Bollworm Pest Status and Results of the 2017 USDA CAPS
Invasive Moth Pest Species Trapping Survey
It is no secret that weeds have been the problem of note that local
producers have been focusing control efforts upon during recent growing
seasons, particularly in cotton. That
made it all the more perplexing for producers when the bollworm and a few other
pests returned in force this year adding to economic inputs and impacts to our
local cotton and other crops this growing season. All and all, the bollworm menace was dealt
with by entomologists and producers pretty well locally and the majority our
crops look to have come through the issues with at least a solid harvest still
ongoing. However, the intensity of the
bollworm pressure and the need to treat several types of Bt cotton along with the
majority of non-Bt cotton fields has brought up many questions about the nature
of the 2017 bollworms. Bollworms had been
largely absent as an economic concern for several growing seasons and no one
regionally had many issues with any type of Bt for bollworm control in many
seasons. So, what was different about
these worms? Were they the dreaded Helicoverpa
armigera, the
old-world bollworm (our native bollworm is Helicoverpa
zea), that entomologist have been warning us is much worse and might show
from abroad any day?
In planning for and attempting
to monitor the arrival of the old-world bollworm and a few other moth pest
species, the local Texas A&M AgriLife IPM Unit was proud to be one partner
of many for a 2017 USDA moth trapping survey.
This trial, along with several others conducted by the Hale, Swisher,
& Floyd IPM Unit, was conducted to help answer these questions. This survey had five trapping locations over
the three-county area and was but one piece of a larger State-wide survey
within a National moth survey. Helicoverpa armigera was but one of five
invasive moth pests trapped for. The
other four were the pink bollworm, European corn borer, Egyptian cottonworm,
and the American cutworm. Moth traps
were set with two in Swisher County, one in northwestern Floyd County, and two
in Hale County. Trapping began on August
1st and continued weekly through September 21st,
completely encompassing peak typical flight patterns for the area.
There
were 427 potential invasive moths trapped on designed pheromone lures total in
2017. All captured moths were first checked
at the IPM Unit’s laboratory in Plainview for preliminary identification. From Plainview there were 46 possible positive
invasive moths forwarded on to the Texas A&M AgriLife Extension Insect
Identification Lab in College Station.
With Helicoverpa armigera and Helicoverpa zea
only visual difference coming through detailed dissection and with the only
working lure still attracting some zea
moths there were a lot of moths to methodically sort through. Of the moths sent for identification through
dissection or closer analysis 42 of the 46 potential moths were old-world
bollworm candidates. Of the 42 old-world
bollworm candidates, 0 were Helicoverpa
armigera.
This
means that our 2017 bollworm issues all came from Helicoverpa zea, the native bollworm. While the results of the survey both
State-wide and Nationally are still being compiled. This is good news locally in that the
old-world bollworm, and the added control difficulties it will bring
with it, are not here yet. This is bad
news in that our native bollworms are getting tougher to kill and it means we
are still on the lookout for the dreaded Helicoverpa armigera and ponder just how bad will
they be?
Adult bollworm moth trap, checked weekly. |
What this study
found and what we witnessed in the field confirms what entomologists from
across the cotton belt where bollworms are an annual pest problem have been
sharing with us. Worms are coming
through Bt and older applied insecticides such as pyrethroids at a more regular
pace. Locally, where we do not see
economic issues with the bollworm annually and rely on moth migrations from
other areas for our flush of bollworm activity, will we see issues in 2018 and
beyond?
bollworm damaged cotton square |
bollworm on cotton leaf |
Much of the answer
to that question is unknown. Much of our
local ‘annual’ bollworm population is a result of unpredictable migration
patterns that might not become clear until the last moment. It is possible that the bollworm migration
will not be as severe as 2017 on any given year. It is also possible that if the moth arrives
again in force that the ag economics of the region will support more grain
crops. If we have more grain crops in
the area, bollworms would tend to favor those crops instead with the grain acting
as a more preferred sink crop for bollworms where they are of limited economic
impact and avoid the less preferred host cotton.
We do know that in
areas across the cotton belt where bollworms are an annual issue, alternate and
improved IPM control plans are going into place with more regularity, and with
some added control costs. There will be
an increased use of the latest and multi-trait Bt and more use of newer and
more bollworm effective insecticides.
These actions should help mitigate bollworm control issues and likely
should be considered locally also. There
has begun a beltwide revisiting of the value of accurate weekly field scouting
across the belt to bring the best and most timely information to producers to
prevent all pests from getting out of hand.
With all factors working together, control measures should remain
economical and prevent unneeded, unexpected, and disastrous loss to crop and
income.
The
only other fact we can be certain of for next year, weeds might not be the only
major factor of control producers consider next year when selecting varieties
and crops.
Blayne
Reed
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