Abstracts

Butler, Casey D. and Robert J. O’Neil. 2007. Life history characteristics of Orius insidiosus (Say) fed Aphis glycines Matsumura. Biological Control, Volume 40 (3): 333-338.

Abstract: The soybean aphid, Aphis glycines Matsumura, is a new invasive pest of soybeans throughout most of the soybean production areas of North America. Field studies have demonstrated that the indigenous predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid early the soybean crop season. Because soybean aphid is newly introduced into North America, the life history characteristics of predators fed this aphid are not known. In laboratory assays, we measured the survival, development, longevity and reproduction of O. insidiosus fed 1, 3, 6 or 12 seconds to third instars of soybean aphid. O. insidiosus nymphal development decreased from 34.0 to 21.4 days as the number of soybean aphid nymphs provided increased from 1 to 6 aphid nymphs daily. Stage-specific mortality was highest at 68% for first instar O. insidiosus nymphs fed 1 soybean aphid nymph per day. Adult longevity (43.9 days) and fecundity (49.7 eggs per female) was highest for O. insidiosus fed 6 soybean aphid nymphs daily, but longevity (23.5 days) and fecundity (10.1 eggs per female) declined for adults fed 1 soybean aphid nymph daily. The intrinsic rate of increase of O. insidiosus ranged from 0.048 to 0.133. Compared to other prey species, soybean aphid is an adequate prey item for O. insidiosus. Our results suggest that O. insidiosus will be most effective in suppressing soybean aphid population growth in the initial phase of the aphid’s colonization of soybeans.

Brosius, Tierney R., Thomas E. Hunt, and Leon G. Higley. The impact of natural enemies on the density and within-plant distribution of soybean aphid (Aphis glycines Matsumura) at the western edge of its range. Presented at the Annual Meeting of the Entomological Society of America, December 2006.

Abstract: Many animal and plant species are transported across the globe each year. The introduction of an exotic pest species often causes devastating losses in its new country of origin. An unfortunate example of such an exotic insect pest is the soybean aphid, Aphis glycines Matsumura, which was discovered in the Great Lakes region of North America in the summer of 2000. Since its introduction the soybean aphid has rapidly moved across the Midwest spreading to 21 U.S. states and three Canadian provinces as of the 2003 growing season. The soybean aphid has become a serious pest of soybean, causing yield losses in the Midwest of up to 30% and costing farmers millions of dollars annually. Understanding how natural enemies impact aphid populations in the field is an important component in developing comprehensive management plan.

The impact of naturally occurring predators in the field on soybean aphid densities and their within-plant distribution was examined using exclusion cages during July-September 2004 and 2005. Plots were surveyed twice weekly for soybean aphid and natural enemy densities. Cage effects on temperature and soybean growth were found to be insignificant. Significant differences in aphid density and aphid location among the soybean plant canopy were found between treatments. These differences between treatments were attributed to the presence of natural enemies which were excluded by caged treatments. Orius insidiosus(Say) was the most commonly occurring predator in the field. The large differences in aphid abundance and aphid location within the plant canopy between years was associated with the higher number of O. insidiosus found in the field in 2005 than in 2004. This study indicates that naturally occurring predators in the field can have a large impact on soybean aphid densities if natural enemies are present at the beginning of the season to suppress aphid population growth.

Chacon, Jeremy M. and George E. Heimpel. Biotic interference of a classical biological control agent of the soybean aphid. Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: Biotic interference of parasitoid biological control agents by resident species can severely hamper biological control efforts. In aphid biological control, where intraguild predators of parasitoids such as coccinellids are often abundant, the risk of biotic interference may be very strong. The myriad of possible ecological interactions a classical biological control agent may be faced with in the field makes pre-release evaluations of biotic interference problematic. However, simulating a release using a surrogate biological control agent may aid in making predictions about the biotic interference that will occur during the actual release. In 2005, we simulated a parasitoid release against the soybean aphid and found that biotic interference of an introduced parasitoid was likely, but that interference would not be strong enough to render the release unworthwhile. In 2007, a permit for releasing Binodoxys communis, the actual biological control agent of soybean aphid, was obtained and B. communis was released in North America. We examined biotic interference against B. communis using a cage study that excluded B. communis, resident natural enemies, or both from soybean aphid infestations, and compared our assessment of B. communis with our 2005 simulation. We also assessed temporal interactions with resident predators, hypothesizing that interference would be strongest late-season, when resident enemies are generally abundant. Finally, we conducted a molecular gut-contents analysis, to determine which predator species / life stages caused biotic interference of B. communis. We present these results, and discuss the implications this work has for soybean aphid biological control.

