Recipient Organization
AUBURN UNIVERSITY
108 M. WHITE SMITH HALL
AUBURN,AL 36849
Performing Department
Biological Sciences
Non Technical Summary
In the Southeastern United States, ants are notorious members of the insect community. This is largely because of the red imported fire ant (Solenopsis invicta) is known for its significant reductions in native insect populations, irritating stings, and resistance to decades of eradication efforts. This ant species is also known for existing in high densities and establishing in high disturbance environments. It is the species' persistence within and preference for disturbance and high densities that contribute to its prevalence within agricultural fields. In agricultural fields, S. invicta and other ant species are known to protect and tend to plant pests (e.g., aphids, scale insects, etc.) in exchange or access to sugar-rich (honeydew) excretions from the plant pests, which can lead to increased pest populations. When present with honeydew-producing insects, ants are known to increase aphid populations, indirectly reducing crop production. However our understanding of the role of S. invicta in agricultural settings is limited to a few studies in a few annual crops (e.g., cotton, soy) and largely ignores native ant species. Ants in the Southeastern United States are relatively species rich (~120+) compared to other regions of North America. This diverse community also likely play an important role in agricultural settings (in addition to S. invicta), particularly in lower disturbance perennial cropping systems (e.g., orchards, stands).The first goal of the proposed Hatch project is to survey ant and insect communities across key economic crops within Alabama using a variety of insect sampling methods (sampling, sweep netting, and visual surveys). This will help to identify the ant species in different crop fields, potentially interacting with honeydew-producing insects and other (beneficial and pest) insects in the community. The second goal is to identify how insect communities change in response to exclusion or removal of ants. Additionally, the project will measure how pest suppression is affected with and without ants across different crop systems. This will help identify which systems and which ant species are playing significant roles within different cropping systems impacting beneficial insects (e.g., pollinators, predators) and plant pests (e.g., aphids, caterpillars). Finally, in systems with ants and honeydew-producing insects the project will explore how ants and their relationship with honeydew-producing insects, impact plant production using field and lab experiments. In systems where ants indirectly have a negative impact on plant health through tending honeydew-producing insects, growers can use ant baits to reduce ant populations and limit these negative interactions. While in others growers can ignore the ants, and take advantage of their benefits. Ants play important role as soil movers, improving aeration, water infiltration, and soil pH. Additionally, native and introduced ants represent a significant amount of terrestrial insect biomass and to maintain that biomass must consume large amounts of insect protein, making them important consumers of plant pests. By improving our understanding of ants in agricultural systems we can improve how best to encourage ants, for example by limiting unnecessary bait applications to maximize their roles as soil movers and consumers. We can also identify when bait applications would serve best to maximize food and fiber production.
Animal Health Component
45%
Research Effort Categories
Basic
45%
Applied
45%
Developmental
10%
Goals / Objectives
Ants are among the most diverse and successful organisms in terrestrial ecosystems, playing an integral part in shaping community structure and ecosystem function. Within agricultural landscapes ants are ubiquitous, and play complex roles in crop fields. The complexity of their roles is driven in part because of the interactions between ants and honeydew-producing insects (e.g., aphids, scale insects). Ants will tend and protect honeydew-producing insects in exchange for access to sugar-rich exudates. In protecting and tending to honeydew-producing insects, ants can cause an increase in plant pest populations. In addition, ant foraging to retrieve exudates can reduce the abundance of beneficial predators and pollinators. While foraging for exudates can also reduce herbivory by killing herbivores or indirectly by disrupting herbivore feeding. Despite decades of work of ants as effective predators, and over a 100 years of exploring ants interacting with honeydew-producing insects, relatively little research explores the effects of trophic interactions within agricultural food webs. Moreover little work examines the effects of ants and their insect mutualists on crop plant production (or fitness). This is best exemplified the minimal published lists of the ant communities in different cropping systems in North America. Overall the goal of my Hatch project is to explore the identity and roles of ants in both perennial (blueberry, peaches, and pecans) and annual (cotton, tomato, and soy) cropping systems on arthropod community structure and ultimately plant fitness. While ants have been shown to tend to honeydew-producing insects in cotton and tomato, the ant-honeydew interactions in other cropping systems is unknown. The selection of blueberry, peaches, and pecans provides a contrast to annual cropping systems and are also key economic crops in the state. This goal will be accomplished through the following three objectives:Objective One: Survey the ant and insect communities in key economic crops (cotton, tomatoes, soy, blueberry, peaches, and pecans) within the state.Objective Two: Assess the roles of ants within each cropping system using ant removal/exclusion experiments to estimate the impact on arthropod community composition and sentinel prey removal.Objective Three: In systems with evidence of ant and honeydew-producing insect interactions, explore how these interactions can impact crop production
Project Methods
To explore the role of ants in agricultural food webs, and specifically the ant-honeydew interactions in economically important crops within the state I will complete the project in three phases. During the first phase I will use standard methods of ant sampling to survey the ant and insect communities in cotton, tomato, soy, blueberry, peaches, and pecans. Ant communities in agricultural fields can be sampled using (90 mL) pitfall transacts (15 traps, separated by 10 m) set out for 48 hours and using ant bait stations (n = 15, pecan sandies in 50cc tubes) set along a perpendicular transect separated by 10 meters. Pecan sandies are commonly used in surveys because they contain an ideal mixture of sugar, protein, and fats and the white crumbs, contrast with most backgrounds and make counting nest density manageable in relatively short period of time. Non-ant insect community will be sampled using aforementioned pitfalls, sweep net sampling (n = 4, 25 meter transects per field), and sticky cards (n = 3 per field). Additionally, the project will use timed visual surveys, with an emphasis on searching for interactions between ants and honeydew-producing insects. Sampling will be repeated three times during the growing season. All ants and honeydew-producing insects will be identified to species. In addition, samples will be sorted to identify key predator groups (e.g., spiders, beetles, bees, wasps), common herbivores (e.g., Lepidoptera, grasshoppers, etc.), and previously reported crop pests (https://www.aces.edu/blog/category/farming/ipm-farming/). Using nonmetric multidimensional scaling (NMDS) the data will assess if and how ant composition differs among the sites. The community data will provide a working list of the ant species found in crop fields and if species identity impacts associated non-ant insect communities. It is important to note that most consider the southeastern United States to be dominated by the red imported fire ants (Solenopsis invicta) and within the crop fields few ant species may exist. However, despite decades of work on S. invicta, few studies have documented their interactions in crop fields, nor have researchers explored the native ant species that are known to persist.During the second phase of the project we will use the community data to guide the design of removal and exclusion experiments to determine the role of ants on community composition and sentinel prey removal. If most crop fields are dominated by S. invicta commercial (fire) ant baits will effectively reduce their populations, but in the case where native ants persist additional poison baits will be added. My previous work has shown honey mixed with a low concentration of fipornil (1 × 10−6% fipronil) in a vials covered with metal hardware cloth is effective at reducing ant populations with no impact on non-ant predators. Through the use of removal experiments we can document how arthropod communities shift in response using similar monitoring techniques as used in previous sampling (pitfalls traps, sticky cards, sweeps, and visual surveys). In addition, we can monitor pest suppression services within the fields using sentinel egg cards (n = 10 per field). Egg cards consist of corn earworm (Helicoverpa zea) eggs (freeze-killed) attached to index cards and placed in petri dishes covered with hardware cloth to exclude ground foraging predators larger than ants from entering the petri dishes allowing us to further isolate the role of ants in prey removal. Egg cards were placed out for 48 h during the same period as each pitfall sampling and the remaining eggs on each card were compared to the initial number of eggs to calculate the mean percent removal. Finally using sentinel plants and plants within crop fields we can use netting and barriers to establish how ants (or their absence) impacts abundance of aphid populations.To explore how ant interactions with honeydew-producing insets impact crop production, I will use greenhouse and field experiments guided by the results from previous season's surveys and experimental work. Surveys will be essential for first identifying the ant species and honeydew-producing insects involved in different crop systems. Subsequently, prior experimental work to exclude ants from plants and aphids will create a framework for manipulating their access to plants and aphids. This work will help elucidate the ideal sample sizes necessary. In greenhouse and field experiments we will use a variety of metrics to evaluate how ants and their interactions with honeydew-producing insects impact plant production. This will include but is not limited to, leaf damage, plant growth, and seed production and will vary depending on crop type.