Insect Updates - Page 15 of 32 - Insects in the City

Hollyhock thrips found in Dallas

Posted on August 23, 2014 by p-porter

Pseudophilothrips (=Liothrips) varicornis damaged althea leaves

Hollyhock thrips damage to Althea observed in Dallas, TX. Notice the tiny red thrips on the leaves and petioles of the plant. Damage progresses from yellowing to death of plant leaves. Click image for larger view.

It’s not too often that I come across an insect that appears to not have been previously recorded in Texas. But thanks to the sharp eyes and instincts of Johnette Taylor of Roundtree Landscaping in Dallas, I’ve added a new plant pest to my “life list”.

Johnette was a little suspicious when a customer reported that an Althea (rose-of-sharon) that she had planted several years ago was yellowing and losing leaves. She noticed some small red insects covering the bark of the trunks, and took a picture with her phone. After an exchange of emails and an initial wrong guess on my part, she asked if it could be a tube-tailed thrips. I admitted that I had never heard of tube-tailed thrips, but after checking into that possibility, I agreed.

Immature hollyhock thrips feeding on an Althea flower bud. Note the dark sunken areas on the bud, apparently where the thrips have fed. Click on image for a larger view.

With a little more online research, and the help of a Florida colleague, and I felt pretty sure about the pest’s exact identity. The hollyhock thrips, Pseudophilothrips (=Liothrips) varicornis, are striking insects. The nymphs are fire engine red, with a sharp black tail. Unlike most thrips, which feed mostly out of sight, inside leaf and flower buds, these insects congregate on the bark, leaves and petioles of the plant. Like all thrips, they have rasping/sucking mouthparts, so the feeding damage is not loss of leaf tissue, rather it will be dark feeding lesions or pits, and yellowing or death of whole leaves.

The hollyhock thrips is thought to be native to California. I could find little about it apart from a nice taxonomic key entry, and a reference to a 1938 paper that records it as causing feeding lesions on plants in the mallow family including Althea, Hibiscus, Sida and Sphaeralcea. The plant I examined did indeed have feeding lesions along the leaf petioles, and the feeding did certainly seem to cause severe damage. There were grayish lesions on both flower buds and leaf petioles, and leaf death was most apparent on the lower branches of the shrub.

Adult hollyhock thrips are black and usually found together with their red offspring.

I don’t know if this insect is relatively new to the Dallas area, or something that’s been here for a long time, flying under the radar. Because of the dramatic damage to the one bush I examined, I’m guessing it may be something new, because gardeners tend to report such things. I would be interested if anyone else is seeing this insect on their mallow plants.

Damage by the hollyhock thrips seems to progress from leaf yellowing to death, as seen on the bush I examined this week.

If you do encounter this thrips, you have several control options. The homeowner I spoke to was having some success with an organic plant oil spray. For this to work, you will have to spray multiple times and make sure you cover all sides of all of the infested plants. I would expect synthetic horticultural sprays to work just as well. Another low-impact spray option would be sprays containing the bacterial-derived insecticide, spinosad. I have not tested this product on this thrips, but spinosad is generally very effective on thrips. Other sprays labeled for thrips control may also produce good results.

Crape myrtle bark scale reduces bloom

Posted on August 14, 2014 by p-porter

Two ‘Natchez’ crape myrtles demonstrate the potential impact of bark scale on the size and number of blooms in early summer. The tree on the left was treated seven weeks earlier with the insecticide dinotefuran, the one on the right was left untreated. Note the smaller blooms and mold-covered bark on the untreated tree. Photo by Jim Robbins, U of Arkansas.

As the crape myrtle bark scale spreads throughout Texas, one of the first questions we hear is “will the scale kill my tree?”

The answer appears to be “no”, at least not often. To date we’ve not been able to show any crape myrtle tree death as a result of a bark scale infestation. But like many sap-feeding scale insects, these little scales can stress and reduce the appearance of the trees, while producing a prodigious amount of sticky “honeydew” that can coat the leaves and anything under the tree (including freshly washed cars).

