Final report for GNE21-248
Project Information
The study focuses on understanding and addressing the economic threat of sour rot in wine grape production, particularly in the eastern US. Sour rot adversely affects grape quality and yields, necessitating labor-intensive sorting during harvest. The disease involves a complex interplay among various insects (Drosophila melanogaster, Drosophila suzukii, yellowjackets, grape berry moths), microbes, and grape berries. Drosophila fruit flies play a crucial role in transmitting sour rot-associated microbes, especially when attracted to cracked berry skin. The invasive D. suzukii further complicates the situation, emerging from berries at an early rot stage. Current management heavily relies on insecticides, but the emergence of resistance underscores the need for sustainable Integrated Pest Management (IPM) strategies.
The study aims to unravel the role of insects as disease vectors, document interactions facilitating sour rot, and understand insect behavior in response to rot-related cues. Choice bioassays reveal significant differences in fly preferences for microbial-inoculated berries. The study also explores whether D. suzukii infestation facilitates subsequent D. melanogaster infestation, with a semi-field experiment indicating a notable increase in sour rot severity. Objective 3 investigates interactions among various sources of berry damage, Drosophila fruit flies, and sour rot. Results suggest heightened disease severity in the presence of Drosophila melanogaster, particularly with yellow jackets and mechanical damage treatments. The study contributes valuable insights into sustainable disease management strategies, emphasizing the importance of developing IPM tactics.
The research provides a comprehensive understanding of the intricate relationships in sour rot ecology, offering potential solutions for more effective and environmentally conscious pest management in vineyards.
The findings of the study were disseminated through various channels, including presentations at the Entomological Society of America, engagement with growers, video production related to sour rot, and newsletters.
1. Understand the role of odors in mediating interactions between sour rot and Drosophila
1A. Assess D. melanogaster behavior in response to odors produced from inoculated and non-inoculated berries
We hypothesize that sour rot-associated microbes alter the volatile composition of berry tissue and thus alter D. melanogaster behavior. We will inoculate grapes with a sour rot-associated microbes and conduct choice bioassays to observe the behavior of D. melanogaster over time. We will also evaluate D. melanogaster preference for odors from treated berries with and without larvae.
1B. Assess volatile profiles of inoculated and non-inoculated berries
We hypothesize that disease associated microbes alter berry odors that D. melanogaster uses to distinguish amongst berries. We will collect volatiles from berries inoculated with yeast and bacteria with or without larvae in laboratory assays and conduct volatile analysis using GCMS. These data will provide insights into possible changes in the volatile profile of berries associated with differences in behavior uncovered in objective 1A.
2. Evaluate whether suzukii infestation facilitates subsequent D. melanogaster infestation
2A. Quantify D. melanogaster behavior when provided with berries with larvae or probing marks by D. suzukii
D. suzukii is active in vineyards earlier than D. melanogaster as they prefer to lay eggs in ripening and ripe berries. We hypothesize that this early berry damage caused by D. suzukii activity allows D. melanogaster to lay eggs in fruit more easily, thereby aggravating sour rot risk. We will evaluate whether D. suzukii activity affect the foraging and oviposition of D. melanogaster through video-recordings of fly behaviors.
2B. Evaluate facilitation of D. melanogaster by D. suzukii in berries and its impact on sour rot incidence and severity in the field
We will specifically test whether injuries and cues left by D. suzukii at different time points increase the likelihood that D. melanogaster lays eggs and how that differentially affects sour rot development in field trial.
3. Assess whether damage from yellow jackets and grape berry moth (GBM) interacts with Drosophila and sour rot development
As grapes ripen, yellow jackets forage on berries for sugars and pulp. GBM larvae feed inside berries during late summer. We hypothesize a synergistic interaction occurs amongst yellow jackets and GBM berry damage, Drosophila flies, and microbes, causing increased sour rot disease. We will conduct a field trial with enclosed grape clusters in mesh bags to manipulate the presence of D. melanogaster, GBM, yellow jackets, and causal microbes.