Costamagna, Alejandro C. and Douglas A. Landis. 2007. Quantifying predation on soybean aphid through direct field observations. Biological Control, Volume 42 (1): 16-24.

Abstract: The soybean aphid, Aphis glycines (Hemiptera: Aphididae), is the most important insect pest attacking soybeans in North America since 2000. Several studies have documented strong impacts of generalist natural enemies on A. glycines populations using predator exclusion cages and correlating predator and aphid abundances. However, to date no studies directly observed and quantified the natural enemy groups that attack A. glycines in North America under field conditions. In 2005, we conducted 72 h of direct observations of predation on natural populations of A. glycines in Michigan. The observations were conducted during three consecutive weeks during morning, afternoon and evening, in replicated 1 m2 areas. A total of 643 predators within 12 groups and 211 predation events on A. glycines were observed. Transient predators such as Harmonia axyridis and Coccinella septempunctata (Coleoptera: Coccinellidae) accounted for most of the observed mortality and were very effective on a per capita basis, despite relatively short residence time in the observed patches. Transient predators responded positively to increased A. glycines field densities. Resident predators, particularly Orius insidiosus (Hemiptera: Anthocoridae), were abundant and accounted for many predation events, but they were not as effective on a per capita basis and did not respond to changes in aphid density. Lower predation was obtained on A. glycines located at the bottom portion of the plants and on alate aphids. We concluded that coccinellids exerted most of the mortality observed and have the potential to rapidly respond to changes in aphid density with high per capita rates of predation.

Costamagna, Alejandro C., Brian P. McCornack, and David W. Ragsdale. Incorporating natural enemies into current economic thresholds for soybean aphid. Presented at the Annual Meeting of the Entomological Society of America, December 2007.

The soybean aphid, Aphis glycines, is currently the most important insect pest of soybeans in the Midwest USA. Previous studies have shown a key role of generalist natural enemies as mortality factors for soybean aphid, capable of providing regulation throughout the entire growing season. However, it is unknown what levels of natural enemy suppression are needed to sustain soybean aphid control and under what conditions aphids escape regulation. We conducted a field study using commercial and experimental fields in five locations in Minnesota to quantify the impact of natural enemies on soybean aphid per capita growth rates. In each location, three fields were sampled for aphid and natural enemy populations weekly throughout the field season. In each field natural enemies were sampled using five METHODS: transect counts, plant counts, quadrat counts, sweep nets, and sticky cards. Natural enemy impacts on soybean aphid were recorded weekly by comparing caged plants with open controls for naturally occurring aphid populations. The results of this study will establish: 1) under what combination of abiotic (temperature) and biotic (natural enemies, plant phenology, etc) factors aphids are likely to escape control, 2) what are the key natural enemies influencing soybean aphid field populations, 3) what are the best sampling methods to monitor those natural enemies, and 4) what levels of natural enemy suppression are needed to maintain soybean aphid under control.

Heidel, T. H. and R. J. O’Neil. Survey of aphids of Indiana and their associated natural enemies as part of a study of nontarget effects of a classical biological control program of the soybean aphid. Presented at the annual meeting of the Entomological Society of America, December 2007.