Thanks to Drs. John Hopkins and Jim Robbins of the University of Arkansas Cooperative Extension Service, we can now show you what we believe is likely to be another impact of these scales on trees–namely, smaller flower clusters and reduced blooming. The above picture was taken of two trees at a church in Little Rock, Arkansas. The tree on the left was treated with Zylam^® Systemic Insecticide on the 28th of May, and the one on the right was left untreated. Zylam^®(active ingredient dinotefuran) was applied as a drench in 5 gallons of water between the trunk and a circle three feet away from the trunk. The picture was taken seven weeks after the treatment was made.

Note that this picture is not the same as a scientific trial, which would involve more trees to ensure that the differences seen here were not accidental. Nevertheless, according to Dr. Hopkins, scale numbers and honeydew were noticeably less on the treated tree. And there was a difference in the average bloom size between the treated and untreated tree, with blooms being noticeably larger on the treated tree.

John estimated that the cost to treat the tree on the left would be approximately $39, not cheap, especially if you have multiple trees to treat. But at least you see what the expected benefit from tree treatment might look like.

The other question we are getting is: “If I treat my crape myrtles with a neonicotinoid insecticide, is it likely to affect the honey bees around my home?” While there is growing concern about the impact of soil-applied neonicotinoid insecticides on honey bee and pollinator health, crape myrtles do not appear to be highly attractive to bees (entomophilic). Currently we don’t believe that a properly applied soil insecticide (following label directions) will have any significant impacts on foraging bees. But if anything changes in that formula, we’ll be sure to let you know. We are also continuing to look for less susceptible varieties of crape myrtle and safer, less expensive treatments for this scale.

What is chikungunya and why should we care?

Posted on July 19, 2014 by p-porter

Who is more attractive to mosquitoes...and why?

The black and white Asian tiger mosquito is one of the two most common potential vectors of chikungunya in Texas

Over 30 years ago as a graduate student taking a course in medical entomology, I learned about all kinds of diseases spread by insects. By far, most of these were tropical and exotic-sounding. I figured that, if I lived and worked in the U.S., my chances of encountering most of these pathogens was practically nil.

Chikungunya (chik-un-GOON-ya) virus was one of those diseases I memorized way back then, and have since mostly forgotten. The chikungunya disease was first described in 1952 during an outbreak in southern Tanzania (east Africa). The name comes from the Makonde language and means “that which bends up”, referring to the contorted, bent-over appearance due to joint pain suffered by those who contract the disease. Sounds bad doesn’t it?

While not as serious as some mosquito-borne diseases, including malaria or Eastern equine encephalitis, or even the neurological form of West Nile virus, this virus is nothing to sneeze at. While some people have mild cases, it frequently comes with a very bad headache, joint pain, rash and fever. There is no treatment for chikungunya, and there is no vaccine to protect you if you go where the disease is active.

When I learned about chikungunya in college, it was found only in eastern Africa and parts of India and Southeast Asia. That distribution has spread in recent years as outbreaks occurred in parts of western Africa and Europe. In December 2013 the first epidemic on our side of the world was reported when the disease made the jump into the islands of the Caribbean. Since 2014 the disease has been spreading like wildfire, with more than a quarter million cases, and over 20 fatalities in the Caribbean.

Chikungunya has been on the radar of U.S. health officials in recent years because of its vectors–those mosquito species that help it spread. The principal vectors of chikungunya, mosquitoes in the genus Aedes, are very common in the U.S., especially since the introduction of the Asian tiger mosquito, Aedes albopictus, in the 1990s. In Texas and in many parts of the South and East today, the most common summertime biting mosquitoes are the tiger mosquito and its close relative, the yellow fever mosquito, Aedes aegypti. These are the species that inevitably bite me whenever I chance a trip outside without repellent in my backyard here in the Dallas area.