Sour rot is an important disease of wine grapes and poses a significant economic threat to grape production, especially in the eastern US, where summer weather is warm and wet. Sour rot reduces the quality of wine grapes by imparting a pungent vinegar smell to the juice. Sour rot also reduces total yield by either disintegrating or rendering the cluster unusable and necessitates high labor costs at harvest associated with the need to sort out diseased berries.
The disease is caused by a complex multi-trophic interaction of insects like Drosophila melanogaster, microbes like acetic acid bacteria and yeast, and grape berries. Drosophila flies are responsible for vectoring sour rot-associated microbes present on their body surface and gut to healthy berries. They are attracted to, and thus disease is often facilitated by, cracks in berry skin caused by mechanical forces, birds, and very likely, insects. Additionally, Drosophila larvae feeding in the berry can facilitate disintegration and aggravate disease symptoms. Moreover, the invasive vinegar fly D. suzukii becomes abundant in vineyards at about the same time grapes begin to ripen and may initiate damage to healthy berries. D. suzukii was found to emerge from berries at a mild-rot stage, and before D. melanogaster emergence, suggesting that D. suzukii oviposition precedes D. melanogaster egg-laying. D. suzukii oviposits by drilling through the fruit surface with their serrated ovipositor. This, plus tunneling by D. suzukii larvae, may provide greater access to fruit for adult D.melanogaster, which lack a serrated ovipositor, resulting in more sour rot disease. Yellowjackets and grape berry moths may also play a role in sour rot ecology via their ability to cause both berry injury and transfer microbes from diseased to healthy clusters. Overall, insects appear to play an important role in sour rot etiology.
Currently, sour rot management relies on weekly insecticide applications, targeting Drosophila fruit flies, coupled with antimicrobial pesticides starting several weeks before harvest. Such heavy reliance on insecticides is not sustainable and has resulted in documented emergence of insecticide resistance in D. melanogaster to several different classes of insecticides.
Thus, the increased resistance problems make imperative the development of suitable IPM tactics for monitoring and managing Drosophila fruit flies below the economic threshold level in vineyards. Growers need to know the activity of insects, mainly D. melanogaster and its interaction with other insects and their contribution to sour rot in vineyards before making any pest management decisions.
The overall purpose of this study is to better elucidate insects’ role as potential vectors and agents of disease, document the classes of insect interactions that facilitate and exacerbate sour rot, and elucidate insect behavior in response to rot-associated cues to improve integrated management strategies for sour rot.
Cooperators
Research
Fly stocks
Fly stocks were reared using a standard cornmeal-based Drosophila diet at Cornell AgriTech, Geneva, NY, in a climate‐controlled chamber at 25 ± 1 °C, 16:8 h light: dark photoperiod, and 60 ± 5% humidity. Chambers were used for behavioral experiments. Newly enclosed flies were moved to new media every 48 h and allowed to mature for 5–7 days before testing Female flies were tested separately.
Grape inoculation
A suspension containing yeast (Metschnikowia pulcherrima) and bacteria (Gluconobacter oxydans), causal microbes of sour rot, were used to inoculate berries. M. pulcherrima were maintained on PDA and Gluconobacter oxydans on LPGA media at 4°C. Bacteria and yeast isolate identity were confirmed with Sanger sequencing using PCR amplicons of 16S ribosomal RNA bacterial gene regions for bacteria and ITS/5.8S rRNA gene regions for yeast (1).
Grapes from a supermarket were used for all experiments following standard practice (2) with slight modifications. Three berries were used for each experimental unit. After surface sterilization, berries were wounded with a sterile toothpick inserted into the berry center. The berries were inoculated by pipetting 50 µl of a microbial suspension into the wound and incubated at 24°C with 12-h light/dark photocycle for five to eight days.
- Understand the role of odors in mediating interactions between sour rot and Drosophila fruit flies.
Choice bioassay
Two gated traps (allow entry of fly but prevent escape), each fitted with a cut 0.7mL centrifuge tube, were used. The traps were wrapped with foil to remove confounding visual cues. Each gated trap included a deli cup (60ml) with four berries, with one set inoculated with bacteria and yeast suspension and the other sham inoculated as treatments. One female D. melanogaster was released into the arena. Behavioral assays began at approximately 10:00 am and ran for a 24-hr. period at 22.5 ± 0.5 °C, after which the location of the fly was recorded. Each cup or beaker was considered a replicate. We ran 10 replicates per day for three days for a total of 30 replicates.
