Ants as control agents of CPB

Cocoa pod borer funding and related issues, especially the use of ants as a possible component of the control and management of the borer in PNG, have been making news headlines recently. Executive manager and principal scientist at the PNG Cocoa Coconut  Institute Dr SAMSON LAUP gives a detailed technical explanation and information on the potential of using ants as a possible candidate to control cocoa pod borer in the cocoa agro-ecosystem. 

THE cocoa pod borer can be managed by biological control.
Where biological control of a particular pest has been successful, the control measure has been environmentally safe, less expensive in the long term (although in the initial establishment is expensive) and, normally, control is permanent when the predator/host relationship reaches a stabilised balance situation.
Ants are potential bio-control agents, behaving mainly as predators. However, most predators are only opportunists, polyphagus and non-specific. Further, many ant species are mobile and very unstable unless feeding on adequate stabilised food source.
Once a sustainable food source is found and identified, the ant settles to produce colonies. When the food source is depleted, the ant colonies shift to other favourable sites.
Most ants feed on sugar extracts derived from honey sources either produced by other insects or certain plants. One of the most common insect which produces honey or sugary substance are called mealy bugs (whitest powdery insects) of the insect sub-order Homoptera.
 Female mealy bug are insects that become sedentary for a period during their life cycle when they are tendering their young or progenies. When in sedentary position, the female mealy bug produces the sugary substances that ants like to feed on.
This sugary substance also produces sooty moulds in fruits which can interfere with the cosmetic or quality of fruits for sale.
Ants partner with the mealy bug, in what is known as a mutualistic relationship, where both partners positively benefit from the association.
The ant collects the sugar extracts from the adult female mealy bug while, at the same time, protecting the adults and its nymphs (called crawlers) from other natural enemies such as insect predators, parasites or other smaller vertebrates and reptiles.
One of the common enemies is a tiny wasp (Hymenoptera-egg parasitoids) that lays its eggs on the mealy bugs and, when the larva hatches, it kills the mealy bugs during its nourishment and growth from the inside of the adult mealy bug. The ant acts as a protector of the mealy bugs and its food source from naturals enemies such as the tiny wasps.
Mealy bugs, although are beneficial in the mutualistic relationship with ants, have been known to transmit serious plant viral infections on a number of important commercial agricultural crops.
Three main insects or disease problems of cocoa are found in the tropics. One is the cocoa pod borer, which is found in the Asian and Oceania regions. The other is called “witches broom”, which is the most serious cocoa problem found in some parts of South America and, thirdly, (most importantly), the “swollen shoot” virus, which is transmitted by a mealy bug species (also protected by ants) in the cocoa-growing countries of the African tropical region.
The black ant, of the dolichoderus species, is being used by Malaysian cocoa farmers against cocoa pod borer.
The ant population and activities is sustained by being fed from a vast population of a specific mealy bug species. Special techniques have been developed in Malaysia to enhance the population of both the mealy bug and the ant species, and also how to enhance the ant effectiveness against cocoa pod borer.
The ant-mealy bug mutualistic relationship may have been adopted and established through an evolutionary period.
The black ant-mealy bug behaviour was discovered and identified in the past, and promoted as part of an integrated pest management (IPM) approach against cocoa pod borer, in the cocoa and coconut agro-ecosystem.
The use of the black ant on cocoa and coconut is now an established farmer management practice in Malaysia. However, it is not possible to introduce the black ant into PNG devoid of its mutualistic mealy bug partner or sugar provider.
Ants are normally predators, so there may be lesser problems with their introduction into the country, but it is not advisable to introduce the mealy bug species because of unforeseeable possible negative consequences on other PNG commercial crops, as is the case with swollen shoot virus on cocoa transmitted by a mealy bug in Africa. There are many millions species of ants on earth, and particularly in PNG, where there is a higher indigenous insect bio-diversity. Many are ant species, both in the natural forest and manmade or agricultural vegetation such as the cocoa and coconut agro-ecosystem.
It may be possible to find and identify indigenous plant foraging ant species in the PNG cocoa ecosystem that has developed a stable and safe mutualistic relationship. To identify any unique and stabilised relationship is a major undertaking which calls for basic research and efficient and effective surveys in many cocoa-growing habitats within PNG.
