sustainably

1. nest string treatment control Choice Test No Choice Test (a) (b) Figs. 1.(a-b). The average amount of four foods taken daily by O. smaragdina in the choice test (left) and no-choice test.(right) (± SEM, n = 6 and n = 3 for the choice and no-choice tests, respectively) through conservation of and Growing mahogany sustainably augmentation the weaver ant, a biological control agent of mahogany pests Grace T. Lim1&2, Scott M. Salom1, Laurence G. Kirton2, Loke T. Kok1, 1Entomology Dept, Virginia Tech, 2Entomology Unit, Forest Research Institute Malaysia Introduction Conclusions Major Studies and Results Mahogany is among the most valuable tropical hardwoods in the world and has been harvested to commercial extinction. Numerous reforestation efforts worldwide with mahogany species, e.g.,Swietenia macrophylla and Khaya ivorensis (Meliaceae) have been foiled by the mahogany shoot borers (Hypsipyla spp., Lepidoptera: Pyralidae) found throughout the tropics. Eight decades of research spanning 23 countries has yet to come up with a reliable, cost-effective and environmentally sound solution to this problem. A complementary series of studies was successfully conducted to conserve and augment weaver ant populations. Assessing Food Preference of the Ant Surveys for Host Plants of the Ant • Methods • A choice and no-choice study used mature weaver ant colonies at FRIM • Choice test (R): 6 ant colonies had ad libitum access to 4 foods: fish, live mealworms, liquid ‘weaver ant formula’ (with body-building protein powder) and honey solution. Food amounts taken recorded daily for 7 d. • The no-choice test was similarly conducted, but gave only one of the 4 foodsto a total of 12colonies. nest • Methods • Four Malaysian habitats, including mangroves (R), were surveyed for host plants of the ant. • All vegetation within 3 m of trail borders along a 1 km line transect was examined for weaver ant nests . • Relocated weaver ant colonies can be conserved by short-term food supplementation • Live mealworms (L) and weaver ant formula are preferred foods that are cheap and simple to apply • Foods should be given for at least 3 months to ensure colony establishment • M. citrifolia is a preferred host plant of the ant that is easy to grow and yields profitable medicinal by-products. Hypsipyla robusta, the Shoot Attacker • Data analysis: Kruskal-Wallis & Friedman’s tests • Results • The ants preferred live mealworms (Fig 1.a) but accepted fish when no choice was given (Fig 1.b). • The ants did not consume much liquid food. • Discussion • Established colonies may get enough honeydew from trophobionts but relocated colonies have few trophobionts and may need ‘high-carb’ supplemental foods. Thus, ‘high-carb’ weaver ant formula and ‘high-protein’ mealworms chosen for next study. • Results • Four host plant species were particularly ant-abundant: Morinda citrifolia (Rubiaceae), Talipariti tiliaceum (Malvaceae), Bruguiera spp. (Rhizophoraceae), Acacia auriculiformis (Fabaceae). Below L-R: The adult female lays eggs on a leaf axil or new shoot that a newly emerged larva will burrow into. The larva later migrates to the terminal shoot; which dies as the pith is consumed; and the tree develops multiple leaders as a result Screening Host Plant Candidates Providing foods directly through supplemental feeding and indirectly by planting alternative host plants with the main crop may well prove to be a reliable approach to growing environmentally-friendly mahogany in partnership with the weaver ant. • Methods • Three favored host plant species from the previous study were tested: M. citrifolia, T. tiliaceum and Bruguiera spp, plus non-host Avicennia officinalis (Acanthaceae) as the control. • Ant preference was evaluated using a ‘relative ant abundance index’, based on ratio of volume of nests : plant crown surface area. • Data analysis: Kruskal-Wallis test. Oecophylla smaragdina, the Shoot Protector! Literature Cited The weaver ant, Oecophylla smaragdina (Hymenoptera: Formicidae), inhibits infestation of mahogany by the shoot borer, Hypsipyla robusta, which attacks mahoganies in Asia, Australia and the Pacific Islands. Bluthgen, N. & Fiedler, K. 2004. Preferences for sugars and amino acids and their conditionality in a diverse nectar-feeding ant community. Journal of Animal Ecology 73:155-166. Griffiths, M.W. 2001. The biology and ecology of Hypsipyla shoot borers. Pp. 74-80 in Floyd, R.B. & Hauxwell, C. (Eds.). Proceedings of an International Workshop on Hypsipyla Shoot Borers in Meliaceae. ACIAR Proceedings Series No 97. Kandy, Sri Lanka, 20-23 August 1996. ACIAR, Canberra. Lim, G.T. & Kirton, L.G. 2003. A preliminary study on the prospects for biological control of the mahogany shoot borer, Hypsipyla robusta (Lep.: Pyral.), by ants(Hymen.: Form.). Pp. 240-244 in Proc. of Intern. Conf. on Forestry and Forest Products Research. Kuala Lumpur, 1-3 October 2001. FRIM, Malaysia. Way, M.J. & Khoo, K.C. 1991. Colony dispersion and nesting habits of the ants, Dolichoderus thoracicus and Oecophylla smaragdina (Hymenoptera: Formicidae), in relation to their success as biological control agents on cocoa. Bulletin of Entomological Research 81(3):341-350. • Results and Discussion • The ant was most abundant on M. citrifolia, followed by T. tiliaceum and Bruguiera spp. (Fig 2. below). • Many ants aggregated on M. citrifolia fruit, imbibing nectar (R). Trophobionts tended by the ant on M. citrifolia posed no pest risk. • M. citrifolia was selected for next study. Ants! It is an aggressive predator of arthropods, including H. robusta (R). It vigilantly patrols its host plant, which includes K. ivorensis (L), building nests from young leaves. • The ant also tends ‘trophobionts’, e.g.,mealybugs (Hemiptera), in exchange for ‘honeydew’ excreta, an important food of the ant. • The leaf nests of this ant can be ‘harvested’ from other trees and introduced to mahogany plantations to protect them. • Protection is needed for the first three years until an unbranched height of 8 m is achieved. Acknowledgements We thank Ms. Saimas Ariffin, Mr. Saiful Azhari, Mr. Shaiful Amri, Ms. Nurziah Ishak, Mr. Fadir Ishak (below), Ms. Hidaya, and Mr. Azmi Mahyuddin (Entomology Section, FRIM) for assistance in conducting the experiments, and Dr Ang Lai Hoe (Ecophysiology Section, FRIM) for use of Hobos. The plant species were identified by Mr Mohd. Asri and Mr Kamarudin Saleh (Botany Section, FRIM). Identification of trophobionts was provided by M. Kosztarab (Virginia Tech) S.H. McKamey and D.R. Williams (USDA-ARS). International collaborative research by Virginia Tech’s Entomology Department and the Forest Research Institute of Malaysia (FRIM) is currently focusing on conservation and augmentation as biological control approaches to enhance the performance of the weaver ant against the shoot borer. Effect of Food Supplementation on the Ant Fig. 2. Relative ant abundance in relation to three host plant species and one non-host plant species of O. smaragdina. • Methods • 12 ant colonies relocated to new mahogany host plants at FRIM. • Half the colonies received weaver ant formula and mealworms (L-R) for 16 weeks. • Ant activity monitored weekly on shoots, around the foods and in nest-building. • Data analysis: GLM ANOVA. Rationale • A weaver ant colony relocated to new host plants can be conserved and • augmented in a ‘two-pronged’ approach: • Short term: Direct food supplementation to meet energetic needs until it is self-sufficient, i.e., has cultivated enough trophobionts. • Long term: Indirect food provision and additional nesting sites in a more stable and diverse mixed-plantation. • Therefore, the objectives of this research program were to identify: • Preferred foods of the ant that aid colony conservation. These foods should be cheap and practical to apply. • 2. A preferred alternate host plant species of the ant that can be easily grown with mahogany as a second crop. Future Work A study is in progress to evaluate effects of mixed-planting M. citrifolia with mahogany on establishment of food-supplemented ant colonies (below). Please contact first author for additional information. E-mail: gracelim@vt.edu. Campus address: 216 Price Hall, Blacksburg VA 24061 This project was supported by the Fulbright Program (administered by the U.S. Department of State, the Institute of International Education, and the Malaysian-American Commission on Educational Exchange), Virginia Tech and FRIM. • Results and Discussion • Food-supplemented (F) colonies had greater colony sizes than the C colonies receiving no food. • For F colonies much weaver ant formula was consumed initially (wk 1-9) then declined while ant activity on shoots and nest-building increased. • F colonies may have ‘weaned off’ the foods after establishing.