In a similar experimental setup, the olfactory preference of D. melanogaster between inoculated berries with and without D. melanogaster larvae were assessed. After inoculation of all berries, each berry of the treatment with larvae received ten D. melanogaster eggs and was incubated for two days to allow eggs to hatch. Choice bioassays as described above were then performed.
The difference in the proportion of flies that choose either of the treatments in choice bioassay was analyzed using a Simple Pearson Chi-square test at α = 0.05.
- Evaluate whether infestation by D. suzukii facilitates the subsequent D. melanogaster infestation
2a. Choice bioassay
The olfactory preference of female D. melanogaster was compared in response to the berries pre-infested with female D. suzukii and artificially probed berries 24 hours before the actual bioassay. For the pre-infested berry treatment, five lab-reared female D. suzukii were exposed to two sterilized berries with intact pedicel for 24 hours before the actual bioassay (starting 3 pm in the evening) in a 100ml sterilized beaker covered with sterilized mesh. Control treatment consisted of two sterilized berries probed with sterilized needles (on average 5 probings) to make it comparable with the actual treatment that consisted of approximately 5-8 probings from flies. The experimental unit consists of a single female D. melanogaster, and treatments consisted of two berries exposed with five female D. suzukii and two artificially probed (using sterilized needle) berries in a 32-ounce sterilized deli-cup with a transparent lid cover for observing behavior and two adjacent meshed holes (dimension) on a side wall for aeration. The movement of insects was tracked visually and by using Etho Vision where we measured a) the number of times D. melanogaster lands (and b) the time spent walking on pre-infested and artificially probed berries. A similar bioassay was conducted to assess and quantify the behavioral response of normal D. suzukii when provided a choice between berries exposed with five female axenic D. suzukii flies (devoid of gut microbes) and artificially probed berries through visual observation. The visual observation and quantification of choice-making behaviors lasted for one and a half hours after which berries from the choice bioassays were left as it is in the same deli cup. After 24 hours, corresponding berries from treatment and control were kept in a separate 32-ounce deli cup to rear out flies, especially D. melanogaster to evaluate whether there is a difference in the number of flies in each treatment.
The differences in duration of each behavior between each treatment was analyzed using a linear mixed model. The differences in the number of times fly select each treatment was analyzed using a generalized linear mixed model with the Poisson distribution in R software version 3.6.3 (4).
2b. Field experiment
At around 15ο Brix, intact, undamaged clusters of the sour rot-susceptible cultivar Vignoles in a research vineyard at Cornell AgriTech were inoculated with a spray solution containing acetic acid bacteria and yeast. A single cluster of grapes were exposed to one of four different treatment conditions enclosed in a fine mesh bag: D. suzukii alone, D. melanogaster alone, with both species together, and with no flies. For treatments with both, we introduced D. melanogaster into the enclosure at different times after the introduction of D. suzukii: 1) D. suzukii and D. melanogaster together 2) D. suzukii infestation followed two days later by D. melanogaster 3) D. suzukii infestation followed three days later by D. melanogaster 4) D. suzukii infestation followed 4 days later by D. melanogaster. We used six females from each species and ten replicates per treatment. Ten days after flies were introduced, sour rot severity was measured, and flies were reared from berries for assessing fly emergence.
- Investigate the interactions among insect damage to berries (yellow jackets, grape berry moth), Drosophila fruit flies, and sour rot
An experiment testing the impact of different types of damage to berries, in the presence or absence of adult D. melanogaster, was conducted in a mature research vineyard at Cornell AgriTech in Geneva, NY planted with the sour rot susceptible “Vignole” cultivar. Eight healthy and intact grape clusters were randomly selected from each of ten different areas (experimental blocks) within the vineyard. Each cluster was sprayed to run off with a suspension of sour rot associated bacteria and yeast using a hand-held spray bottle and then bagged using white polyester paint strainer mesh bags (27.94-0.95 cm, 25.4 cm, 2.54 cm; Trimaco, Inc., Morrisvelle, NC, USA) one week before the initiation of treatments. The experiment was conducted both in 2021 and 2022.
