro-invasive form of the west Nile virus disease. He excelled at encouraging others to share their stories of illness and recovery.  After attending many of his survivor group meetings, the inspiration he and his wife Roberta instilled in other survivors was apparent.

Dallas has lost a remarkable man; and I am grateful to have had the chance to know him, even if just a limited acquaintance. In my encounters with him he was always positive and humble, and had a way of making others feel important.

The Dallas County Medical Society notes that “Dr. Read’s outstanding dedication to the practice of medicine and the patients of Texas will be honored by the Texas Medical Association as he receives, posthumously, the TMA Distinguished Service Award at the upcoming TEXMED conference in Dallas in May. He received the Charles Max Cole, MD Leadership Award from the Dallas County Medical Society in 2010.

“He is survived by his adoring wife of 50 years, Roberta, daughters Alison, and Sarah Read (Bob) Gehrenbeck and two grandchildren Henry Read and Theo Don Gehrenbeck. He is also survived by his brother, Nat (Linda) Read.  Visitation is scheduled for Friday evening, March 29 at Restland Funeral Home, 13005 Greenville Ave., Dallas. Services will be at 10:00 a.m. on Saturday, March 30 at Preston Hollow Presbyterian Church.”

Godspeed Dr. Read.