Source: MICHIGAN STATE UNIV submitted to
INTEGRATING NEW NATURAL ENEMIES INTO SOYBEAN APHID BIOLOGICAL CONTROL
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0199943
Grant No.
2004-34103-14491
Project No.
MICL08323
Proposal No.
2004-02825
Multistate No.
(N/A)
Program Code
QQ
Project Start Date
Jun 15, 2004
Project End Date
Jun 14, 2006
Grant Year
2004
Project Director
Brewer, M. J.
Recipient Organization
MICHIGAN STATE UNIV
(N/A)
EAST LANSING,MI 48824
Performing Department
ENTOMOLOGY
Non Technical Summary
Soybean aphid is a pest of North Central Region soybean and is in its early phase of invasion. Seed yield loss of 40 percent has been recorded, despite widespread insecticide applications. As an alternative to insecticides, we propose to identify strategies to integrate parasitoids recently detected attacking soybean aphid into the well established predator complex to increase biological suppression of soybean aphid.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2151820107035%
2151820113035%
2161820107015%
2161820113015%
Goals / Objectives
As an alternative to insecticides, we propose to identify optimal strategies to integrate parasitoids into the current predator complex to increase biological suppression of soybean aphid. To do so we need to understand the species and relative rates at which resident and introduced parasitoids are adapting to soybean aphid. We also need to know if the existing predator community will facilitate or interfere with this adaptation and if combinations of natural enemies will result in increased biological control. Finally we need to determine if we can enhance the success of parasitoid adaptation by creating conditions for successful parasitoid/host interactions. Our specific questions are: a. Have aphid parasitoids adapted to search for soybean aphid in soybean fields? b. Is the extant predator complex limiting or enhancing survival and impacts of parasitoids? c. Will 'adaptation nurseries' promote more rapid introgression of parasitoids into the complex of soybean aphid natural enemies?
Project Methods
Experiments will be conducted at the Kellogg Biological Station Long Term Ecological Research site located in southwest Michigan. The major predators and parasitoids are known to be present at this site. The main experimental site contains 1-ha cropping systems of a corn-soybean-wheat rotation with each crop occurring once every three years and alfalfa that occurs every year. Each plot is replicated six times in a RCB design. In a nearby smaller scale biodiversity plot, a full factorial arrangement of crop rotations (corn, soybean and wheat alone, and in all possible combinations of crop rotation orders) are each replicated four times in 10 x 30 m plots, with each crop occurring every year. Additional work will be done at research plots in East Lansing, Michigan. Specific approaches are Objective a. The biodiversity soybean plots will be used to determine which parasitoids actually search for soybean aphid in soybean. This setting optimizes opportunity for parasitoids occurring in highly heterogeneous, small spatial scale habitat mixtures to bridge onto soybean aphid in soybean. During three stages of soybean and soybean aphid growth, soybean aphid infested plant material will be exposed to parasitism, parasitized aphids will be reared, and resulting offspring will be identified to species. Complementary data will be collected to assess soybean aphid populations through the growing season, and to compare ability of selected parasitoids found in soybean to parasitize soybean aphid in laboratory exposures. Objective b. Impacts on soybean aphid and parasitoid population growth will be examined using cages that exclude the existing natural enemy community versus sham cages that do not exclude enemies. Cages will be infested with soybean aphid at levels mimicking the infestation in surrounding the crop (minimum of 20 aphids per cage) of which 50% will be previously parasitized by L. testaceipes in the laboratory (determined by dissection of sub samples) and 50% unparasitized. We will sample aphid and predator populations in cages and associated plots up to 4 weeks post inoculation. We will measure on 10 randomly selected plants per cage: number of adult and nymph aphids, number and location of intact and predator damaged mummies, and predator density. Objective c. We will contrast parasitoid colonization of soybean aphid in soybeans in the biodiversity plots with and without partial predator exclusion. Two square meter plots of soybean in each replicate will be infested with soybean aphid. One half of these will be randomly selected and covered with a medium mesh cover that prevent coccinellids, syrphids and lacewings from entering but allows aphid and parasitoid immigration and emigration.

