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Trio of pests threaten Texas crops and peopleTrio of pests threaten Texas crops and people

Mosquitoes, armyworms and fruit-damaging flies invade Texas.

August 1, 2014

8 Min Read
<p>The Aedes albopictus or Asian tiger mosquito (shown here) is one of the two mosquito species known to commonly transmit chikungunya. The other is Aedes aegypti. Both species are found in Texas.</p>

Texas AgriLife media specialists report this week on a trio of pests that threaten crops, fruits and humans.

Fall armyworms are coming in early this year, aided by unseasonable rains. A tiny pest, the spotted wing drosophila, could do significant damage to Texas fruit production. And the Aedes aegypti and Aedes albopictus mosquitoes are responsible for several cases of chikungunya disease in the state. Those mosquitoes are found in Texas.

Paul Schattenberg reports that chikungunya, a viral disease transmitted by mosquitoes, has been identified in five Texas counties — four of them in South Central Texas — and may become endemic to the state, according to Texas A&M AgriLife Extension Service entomologists.

“The first confirmed case of the disease in Texas was in Williamson County, and the most recent confirmed case was in Bexar County,” said Molly Keck, AgriLife Extension entomologist and integrated pest management specialist, Bexar County.

According to the Texas Department of State Health Services, cases have also been confirmed in Gonzales, Travis and Harris counties.

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The Centers for Disease Control and Prevention website notes chikungunya is not considered fatal, but can have serious symptoms, including severe joint pain and swelling, fever, muscle pain, headache and rash. Those most at risk are the very young, people over 65 and individuals with chronic medical conditions. The virus is not spread from person to person, and there is no treatment other than managing the symptoms.

Keck said the disease is fairly well known in Africa, Asia and Europe, but has more recently found its way into the Caribbean and the Americas.


Seek medical attention

“Since the virus is known to be in the area, people who have symptoms should go to a physician to determine what is causing their illness,” said Wizzie Brown, AgriLife Extension entomologist, Travis County. “A blood test is required to test for chikungunya.”

Brown said if people treat their symptoms at home without seeing a doctor, it can cause instances of the disease to be under-reported.

Keck noted it is “very likely” that chikungunya can become endemic to Texas, possibly on a greater scale than the West Nile virus.

“With West Nile, birds are the primary host and humans are the final or end host,” she explained. “The virus never reaches a high enough level in our bodies for a mosquito to pick it up from us. Therefore, there is a third player, birds, necessary for transmission of West Nile. But they are not necessary as a vector for chikungunya.”

Sonja Swiger, AgriLife Extension entomologist at the Texas A&M AgriLife Research and Extension Center in Stephenville, said health officials now know of two cases in Florida where people were exposed to chikungunya locally, most likely through a mosquito vector.

“These individuals had not traveled to any of the areas where the disease is prevalent,” Swiger said. “At this point, it seems like just a matter of time before the virus spreads more widely in the U.S.”

She said both Aedes aegypti and Aedes albopictus mosquitoes can carry the disease, but A. aegypti is primarily found in the southern U.S. while A. albopictushas has a much greater geographic range. Mapping of the two species by the Centers for Disease Control and Prevention shows A. aegypti is found in scattered areas of the southern U.S., whereas A. albopictus, or the “Asian tiger mosquito,” is found widely dispersed throughout the south central, southeastern and mid-Atlantic regions of the country.

For more information about chikungunya, go to http://www.cdc.gov/chikungunya/.


Prevention recommended

Best course of action is to prevent mosquito bites “And now that we have confirmed cases in Texas, it would also be wise to apply insect repellent anytime you spend time outdoors, not just during dawn and dusk when mosquitoes are typically the most active,” Keck said.. The mosquito species that transmit chikungunya are extremely active during the day.”

Keck said the most effective repellents are those containing DEET.

“Repellents with up to 30 percent DEET are usually safe for young children, but should not be used on babies or infants,” she said. “Extension recommends repellents approved by the EPA and recommended by the CDC for their ability to effectively repel mosquitoes for extended periods of time. These include DEET, picaridin, IR3535 and oil of lemon eucalyptus.”

If you need to be outside, try to wear light-colored, loose-fitting shirts or tops with long sleeves and pants, she said.

“It helps to spray repellent on your clothes too,” Keck added.

Eliminating breeding sites is also a critical control strategy, Keck says. Homeowners should empty any containers, tires, buckets, bags, birdbaths or other items that may capture rainwater and become a mosquito breeding ground.

