Effect of Ground Cover Management on Predators and Predation of Halyomorpha halys in Georgia Peach Orchards

Progress report for GS20-233

Project Type: Graduate Student
Funds awarded in 2020: $16,111.00
Projected End Date: 08/31/2022
Grant Recipient: University of Georgia
Region: Southern
State: Georgia
Graduate Student:
Major Professor:
Brett Blaauw
University of Georgia
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Project Information

Summary:

Halyomorpha halys is an invasive stink bug that causes damage to multiple commodities including peaches. Currently, there are few integrated pest management tactics available for H. halys, and research on natural enemies in the United States is skewed towards parasitoids and predators of eggs. In Chinese peach production, ground cover manipulation is a successful integrated pest management strategy for controlling arthropod pests. We propose using data from pitfall traps and molecular gut content analysis to identify ground-dwelling predators of H. halys and determine how ground cover management practices used in the Southeastern United States enhance biological control of H. halys nymphs.

Project Objectives:
  1. To identify the predators of BMSB that are present in Georgia peach orchards.
  2. To understand how existing ground cover management practices in Southeastern peach production impact communities of predators and their predation of BMSB.

Research

Materials and methods:

Figure 1. Brown marmorated stink bug nymph feeding on a developing peach.
Figure 2. Comparison of (A) external damage with (B) internal corking damage of a peach fruit due to brown marmorated stink bug feeding.
Figure 3. A spined soldier bug nymph feeding on a brown marmorated stink bug nymph.

1. To identify the predators of BMSB that are present in Georgia peach orchards.

For two weeks each month during the months of May, July and August, we will collect pitfall trap samples from a total of 16 plots in experimental peach orchards at the UGA Horticulture Research Farm in Watkinsville, Georgia, as well as from other peach orchards in Fort Valley and Byron, Georgia and Edgefield, South Carolina. Experimental plots measure 15m by 30m with a pyramid trap baited with BMSB aggregation pheromone at the center and 4 pitfall traps 2m away from the center. Baited pheromone traps are a standard monitoring tool for BMSB and are used here to assure the presence of BMSB in the plots. Pitfall samples will be collected on a biweekly basis for each week of the study between intervals of 12 to 24 hours to ensure quality of specimens for gut content analysis and to avoid total evaporation of ethanol. The pitfall traps that will be used are considered, "dry" pitfall traps, which contain several glass marbles of varying sizes in plastic deli cups that create small chambers to keep the different arthropods separated. Specimens will be removed from the cups and transferred to individual microcentrifuge tubes containing 70% ethanol and will be stored at -20℃ during storage to preserve DNA in the gut contents. Collected specimens will be identified to one of 5 broad categories: ground beetles, predaceous Hemiptera, ants, and spiders. Additional categories may be added if any predators not within these categories is particularly common, and identification may go to a more specific level if a single family, genus, or species appears to be common. To identify whether the predators have attacked BMSB, predators will be dissected and subject to gut content analysis via polymerase chain reaction (PCR) using primers for BMSB as well as other common prey insects including other peach pests like tarnished plant bug (Lygus lineolaris). Additionally, for each month of the study, one trial will be conducted at the UGA Horticulture Research Farm consisting of mark, release, and recapture (MRR) of 3rd instar BMSB nymphs and sentinel egg masses. Releases of nymphs and sentinel egg masses will be placed 2m from the center of each plot. This will provide an additional way to measure predation activity on BMSB.

2. To understand how existing ground cover management practices in Southeastern peach production impact communities of predators and their predation of BMSB.

Each of the 16 experimental plots at the UGA Horticulture Research Farm will be subject to one of four ground cover treatments: unmowed vegetation (vegetation will be allowed to grow freely), mowed vegetation (vegetation will be mowed at 3 inches), bare ground (vegetation removed using herbicides), and nimblewill (grown from seed and allowed to grow freely). Nimblewill is of interest because the results from Meyer et al. (1992) suggest that nimblewill is effective at crowding out undesirable weeds without competing with peach trees or harboring pests such as nematodes or spider mites. A buffer of mowed vegetation will be maintained between each treatment plot to prevent overlap between treatments. Using the methods for collecting predators presented above, we will be able to compare pitfall captures and the results of PCR to determine whether ground cover treatment has an effect on predator communities and their predation of BMSB.

Pitfall captures will allow us to gather data on predator activity in relation to  ground cover treatments. By running gut content analysis on collected predators using PCR, we will determine what groups of epigeal predators feed on BMSB. This will allow us to determine which epigeal predators are the predominant predators of BMSB and if different ground cover treatments influence predation rates.

Statistical analysis:

To determine the effects ground cover has on predator abundance, and diversity, we will use generalized mixed models (GLMM) and Tukey’s HSD to distinguish ground cover treatment effects. Similarly, we will assess differences in predation frequency on BSMB related to ground cover treatments using GLMM, and rank predators by frequency of predation to derive an initial picture of which predators commonly provide biocontrol services on BMSB.

Research results and discussion:

This is the first season of this project. The research plots were prepared at the UGA Horticulture Research Farm in November of 2020, which included the herbicide treatment and the planting of the nimblewill seeds. An additional herbicide treatment will likely be needed this spring prior to sampling in order to ensure that the herbicide treatment plots remain free from plants.

The supplies and sampling materials have been arranged and we anticipate beginning our project sampling in May 2021 to correspond with the natural phenology of the brown marmorated stink bugs as their eggs hatch and the immature begin to develop and disperse. 

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

As this is the first season for the funding of this project, we have not begun sampling and subsequently have not completed any outreach or outcomes. 

Project Outcomes

Project outcomes:

Not applicable at this stage of the project. 

Knowledge Gained:

Not applicable at this stage of the project. 

Recommendations:

Not applicable at this stage of the project. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.