Appendix ES-11 Alien Snail Control in Nurseries Alien snail control in nurseries Report to the Oahu Army Natural Resources Program (OANRP) Prepared by Norine W. Yeung and Robert H. Cowie 30 November 2012 Pacific Biosciences Research Center University of Hawaii 3050 Maile Way, Gilmore 408 Honolulu, Hawaii 96822 Phone: (808) 956 4909/0956 E-mail: [email protected] [email protected] 1 Appendix ES-11 Alien Snail Control in Nurseries BACKGROUND AND PURPOSE From the basic perspective of habitat restoration, non-native species should not be introduced to areas where they are not present. Specifically, non-native snails and slugs (hereafter ‘snails’) may impact both native vegetation (Joe & Daehler 2008) and native snails (Meyer & Cowie 2010a, b, Sugiura et al. 2011) in areas to which they are introduced. Therefore, it is important that plants to be outplanted, as well as equipment and vehicles used to transport plants, are free of non-native snails. This requires appropriate management practices and control measures to be adopted in the nurseries. For some time the OANRP has been planning to outplant native Hawaiian plants on military land on Oahu as part of its ecological restoration efforts. A major problem associated with this effort is that the plants grown in the nurseries for outplanting can become infested with non- native snails (Cowie et al. 2008), some of which, especially as juveniles, are very small (on the order of 1-2 mm). Preliminary discussions and visits to the Schofield baseyard and the nursery at the Nike site took place prior to the implementation of this agreement and the start of the project. The following two main issues were identified as needing addressing. Salt Barriers: Currently, the legs of the greenhouse benches are placed in pots filled with salt, which acts as a barrier preventing snails from climbing up the legs and into the pots on the benches. The problems with this method are 1) increased corrosion of the posts used to support the frame structure, and 2) the potential for damage caused by the long-term accumulation of salt in the ground at the nursery sites. Facility Sanitation: It is important that non-native snails are not transported on equipment as well as on the actual plants to be outplanted. To reduce the possibility of this happening, there should be no areas in or around the OANRP facilities suitable for snails to live. PROPOSED WORK Ideally, the use of salt barriers, though apparently effective, would be stopped. In order to do this, it would be necessary to demonstrate that snails are no longer able to access the greenhouse benches. Alternative barriers to salt should be considered, or at least methods of preventing the salt from dissolving by blocking rain and water draining from the benches. However, if thorough surveys of the nurseries showed that snails were not found either inside the nursery or for some distance outside it, then once they were eradicated from the plants, the salt barriers could be removed. The objectives originally proposed under this agreement were as follows. 1) Thoroughly inspect all baseyards and nurseries (including nurseries supplying plants to OANRP under contract) to identify management practices that may facilitate contamination by snails of plants for outplanting as well as areas that may act as 2 Appendix ES-11 Alien Snail Control in Nurseries sources for ingress of snails into the facilities, and provide a report detailing these findings. 2) Undertake surveys to establish which species of snails, if any, occur in and around all baseyards and nurseries, and incorporate the results into the report in 1), above. 3) Perform experiments to test whether, once snails have been eradicated from plants, the plants can be re-colonized in the absence of bench leg barriers, given appropriate facility sanitation (to be done at the Nike site nurseries). 4) Undertake studies of life-cycles of key snail species (e.g. Zonitoides arboreus, Succinea tenella, Oxychilus alliarius) in order to develop post-control inspection protocols to declare plants clean of snails that adequately account for the length of time required for growth and reproduction, and test these protocols (to be done in the laboratory at UH). 5) Develop and write revised MIP sanitation guidelines for snails, appropriate for all baseyards and nurseries, to include inspection protocols. 6) Develop and write control strategies focused on key target species. 