Statewide Survey of Leptopilina japonica, a Previously Unreported Parasitoid of the Invasive Spotted Wing Drosophila in Alabama.

Commodities

Practices

We propose to increase the sustainability of soft fruit and berry crop production in Alabama with this first survey to investigate the presence and abundance of parasitoid wasps in Alabama. The outcome of the survey will provide information on the biological control of a key pest. The use of parasitoids will be an important IPM strategy for SWD in Alabama. Biological control is one of the foundations of the integrated control concept (Stern and van den Bosch 1959), yet in many conventional production systems, biological control is not a core management tactic. If biological control is successful, pest populations can be reduced to levels that do not require aggressive insecticide use. Our preliminary result has confirmed the presence of L. japonica in wild elderberries. Whether this parasitoid can develop in cultivated and other uncultivated berries will be identified by this survey. This research will focus on identifying berry crops that can maintain high populations of L. japonica and we hypothesize that wild berries will have more L. japonica emerging because no insecticides are applied to them. We will provide information on the numbers of L. japonica in different cropping systems. We will work directly with farmers to collect berries and set traps in different fields to capture both SWD and L. japonica. In collaboration with our farmer cooperators, we will organize field days or workshops where farmers can learn about biological control in real-world settings. Working with farmers will allow them to see the practical benefits firsthand and evaluate the effectiveness of the biocontrol strategy for their specific crops. We will develop easy-to-understand fact sheets, brochures, or pamphlets that explain what biological control is, how it works, and how to use it. These materials will be concise, visually appealing, and practical for busy farmers. We will provide detailed, step-by-step guides on how to use biological control agents, including best practices for monitoring pest populations, introducing biocontrol organisms, and evaluating effectiveness.

Approaches and Methods

Study location. The proposed study will involve field studies. Field observations will be carried out in cultivated and uncultivated berry and soft fruit farms in Alabama. Space limitations will not permit a detailed description of some methodologies.

 Methods for Objective 1: Determine the spread and abundance of L. japonica

The state will be demarcated into three regions: northern (counties east and west of Madison County), central (counties east and west of Montgomery County), and southern (counties located east and west of Mobile County) regions. In each region, two soft fruit farms (either blueberry, elderberry, or blackberry) and two wooded areas with wild berries will be identified. Efforts will be made to locate farms with a known history of agronomic and pest management practices. In each farm and wooded area, 10 plants will be randomly selected and tagged for subsequent data collection. The plants will be selected from the different sections of the farms and forests. Thus, two plants will be selected at the center, east, north, south, and west sections of the farm or wooded area. Before, during and after color break of maturing berries or fruits, monthly visits will be made to collect berries and fruits from each selected plant. During each visit, the collected berries will be stored in Ziploc^® bags and sent to the laboratory and incubated until adult SWDs and other insects emerge. All emerged insects will be collected and prepared using appropriate taxonomical procedures and sent to USDA Systematic Laboratory in Maryland for proper identification.

Since there are reports that have shown that the parasitoids can be captured on yellow and red sticky cards, we will also deploy these cards in each location to monitor the parasitoids and SWD. In addition, HOBO data loggers will be set in each location to record temperature, humidity, and precipitation within the period of the experiment. We will use appropriate statistical methods to analyze SWD and parasitoid numbers and weather variables. Some of the analyses to be used include simple and multiple regression analyses, one and two analyses of variance, etc. The results from this study will reveal the presence and abundance of other indigenous natural enemies and emerging pests in the fruit crop system in different locations.

Although this survey will mainly focus on SWD and the parasitoid, we will also collect data on other insects if present. We will record the GPS for each location. The GPS points will help us to use GIS tools to understand if there are spatial factors such as forest, habitat, water body, human settlements, etc., responsible for the number of insects collected at the different locations.

Methods for Objective 2: Determine larval load of SWD and L. japonica in different berry crops

Larval load refers to the number or density of insect larvae present in a particular environment, such as within a host plant, animal, or a specific habitat. It typically describes the abundance of larvae in each area or on a host, which can be important for assessing the severity of an infestation, the potential impact on crops or other systems, and the effectiveness of pest management strategies (Kraus and Wainwright, 1994). In the case of a crop pest, such as spotted wing drosophila, the larval load is the number of larvae found inside the fruit or a given number of fruits or berries. A high larval load would indicate a severe infestation and potential crop damage. In biological control, monitoring the larval load is crucial for evaluating the effectiveness of natural enemies (such as parasitoid wasps) that target the larvae of the pest insect. A reduced larval load would suggest that the biocontrol agent is successfully controlling the pest. We will determine the larval load for both SWD and the parasitoid to provide us with an estimation of the effectiveness of L. japonica and other parasitoids.

To do this, we will randomly pick 100 ripe berries from 5 bushes each on the perimeter (1 bush on each edge, if possible) and 100 ripe berries from 5 bushes in the interior of the plot. The 100 berries will be separated and replicated into 10 berries and weighed. Each set of 10 berries will be packed into a single Styrofoam cup with paper towel at the bottom to prevent larval drowning. The container with the berries will be placed in insect cages measuring 30 x 30 x 30 cm (MegaView Science Co., Taichung, Taiwan) and put in room temperatures ranging from 24-26°C and 40-70% RH. The experiment will be monitored daily and all insects that will emerge will be collected and counted. SWD counts will be separated into males and females and recorded. The larval load will be calculated per weight of berry basis. The data will be analyzed using Microsoft Excel and JMP statistical software version 2021.