Progress 06/15/04 to 06/14/06

Outputs
We conducted field studies to 1) assess extant parasitoid and predatory fly species that may be adapting to prey upon the invasive Aphis glycines, soybean aphid, and 2) examine the role of predators in limiting parasitoid impacts via intraguild predation. For objective 1, in replicated large plots we detected parasitoids and predatory flies attacking sentinel A. glycines on potted soybean plants placed in soybean as well as other crops (alfalfa, corn, and wheat) and noncropped vegetation (early successional vegetation, poplar stands, and young forest). We also directly observed aphids and aphid enemies present on plants in the crop plots. In 2004 and 2005, we detected five species of parasitoids and eleven species of predatory flies parasitizing sentinel A. glycines. Most common (summed across all habitats) utilizing A. glycines were the parasitoids Aphelinus asychis, Lysiphlebus testaceipes, and a newly described species Binodoxys kelloggensis, and the flies Aphidoletes aphidimyza, Allograpta oblique, and Sphaerophoria contigua. The other species were detected infrequently and in trace numbers, potentially only representing incidental use of A. glycines. Variation in habitat affinity was detected: L. testaceipes, A. oblique, and S. contigua utilized A. glycines placed in all crop and noncropped habitats; B. kelloggensis was principally found utilizing A. glycines placed in noncropped early successional vegetation and poplar stands; A. asychis most commonly utilized A. glycines placed in soybean; and A. aphidimyza was most common in soybean and other cropped plots. Overall, predatory flies were considerably less habitat specific than parasitoids. Percent field parasitism of A. glycines in soybean as measured by field inspection for mummies was disappointing, never exceeding 1% even among the most common species. Predatory flies were commonly found preying on A. glycines in soybean. For objective 2, a field experiment was aimed at examining the role of predators in limiting parasitoid impacts via intraguild predation (IGP). Using tomato cage frames covered with mesh we differentially excluded all natural enemies (< 1 mm mesh, Aphid treatment) or only large predators (2 mm mesh, Mesh treatment), thus allowing natural parasitism to occur protected from IGP by large predators. We also included un-caged plants with and without A. glycines manipulation (Open and Field treatments), plants enclosed with a sham cage (Sham treatment) as a cage control, and plants caged without A. glycines (Plant treatment). All cages and the open treatment were enclosed by a plastic cylinder coated on the outside with Tanglefoot to prevent ants from entering and tending aphids. Our results showed strong impact from large predators (mainly Coccinellidae) but very low parasitism and predation achieved by extant parasitoid populations or small predators. Intraguid predation did not play a limiting role in parasitism. Large predator impacts on A. glycines resulted in a trophic cascade that significantly increased soybean height, biomass, and yield to similar levels than plants in which aphids were excluded.

Impacts
There is a substantial complex of parasitoid and predatory fly species utilizing A. glycines, potentially supplementing other previously known predators of soybean aphid, particularly predatory flies which were commonly detected feeding on A. glycines in soybean. These data reflect challenges (most substantially habitat affinity) of parasitoid use of A. glycines, and bode well for predatory flies using A. glycines in soybean.

Publications

  • Pike, K. S., P. Stary, M. J. Brewer, T. Noma, S. Langley, AND M. Kaiser. 2006. A new species of Binodoxys (Hymenoptera: Braconidae, Aphidiinae), parasitoid of the soybean aphid, Aphis glycines Matsumura, with comments on biocontrol. Proc. Entomol. Soc. Wash. In press.
  • Costamagna, A.C. 2006. Do varying natural enemy assemblages impact Aphis glycines population dynamics? Ph. D. Dissertation, Department of Entomology, Michigan State Univ., East Lansing. 189 pp.
  • Costamagna, A. C., and D. A. Landis. 2006. Predators exert top-down control of soybean aphid across a gradient of agricultural management systems. Ecological Applications. In press.