The layout of the experiment was structured as a 4 X 2 factorial design which consisted of four injury treatments and two fly treatments (presence or absence of D. melanogaster) (Figure 1, Table 1). Injury treatments consisted of 1) Control (no - injury), 2) Mechanical damage, 3) Damage by two adult yellowjackets collected from local vineyards on the day of release, 4) Damage by five second instar grape berry moth larvae, obtained from a laboratory colony. Mechanical damage was made with the tips of scissors on five haphazardly selected berries per cluster, sterilizing scissors between clusters by dipping in 75% ethanol. The number of yellowjackets and GBM larvae placed in bags was determined based on a rough estimate that they would cause feeding damage on approximately 20% of berries in a cluster. Yellowjackets were replaced in bags when both initially introduced yellowjackets died after two days to ensure that there was continuous damage prior to the introduction of D. melanogaster. The clusters assigned with the four damage treatments remained bagged for a week after which ten D. melanogaster (4 males and 6 females, 7-10 days post eclosion) from the laboratory stock colony were introduced into bags assigned to the fly treatment. The insects were allowed to interact in the bagged clusters for an additional week after which bags with clusters were brought to the lab to estimate sour rot severity. Additionally, after rating for sour rot, clusters were placed in deli cup containers (473 ml, Prime Source, St Louis, MO) with nylon mesh on the bottom and placed over a second deli cup container (946 ml, Prime Source, St Louis, MO) to rear out Drosophila. In 2021, flies were reared from both clusters that received D. melanogaster and clusters that did not receive flies whereas in 2022, we only reared flies from clusters that received flies. The percentage of sour rot per cluster was rated by visual observation based on the percentage of berries that showed typical brown coloration imparting pungent vinegar smell. D. melanogaster emergence was measured as the number of flies reared out over a week. The mass of each cluster was also determined before rearing flies using an electronic balance.
For objectives 2b) and 3), we used a linear mixed model to analyze the severity of sour rot among treatments using ‘nlme’ package. Additionally, we used a generalized linear model with random effect and Poisson distribution using ‘lme4’ package in R version 3.6.3 (4) to analyze the number of flies reared from the treatments.
- Understand the role of odors in mediating interactions between sour rot and Drosophila fruit flies.
Choice bioassay
Two gated traps (allow entry of fly but prevent escape), each fitted with a cut 0.7mL centrifuge tube, were used. The traps were wrapped with foil to remove confounding visual cues. Each gated trap included a deli cup (60ml) with four berries, with one set inoculated with bacteria and yeast suspension and the other sham inoculated as treatments. One female or male D. melanogaster was released into the arena. Behavioral assays began at approximately 10:00 am and run for a 24-hr. period at 22.5 ± 0.5 °C, after which the location of the fly was recorded. Each cup or beaker was considered a replicate. We ran 10 replicates per day for three days for a total of 30 replicates.
In a similar experimental setup, the olfactory preference of D. melanogaster between inoculated berries with and without D. melanogaster larvae were also assessed. After inoculation of all berries, each berry of the treatment with larvae received ten D. melanogaster eggs and incubated for two days to allow eggs to hatch. Choice bioassays as described above were then performed.
The difference in the proportion of flies that chose either of the treatments in the choice bioassay were analyzed using a Simple Pearson Chi-square test at α = 0.05.
Results:
At a significance level of 0.05, we can conclude that the preference of female D. melanogaster in response to microbes-inoculated berries is significantly different from the preference in response to non-inoculated injured (sham) berries. (Pearson chi-square = 10, df= 1, p-value = 0.002). However, no difference in female D. melanogaster preference was observed when subjected to treatments for inoculated berries with and without D. melanogaster larvae (Pearson chi-square = 1.07, df= 1, p-value = 0.30).
