This post is taken directly from an Agrilife Communications news story.
By: Robert Burns
‘Stealthy’ pest damages inside of
stems – not outside
Photo Caption: Bermuda grass stem maggot infestation begins when the
adult fly lays its eggs on a stem near a node, according to Dr. Allen Knutson,
Texas A&M AgriLife Extension Service entomologist, Dallas. (Photo by Dr.
Dennis Hancock, University of Georgia forage Extension specialist)
Writer: Robert Burns, 903-834-6191,
rd-burns@tamu.edu
OVERTON — The presence of a new Bermuda grass pest has been confirmed in Van
Zandt County, and producers are advised to be on the lookout, said Texas
A&M AgriLife Extension Service experts.
Unlike other insects that attack plants from the outside, the Bermuda grass
stem maggot damages them from inside, according to
Dr. Vanessa
Corriher-Olson, AgriLife Extension forage specialist, Overton.
“Basically, they consume material inside the stem, unlike armyworms or
grasshoppers, where the damage is external,” she said.
Corriher-Olson did her graduate work in Georgia, where the pest has had a
presence since 2010, and she is familiar with the damage it does. The Van Zandt
field is the first confirmed instance of the pest in Texas.
She said the pest is native to southern Asia, common from Japan to Pakistan.
Somehow it made its way to the U.S., where it was found in three Georgia
counties.
Bermuda grass stem larvae are yellow and less than an
eighth inch long. (Photo by Dr. Dennis Hancock, University of Georgia forage
Extension specialist)
“It’s relatively new to the U.S., and very little is known about its life
cycle yet,” Corriher-Olson said.
“It is not yet known how damaging this insect will be in Texas,” said
Dr.
Allen Knutson, the AgriLife Extension entomologist at Dallas who
confirmed the identity of larva found in a Van Zandt County field of irrigated
Bermuda grass this summer.
What is known is infestation begins when the adult fly lays its eggs on a
Bermuda grass stem near a node, Knutson said. The larvae, which grow to be
about an eighth-inch long, look like a pale yellow maggot. They burrow into the
Bermuda grass shoot to feed. This feeding causes the top two to three leaves to
wither and die. Cutting open the stem just below these dead leaves will reveal
the maggot and the brownish feeding site on the stem.
The adult flies may go unnoticed; they are small with dark eyes, Knutson
said.
The early stages of an infestation may go unnoticed too, Corriher-Olson
added.
“People are not going to realize they have the pest until they see the
damage,” she said. “It looks similar to what you might see from a light frost.
Stem tops are whitish or lighter in color than unaffected plants. Only the top
parts of the shoots are damaged. The lower leaves on the shoot remain green.
The leaves above the feeding site wither and die.”
To further complicate identification, the larva may have already developed
into flies and left the plant before their damage is apparent, Corriher-Olson
said. And there may be several generations each summer. The fly’s life cycle is
usually about three weeks, but it can be as short as 12 days.
Dr. Larry
Redmon, AgriLife Extension state forage specialist, College
Station, noted unconfirmed reports of the Bermuda grass stem maggot have been
coming to his office since last year.
“We had a call from a producer in Waller County during 2012, which was the
first one I know of,” he said. “Additionally, we have had a report of what
appears to be stem maggot damage in Comanche County this year.”
The amount of yield reduction seems to depend upon growing conditions,
Corriher-Olson noted.
Photo Cutline: Damage done by the infestation begins when the adult
fly lays its eggs stem nodes. The damage looks similar to what one might see
from a light frost, according to Dr. Vanessa Corriher-Olson, Texas A&M
AgriLife Extension Service forage specialist, Overton.(Photo by Dr. Dennis
Hancock, University of Georgia forage Extension specialist)
“Typically, damage is more likely to be found in a hay meadow, not in a
grazed field, because the flies won’t have time to complete their life cycle,”
she said.
Management strategies depend upon how near the hay crop is to harvest when
the damage is identified, Corriher-Olson said.
“If damage is found within one week of harvest, the recommendation from
Georgia is to harvest as soon as possible,” she said. “The longer they wait,
the more likely the damage will spread, and there will be further reduction in
yields.”
If the pest and its damage are confirmed one to three weeks after the
previous harvest, the recommendation is to cut the damaged areas, bale the damaged
grass, and remove it from the fields, Corriher-Olson said.
“The only threat posed by leaving the hay in the field is that it’ll compete
with any attempts of the plant to regrow, therefore decreasing the yield of the
next cutting. Leaving the hay in the field does not increase infestation,” she
said. “It’s unlikely that the damaged areas will contribute significantly to
yields during the next harvest.”
The pest can also be controlled with foliar applications of several
inexpensive insecticides, Knutson said. Current recommendations are to treat
after a cutting if damage levels are high.
However, economic thresholds for treatment in Texas have not yet been
established, he said.
All three AgriLife Extension specialists recommend producers who suspect
they have an infestation contact the AgriLife Extension agent in their county
to confirm they have the pest before treating or using other control measures.
Contact information for all offices may be found at
http://counties.agrilife.org/ .
They may also contact Corriher-Olson at 903-834-6191,
vacorriher@ag.tamu.edu“>vacorriher@ag.tamu.edu.
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