Abstract: Since its discovery in 2000, the soybean aphid (Aphis glycines Matsumura) has become the most economically important pest of US soybean production, and classical biological control is being attempted in several Midwest states. Rising concerns over non-target effects in classical biological control have resulted in an increased effort to reduce such effects through the study of potential non-target organisms. As part of a multi-state effort to assess potential non-target effects in soybean aphid biological control, a survey of native aphids and their associated natural enemies was conducted at six Indiana prairies in 2006 and 2007. The aphid survey provided information on aphid species present in Indiana and the natural enemies of these aphids, particularly parasitoids. Factors such as the taxonomy, phenology, abundance, distribution, and natural enemy load were used in assessing the risk of non-target effects on individual aphid species. Results from the aphid survey and risk assessment will be discussed.

Krass, Heidi and Eileen M. Cullen. Efficacy and non–target effects of national organic program-compliant insecticides for soybean aphid (Aphis glycines) and multicolored Asian lady beetle (Harmonia axyridis). Presented at the Annual Meeting of the Entomological Society of America, December 2006.

While organic soybean growers rely primarily on cultural practices and biological control to manage insect pests, aphid densities periodically overcome these measures. In this study, we evaluated efficacy of four Organic Materials Review Institute or National List allowed insecticides against Aphis glycines. Because biological control is a required component of soybean aphid management in organic systems, insecticides must be compatible with biological control agents. The Asian lady beetle (Harmonia axyridis) is a key predator of soybean aphid in soybeans in the Midwest. We included H. axyridis in our study to determine non-target effects of the insecticides.

Treatments included pyrethrum [PyGanic® EC 1.4 (2.92 l/ha], azadirachtin [Neemix® 4.5 EC .511 l/ha], insecticidal soap [M-Pede® 4.68 l/ha], and a narrow range horticultural mineral oil, [Omni Supreme® 18.68 l/ha]. Treatments, including a water control, were applied in a completely randomized block design laboratory bioassay using a Potter Spray Tower at the highest labeled field rate for aphids in soybeans or legume crops. Cohort A. glycines adults and nymphs were monitored for mortality to determine efficacy. H. axyridis eggs, first instar, third instar, pupae and adults were monitored for mortality to determine non-target effects. Results are discussed within the context of establishing fundamental information about the effectiveness of these materials against the soybean aphid and important considerations for related on-farm field experiments in certified organic soybeans.

Loden, Anthony S. and George E. Heimpel. Phoretic association of Binodoxys communis (Hymenoptera: Braconidae) and the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae). Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: The aphidiine braconid Binodoxys communis is currently in its first year of release as a classical biological control agent against the soybean aphid, Aphis glycines Matsumura. Like most aphid species, the soybean aphid produces both winged (alate) and wingless stages. Adult alates typically leave the natal plant to colonize new plants, fields and habitats throughout the growing season (summer migrants) and early fall (gynoparae). This study examines the phoretic association between B. communis and the soybean aphid to determine: 1) the parasitism rate of alate and alatoid nymph in the field and 2) whether or not parasitized alates have the capability to transport B. communis eggs and young larvae away from the natal plant. Thirty B. communis females and 20 males were released into 15cm diameter x 100cm tall field cages capped with an inverse funnel leading to a removable collection cup. Alates were collected daily over the course of 10 days and placed on individually caged, non-infested soybean plants. After 10 days, these plants were examined for the presence of mummies as an indicator for the phoretic movement of B. communis within soybean aphid alates. In addition, aphid and mummy counts were conducted on the original field cage plants after 10 days to determine overall alate and alatoid nymph parasitism rates. The results of this study reveal the potential dispersal capability of B. communis in the field and will aid in the development of future region-wide release strategies.

Noma, Takuji and Michael Brewer. Seasonal abundance of aphid predators and parasitoids in summer and overwintering host vegetation of soybean aphid. Presented at the Annual Meeting of the Entomological Society of American, December 2007.

Abstract: We monitored predators and parasitoids attacking soybean aphid (Aphis glycines Matsumura) in summer (soybean fields) and overwintering (buckthorn bushes) habitats of soybean aphid in 2005 and 2006. Potted soybean plants infested with soybean aphid were used to periodically sample aphid enemies in these two habitats between May and October. Our objective is to assess habitat affiliation and seasonality associated with aphid enemy species occurring in the contrasting soybean aphid habitats. The preliminary assessment of 2005 data indicated that predatory flies (Cecidomyiidae and Syrphidae) generally occurred at similar seasonal abundances between soybean fields and buckthorn bushes, while parasitoids (Aphelinidae and Braconidae) were found mostly in soybean and not buckthorn.