- Evaluate whether infestation by D. suzukii facilitates the subsequent D. melanogaster infestation
The olfactory preference of female D. melanogaster was compared in response to the berries pre-infested with female D. suzukii and artificially probed berries 24 hours before the actual bioassay. For the pre-infested berry treatment, five lab-reared female D. suzukii were exposed to two sterilized berries with intact pedicel for 24 hours before the actual bioassay (starting 3 pm in the evening) in a 100ml sterilized beaker covered with sterilized mesh. Control treatment consisted of two sterilized berries probed with sterilized needles (on average 5 probings) to make it comparable with the actual treatment that consisted of approximately 5-8 probings from flies. The experimental unit consisted of a single female D. melanogaster, and treatments consisted of two berries exposed with five female D. suzukii and two artificially probed (using sterilized needle) berries in a 32-ounce sterilized deli-cup with a transparent lid cover for observing behavior and two adjacent meshed holes (dimension) on a side wall for aeration. The movement of insects was tracked visually and by using Etho Vision where we measured a) the number of times D. melanogaster lands (and b) the time spent walking on pre-infested and artificially probed berries. A similar bioassay was conducted to assess and quantify the behavioral response of normal D. suzukii when provided a choice between berries exposed with five female axenic D. suzukii flies (devoid of gut microbes) and artificially probed berries through visual observation. The visual observation and quantification of choice-making behaviors lasted for one and a half hours after which berries from the choice bioassays were left as it is in the same deli cup. After 24 hours, corresponding berries from treatment and control were kept in a separate 32-ounce deli cup to rear out flies, especially D. melanogaster to evaluate whether there is a difference in the number of flies in each treatment.
The differences in duration of each behavior between each treatment was analyzed using a linear mixed model. The differences in the number of times fly select each treatment was analyzed using a generalized linear mixed model with the Poisson distribution in R software version 3.6.3 (4).
Results:
Twelve replicated bioassays were conducted to test whether the normal D. melanogaster prefers to land onto and spend more time on the berries pre-infested by five female lab-reared D. suzukii. Looking at the heatmap from Etho Vision, we can vaguely state that lab-reared D. melanogaster prefers to spend more often in berries that are pre-infested or probed by normal D. suzukii (Objective 2 figures: Figure 1).
Twenty replicated bioassays were conducted to quantify the landing behaviors of D. melanogaster in response to the normal fly-probed and mechanically probed berries, D. melanogaster spent more time and frequently landed on normal fly-probed berries (36.79 ± 7.86 seconds, number of times landed = 33) compared to mechanically probed berries (3.85 ± 1.14 seconds, number of times landed = 13). D. melanogaster female was allowed to lay eggs in a choice bioassay trial set up for quantification study after one and half hours of visual observation. Then, flies were reared out in a separate deli cups. We did not observe a difference in the number of reared D. melanogaster adults between axenic fly-probed (0.25 ± 0.12) and mechanically probed (0.13 ±0.76) berries (Objective 2 figures: Figure 2). A similar result was found between normal fly-probed (0.25 ± 0.12) and mechanically probed berries (0.13 ± 0.06) (Objective 2 figures: Figure 3).
Normal D. melanogaster females spent almost equal time in axenic fly-probed berries (24.82 ± 4.2 seconds) and mechanically probed berries (23.47 ± 3.3 seconds) (Objective 2 figures: Figure 4).
Field experiment
A semi-field experiment was conducted to test whether pre-infestation of grape berries by D. suzukii at a different time increases sour rot severity by facilitating D. melanogaster to lay a high number of eggs compared to negative control and positive control.
At around 15ο Brix, intact clusters of “Vignoles”, a sour rot susceptible cultivar, were inoculated with a spray solution containing acetic acid bacteria and yeast in a vineyard at Cornell Agritech Research North (GPS). A single cluster of grapes was randomly assigned to one of the following treatments. The treatments included: 1) D. suzukii and D. melanogaster together 2) D. suzukii infestation followed two days later by D. melanogaster 3) D. suzukii infestation followed three days later by D. melanogaster 4) Berries with microbes only (positive control) 5) Berries without any treatment (negative control) 6) Berries with D. melanogaster only 7) Berries with D. suzukii only. We introduced D. melanogaster into the bag enclosure at different times after the introduction of D. suzukii. We used ten (four male and six female) Drosophila species in respective treatments, and we had ten replicated treatments. Ten days after flies were introduced, sour rot severity was measured, and flies were reared from berries to assess fly emergence.