Unlike West Nile virus, birds are not involved in the chikungunya disease cycle. As far as we know, the virus can only be transmitted by the mosquitoes among primates. In Africa, the disease lurks both within humans and non-human primates, such as baboons and monkeys. For the virus to take hold here in the U.S., it would have to be common enough to reach an epidemic tipping point. This would occur when enough people were infected to start a cycle from human to mosquito to human again.

We may not have yet reached that tipping point, but we could get there easily. This week the first locally acquired cases were reported in Florida. These were the first cases reported where the victims had not recently traveled to the Caribbean, or other places where the disease is found. According to the CDC, between 2006 and 2013 we averaged about 28 cases of chikungunya annually from travelers. Since the beginning of this year there have been 243 travel-associated cases in the U.S. And, according to a July 15 release by the Texas Department of State Health Services, five cases have been reported in Texas so far this summer.

So should Texans be worried about chikungunya? If you plan travel to the Caribbean this year, definitely! Make sure to carry repellent and use it liberally during your travels to any Caribbean island. At home there is little risk yet; but this could change. As the number of sick travelers returning from Caribbean cruises and high school missions trips increases, the risk of locally acquired chikungunya will increase. All the more reason for listening when health officials remind us of the four Ds:

Drain and dump standing water
Dusk and dawn are the highest risk times for mosquitoes (though the Aedes mosquitoes are active all day)
Dress in long sleeved shirts and long pants when outdoors
DEET is an ingredient to look for in your insect repellent (or another effective choice such as lemon oil of eucalyptus, picaridin, p-menthane 3,8-diol or IR3535).

Never more than 5 feet from a (wolf) spider

Posted on July 8, 2014 by p-porter

The Rabidosa rabida on my computer monitor stand had a good 2 1/2 inch leg span.

I was reminded the other day of the old saying “You’re never more than five feet from a spider”. I was working on the computer when I glanced up from my keyboard to look into the face of a BIG wolf spider. It was sitting on the base of my computer monitor about 2 feet away.

After the initial startle reaction (even entomologists are human) I had to smile. I really do like spiders–if not especially on my keyboard–and I was thinking how most of my non-entomologist friends would react to such a close encounter with a wolf spider.

Wolf spiders are very common around homes, even in our supposedly sterile manicured Texas lawns. One year I did a little experiment in my back yard and poured a bucket full of soapy water on a couple of square feet (this is a common method used to flush insects hiding in turf). By far the most common thing to come crawling to the tips of the grass were wolf spiders, over a dozen. It was a good reminder that even relatively simple ecosystems like lawns have an impressive amount of biological activity. It also explains why wolf spiders are one of the most common spiders submitted to my office for identification… it’s only a short jog from the lawn to that little crack under the house door.

Wolf spiders are hunting spiders. This means they don’t sit passively on their web, but go out and search for food. Unlike their namesakes, they don’t necessarily chase down prey, but go to a likely location and wait for a tasty insect or other small arthropod to come along. When things get slow, they pick up and move to a new location. According Richard Bradley’s Common Spiders of North America, there are at least 238 different species of wolf spiders in America north of Mexico. They can be found in just about any habitat, from the beach tidal zones to the highest mountaintops. Most wolf spiders are nocturnal, coming out at night to hunt.

One thing I didn’t know about wolf spiders, till reading Bradley’s book was that they use silk draglines to keep in touch with other wolf spiders. When wolf spiders wander, they lay down these silk lines. When a male spider encounters the line of female, he may follow it to find her (the original pick-up line?).

This time of year, in mid summer, female wolf spiders may frequently be seen carrying egg sacs, and eventually brood, on their backs. This type of parental care allows the female to regulate temperatures for the eggs and young, and gives an added degree of protection during their young lives.