Noma, Takuji and Michael J. Brewer. Pathogens of soybean aphid and other aphids in Michigan soybean production areas. Presented at the Annual Meeting of the Entomological Society of American, December 2007.

Abstract: Pathogens of soybean aphid and other aphid species present on other crops in soybean production regions were surveyed in Michigan in 2005 and 2006. Soybean aphid occurred at moderate to high numbers in 2005 (150 to 1,000 aphids per plant) and was much less common in 2006 as of July. Aphid pathogens were sampled four times each year. Fungal infection of soybean aphid was detected in early August of 2005 during or soon after peak aphid populations. All cases of soybean aphid infection were caused by the fungal species Pandora neoaphidis. Higher proportions of alates (up to 90 %) were infected than apterae (up to 3 %). Pandora neoaphidis also infected pea aphid on alfalfa, and spotted alfalfa aphid was infected by Zoophthora sp. Three other species of aphids were found on corn and wheat, but they occurred at low numbers and no visual signs of infection were observed. These results indicate that fungal pathogens contribute to soybean aphid mortality, epizootics occur, and other infections occur on aphids in alfalfa found in the soybean production region of Michigan.

Ohnesorg, Wayne J. and and Matthew E. O'Neal. Are Iowa prairies a source for soybean aphid (Aphis glycines) predators? Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: There is growing interest in whether native, perennial habitats can serve as reservoirs and refugia for natural enemies of annual crop pests. In Iowa, prairies once covered the majority of the landscape, and there is a desire to reconstruct these habitats for the improvement of ecosystem services. We investigated the aphidophagous community within prairies if they contained species important for soybean aphid management, such as Coccinellidae. Prairies were selected based on distinct categories of restoration; 10 reconstructed prairies that had been seeded into agricultural fields, 11 native prairies that had not been seeded into, and 10 reconstructed prairies adjacent to native prairies. Prairies were selected by these categories to account for variations in habitat quality and subsequent community associations.

During 2006 and 2007 prairies were sampled for aphid predators using sweep nets. Sampling was conducted weekly on 3 sites while the rest were sampled once a month. We found 33 species or families considered predators of soybean aphid, of which, 4.3% were coccinellids. In general we observed a coccinellid community dominated by native species (Brachiacantha decempustulata, Brachiacantha ursina, Colleomegilla maculatta, Cycloneda munda, Diomus sp., Hippodamia convergens, Hippodamia parenthesis, Hyperaspis sp., and Microweisea sp.) with few if any invasives (Coccinella septempunctata and Harmonia axyridis). This is in sharp contrast to Iowa soybean fields were invasive coccinellids dominate. We will discuss the impact of prairie restoration on the aphidophagous community and to what extent these habitats may improve the biological control of soybean aphids.

O'Neal, Matthew E., M. Felicitas Avendano, Gregory L. Tylka, Terry Niblack, Michael Gray, and Josh Heeren. Toward integrated management of the soybean cyst nematode and soybean aphids. Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: Soybean cyst nematode (SCN), Heterodera glycines, and soybean aphid, (Aphis glycines) can account for 30-50% soybean yield reductions in the north central United States. These pests have common geographical distribution and their life histories overlap during the growing season. Currently, nematodes and aphids are managed individually with no understanding of, or consideration for, the potential interactions that may occur between these two classes of soybean pests. Our goal is to elucidate if current IPM strategies need to be altered to account for the interaction of SCN and soybean aphid. Our objectives are to answer (1) if soybean aphids are more or less attracted to soybean infected with SCN than to noninfected plants, (2) if soybean aphid and SCN reproduction is greater in the presence of each other and if this interaction varies by the type of host genetics conferring SCN resistance, and (3) how these pests affect soybean yield quantity and quality. We report a series of experiments to address these objectives. Using laboratory-based, behavioral assays we have characterize soybean aphid orientation to soybeans infected and noninfected with SCN. Field experiments conducted in microplots established in noninfested or SCN-infested soil will address objectives 2 and 3. To address objective 3, entire microplots were caged and infected with either soybean aphids, SCN, both, or neither pest. Completion of these objectives will result in an expanded knowledge base that will lead to improved recommendations for managing both SCN and these insect pests of soybean.

