1. Please state project objectives and what work was done this quarter to address them:
Objective 1: Document laboratory and field biology- reproduction, development time, where snails lay eggs, periods of life stage activity
Field activity of snails: We have continued the biweekly monitoring of snail activity in 3 groves in central Florida to better describe activity patterns. From out most recent observations, we have found that these snails will seek refuge from the cold by burrowing into the soil. We do not know at what temperature they seek this refuge or how deep they bury themselves. Based on this observation, if time permits later in the project, we will evaluate the temperature cues that trigger this burying action. We are confident that this is not a true overwintering behavior as they have been found active in the groves on warmer days.
Reproduction and development time: Snail rearing is going well, with very limited mortality observed. We have successfully produced a small number of additional snail eggs and hatchlings. These snails are being reared and monitored in our environmental chambers, with the hope of determining the growth rate of this species. If we can produce more eggs in the spring, then we can perform additional experiments in which we evaluate potential natural enemies of the snails in a laboratory setting.
Objective 2: Determine factors that influence snail movement/dispersal
Based on observational data, we are beginning to understand the role of temperature in snail activity (see obj 1). These observations will be used to develop more detailed testing.
Because of reports and questions regarding the impacts of these snails on trees inside IPCs, we designed a small study to better describe the impacts of snail density on tree damage. Not surprisingly, the proportion of foliar damage increased in association with snail density and time of exposure. These data support the need for control measures which either present snails from entering IPCs or can kill the snails inside the IPCs to reduce damage to young trees.
Additionally, we have initiated an experiment in which we will attempt to identify potential snail deterrents. If the primary impact of the snails in citrus is interference with irrigation equipment, then identifying a deterrent that will reduce snail interaction with the equipment will allow growers to reduce snail impact without needing to kill the snails, which may ultimately be cheaper and logistically easier. Based on the literature and preliminary testing, we have identified several potential materials to trial in a laboratory setting. These trials will be initiated in January.
Objective 3: Field evaluation of baits
We have optimized the semi-field testing arenas for bait and pesticide screening based on our trials and errors as described in the September report. Using the new arenas, we have been able to better evaluate a subset of both baits and grower-reported chemistries that look promising for use in snail management programs. From the testing completed this fall, none of the baits tested (Deadline GT, Deadline MP, and Slugger) had greater than 45% mortality in both the field arenas and the lab arenas, while one commonly used insecticide, Agriflex (8 oz/a), had over 90% mortality. This chemistry is not labelled for use on snails, but with additional testing we may be able to support label expansion for the company. If growers are already using this product for other pests, they may gain additional benefits for snail control. We have many more chemistries to test in a similar fashion.
Objective 4: Determine if arthropod or mammalian predators exist in groves for Bulimulus bonariensis
Camera and Pitfall Trap Progress: We have developed a camera trapping method that will address this objective. We have deployed the camera traps under various conditions in citrus and other environments, and it has worked quite well to record natural enemy activity. Pitfall traps were deployed at the same time. Pitfall trap specimens will be identified, and their gut content analyzed to determine if they have consumed snails. The gut content of the snails will also be analyzed to determine the extent to which the snails are consuming citrus and other plants. This work will continue throughout the winter and spring.
Snail mites: In November, additional mites were dissected out of snails collected earlier in the year and imaged (see figures). Mite specimens have been sent to collaborators at FDACs to begin the process of describing this new species. We hope to perform experiments on the impact of the mites on snail mortality in the laboratory and field as time and resources allow.
2. Please state what work is anticipated for next quarter:
Obj 1: We will continue biweekly monitoring of populations at all three sites (field) and begin developing population within-field aggregation/activity models. We were delayed in starting work towards lifetables last quarter and anticipate being able to start collecting data towards developing these if we can get enough eggs. We have mating chambers set up in the lab and have been monitoring for eggs every other day. If we cannot get sufficient eggs to work with by the start of February, we will pivot to focus on the relationship of snails to temperature (Obj. 2).
Obj 2: Once snail activity resumes in groves, we can resume the study of their dispersal behaviors. Trees previously used for density experiments have been repotted and given time to recover from feeding. These trees will be repotted into larger arenas with 2 trees/arena. We will induce damage to one tree per pair and evaluate snail attraction to damaged vs undamaged trees. Snail deterrent evaluations will also being in the Quinn lab.
Obj 3: Once snail activity has resumed in groves, we will continue with bait and pesticide evaluations to provide growers options for management of this pest.
Obj 4: Once snail activity has resumed in groves, pitfall trapping will be continued to look for potential arthropod predators of these snails.
3. Please state budget status (underspend or overspend, and why): At the most recent RMC meeting, our project was underspent due to staffing challenges and we have received a 6 month NCE prior to the awarding of year 2 funds.
4. Please show all potential commercialization products resulting from this research, and the status of each: Nothing yet