Soybean aphid infestations increasing quickly in some fields

Robert Koch, Extension entomologist, and Bruce Potter, Extension IPM specialist

Infestations of soybean aphid are increasing quickly in some Minnesota soybean fields, with some fields exceeding treatment thresholds (more than 250 aphids per plant). However, infestations are variable across the landscape (i.e., some fields still have very few aphids), so scouting is essential to know the status of the infestation in individual fields. Large numbers of alate (winged form) soybean aphids are now being produced in “hot spots” of many fields to disperse and colonize both nearby and distant soybeans. As the growing season progresses, late-planted, or otherwise less mature soybean fields will be particularly attractive and suitable for aphid population growth. Be advised that over the past week, fields in several areas of Minnesota have been inundated with alate aphids and their tiny offspring.

If you need to refresh your memory on scouting for this pest, take a look at “Scouting for Soybean Aphid”.

Use the threshold 250 aphids per plant (with more than 80 percent of the plants infested with aphids, and the aphid population increasing) to determine when to treat fields for aphids. Remember that this threshold is the trigger point to begin lining up an insecticide application within the next 5-7 days. Infestations at this threshold are not affecting soybean yields, but they indicate that the infestations are likely to reach such damaging levels in the near future. Further guidance related to this decision making can be found in “Fact-Based Soybean Aphid Insecticide Recommendations”, which was written by a team of extension entomologists from across the Midwest.

If an insecticide application is needed to protect soybean from soybean aphid, carefully consider the insecticide options available. There has been some confusion about the regulatory status of chlorpyrifos-containing insecticides for use against soybean pests. For 2024, chlorpyrifos-containing products that are registered for use in Minnesota can be used for the crops/purposes listed on their labels. Remember that some populations of soybean aphid are resistant to some pyrethroid (group 3A) insecticides. Finally, newer insecticides such as sulfoxaflor, flupyradifurone, and afidopyropen not only control soybean aphids, but have the benefit of being gentler on aphid predators and parasites.

Table 1. Insecticides labeled for control of soybean aphid in Minnesota, 2024.* 

Insecticide group	Common name	Individual A.I. (example)	Formulated mixtures (examples)
1A - Carbamate	methomyl	Lannate, Nudrin
1B - Organophosphate	acephate	Acephate, Bracket 97, Orthene 97
	chlorpyrifos*	Govern, Pilot, Warhawk	Lambdafos, Match-Up
	dimethoate	Dimethoate, Dimate
3A- Synthetic pyrethroid	alpha-cypermethrin	Fastac	Renestra
	beta-cyfluthrin	Baythroid	Leverage
	bifenthrin	Bifenture, Brigade 2EC, Discipline, Ethos XB, Fanfare, Tundra EC, Sniper	Elevest, Hero, Justice, Ridgeback, Skyraider, Triple Crown, Tundra Supreme
	cyfluthrin	Tombstone
	deltamethrin	Batallion, Delta Gold
	esfenvalerate	Adjourn, Asana XL
	gamma-cyhalothrin	Declare, Proaxis
	lambda-cypermethrin	Grizzly Z, Grizzly Too, Lambda-Cy, LambdaStar, Lamcap, Province, Silencer VC, Tiaga Z, Warrior II	Besiege, Double Take, Endigo
	zeta-cypermethrin	Mustang Maxx, Respect	Hero, Steed, Triple Crown
4A - Neonicotinoid	acetamiprid		Justice
	clothianadin	Belay
	imidacloprid	Advise4, Alias, Nuprid Prey, Sherpa	Brigadier, Leverage, Skyraider Triple Crown
	thiamethoxam		Endigo
4C - Sulfoximine	sulfoxaflor	Transform	Ridgeback
4D - Butenolide	flupyradifurone	Sivanto
9D -Pyropene	afidopyropen	Inscalis (Sefina)	Renestra

Not a complete list of product names.
*The list of chlorpyrifos formulations registered with the State of Minnesota is changing. Some formulations may not be currently registered for use in Minnesota.
Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.