Results:
A significant difference in sour rot percentage was observed between the negative control treatment and the D. suzukii-only treatment (Z= -3.14, P = 0.03). Although statistically insignificant, sour rot percentage in the negative control treatment and the treatment exposed with D. melanogaster two days after exposure to D. suzukii was nearly statistically significant (Z= -2.94, P = 0.05) (Objective 2 figures: Figure 5).
Objective 3. Investigate the interactions among insect damage to berries (yellow jackets, grape berry moth), Drosophila fruit flies, and sour rot: For the experiment, we selected healthy, undamaged grape clusters in vineyards in Cornell Agritech, Research North at Vignole vineyards. Each cluster was bagged after spraying sour rot microbes suspension. Four different levels of injury treatment were (1) Control, (2) Yellow Jackets, (3) Grape Berry moth (4) Mechanical damage, where each level was allowed to interact in the presence or absence of Drosophila melanogaster flies. Eight different enclosed clusters were exposed to different treatments in 10 replicates.
Results: As a result, we did not observe much impact of grape berry moth on sour rot severity. However, when berries were subjected to treatments such as yellow jackets and mechanical damage, disease severity increased, mainly in the presence of Drosophila melanogaster compared to undamaged control and treatments without flies from both years (2021 and 2022) studies (Objective3-figures: Figure. 1). Similarly, when we reared out flies from the bagged clusters subjected to injury and Drosophila fruit fly treatments in a deli-cup in the laboratory, more adult flies emerged from the berries (Objective3-figures: Figure. 2) that were subjected to yellow jackets and mechanical damage in the presence of Drosophila fruitflies. The result from the rearing study suggests that mechanical injury and injury by yellow jackets facilitates Drosophila fruit fly oviposition, resulting in more number flies, leading to a higher sour rot percentage compared to the control. We could not understand the role of the grape berry moth in sour rot due to the poor establishment of grape berry moth larvae in clusters in vineyards.
The first-year study somewhat elucidated the role of multiple insects in sour rot etiology, providing new insights into sustainable disease management strategies. The second-year study showed a similar trend as the first-year study. Although GBM larvae were established in the second-year study, we did not find a significant difference in sour rot severity and fly number in the presence and in absence of Drosophila fruit flies. The graphs showing the final result of this trial are attached in the add media folder that states Objective3-figures.
In conclusion, the comprehensive study on the interactions between sour rot, Drosophila fruit flies, and associated factors has provided valuable insights into the complex dynamics of this economically significant threat to wine grape production. The research elucidated the multi-trophic nature of sour rot, involving interactions among insects, microbes, and grape berries.
The study highlighted the important role of Drosophila melanogaster and Drosophila suzukii in the transmission of sour rot-associated microbes, emphasizing their impact on grape quality and yield. The preference of D. melanogaster for microbes-inoculated berries over non-inoculated ones showcased the insect's involvement in disease facilitation. Additionally, the investigation into the olfactory preferences of D. melanogaster in response to pre-infested berries further emphasized the importance of insect behavior in sour rot ecology.The field experiments, including semi-field trials and assessments of insect damage interactions, provided practical insights. The observed increase in sour rot severity in the presence of yellow jackets and mechanical damage, especially in conjunction with Drosophila melanogaster, underscored the interconnectedness of insect activities and disease progression. The study also explored the potential role of D. suzukii in initiating sour rot through oviposition, shedding light on the temporal aspects of insect infestations. Our bagged experiment to understand the role of injuries by different insect agents This elucidates that there is a need to manage birds, hail, or yellow jacket injuries in vineyards to manage the disease in a sustainable way.
Our findings emphasize the importance of addressing injuries within grape clusters to diminish the risk of severe sour rot. The study highlights the involvement of external agents, like yellowjackets, in the etiology of sour rot. Various yellowjacket species, capable of causing damage to intact berries, were observed in Finger Lakes commercial vineyards during late summer. These observations underscore the necessity of acknowledging the potential role played by yellowjackets in transmitting sour rot and the potential need for their control. Overall, these results emphasize the importance of managing injuries and the agents causing them in vineyards. This may involve adopting sustainable strategies, such as reinforcing berry cuticles, manipulating the behavior of injury agents or using physical barriers to injury agents. Growers need to keep an eye on Drosophila fruit flies that can disseminate sour rot microbes and aggravate the complex and take proper management approaches.