A great activity to do with kids (or just for yourself) is to go out in the lawn (or even better, an unmowed field) at night with a flashlight. Put the flashlight up next to your face and shine it in the grass or weeds. It normally doesn’t take long to notice little sets of reflective eyes shining back at you. Chances are these are wolf spiders. The main pair of eyes on wolf spiders face forward and are large enough to reflect light that can be seen by human eyes. If you have a cup and a credit card you can usually catch these spiders and admire them before releasing them back to their natural haunts.

After having its picture taken, my spider ended up being transported to the green lawn outside my office. I encourage you to do the same the next time you see a big wolf spider indoors. It won’t be able to hear your screams anyway.

National Pollinator Week coming soon

Posted on June 2, 2014 by p-porter

Hundreds of species of bees pollinate flowers.

National Pollinator Week this year is June 16-22. Here’s to hoping 2014 will be looking up for honey bees and other native pollinators. Last year during National Pollinator Week a pesticide misapplication led to a highly publicized bee kill in Wilsonville, OR. But this year we’ll start with some good news. Honey bee colony winter survival was up slightly this year, though still below expected survival levels prior to the advent of colony collapse disorder (CCD).

In celebration of the week, I thought I would share with you some news and interesting facts about bees and other pollinators:

An estimated 200,000 species of insects (about 20% of all known species) pollinate plants at least occasionally, but by far the most important pollinators are the bees and wasps. Bees are covered with specialized hairs that are very “sticky” for pollen, making them some of the best pollinators in the world.
A single honey bee worker makes anywhere from 50 to 1,000 flower visits on each nectar-collecting trip from the hive. It takes one colony of approximately 30,000 bees to pollinate one acre of fruit trees.
In south Texas, it is not uncommon to encounter Brachygastra mellifica, also known as the Mexican Honey Wasp, or Mexican honey bee. This wasp is one of the very few non-bees to produce and store honey. They make large, enclosed paper nests, similar to a hornet, but they are actually most closely related to paper wasps, which are predators and not nectar-and pollen-feeders. The honey was, and still is, used by humans in the Americas, and is said to be quite good.
Mexican honey wasp nest in Uvalde, TX. Photo courtesy Bugguide, Photographer Jason Penney.
Insect pollinators are mostly red-blind, so being red is not a big advantage to flowers wishing to attract insects. In the New World, however, we have over 300 species of hummingbirds (which do see red) that feed on nectar and can pollinate plants. So there is an advantage to red blooms–at least where hummingbirds exist. In Europe, where there are no hummingbirds, red flowers are rare.
The biological purpose of flowers as visual and olfactory lures for insects was not understood until late in the 18th Century, when Christian Konrad Sprengel published on plant sexuality and argued that colorful flowers serve to attract pollinating insects. Almost 70 years later Charles Darwin, recognizing the importance of Sprengel’s work, completed our basic understanding of why plants need insect pollination by showing the importance of cross pollination (hybrid vigor) to the long-term health and vitality of plants.
Many native plant pollinators are threatened and disappearing with the growth of urbanization. We can help slow this trend by the ways we plant and maintain our own gardens and landscapes. Michigan State University just posted an interesting and informative set of recommendations on how to conserve and encourage pollinators in your backyard.
A Harvard University researcher recently published data that he claims proves that insecticides are the cause of CCD. However, his methodology and conclusions are being widely panned by others in the scientific and beekeeping community. Most bee biologists believe that pesticides are one of several factors, including some new parasites and diseases, that threaten the economic viability of commercial beekeeping today.
It seems to be mostly domestic bees that are affected by CCD. Judging by the numbers of calls we get each year complaining about unwanted bee colonies showing up in backyards and walls of homes, wild bees do not seem to be affected by CCD.

Beekeeping Clinic

Posted on May 14, 2014 by p-porter

bee hives on stakes

If you’re a beekeeper, you won’t want to miss out on the upcoming Summer Clinic in Bryan, TX on June 7. Hosted by Texas A&M University Assistant Professor of Apiculture, Dr. Juliana Rangel, the clinic will discuss recent research projects, and subjects of interest to all beekeepers. There will even be a hands-on session with Bill Baxter (bring bee suit and veil for this one), and a session on dos and don’t about teaching the public about bees. Best of all it will be an opportunity to tour the (relatively) new Honey Bee Lab, and meet the (also relatively new) staff.

The clinic is also hosted by the Williamson and Montgomery County Area Beekeepers’ Associations. Bring your own chair and bottled water and get ready for a brain-expanding treat. Cost is $25 for adults and $10 for children. For registration information, check here. RSVPs are due by May 31.

The “Mother” bug II

Posted on May 12, 2014 by p-porter

Sehirus cinctus nymphs clustered in a sidewalk joint. Photo courtesy of Zach Davis, Texas A&M AgriLife.

I’ve been receiving calls about a small red and black insect that is extremely common at the moment. It’s scientific name is Sehirus cinctus, but it is also known as the white-margined burrowing bug. Due to it’s commonness around Mother’s Day, and its motherly habits, I kind of like the name “Mother bug”, which I used in another post.

Several years ago I got a call from a graduate student doing a study on the unique behavior of these insects. He wanted to drive all the way from Notre Dame University to Texas to collect some of these bugs. It turns out that over the years the biology of mother bugs has captured the attention of a number of ecologists and scientists interested in insect social behavior.

The mother bug has an unusual habit (for an insect). After birth she hangs around the underground cell where she lays her eggs. Should a predator come by, in a selfless act of motherhood, she flings herself between the intruder and her eggs. Once the eggs hatch, she brings seeds for the little “buglets” to feed on, before she practices tough love and leaves them to fend for themselves.

Closeup of the nymphs. Photo courtesy Sonja Swiger.

Closeup of the nymphs. Photo courtesy of Zach Davis.

After the mother leaves the nest, the young appear to stay together, sometimes in large clusters. The reports I’ve received involve seeing hundreds of the nymphs in the cracks of pavement. They are also common in the crack in the ground. I suspect that with some recent rains, and the swelling of the soil, many of these cute little insects are migrating to expansion joints in sidewalks and other pavement areas.

These insects are nothing to fear, and should not need any special attention. If you’re tempted to step on them, just remember this: “every bug has a mother too”.

Most attractive contest

Posted on May 7, 2014 by p-porter

Mosquitoes use a variety of ways to find hosts, including body odors, carbon dioxide and heat.

Where are you on the mosquito attractiveness scale? Are you a “1” or a “10”? Me? I know that I’m more attractive to mosquitoes than my wife (she is much more susceptible to poison ivy… I think I’ll be content). I suspect that I’m not a ten, though. Several years ago I was asked to visit a Plano resident who was very upset about the mosquito problem around her home. After searching her yard and poking about the surrounding neighborhood, the city health official and I had not encountered a single mosquito. Yet the woman was adamant that the problem was unbearable. While she was talking, a mosquito came down and landed on her arm. First one we had seen all day. I left the home being thankful I wasn’t her.

Science seems to agree that people do vary substantially in their attractiveness to mosquitoes; but the exact mechanisms remain unknown. I spoke today with a friend and colleague, Dr. Mustapha Debboun, a military entomologist and one of the leading researchers on insect repellents in the U.S. “We know some people are more attractive to mosquitoes,” he said. “But we still don’t know exactly why, or all the compounds involved.”

It turns out that the question is difficult. Many studies suggest that this or that chemical is attractive to a certain type of mosquito; but results vary according to mosquito, the concentration of the particular chemical, and levels of other human odor components.