Progress 01/01/05 to 12/31/05

Outputs
We conducted field studies to 1) assess extant parasitoid species that have adapted to prey upon Aphis glycines, the soybean aphid, and 2) examine the role of predators in limiting parasitoid impacts via intraguild predation. For objective 1, we sampled aphid parasitoids in soybean as well as other surrounding habitats (alfalfa, corn, wheat, and early successional vegetation). We periodically exposed sentinel A. glycines placed on potted soybean plants to detect parasitoids and predatory flies capable of attacking A. glycines. We also inspected individual plants in these crop plots to directly observe and identify aphids and aphid enemies present. From a series of four sampling dates, we detected 6 species of parasitoids and 7 species of predatory flies parasitizing sentinel A. glycines. The enemy fauna attacking A. glycines placed in soybean was about the same or only modestly lower in species number (4 parasitoids and 7 predatory flies) than in other crops (4 parasitoids and 7 predatory flies) and likely higher in species number than in early successional habitat (2 parasitoids and 2 predatory flies [data in noncropped habitat is still being processed]). Two parasitoids (Aphelinus asychis and Lysiphlebus testaceipes) and 3 predatory flies (Aphidoletes aphidimyza, Sphaerophoria contigua, Toxomerus marginatus) were found parasitizing and preying upon A. glycines only or A. glycines and other aphid species in alfalfa, corn, and wheat; while 2 other parasitoids (Aphelinus albipodus and Binodoxys new sp.) were limited to parasitizing aphid species other than A. glycines. Parasitoid variation in habitat affinity was also detected: L. testaceipes was more common in more habitats and Binodoxys new sp. was much more habitat specific to noncropped vegetation. Overall % field parasitism as measured by field inspection for mummies did not exceeding 1%. Predatory flies were less habitat specific than parasitoids were commonly found preying on A. glycines in soybean. For objective 2, we replicated a 2004 field experiment aimed at examining the role of predators in limiting parasitoid impacts via intraguild predation (IGP). Using tomato cage frames covered with mesh we differentially excluded all natural enemies (< 1 mm mesh, Aphid treatment) or only large predators (2 mm mesh, Mesh treatment), thus allowing natural parasitism to occur protected from IGP by large predators. We also included un-caged plants with and without A. glycines manipulation (Open and Field treatments), plants enclosed with a sham cage (Sham treatment) as a cage control, and plants caged without A. glycines (Plant treatment). All cages and the open treatment were enclosed by a plastic cylinder coated on the outside with Tanglefoot to prevent ants from entering and tending aphids. Our preliminary results showed strong impact from large predators (mainly Coccinellidae) but very low parasitism and predation achieved by extant parasitoid populations or small predators. Large predator impacts on A. glycines resulted in a trophic cascade that significantly increased soybean height, biomass, and yield to similar levels than plants in which aphids were excluded.

Impacts
As an alternative to insecticides, parasitoids can be integrated into the extant predator complex, as judged by a substantial complex of parasitoid species utilizing A. glycines and the lack of significant intraguild predation on parasitoids. Habitat affinity of some of the parasitoids will likely present additional challenges to utilization of A. glycines in soybean; whereas predatory flies were common among crops inspected. These data bode well for adaptation of predatory flies to A. glycines in soybean, and may add to the biosuppression of A. glycines by large predators.

Publications

  • No publications reported this period


Progress 01/01/04 to 12/31/04

Outputs
During the first year of this project, we conducted field studies in southern Michigan to address the following three objectives: 1) assess extant parasitoid species that have adapted to prey upon Aphis glycines, the soybean aphid, and 2) examine the role of predators in limiting parasitoid impacts via intraguild predation. For objective 1 (parasitoids adapting to prey on A. glycines), we sampled aphid parasitoids in soybean as well as other surrounding habitats (alfalfa, corn, and wheat-clover) to understand aphid-enemy-habitat interactions. We periodically exposed potted soybean plants infested with A. glycines to detect parasitoids attacking A. glycines in soybean and other crop plots. During the sampling with potted plants, we also inspected individual plants in these crop plots to directly observe and identify aphids and aphid enemies present. From a series of two sampling schemes, we detected a total of seven species of aphids and eight species of aphid parasitoids in various crop plots in 2004. Of eight parasitoid species, six species were found parasitizing A. glycines only or A. glycines and other aphid species. Two other parasitoid species were limited to prey upon aphid species other than A. glycines, exhibiting no signs of adapting to A. glycines as a host. We are still in a process of assessing the relative importance of various crops as habitats of parasitoids relevant in soybean aphid control. The most abundant A. glycines parasitoid collected was Lysiphlebus testaceipes, a cosmopolitan species. Another soybean aphid parasitoid we sampled (Binodoxys sp.) was confirmed to be a new species to the science first discovered in this study. For objective 2 (intraguild predation), we conducted a cage experiment (1x1x1 meter) in which we manipulated mesh sizes to differentially exclude all natural enemies or only large predators from the cages. We also included un-caged plants with and without aphid manipulation, plants enclosed with a sham cage as a cage control, and plants caged without aphids. Our preliminary results showed strong impacts from predators (mainly Coccinellidae). We observed direct evidence of intraguild predation (mummies being consumed).

Impacts
As an alternative to insecticides, we wish to identify optimal strategies to integrate parasitoids into the extant predator complex to increase biological suppression of soybean aphid. Integrating effective biological control into soybean management scheme will lessen SBA outbreaks and needs for chemical control. Such an IPM approach will benefit soybean industry by reducing spray costs, soybean damage, and risks of soybean pests developing insecticide resistance, thereby increasing productivity and environmental protection.

Publications

  • No publications reported this period