Soybean aphid infestations and reports of failures of pyrethroid insecticides to control soybean aphid
Robert Koch (Extension Entomologist), Ian MacRae (Extension
Entomologist), Bruce Potter (Extension IPM Specialist), and Phil Glogoza (Extension
Educator – Crops)
By now you should be scouting your soybean fields for
soybean aphid on a regular basis. Soybean
aphid can be found in most fields throughout the state and populations have
reached economic threshold (250 aphids per plant) in some fields in northwest
Minnesota and have require insecticide application to protect soybean
yield. In northwest Minnesota (especially
around Norman County), applications of pyrethroid insecticides are failing to
adequately control aphid populations in some, but not all, fields.
This is the third year in a row that we have received
reports of failures of pyrethroids to control soybean aphid in Minnesota. In 2015 and 2016, field-level failures of
pyrethroid insecticides were reported (Figure 1) and pyrethroid resistant
populations of soybean aphid were confirmed in Minnesota, particularly in parts
of southwest Minnesota. In addition, a
resistant aphid population was also found near Crookston in northwest Minnesota
in 2016, just north of the area experiencing problems this year.
Figure 3: Locations of reported field-level performance
problems of pyrethroids for soybean aphid management. Red indicates areas with
more widespread reports of performance problems.
A few scattered fields at economic threshold have also been
found in areas farther south this year. The
susceptibility to pyrethroid insecticides of these aphid populations is not yet
known. If aphid populations continue to build,
fields in other parts of Minnesota could also require insecticide application
in the coming weeks.
Here, we provide recommendations for management of soybean
aphid with uncertain insecticide resistance status.
Insecticide choice:
Despite the documentation of insecticide resistance in Minnesota, pyrethroid
insecticides have worked well for soybean aphid control in most parts of the
state the last two years. Therefore,
these products may continue to work well for many soybean aphid
applications. Use full labeled rates of
insecticide and high water volumes.
However, an insecticide not
containing a pyrethroid may be preferred for the first application, if
threshold-level aphid infestations occur in fields in areas where:
- failures were experienced in previous years (Figure 1) or
- in the area experiencing failures this year (near Norman County).
See Table 1 at end of article for list of insecticides for soybean
aphid control.
Post-treatment
scouting: We can no longer assume our insecticide applications will always effectively
control soybean aphid. Therefore, it is
important to scout fields three to five days after an insecticide application
to determine if adequate control of the pest was achieved. A follow-up application may be needed to
protect yield.
Alternate insecticide
groups: If an additional insecticide application is required for a field,
switch to a different insecticide group (Table 1). Insecticide group numbers are listed on the label. Alternation of individual insecticide groups
is generally more effective for insecticide resistance management.
Several formulated mixtures (pre-mixes) are labeled for
soybean aphid management (Table 1). Use
of insecticide mixtures is generally discouraged from the perspective of
insecticide resistance management. Be
aware that the different insecticides in some formulated mixtures are at
reduced rates compared to products with single insecticides. Use of insecticide mixtures can further
complicate alternation of insecticide groups for any additional applications
that may be required. In addition, the
value of the multiple insecticides in a mixture may be less if the pest has
already developed resistance to one of the insecticides in the mixture.
Further resistance management recommendations can be found
in “Insecticide resistance management in soybean”.
Determining
resistance: Several factors can cause an insecticide application not to
perform as expected. Before assuming resistance, you must rule out factors such
as misapplication of the insecticide, unfavorable weather, and recolonization
by the pest. Potential cases of soybean
aphid resistance to insecticides can be reported directly to us, or through a U
of MN Extension webpage “Report Insecticide Failures for Soybean Aphid”.
Scouting: A
refresher on scouting recommendations for soybean aphid can be found in “Scouting for soybean aphid”. The average
number of aphids per plant for a field should then be related to the economic
threshold of 250 aphids per plan (with most plants infested and aphid
populations increasing) to determine if an insecticide application is
necessary. An overview of the economic
threshold for soybean aphid and its continued validity for management of this
pest can be found in “Just the facts: A review of the biology and economics behind soybean aphid insecticide recommendations”.
Table 1. Foliar
insecticides for soybean aphid.
Representative
products
|
||||
Group
|
Class
|
Active
ingredient
|
Individual
active ingredient
|
Formulated
mixtures
|
1A
|
Carbamate
|
methomyl
|
Lannate
|
|
Organophosphate
|
acephate
|
Acephate
|
||
1B
|
Organophosphate
|
chlorpyrifos
|
Lorsban Advanced, Chlorpyrifos, Govern, Hatchet,
Nufos, Vulcan, Warhawk, Whirlwind, Yuma
|
Tundra Supreme, Cobalt, Cobalt Advanced,
Stallion, Match-Up
|
Organophosphate
|
dimethoate
|
Dimethoate
|
||
3A
|
Synthetic pyrethroid
|
alpha-cypermethrin
|
Fastac
|
|
beta-cyfluthrin
|
Baythroid
|
Leverage
|
||
bifenthrin
|
Tundra, Sniper, Fanfare, Discipline, Brigade,
Bifenture
|
Justice, Match-Up, Tundra Supreme, Brigadier,
Swagger, Skyraider, Hero, Steed, Triple Crown
|
||
cyfluthrin
|
Tombstone
|
|||
deltamethrin
|
Delta Gold, Batallion
|
|||
esfenvalerate
|
Asana XL, Adjourn
|
|||
gamma-cyhalothrin
|
Declare, Proaxis
|
Cobalt
|
||
lambda-cyhalothrin
|
Warrior II, Grizzly Z, LambdaStar, Lambda-Cy,
Lamcap, Province, Silencer VC, Taiga Z
|
Besiege, Cobalt Advanced, Double Take, Endigo,
Seeker
|
||
permethrin
|
Arctic
|
|||
zeta-cypermethrin
|
Mustang Maxx, Respect
|
Hero, Steed, Stallion, Triple Crown
|
||
4A
|
Neonicotinoid
|
acetamiprid
|
Justice
|
|
Neonicotinoid
|
clothianidin
|
Belay
|
||
Neonicotinoid
|
imidacloprid
|
Prey, Admire Pro, ADAMA Alias, Wrangler, Nuprid,
Sherpa
|
Leverage, Brigadier, Swagger, Skyraider, Triple
Crown
|
|
Neonicotinoid
|
thiamethoxam
|
Endigo
|
||
4D
|
Butenolide
|
Flupyradifurone
|
Sivanto Prime
|
|
28
|
Anthranilic diamide
|
Chlorantraniliprole
|
Besiege
|
This list is not
all-inclusive and can change with the introduction of new products; always
check the products label, consult with a qualified individual.
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