Depending on who you read, the number of human volatile chemicals emitted from the skin vary from 100 or so, to over 200 different compounds. We know that mosquitoes are attracted by some of these chemicals, especially carbon dioxide, lactic acid, and octenol. But things are more complicated. We know, for example, that some of the chemicals known to attract mosquitoes can be repellent in the wrong concentrations. Other chemicals we produce mostly repel mosquitoes. Add to this the fact that mosquitoes are also influenced by body heat and humidity, and the situation gets complex quickly. When given a choice, mosquitoes always prefer a real human to a trap emitting CO2, lactic acid and octenol.

One of the most recent areas of research interest is the effect of skin-inhabiting bacteria on body odor and attraction to mosquitoes. Despite our cultural obsession with cleanliness and daily showers, we all harbor lots of bacteria on our skin. Up to 3% of our total body weight is estimated to consist of the bacteria in our gut, in our mouths and nose and on our skin. Most skin bacteria are not necessarily harmful to us, but feed on the various oils and fatty acids emitted by the skin. The waste products of this daily banquet are chemical compounds excreted by bacteria, some of which are also attractive (or repellent) to mosquitoes.

I asked Debboun whether there was any truth to the fact that people who consume alcohol are more attractive to mosquitoes. I had read in a couple of sources that alcohol consumption seems to be one of the more well established factors that can increase a person’s attractiveness to mosquitoes. He admitted there was some anecdotal relationships between beer and bites, but insisted that even if it is true, we still lack solid evidence to show why alcohol would make us more attractive to mosquitoes. Similarly, he said, there is no proof that taking Vitamin B, as claimed by many, confers repellency to mosquitoes.

We know that some externally applied compounds can make us either repellent or chemically invisible to mosquitoes. The best example is DEET, the most popular and effective ingredient in insect repellents. In common use since the 1950s, scientists still argue about how exactly DEET works. It appears that DEET acts by blocking antennal receptors (where insects smell) to prevent them from sensing our body chemicals, especially lactic acid. But the complete picture of how DEET works so well is still debated.

Regardless of how they work, it is critical for all of us who spend time outdoors this summer to make use of a good repellent. For a comparison of the major repellents, see the repellent calculator provided by the U.S. Environmental Protection Agency.

One researcher suggests that perhaps the key is not how attractive we are to mosquitoes. It’s who we hang out with. To protect yourself from mosquitoes you just need to find someone who is more attractive than you are and hang out with them. Come to think of it, my wife must have figured that out a long time ago.

Time to bait for fire ants!

Posted on May 6, 2014 by p-porter

If you haven’t tried them yet, fire ant baits are the best tools for really managing fire ants. They are relatively inexpensive, require little labor to apply, and are safe for both you and the environment. The biggest drawback of baits is that they cannot be used all year round. Instead applications must be timed to periods when fire ants are actively looking for food, foraging in ant worker lingo.

An inexpensive cooking thermometer can tell you the best time to apply fire ant baits.

Many years ago a researcher at Florida State University, named Sanford Porter, spent an entire year of his life (three times a day, once a week) monitoring fire ants coming to little bits of hot dog. Along the way he carefully monitored surface and below-ground soil temperatures, relative humidity, time of day, soil moisture, rainfall, and air temperature. Porter found that the best way to tell when fire ants would be out foraging (and thus, when they are most likely to find and collect bait) was when the temperature of the soil at about an inch was between 70 and 95 degrees F. While fire ants will forage outside that range, these are their favorite temperatures.

This morning and afternoon I went outdoors and took the soil temperature in the lawn surrounding my office in Dallas, TX. The temperatures at one inch averaged between 74 and 82 degrees, in morning and afternoon. This is the sweet spot for fire ants, and lets me know that fire ant baiting season is back again!

The best time of year for fire ant bait applications in north Texas is usually between May and September. While the ideal baiting time will vary from north to south, the soil temperature rule of thumb seems pretty consistent. You can check your own soil temperature with an inexpensive metal thermometer, like those used for outdoor grilling.

