Pests > Pest Management > Biological control > Bioagents – insects > Wasmania acupuncta, Solomon Islands

Pests > Pest Management > Biological control > Bioagents – insects > Wasmania acupuncta, Solomon Islands

Pests Pest Management Biological control Bioagents – insects Wasmania acupuncta, Solomon Islands

Wasmannia auropunctata, (?)introduced, Solomon Islands

January 2012. This email caused quite a discussion! The point of conjecture was whether the ant was intentionally introduced to Solomon Islands. The paper says it was “originally introduced as a biological control agent against nut-fall bus (Amblypelta sp. around so years ago ….), but many people who were in the Solomon Islands at or soon after the time of the supposed introduced vehemently maintained that it was an intentional introduction; the pathway of introduction is unknown.

The ant was found first in the Russell Islands by Jim Stapley in the 1960s soon after he had arrived to take up his post as entomologist. Yandina and other islands in the group were planted to coconut belonging to Lever Bros., so it is possible that there was an accidental introduction of the ant from people coming from other countries. It is unlikely that the company would have deliberately introduced the ant as Amblypelta was not a problem on the plantations of the Russell Islands.

As proof of purposeful introduction, the paper sites Ikin (1984) Quarterly Newsletter. FAO. Asia Pacific Plant Protection Commission 27: 8. However, the citation is simply a note from Bob Macfarlane presumably to Bob Ikin who passed it to FAO. It says: “It is not known how and when the ant entered and established in Solomon Islands. It is believed that the ant has been there for at least 10”.

As one member write: “The abstract states that Wasmannia auropunctata‘was originally introduced as a biological control against nut-fall bugs’. It is an introduced species, and it is reported to be an effective biological control agent of Amblypeltaon coconut. However, I am not aware of any documentation that it was deliberately introduced as a biological control agent. It is not included in the BIOCAT database of deliberately introduced insect biological control agents (1) for which CABI is currently finalising an update. Can those better informed than me comment on this aspect?” See Greathead, D.J. & Greathead, A.H. (1992) Biological control of insect pests by insect parasitoids and predators: the BIOCAT database. Biocontrol News and Information 13: 61-68.

Here is the abstract from the paper that caused the discussion:

Fasi, J., G. Brodie and C. Vanderwoude (2013). “Increases in crop pests caused by Wasmannia auropunctata in Solomon Islands subsistence gardens.”Journal of Applied Entomology. (Online Version of Record published before inclusion in an issue).

Keywords: Cyrtohinus fulvus; hemiptera; little fire ant; taro; Tarophagus; Wasmannia auropunctata

Abstract: The impacts of Wasmannia auropunctata(the little fire ant) on the native biota and subsistence agriculture in the Solomon Islands are poorly understood. This species was originally introduced as a biological control against nut-fall bugs (Amblypelta sp.) around 30 years ago and in the intervening time has spread throughout the Solomon Islands, aided movement of produce and planting material. It is now itself a major pest of coconut, cocoa and subsistence agriculture. In this study, we show the negative effects of this invasive ant on subsistence agriculture in the Solomon Islands. We do this by (i) assessing the presence of insect pests that develop a mutual relationship with W. auropunctata on four common subsistence crops; and (ii) measuring the impact of a significant pest (Tarophagus sp.) and its natural predator the bug Cyrtohinus fulvus, in the presence and absence of W. auropunctataon taro crops. The existence of insect pests that form a mutual relationship with W. auropunctatawas measured in a total of 36 gardens of the four subsistence crops. This was conducted through standardized visual searches, plus identification and collecting from randomly selected plants within the gardens. A number of additional insect pests causing major problems to subsistence crops have also developed mutual relationships with W. auropunctata. Infested taro gardens have more Tarophagus sp. compared with taro plants that are free of the little fire ant. The presence and abundance of Wasmannia therefore has the potential to inflict considerable crop loss in rural subsistence gardens in the Solomon Islands.

John Fasi (corresponding author), School of Education, Solomon Islands College of Higher Education, P O Box R113, Honiara, Solomon Islands. E-mail: [email protected].

One of the authors wrote to PestNet as follows:

I believe John is away from email and may be unable to enlighten everybody, so I will try to fill in some gaps.

Wasmannia is a very recent introduction to the PNG mainland. I have conducted surveys at points of entry in Port Moresby, Lae, Wewak, Vanimo, Madang, Lihir, Rabaul and Kimbe in 2006 and 2007. At that time, I confirmed the presence of W. auropunctata in a suburb of Wewak. This was first detected and reported by a NAQIA officer (Sophie Numbuck) and this infestation covered only 2 hectares in 2006. Since then several other small infestations have been found in villages in Yangoru. All infestations appear linked to returning Peacekeepers from the Bougaineville crisis. I have not been to Bougainville but am told it is well established there.

It seems more likely the spread of wasmannia has been from SI to PNG via Bougainville. Entry to Bougainville from SI seems plausible via the 3 mile sea barrier between the Shortlands and Buka (maybe through the markets at Buin). How it arrived in SI is a mystery and we rely on the unrefereed paper by Ikin (1984) to support our statement of a deliberate introduction.

The presence of LFA in the Melanesian region is a bit of a mystery. This species reproduces clonally which actually allows genetists to accurately map its origins and spread through the Pacific region. Foucaud and colleagues were able to demonstrate the presence of the same clonal lines in Vanuatu, Cairns, PNG, and SI and show the LFA in New Caledonia were distinctly different (but identical to those in French Polynesia, former French islands in the Caribbean, and west Africa). It is interesting to note that this paper suggests there were at least 5 separate primary introductions to the Pacific region of this ant before secondary spread to other islands. An accidental introduction to SI is possible but a deliberate one more probably given lines of trade in the region.

If a deliberate introduction, I in no way would associate this with the very noble science of biological control and I’m sure my co-authors would agree with me on this point. Far more likely it would have been a “grey” introduction by an individual with no training in this field.

Foucaud, J. Orivel, J. Loiseau, A. Delabie, J.H.C. Jourdan, H. Konghouleux, D. Vonshak, M. Tindo, M. Mercier, J. Fresneau, D. Mikissa, J. McGlynn, T. Mikheyev, A.S. Oettler, J. and Estoup, A. (2010). Worldwide invasion by the little fire ant: routes of introduction and eco-evolutionary pathways. Evolutionary Applications. 1-13.

Ikin R, 1984. Cocoa tree-ant. Quarterly Newsletter. FAO. Asia Pacific Plant ProtectionCommission 27: 8.