Pavak, Daniel M., Alan Sundermeier, and Luke Sundermeier. Predatory arthropod communities in Ohio soybean agroecosystems infested with the soybean aphid, Aphis glycines. Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: Soybean agroecosystems infested with soybean aphid, Aphis glycines (Hemiptera: Aphididae) during 2007 in northwest Ohio were surveyed to determine predatory arthropod communities present. Predatory arthropods were sampled by sweep netting, yellow sticky traps, and direct observations of aphid-infested plants. Soybeans were sampled from time of emergence in May until senescence in late summer. Predatory arthropods included several species of ladybird beetles (Coccinellidae), such as Harmonia axyridis, Coccinella septempunctata, and Coleomegilla maculata, the predatory hemipteran, Orius insidiosus (Anthocoridae), and other predatory Hemiptera (Nabidae and Reduviidae), green lacewings(Neuroptera: Chrysopidae), and spiders (Araneae). A number of these predatory arthropod species may have potential as biological control agents of Aphis glycines in Ohio.

Tilmon, Kelley J. , Deirdre A. Prischmann, Louis Hesler, and Jonathan Lundgren. Impact of Harmonia axyridis and Orius spp. on soybean aphids in a field cage experiment. Presented at the Annual Meeting of the Entomological Society of America, December 2007.

Abstract: A rich guild of predators and parasitoids prey upon the soybean aphid (Aphis glycines Matsumura), leading to potentially complex ecological interactions which may vary with time, region, local and landscape factors. It is clear from a number of studies that natural enemies are a significant source of mortality and control for the soybean aphid. Less clear is the relative importance of different species of natural enemies under different conditions. This question is relevant for the refinement of IPM approaches and the development of conservation biocontrol strategies, but is difficult to tease apart in the field. Field cage studies have limitations, but they allow us to investigate the nature of some of these interactions under controlled conditions. In this experiment we studied the impact of Harmonia axyridis (Pallas) and Orius spp., acting both separately and in combination, on soybean aphid populations already at outbreak levels in large field cages.

Wyckhuys, K. A. G., R. L. Koch, and G. E. Heimpel. 2007. Physical and ant-mediated refuges from parasitism: implications for non-target effects in biological control. Biological Control 40: 306-313.

Abstract: A promising natural enemy for release against the Asian soybean aphid, Aphis glycines Matsumura, in North America is the aphidiine braconid wasp Binodoxys communis (Gahan). The aphid Aphis monardae Oestlund, a native of North America’s tall-grass prairies, is a non-target species that may be at risk from releases of B. communis. This paper describes ecological facets of A. monardae populations in their native habitat that could protect them from attack by this exotic biological control agent. In prairie habitats, A. monardae populations aggregate in flower heads of their host plant, Monarda fistulosa L. On this host plant, aphids are also commonly tended by four ant species, and ant-tended colonies are larger than un-attended colonies. Laboratory studies showed that parasitism rates of A. monardae by B. communis are significantly higher on vegetative M. fistulosa than on M. fistulosa flower heads. In addition, attendance of A. monardae by the ant Lasius neoniger Emery significantly decreased parasitism by B. communis. Ants attacked and killed host-seeking adult parasitoids, and preyed upon B. communis mummies. No evidence was found that B. communis reared from A. monardae are less susceptible to attack by ants than parasitoids reared from A. glycines. M. fistulosa flower heads and attendance by L. neoniger may act as refuges for A. monardae against B. communis. Our work describes spatial refuges as ecological filters that separate non-target organisms from exotic natural enemies. Implications for classical biological control of A. glycines are discussed.