Understanding Spotted Wing Drosophila’s Role as a Vector for Fruit Rot Fungi in Fall Red Raspberries

View the project final report

Commodities

• Fruits: berries (brambles)

Practices

• Pest Management: disease vectors, integrated pest management

Spotted wing drosophila (SWD; Drosophila suzukii) is an invasive fruit fly that has emerged as a serious pest of soft-skinned fruit, particularly fall-fruiting red raspberries. In raspberries, SWD encounters a diverse microbial community that includes two important fruit rot pathogens, Botrytis cinerea and Cladosporium cladosporioides. Previous studies have demonstrated that larval SWD co-occur with and feed on both species of fruit rot fungi, indicating an association between these pests. However, many aspect of their interactions remain unclear, including the extent to which SWD impacts disease epidemiology. Understanding these relationships may have important implications for small fruit production. For instance, a vectoring relationship between SWD and Botrytis or Cladosporium could increase pre-harvest fruit rot incidence and severity, consequentially reducing marketable yield. To better understand these relationships, we will assess SWD’s role as a potential vector of both Botrytis and Cladosporium in this project. Specific objectives include quantifying Botrytis and Cladosporium on field-collected flies and evaluating host preference for diseased versus healthy fruit. These studies will provide a measure of how frequently adult SWD encounter and acquire fungal propagules (spores) under field conditions. Laboratory assays will also be conducted to assess SWD’s ability to vector Botrytis and Cladosporium, a proof-of-concept experiment that could justify larger, field-based studies of SWD-fungal interactions. Taken together, these studies will generate information that can be used to develop more targeted pest and pathogen management programs in raspberries, improving agricultural sustainability and profitability.

In this study, I will use a combination of field and laboratory-based approaches to evaluate how interactions between Botrytis and Cladosporium fruit rots and SWD impact pest and disease dynamics in primocane red raspberries. Specific objectives are to:

1.Evaluate the ability of SWD to acquire and transmit Botrytis or Cladosporium propagules under laboratory conditions. These experiments will provide a proof-of-concept for SWD’s vectoring ability and will justify future, field-based experiments to further study SWD’s impact on disease epidemiology.

2.Evaluate how Botrytis and Cladosporium fruit rot impact SWD feeding and oviposition decisions. Understanding these behavioral impacts will help us understand how frequently adult flies encounter and potentially acquire Botrytis or Cladosporium propagules under field conditions.

3.Survey field-collected SWD for associations with plant pathogenic fungi. This will allow us to determine the frequency and mechanism by which adult SWD acquire fungal propagules under field conditions