By the way, soil temperature is also changes throughout the day. Today, anytime during the day would be a good time to broadcast a fire ant bait. But as any seasoned Texan will tell you, there’s a mighty big difference in temperatures between May and July. In July soil temperatures, even at one inch-depth, soar well over 100 degrees, effectively shutting down most fire ant foraging during the day.

During the hot months, the best time to apply fire ant bait is late in the evening. Bait applied in the morning hours, even when soil temperatures are still favorable, are exposed to high temperatures and bright sunlight, both of which are likely to render bait less tasty to ants. By applying baits late in the day, they will be available to fire ants during their most favored time for foraging, throughout the night.

To learn more about the benefits of baiting for fire ants, and how to select the right bait product, see the Texas Two Step Method brochure. And serve those fire ants some tasty baits.

Gall insects most active in the spring

Posted on April 3, 2014 by p-porter

Newly emerging leaves, twigs and flower parts are the most common sites for gall-maker egg laying and gall formation

Every year I receive numerous questions about strange, misshapen growths on the leaves or stems of trees. These growths, called galls, are often the result of insect egg-laying or feeding.

Galls themselves are tumor-like growths produced by the plant in response to chemicals injected into the plant by the adult or larval gall-making insect. The shape, size and form of the gall is determined by the precise chemicals chemicals used by each species of gall-maker. The mechanisms of gall formation, and how these chemicals result in very distinctive and unique galls is still poorly understood.

Vein pocket galls on the underside of southern red oak leaves, Quercus schumardii, are caused by a tiny midge fly. Numbers of these midges in some years can be severe enough to cause noticeable aesthetic damage to trees–unusual for most galls.

Most gall making insects are tiny wasps in the plant-gall making family called the Cynipidae (SIGH nip id EE). Other common galls are caused by tiny flies called gall midges. And some, like the hackberry nipplegall maker that was so common in homes last fall, are relatives of leafhoppers, called psyllids. The interesting thing is that each gall making insects make a distinctive and unique gall–unique enough that it is possible to identify the gall-maker by its gall. If you want to look for galls in our area, most galls will be found on oak and hackberry trees. It’s not usually difficult to find multiple kinds of galls on a single tree.

So today, as you look out on the spring landscape, with its rapidly greening trees, you can be sure that gall-making insects are quite hard at work. Gall formation usually takes place in the spring, when leaves and flowers and stems are rapidly growing. Only during this time of rapid cell division and growth can these insects bend plant cell division to do their bidding. Once a leaf or stem has stopped growing, these hormone-like chemicals can no longer affect the plant.

A wasp-caused gall on live oak leaves.

The purpose for insect-induced galls seems to be to provide a sheltered feeding site for the gall-maker. Because galls provide benefit for the insect at little expense to the plant (only a very few galls seem to affect plant growth or overall appearance significantly), this is sometimes referred to as a form of commensal relationship. The good news for the gardener or tree owner is that galls rarely cause much harm to plants.

Once a gall has formed on a plant, there is no need to kill the insect inside, as whatever energy loss will be suffered by the plant has already occurred. In addition, short of ripping the galls off of the plant, there is no way to kill gall making insects inside their protective homes. So its always best to let sleeping galls lie, and worry about other, more productive things–like getting your taxes done by April 15.

If there was a need to control galls on a tree, now would be the only time to do it. Sprays applied early in the spring could theoretically kill adult gall-making wasps or midges before they can inject their disfiguring drugs. But little research has gone into this practice and I don’t generally advise it.

Instead, as you gaze on the swelling buds and rapidly greening trees in your backyard, just take a minute to consider the gall-making insect. In addition to all the other rituals of spring, these tiny creatures are working like crazy out there to provide little bug caves, or retreats, for their offspring.

For more information, and pictures of common Texas galls, see our publication on galls at http://agrilifelearn.tamu.edu/product-p/e-397.htm

Insects in the City

The best in science-based, pest management solutions from Texas A&M AgriLife Extension Service