Also, repair leaky pipes, mow tall grass, trim brush and shrubbery, empty wading pools, and fill in depressions in trees with mortar or sand. Labeled insecticide also May be helpful.

Entomologists say taking these measures may not keep someone from getting bitten by mosquitoes, but precautions can significantly reduce the number of bites, which will reduce the chance of becoming infected by a mosquito-borne disease.


Robert Burns reports on two pests that pose threats to Texas crops. Fall armyworms are more like “summer” armyworms this year due to unseasonable rains, according to Allen Knutson, Texas AgriLife Extension entomologist, Dallas.

“It’s related to the rains we’ve had in July,” which set up conditions favorable for both crops and armyworms, Knutson said.  It’s early for fall armyworms. This year, more rain – sometimes in quite heavy amounts – came in late June and early July. “It’s an interesting situation,” he said. “Armyworms cannot overwinter in the northern parts of Texas. It’s too cold for them. They all die off in the first cold weather in November. But they continue to survive in the upper Gulf Coast.”

Armyworms are the larval form of a migrating moth. In the spring, the moths begin migrating northward from the Gulf Coast, looking for favorable places to lay eggs. There are indications that the migrating moth populations are higher this year, he said.


Fruit threat

Burns also reports on a tiny insect, the spotted wing drosophila, which could cause big damage to Texas fruit growers, perhaps even ruining an entire crop, according to Texas A&M AgriLife Extension Service entomologist Erfan Vafaie, Overton.

Crops at risk include apples, Asian pears, Asian plums, blackberries, blueberries, boysenberries, cherries, cold hardy kiwis, elderberries, grapes, Italian plums, mulberries, nectarines, peaches, persimmons, plumcots, raspberries, strawberries and tomatoes

The spotted wing drosophila, a member of the vinegar fly genus, may resemble the common fruit flies, Vafaie said. But ordinary fruit flies don’t have the ability to break through the skin of berries, grapes, pears and other thin-skinned fruit.

But the female spotted wing drosophila uses a saw-like tubular organ, called the ovipositor, to hack into fresh fruit to deposit their eggs.

The eggs and the resulting larvae are microscopic and pose no risk to anyone consuming them, but by creating small tears in the skin, the spotted wing drosophila opens up the fruit to invasion by bacteria and mold, which accelerates spoilage, Vafaie said.

“They do pose risk to the fruit on their own as well,” he said. “By consuming the fruit, they can cause it to soften from the inside-out.”

In June, Vafaie found the insects in traps set as part of a high tunnel strawberry project he was working on with Dr. Russ Wallace, AgriLife Extension vegetable specialist, Lubbock.

He was not surprised to find the insect, which was introduced into the U.S. via California about 2008. He was “somewhat” surprised, however, to find relatively high numbers of the insect because there had been, to his knowledge, no previous reports by Texas growers of the insect or its damage.

“One trap had 26 female and three male SWD, out of about 60 flies total caught in the trap, a high proportion of SWD,” he said.

In Canada, as in some U.S. states, there is awareness of the pest because of the damage it can cause.

But is the spotted wing drosophila really a big risk to Texas fruit growers?

Vafaie said the first step is to more widely monitor for the insect. Fruit fly traps are easy and inexpensive to construct. See the YouTube video at http://bit.ly/1nIczx1 for how to build a trap.

Distinguishing the spotted wing drosophila from other fruit flies is a little more difficult, he said.

People with a trained eye and excellent vision will be able to see the black spot on the male fly’s first wing vein, Vafaie said. The females are distinguishable by the serrated ovipositor, but only by using a microscope.

Suspect insects can also be delivered to Vafaie for identification.

“Place suspect flies into a sealable plastic container with 70 percent or higher isopropyl alcohol, which will help preserve the flies,” he said. “No plastic bags, as they may leak. No live insects as it’s against U.S. Postal Service rules to do so.

“Include as much information as possible with the container, such as your name, date, contact information, where you found it and what fruit crops are nearby.”

Mail the package to: Erfan Vafaie, Texas A&M AgriLife Research and Extension Center, 1710 Farm-to-Market Road 3053 North, Overton, TX 75684.

For more information about shipping or identification of specimens, contact Vafaie at 903-834-6191 or [email protected].

There is also more information on Vafaie’s blog at http://sixleggedaggie.com/news.




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