Western Bean Cutworm Scouting
It is time to start thinking about scheduling for scouting for western bean cutworm an important pest of corn and dry beans. Larval feeding damages both crops through reduced yield and quality. In corn, direct feeding losses may be compounded by fungal infections associated with larval feeding and waste products. In dry beans, damaged or “worm-chewed” beans are a significant quality factor for both processed and bagged dry beans.
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[00:00:00.254]This is Amy Timmerman with
[00:00:03.664]and this week's
[00:00:05.494]It is time to start thinking
about scheduling for scouting
[00:00:08.421]for western bean cutworm an
important pest of corn and dry beans.
[00:00:12.121]Larval feeding damages both crops
through reduced yield and quality.
[00:00:16.421]In corn, direct feeding losses
may be compounded by
[00:00:19.764]fungal infections associated with
larval feeding and waste products.
[00:00:24.335]In dry beans, damaged
or “worm-chewed” beans
[00:00:28.045]are a significant quality factor for
both processed and bagged dry beans.
[00:00:32.123]Western bean cutworm moths prefer
to lay their eggs on corn plants
[00:00:35.763]when they are approaching
[00:00:37.953]as the tassel is the preferred
food source for newly hatched
[00:00:40.763]Western bean cutworm larvae.
[00:00:43.143]A match between the flight of the
moths and the late whorl to
[00:00:46.336]early tassel stage of corn can
result in high levels of infestation.
[00:00:50.794]Western bean cutworm has
one generation per year
[00:00:54.114]with moth emergence usually
beginning in early July.
[00:00:57.182]The emergence date
can be predicted by
[00:01:02.002]Starting heat unit
accumulations on May 1,
[00:01:05.012]using a base air
temperature of 50°F,
[00:01:07.412]growing degree days for 25
percent moth emergence is 1,319,
[00:01:14.215]50 percent is 1422,
and 75 percent is 1536.
[00:01:21.449]Overall, the estimated dates
for Western bean cutworm flight
[00:01:24.945]in 2023 are similar to
those from 2021and 2022,
[00:01:30.301]although some areas have
predicted earlier flights
[00:01:33.391]compared to last year (such
as Ainsworth and Concord, Nebraska).
[00:01:37.051]For Ainsworth 25% flight is predicted
to occur around July 15th.
[00:01:43.038]Western bean cutworm eggs
can be found on the upper
[00:01:45.878]surfaces of corn leaves, and the
lower surfaces of dry bean leaves.
[00:01:49.688]Eggs are found in masses ranging from
five to 200, with an average of 50-85.
[00:01:55.471]When first laid,
the eggs will be white
[00:01:58.091]and gradually darken during
the five- to seven-day development.
[00:02:01.124]Freshly hatched larvae will first eat the
eggshells before consuming the host plant.
[00:02:06.530]Older larvae can be
identified by two dark
[00:02:09.730]rectangular spots directly
behind their head.
[00:02:12.730]Adult moths are identifiable by a white
band on the anterior margin on the
[00:02:18.710]forewing followed by a white circle
halfway down the wing and a
[00:02:22.280]white crescent located
two-thirds down the wing.
[00:02:26.280]Western bean cutworm moths
are about three-fourths of an
[00:02:29.250]inch long by 1.5 inches wide.
[00:02:32.070]It is more difficult to scout dry bean
fields for Western bean cutworm,
[00:02:35.495]but pheromone traps can be used to
provide an estimate of a possible
[00:02:39.495]infestation and should be installed
prior to the predicted 5% flight date.
[00:02:44.399]If fewer than 700 moths are
caught up to peak, there is low risk;
[00:02:48.489]if more than 700 but fewer than
1,000 moths are caught
[00:02:52.504]then there is moderate risk;
and if there are more than
[00:02:56.172]1,000 moths caught
then the risk if high.
[00:02:59.129]If an insecticide
application is warranted,
[00:03:01.269]it should be made 10-21
days after peak flight
[00:03:05.238]in dry bean and when 95%
of plants have tasseled in corn.
[00:03:09.764]For more information
on insecticide options
[00:03:12.394]contact your local extension office
or on the University of Nebraska–Lincoln
[00:03:16.614]Department of Entomology website
[00:03:22.651]This has been Amy Timmerman
with Nebraska Extension.
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