TRIAL PROTOCOL: EXPERIMENTAL ERADICATION OF LITTLE FIRE ANTS IN KALIHIWAI, KAUAI,USING A COMBINATION-TREATMENT APPROACH CONTENTS

Transcription

1 TRIAL PROTOCOL: EXPERIMENTAL ERADICATION OF LITTLE FIRE ANTS IN KALIHIWAI, KAUAI,USING A COMBINATION-TREATMENT APPROACH Cas Vanderwoude Hawaii Ant Lab, Pacific Cooperative Studies Unit University of Hawaii 16 E. Lanikaula St, Hilo. HI CONTENTS Trial Protocol: experimental eradication of Little Fire Ants in Kalihiwai, Kauai,using a combinationtreatment approach... 1 Problem Statement... 1 Project approach... 2 The site... 3 Proposed treatment regime... 4 Zone 1. Open Space treatment... 4 Zone 2. Vegetation treatment... 5 Zone 3. Food plants... 5 Zone 4. Steep slopes... 5 Project risk analysis... 5 Open areas... 5 Vegetation greater than 2 meters... 6 Food plants... 6 Steep slopes... 6 Experimental layout and plot design... 6 Measurements... 6 References... 7 PROBLEM STATEMENT The Little Fire Ant (LFA) (Wasmannia auropunctata) is a serious agricultural and environmental pest (Delabie, 1990; Fabres and Brown jnr, 1978). It is widespread on the east coast of the island of Hawai`i, and has also been detected on Maui, Kailua-Kona and the island of Kauai (Conant and Hirayama, 2000; 1

2 Vanderwoude and Nadeau, 2009; Vanderwoude et al., 2010). The infestation on Maui was limited to a single location, approximately 1-2 acres, and an eradication was attempted in To date, it appears this has been successful (Vanderwoude et al., 2010). The infestations in Kailua-Kona are sparsely scattered and the dry climate will reduce spread and assist control efforts there. Eradication efforts have been underway for the small population of LFA on Kauai since its discovery in 2000 (Null and Gundersen, 2007). These have been hampered by a number of factors including access, steep terrain and a lack of suitable control products to treat arboreal colonies. This species presents major control challenges, primarily because they nest in both arboreal and groundlevel (epigeic) microhabitat. Additionally, their colonies are small, very numerous, polygynous and interconnected. Population numbers, even when measured by the most conservative means, may be in excess of 240 million workers per hectare (Souza et al., 2008). Little applied research on controlling this species in all but the most simple habitats has been conducted. In Kauai, access issues appear to have been resolved, providing an opportunity to test a combinationtreatment approach to eradicating this pest. A number of bait products currently registered for use in Hawai`i are suitable for control of LFA and appear to be efficacious for epigeic colonies. These baits are granular and easy to spread. Their limitation lies in an inability to be easily deployed on vegetation where a substantial portion of LFA colonies are located. It is proposed that this site be used to test an approach which targets epigeic colonies with granular bait products and arboreal colonies with a gel product formulated specifically for this species. PROJECT APPROACH The aim of this experiment is to provide efficacy data that will contribute to the development of Little Fire Ant control prescriptions in situations where both epigeic and arboreal populations exist. The experiment will be established over a 8.1 acre area in Kalihiwai that comprises the entire infested area on Kauai. Results of this experiment, once refined, can be transferred to other situations where arboreal control of Little Fire Ants is needed and provide data for a Section 18 petition. 2

3 Figure 1. Aerial views of Kauai and Kalihiwai Bay. The site The treatment site is on the north shore of Kauai, immediately east of Kalihiwai Bay (Figure 1). There is a mixture of different land types present including urban structures, open space, a vegetable garden, landscaping and natural vegetation. The western boundary is extremely steep and access difficult. The infested area covers 8.1 acres and spans three properties: TMK , TMK and TMK 3

4 All property owners are to consent to treatment before this project is undertaken. PROPOSED TREATMENT REGIME Four treatment zones are recognized (Figure 2), each with a different treatment strategy: 1. Open space (2.07 ac) 2. Vegetation greater than 1.5 m in height (5.94 ac) 3. Plants grown for food (1000 ft 2 ) 4. Western boundary where slope exceeds 30 0 (2.19 ac) Figure 2. map of infested area showing treatment zone and TMK boundaries. (Figure prepared by J. Chapman, Kauai Invasive Species Committee). Zone 1. Open Space treatment The Open Space zone will be treated eight times over 12 months with Amdro Block (EPA reg ), 4