The CPB (aggressive type) has been in PNG for more than five years and there has, probably, been ample time for certain insect predators or parasites to learn and home in on CPB as a potential favourable host. Sometimes, the establishment of a stabilised relationship may take a long time. 
Funding resource would be required for these basic studies and to further understand the unique biological behaviour involved.
In the CPB strategy formulated by PNGCCI last year, the avenue for use of biological control is also captured as one of the major areas of research for CPB control. The study of ant behaviour is an integral part of these CPB bio-control studies.
The red ants, reported in the media by villagers in East New Britain, could be the oecophylla, commonly known as the kurakum ant, or the Anoplolepis longipes, commonly known as the crazy ant which is a well-known predator of both insects and cocoa trees.
The kurakum ant is an inconvenience neighbour in many cocoa blocks.
Like most ants species, it releases formic acids which can be very discomforting to sores on the farmer’s legs or the eyes. This ant can also aggressively bite and attack when disturbed.
The crazy ant is also unstable, mobile or nomadic if the food sources are depleted or absent in an area, and actively communicate these phenomena to other members of the species in the same area.
Farmers in PNG, sometimes, see a lot of mealy bugs on the cocoa pod.
This bug is indigenous to PNG and is a minor pest of cocoa, but not economically significant. The mealy bug is called Planococcus pacificus. Ant, such as the crazy ant, collects honey-dew from this mealy bug for food. There are other homopterans insects as well, such as scales insects (Coccus viridis), membracids (Maurya spp) and aphids (Toxoptera auranti) which also produce honey dew and are collected by the crazy ant. It may be possible to study this mutualistic relationship in detail and identify if the relationship can be manipulated and enhanced for the control of cocoa pod borer.
These are some of the basic studies that are necessary to contribute solution to the problem of cocoa pod borer.
A team from the PNG Cocoa Coconut Institute will investigate the claims made in the media that an ant specie has been observed controlling cocoa pod borer in one of the villages in East New Britain.
Ant belongs to the family called formicidae of the order hymenoptera. There are many families of that order that have been identified as potential parasites, egg parasitoids or pupal parasitoids of cocoa pod borer. These have been identified in Malaysia, Indonesia, Borneo, Sri Lanka, the Philippines and PNG.
In the past, scientists from Malaysia have also searched in PNG for more potential bio-control candidates to control cocoa pod borer because PNG has a higher natural insect bio-diversity and it also been presumed that the origin of the borer may even be PNG. This is because samples or specimens of cocoa pod borer (non-aggressive) were discovered on cocoa in PNG more than 70 years ago (1936).
A number of potential research areas for cocoa pod borer and biological control have been indicated to be significant areas of focus by PNGCCI. This includes more research into the use of ant as potential bio-control agents for cocoa pod borer.
Normally, biological control is expensive in the initial establishment but, once the ideal selected agents are identified and released with satisfactory outcome, the whole programme becomes inexpensive, sustainable, environmentally safe and long-term control is achieved.
Although PNGCCI has the scientific capacity and capability to carry out these necessary researches and studies, it has not been given the opportunity to do so.
It was mentioned recently in the media that so much money had been given to fight cocoa pod borer.
But, as the divisional head of all researches on cocoa at the institute and throughout the country, I have yet to be given funding for basic research and applied research on the pest since the cocoa pod borer arrived in 2006.
Cocoa research submitted a proposal on cocoa pod borer to the government in 2009 for a detailed basic research. This proposal was never funded, although we heard funding was provided for other non-research cocoa pod borer activities.
Until today, the cocoa research of PNGCCI has never received any funding for basic research on cocoa pod borer in the PNG situation. As a consequence, we never venture into the necessary basic and important research required for permanent control of cocoa pod borer in PNG.
The priority of the team is on other research approaches for cocoa pod borer in partnership with the Commonwealth Agriculture Bureau International (Cabi), MAST Chocolate Confectionary and the University of Sydney with funding from ACIAR. This is an international and regional project, although cocoa pod borer has its own research specifications.
The project emphasised on applied research in which there is a promotion of the different technologies and management practices of cocoa pod borer within the new concept of “farmer field school”.
The concept focuses on smallholder cocoa farmers.
There are many basic unanswered questions relating to the issues of cocoa pod borer in PNG but, without basic research and studies, these cannot be answered.
We hope that, in future, CPB funding for basic research is channelled properly to the people who are responsible and who are implementers of government and institute’s agenda for the cocoa industry in PNG.