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Biocontrol introduction

Target pest: Alternanthera philoxeroides (Caryophyllales: Amaranthaceae), alligator weed

Agent introduced: Arcola malloi (Lepidoptera: Pyralidae) = Vogtia malloi Pastrana, alligator weed moth

Imported: 1982, 1983, 1984, 1987

Import source: South America via Florida and Australia

Released: 1984, 1987-88

Release details: Approximately 10,000 larvae released near Woodhill, Dargaville and Whangarei in 1984 but did not establish. In 1987-88 12 releases, each consisting of 5,000 eggs and/or neonate larvae or 1,000-2,000 2nd or 3rd instar larvae and at 10 sites in Northland and Auckland establishment ocurred.

Establishment: Winks (2007) - patchily established in Northland and Auckland but not as common as the alligator weed beetle (Agasicles hygrophila).

Impacts on target: Winks (2007) - large populations cause considerable damage to alligator weed and give control in some lakes and ponds. Larvae are unable to control the weed in running water that is regularly flooded and are not suited to low temperatures. Inhabits terrestrial populations of alligator weed but cannot exert sufficient control there. Landcare Research (2017e) - it is estimated that the biocontrol agents (A. malloi and the beetle Agasicles hygrophila) are saving around $505,000 per year in Auckland and Northland, with a resulting benefit to cost ratio of 101:1.

Impacts on non-targets: Paynter et al. (2004) - surveys record A. malloi only feeding on target plant, although lab tests predicted minor non-target damage on Alternanthera sessilis.


Cameron PJ, Hill RL, Bain J and Thomas WP (1989). A Review of Biological Control of Invertebrate Pests and Weeds in New Zealand 1874-1987. Technical Communication No 10. CAB International Institute of Biological Control. DSIR Entomology Division. 424p.

Landcare Research (2007). New Zealand Arthropod Collection (NZAC) Biological Control Voucher Collection. http://www.landcareresearch.co.nz/resources/collections/nzac/holdings/biological-control-voucher-collection

Landcare Research (2017e). Alligator weed: a financial snapshot. Weed Biocontrol: What's New? 81: 4 http://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/issue-81

Paynter, Q.E., Fowler, A.H., Gourlay, M.L., Haines, M.L., Harman, H.M., Hona, S.R., Peterson, P.G., Smith, L.A., Wilson-Davey, J.R.A., Winks, C.J. and Withers, T.M. (2004). Safety in New Zealand weed biocontrol: A nationwide survey for impacts on non-target plants New Zealand Plant Protection 57: 102-107

Winks C (2007). Alligator Weed Moth. In The Biological Control of Weeds Book (Landcare Research) http://www.landcareresearch.co.nz/research/biocons/weeds/book/documents/Alligator_Weed_Moth.pdf