5 Amdro Fire Ant Bait (EPA reg ), Amdro Pro (EPA reg ) Maxforce Complete (EPA reg ), or Probait (EPA reg ). All are granular ant baits containing hydramethylnon ( %). All products are labeled for use in the situation being treated. These will be applied using a hand-held bait spreader and a Solo blower. Zone 2. Vegetation treatment This zone will be treated eight times over 12 months using a combination of granular baits applied to the ground where feasible and a gel mixture applied to foliage. Granular baits will be the same type used for the Open Space zone. The gel mixture will consist of the following: 1. Tango (49g/kg S-methoprene) at a rate to provide 2.5g/kg a.i. in finished mix, OR Provaunt (300g/kg indoxacarb) at a rate to provide 1.8g/kg a.i. in finished mix, and 2. Cargill brand corn oil (or similar) at a rate of 300g/kg finished mix, and 3. Xanthan gum at 10g/kg finished mix, and 4. Water, and 5. Torula yeast (30g/kg finished mix) or peanut butter (30g/kg finished mix). The initial 4 treatments will consist of the Tango gel mix (see 2(ee) recommendation labeling), and the final 4 treatments will consist of the Provaunt gel mix. The mixture will be applied at a rate sufficient to obtain adequate coverage on each branch up to 20kg per hectare (approximately 8.1kg per acre). The gel will be applied by a variety of air powered devices designed to distribute spots of the mixture ranging from approximately 1g to 5g in size. This approach has previously been employed for eradication of LFA at a site on Maui and efficacy has been established (Vanderwoude et al., 2010). Zone 3. Food plants There is a small vegetable garden on one property. This will not be treated. No food plants are to be treated under this proposal. There are a number of coconut palms on the properties, however, these are trimmed and fruit removed prior to ripening. These coconut trees will be treated. Zone 4. Steep slopes The western boundary of the infested area is too steep for conventional access. The lower portions are adjacent to the high-tide mark of Kalihiwai bay. This zone will not be treated under this proposed experimental use permit. Open areas PROJECT RISK ANALYSIS No risks anticipated that would be not be present on a non-experimental operation of the same type. Bait products, distribution devices, re-entry and PPE are all adequately covered by the product labels. 5

6 Vegetation greater than 2 meters While the chemicals are broadly being used in accordance with label provisions, the registrant may not have foreseen a use pattern where the product was being applied at heights greater than 2 meters. Personal protective equipment stipulated on the label includes: Long sleeved shirt, long pants, shoes and socks Chemical resistant gloves (>14 mil for mixing and waterproof once product diluted) Applying pesticides above 2 meters presents additional operator safety issues including spill drift and overspray onto the head and face of the operator. Operators under this EUP will also wear the following personal protective equipment: Eye protection Headwear (a hat, cap or similar) Food plants No food plants will be treated. Coconut palm will be treated and any fruit present is to be removed prior to ripening or destroyed. Steep slopes The steep slopes on the western boundary of the infested area terminate at the high tide mark of Kalihiwai Bay. These slopes are not readily accessible by operators, and present a number of risks. This area will remain untreated under this permit, with a separate application submitted at a later time. EXPERIMENTAL LAYOUT AND PLOT DESIGN No control plots are possible as LFA are under active eradication at this site. However, ant abundance in previous experiments with untreated plots remain constantly high regardless of season. MEASUREMENTS Treatment boundaries will be defined after a thorough survey of the current putative infestation boundary. The boundaries will be re-surveyed six and twelve months after treatment begins, and continue after the last treatment for a period of two years. Prior to each treatment operation, ant recruitment to 8 lures consisting of plastic vials primed with peanut butter will be measured in each of the four treatment zones. These will be pseudo-replicated four times in each zone with the exception of the vegetable garden where there will be two replicates. In vegetated areas, two replicates will be located on the ground and two in vegetation. Efficacy will be determined by the mean number of ants at lures as a percentage of pre-treatment counts. Statistical testing will comprise a chi test and results plotted graphically. 6

7 After the last treatment operation, the entire infested site will be surveyed. Due to the large size and inaccessible nature of the terrain, this may be conducted as a series of smaller surveys through time. This survey will be repeated one and two years after treatment ceases before eradication is complete. REFERENCES Conant P., Hirayama C. (2000) Wasmannia auropunctata (Hymenoptera:Formicidae): established on the Island of Hawaii. Bishop Museum Occasional Papers 64: Delabie J.H.C. (1990) The ant problems of cocoa farms in Brazil, in: R. K. Vander Meer, et al. (Eds.), Applied myrmecology: A world perspective, Westview Press. pp Fabres G., Brown jnr W. (1978) The recent introduction of the pest ant Wasmannia auropunctata into New Caledonia. Journal of the Australian Entomological Society 17: Null W., Gundersen K. (2007) Little Fire Ant Wasmannia auropunctata: Its Presence on Kauai. Kauai Invasive Species Committee, Hawaii, USA. pp. 47. Souza E., Follett P.A., Price D.K., Stacy E.A. (2008) Field suppression of the invasive ant Wasmannia auropunctata (Hymenoptera: Formicidae) in a tropical fruit orchard in Hawaii. Journal of Economic Entomology 101: Vanderwoude C., Nadeau B. (2009) Application methods for paste bait formulations in control of ants in arboreal situations. Proceedings of the Hawaiian Entomological Society 41: Vanderwoude C., Onuma K., Reimer N. (2010) Eradicating Wasmannia auropunctata (Hymenoptera: Formicidae) from Maui, Hawaii: The Use of Combination Treatments to Control an Arboreal Invasive Ant. Proceedings of the Hawaiian Entomological Society 42: