1. II. Abundance is highest in the wildflower treatment.
Using emergence traps to monitor nesting preferences of beneficial wasps in agricultural landscapes
Shiala Naranjo, Julia Brokaw, Erin Forster, Jason Gibbs and Rufus Isaacs
Department of Entomology, Michigan State University
Methods
Emergence trapping occurred between 6-31 May 2016 at 3 different blueberry farms in western Michigan.
10 traps were placed in 4 habitats: woods, flowers, crop, and grass.
Traps were set out 3 times at each farm after sunset for 3-6 sampling days with appropriate conditions for wasp emergence.
Abstract
Wasps are under-appreciated but important natural enemies in agricultural landscapes that provide critical pest management services to crop fields. Relatively little is known about the life history of wasp communities, despite their economic importance and potential use in integrated pest management programs. Enhancing habitat by adding wildflowers is a well-documented approach to attracting numerous beneficial insects to crop fields. Blueberries are a valuable crop grown in Michigan with a need for pest control. To document how various habitats in and surrounding farmland affect the density of wasps, forty 60 cm2 emergence traps were placed in four different habitats around blueberry fields: wildflower plantings, woodlots, grassy margins, and between blueberry bushes. Traps were placed at dusk at three farms simultaneously and left for 3 days during three rounds of sampling at each farm. The abundance of wasps was determined and compared between habitats, revealing that wasps preferred wildflower plantings. Our results will guide management strategies on preserving natural areas surrounding farmland and provide recommendations for integrated pest management strategies for crop pests.
Background
Predatory and parasitic wasps play an important role in reducing herbivore damage to plants.
By using nectar and honeydew resources wasps may enhance; (1) adult survival, (2)  host searching rate, and (3) egg maturation rate.
Wildflower plants can increase beneficial insect abundance (Blaauw & Isaacs 2015).
The relative spatial and temporal distribution of food and hosts is also likely a factor to consider in the movement of parasitoids from food and host sites (Lewis et al. 1998).
Figure 2. Highbush blueberry farm with 4 habitats sampled using emergence traps.
II. Abundance is highest in the wildflower treatment.
Results
I. Several wasp families are present in habitats in crop fields
III. Wasp diversity and richness is highest in wildflower habitats.
Shannon’s Index
crop
flower
grass
woods a
Figure 4. Wildflower habitats had greater Shannon Index diversity than other habitats. Letters indicate significance using Tukey HSG. b b b
woods
Estimated richness
crop
grass
flower
II. Wasp abundance is greatest in wildflower habitats. a
Figure 5. Morpho-species accumulation curves show greater richness in the wildflower habitat.
Figure 3. Abundance of wasps by habitat. Letters indicate significance using Tukey HSD. b b b
Questions
I. What is the predatory and parasitic wasp community in blueberry fields?
II. Do wildflower habitats increase wasp abundance?
III. Which habitat houses the greatest wasp richness and diversity?
Conclusion
Blueberry fields and neighboring habitats house a diversity of predatory and parasitoid wasps.
Wildflower plantings had consistently greater abundance, richness and diversity of beneficial wasps than other habitats, including generalist predatory Vespula and parasitoid ichneumonids wasps.
Grassy margins had greater relative abundance of Tiphia wasps, supporting evidence that these are preferred habitats of their scarab beetle hosts.
Additional sampling and more precise species-level identification is needed to better understand wasp diversity in agricultural landscapes and its relationship to prey and host abundance and pest control service
References
Blaauw, BR & Isaacs R (2015) Wildflower plantings enhance the abundance of natural enemies and their services in adjacent blueberry fields. Biological Control 91:
Lewis, WJ et al. (1998) Understanding how parasitoids balance food and host needs: importance to biological control. Biological Control 11:
Tooker, JF & Hanks, LM (200) Influence of plant community structure on natural enemies of pine needle scale (Homoptera: Diaspididae) in urban landscapes. Environmental Entomology 29:
Acknowledgments
We would like to thank Karlis Galens, Dennis Hartmann and Lance Fritz for access to sites, Syngenta for funding, John Fricke for advice on wasp identification, Katherine Odanaka, Olivia Horton and Emily May for field assistance and study design.
Figure 1. Tiphia are both pollinators (adults) and ectoparasites (larvae) of beetle larva (Tooker and Hanks 2000).