Impact of Reduced-Risk Insecticides on Soybean Aphid and Associated Natural Enemies

Abstract

Insect predators in North America suppress Aphis glycinesMatsumura (Hemiptera: Aphididae) populations; however, insecticides are required when populations reach economically damaging levels. Currently, insecticides used to manage A. glycines are broad-spectrum (pyrethroids and organophosphates), and probably reduce beneficial insect abundance in soybean, Glycine max (L.) Merr. Our goal was to determine whether insecticides considered reduced-risk by the Environmental Protection Agency could protect soybean yield from A. glycines herbivory while having a limited impact on the aphid's natural enemies. We compared three insecticides (imidacloprid, thiamethoxam, and pymetrozine,) to a broad-spectrum insecticide (λ-cyhalothrin) and an untreated control using two application methods. We applied neonicotinoid insecticides to seeds (imidacloprid and thiamethoxam) as well as foliage (imidacloprid); pymetrozine and λ-cyhalothrin were applied only to foliage. Foliage-applied insecticides had lower A. glycines populations and higher yields than the seed-applied insecticides. Among foliage-applied insecticides, pymetrozine and imidacloprid had an intermediate level of A. glycines population and yield protection compared with λ-cyhalothrin and the untreated control. We monitored natural enemies with yellow sticky cards, sweep-nets, and direct observation. Before foliar insecticides were applied (i.e., before aphid populations developed) seed treatments had no observable effect on the abundance of natural enemies. After foliar insecticides were applied, differences in natural enemy abundance were observed when sampled with sweep-nets and direct observation but not with yellow sticky cards. Based on the first two sampling methods, pymetrozine and the foliage-applied imidacloprid had intermediate abundances of natural enemies compared with the untreated control and λ-cyhalothrin. KeywordsGlycine max, biological control, insecticide regulation, conservation, nontarget impacts Disciplines Agriculture | Entomology CommentsThis article is from Journal of Economic Entomology 102 (5) ABSTRACT Insect predators in North America suppress Aphis glycines Matsumura (Hemiptera: Aphididae) populations; however, insecticides are required when populations reach economically damaging levels. Currently, insecticides used to manage A. glycines are broad-spectrum (pyrethroids and organophosphates), and probably reduce beneÞcial insect abundance in soybean, Glycine max (L.) Merr. Our goal was to determine whether insecticides considered reduced-risk by the Environmental Protection Agency could protect soybean yield from A. glycines herbivory while having a limited impact on the aphidÕs natural enemies. We compared three insecticides (imidacloprid, thiamethoxam, and pymetrozine,) to a broad-spectrum insecticide (-cyhalothrin) and an untreated control using two application methods. We applied neonicotinoid insecticides to seeds (imidacloprid and thiamethoxam) as well as foliage (imidacloprid); pymetrozine and -cyhalothrin were applied only to ...

Thiamethoxam Toxicity and Effects on Consumption Behavior in Orius insidiosus (Hemiptera: Anthocoridae) on Soybean

“…Such information could allow a better characterization of the exposure levels to thiamethoxam in the field and a more accurate characterization of risk of neonicotinoids to beneficial species in soybean crops. The results on the abundance of O. insidiosus in soybean fields with neonicotinoid seed treatments are consistent with the studies by Ohnesorg et al (2009) and Seagraves and Lundgren (2012), where no significant differences in O. insidiosus abundance were observed between fields derived from neonicotinoid treated and untreated fields. Orius insidiosus is a generalist predator consuming thrips, pollen, and nectar from flowers, vegetative tissue, and aphids in soybean fields (Rutledge and O'Neil 2005).…”

Effect of Soybean Varieties on Survival and Fecundity of Western Corn Rootworm

“…Broad-spectrum insecticides are the most commonly applied treatment for control of A. glycines (Olson et al 2008), and these insecticides negatively affect a wide range of insect taxa (Ohnesorg et al 2009). Application of insecticide to soybean Þelds likely will reduce selection for rotation-resistance in D. v. virgifera.…”

What Is the Economic Threshold of Soybean Aphids (Hemiptera: Aphididae) in Enemy-Free Space?

“…A growing body of literature suggests that the level of natural enemy induced mortality of the soybean aphid may be diminishing due to agricultural practices (Landis et al 2008, Ohnesorg et al 2009, Schmidt et al 2010. Olson et al (2008) reported that the most commonly used insecticides for control of soybean aphids in the Midwest included Asana, Lorsban, Mustang, and Warrior; all are considered broad-spectrum in nature and reduce natural enemy populations in addition to aphids (Ohnesorg et al 2009).…”

“…Olson et al (2008) reported that the most commonly used insecticides for control of soybean aphids in the Midwest included Asana, Lorsban, Mustang, and Warrior; all are considered broad-spectrum in nature and reduce natural enemy populations in addition to aphids (Ohnesorg et al 2009). The research presented here is the Þrst step in analyzing how our current soybean aphid management practices will respond to the changing soybean agricultural ecosystem in the midwestern United States.…”

“…Pesticide use in soybean also has increased since the introduction of the soybean aphid to the United States (NASSÐUSDA 1999(NASSÐUSDA , 2005. The primary insecticides to control the soybean aphid are broad spectrum in effect, reducing natural enemy populations along with aphid populations (Jeffries and Lawton 1984, Johnson et al 2008, Ohnesorg et al 2009). Removal of natural enemies from an agroecosystem can lead to rapid recolonization by a pest and secondary outbreaks due to the creation of enemy-free space (Jeffries and Lawton 1984).…”