7) Collaborate with OANRP personnel in writing up the protocols and procedures for publication in the pest management literature. MODIFICATIONS TO THE PROPOSED WORK As the project progressed, and in discussion with OANRP personnel, the above objectives were modified as follows. Objectives 1, 2 and 6 were retained and the combined report detailing our findings and recommendations is provided as part of this overall project report. Objective 3 was modified and divided into two parts: 1) laboratory experiments to test alternative nursery bench leg barriers, and 2) provision of a protocol for monitoring the area around the nurseries, to be implemented by OANRP personnel at the Nike site nursery. The results of the experiments and the protocol provided to the OANRP are provided as part of this overall project report. Objective 4 was scaled back to focus only on Zonitoides arboreus as the major species of concern. Following a literature search, we determined that sufficient information was available regarding the life-cycle of Zonitoides arboreus and the relevant citations were provided to OANRP personnel. These citations are listed as part of this overall project report. Objective 5 was addressed as requested and the revised MIP sanitation guidelines are provided as part of this overall report. Objective 7 will be addressed in the future following discussion with OANRP personnel regarding which aspects of the overall project warrant publication in the peer-reviewed literature. 3 Appendix ES-11 Alien Snail Control in Nurseries BASEYARD AND NURSERY SURVEYS AND MANAGEMENT PRACTICES Surveys Surveys were carried out by experienced snail biologists at four nurseries (Table 1). Surveys at the Nike nursery encompassed the OANRP section and the DLNR (State of Hawaii, Department of Land and Natural Resources) section as well as areas in the immediate vicinity but outside of the nursery. The results from these three surveys were kept separate. The other OANRP nursery surveyed was that at the East Base. In addition, Kay’s Fernery and the Lyon Arboretum rare plant nursery were also surveyed, these being nurseries from which OANRP would like to obtain certain plant species for outplanting. Results The species found during the surveys are listed in Table 1. Some species could not be identified to species and in the case of Tornatellidinae and Pacificellinae only to subfamily. Summary Only one live snail (Euglandina rosea) was found in the OANRP greenhouse at the Nike nursery. Several live non-native snails were found in the DLNR Nike greenhouse as well as in areas around both greenhouses. At the East Base nursery, no live snails were found in the nursery area, but one live non-native snail (Bradybaena similaris) was found immediately outside the nursery area, in a patch of grass on the side of the road. Many live non-native snails were found at Kay’s Fernery and Lyon Arboretum (rare plant nursery/greenhouse). In particular, a non-native snail (Sinployea sp.), previously not recorded in the Hawaiian Islands, was found at the Lyon Arboretum nursery. Management practices The baseyards and OANRP nurseries are generally clean and tidy and probably not major sources of contamination of plants by snails. However, the DLNR Nike greenhouse, Kay’s Fernery and Lyon Arboretum need substantial improvement to minimize snail infestation. The DLNR Nike greenhouse is a concern as the facility is located only several meters away from the OANRP greenhouse and may be a continual source of non-native snails. The following practices should be followed to minimize the potential for contamination. The key is to maintain the facilities free of snails this is done primarily simply by minimizing places for them to hide. Please see also the modified MIP Sanitation Guidelines (below). Minimize hiding places for snails, especially those that provide high humidity microhabitats not exposed to direct sunlight, in and around the facility. This might include removing (best) or raising off the ground (better than leaving on the ground) various materials and objects such as stacks of plant pots, piles of wood, packing materials, fencing equipment, plastic sheeting, junk and trash. 4 Appendix ES-11 Alien Snail Control in Nurseries Remove weedy vegetation in and around the facility. If there are lawn areas, keep them well mown. Remove moss growing on or around equipment (e.g. concrete blocks, nursery bench siding) and on the surface of soil in pots. Monitor the facility on a regular basis to look for snails or signs of snail presence. Look for slime trails and damage to plants. Empty shells may indicate the presence of live individuals. Check around pots in nurseries, in the immediate vicinity of greenhouses and around the perimeter of the nurseries and baseyards. Check likely hiding places for snails, under the various items mentioned above but also in weedy vegetation (which ideally should have been removed), water supply on/off tap housings (i.e. Buffalo boxes) and in vegetated areas at the bases of building walls and sidewalk edges. In nurseries check the undersides of plant pots as well as the upper two centimeters of earth/medium in pots. In nurseries keep the area around plants and in pots clear of leaf litter. If feasible, establish an inhospitable buffer area (e.g. bare concrete, gravel) 3-4 m wide around the facility. Manually dispose of any snails found. Wear gloves or use a suitable implement to handle them as they may contain parasites that could infect humans.