We also shared the knowledge generated from our study by disseminating the research findings through presentations at scientific conferences, engaging with grape growers, producing video, and sharing newsletters with diverse audiences.
As the grape industry faces challenges related to insecticide resistance and sustainability, the insights gained from this study contribute to the foundation of more effective and environmentally conscious sour rot management practices. Moving forward, continued collaboration between researchers, growers, and industry stakeholders will be essential for implementing and refining strategies that mitigate the impact of sour rot on wine grape production.
Education & Outreach Activities and Participation Summary
Participation Summary:
We have communicated results to growers, extension educators, and other relevant stakeholders through newsletter articles that can be open-accessed in Appellation Cornell. Some of the results have been presented among growers-oriented and stakeholders-oriented seminars such as the Long Island Fruit and Vegetable Updates and national conferences such as the Entomological Society of America. Similarly, we have extended the information to growers and stakeholders through platforms like Twitter sharing the newsletter that includes some of the results related to the work from the SARE Grant. Videos relating to the background and a few results associated with the objectives outlined in the proposal have been submitted to the American Journal of Enology and Viticulture and the storyboard is currently under review. Similarly, we have submitted an article that built up from one of our objectives to American Journal of Viticulture and Enology and is currently under the review process.
Project Outcomes
From our first and second-year trials to investigate the third project objective, we learned that injuries are a very important component of sour rot disease, and yellow jackets- apart from creating annoyance among growers--are responsible for creating injuries in berries that facilitate sour rot. From the results so far, we can confirm that growers need to be concerned about potential berry injuries and adopt yellow jacket management in vineyards for holistic management of the disease.
While conducting an experiment to investigate our third objective, we empirically knew that injuries play a major role in sour rot and the agents of injuries could be as large as mechanical damage (that mimic bird damage or hail damage) or yellow jackets that were captured from vineyards. Despite having sour rot microbes in all the tested clusters, the presence of Drosophila melanogaster only did not cause sour rot at visual and olfactory detection levels at least from our one-year study. This elucidates that there is a need to manage birds, hail, or yellow jacket injuries in vineyards to manage the disease in a sustainable way. Although in our first-year study, we did not get a good establishment of grape berry moth larvae into the berries to be able to understand the role of injury by grape berry moth (GBM) in sour rot in the presence and absence of Drosophila fruit flies. We changed the protocol for deploying GBM larvae where we deployed second instar larvae directly on the berries that caused damage in berries and established well. However, based on the result, we understood that GBM in the presence of Drosophila melanogaster did not produce a similar level of sour rot as we observed in other treatments.
I am interested in solving growers' problems by understanding the pest behavior that would facilitate the development of sustainable agricultural pest management.
In our exploration of the role of insects in sour rot disease, we faced challenges in establishing grape berry moth larvae on bagged grape clusters, despite our persistent efforts. While we haven't applied for research grants to expand this project, we anticipate delving deeper into the understanding of the grape berry moth's role in sour rot disease under controlled conditions. Through numerous trial-and-error processes, we have improved our yellow jacket capturing techniques in vineyards, streamlining our approach for future experiments.We caught a yellowjacket by directly placing an empty vial while it was focused on chewing berries. We closed the lid as soon as it was trapped, ensuring its head was towards the closed side of the vial. Furthermore, we acquired the skill of keying out yellow jackets to identify the species used in the bagged trial. Throughout the experiment, various yellow jackets from different genera and species were observed. This highlights the importance of addressing injuries specific to certain yellow jacket species that lead to sour rot. As a future direction, we can explore assessing the microbial community in yellow jackets, providing insights into their role as vectors in the etiology of sour rot disease in vineyards.
Likewise, we modified the protocol for deploying grape berry moths in the bagged experiment. In the initial year, we placed grape berry moth larvae in a slice of commercial berry, but it didn't establish well. However, in the second year, we directly deployed larvae on the experimental grape cluster, achieving successful establishment in the berries, allowing us to continue the study.