Mangoes are an important smallholder and commercial crop in southeast Asian countries and are the most important commercial crop in northern Australia. In order to reduce dependency on the heavy use of chemical insecticides to control insect pests in mango orchards, this research will develop an integrated pest management model, which concentrates on the use of a natural enemy species (the weaver ant) together with farming strategy and soft chemicals.

Five milestones in the first year of research have been successfully achieved in the Australian program.

Data obtained in field surveys, field monitoring, field experiments and laboratory trials in 2001 suggested that weaver ants can successfully control the leaf hoppers, the red-banded thrips, the fruit spotting bug, the mango leafroller, the seed weevil and fruit flies. These six species are key insect pests in mango orchards in the Northern Territory. However, the ants have a mutual relationship with mealybugs and flat scales.

The use of weaver ants in mango orchards did not influence fruit quality or yield. These results should give mango growers confidence that weaver ants are not a pest in their orchards.

Data of parasite levels between trees with weaver ants, trees without the ants and trees protected by insecticides were collected. The data analysis is in progress.

Farmers who are involved in this research did not consider the aggressiveness of the ants in harvest and pruning to be a problem. Field trials with water spray on fruits with weaver ants were done to reduce the ant activity, and the data analysis is in progress.

In experiments designed to reduce the populations of mealybugs and flat scales, we found that potassium soap (1%) is better than neem oil and petroleum spray oils, and it did not kill weaver ants but reduced mealybugs populations by 33%. The use of soft chemicals will complement the use of weaver ants to achieve a good balance between weaver ants and populations of mealybugs and/or flat scales.

Field surveys, field monitoring, field experiments and laboratory trials set up in 2001 will be repeated in 2002 to confirm our preliminary results obtained in 2001. will be confirmed next year. To construct an IPM model for mango growers, two more objectives (stabilising weaver ant populations and the effect of mix cropping on insect pests and their natural enemies) will be started in 2002.

In the Vietnam program, field experiments were started January 2002. Field work in the Thailand program just started in May 2002. Due to the delay of the programs in Vietnam and Thailand, few results are available at this time from these countries.

There are seven milestones for this reporting period, and these milestones have been successfully achieved.

Based on the data obtained in the field monitoring, field experiments and laboratory trials in 2002, similar yields and better quality of fruits were achieved from trees with weaver ants plus soft chemicals (43.3 fruits/tree and 28.1% of first class fruits) compared to trees protected by chemical insecticides (37.9 fruits/tree and 9.1% of first class fruits). Higher yields and better or similar quality of fruits were produced in trees with weaver ants (59.5 - 147.2 fruits/tree and 55.0 - 62.7% of first class fruits) than in trees without weaver ants (31.8 - 87.2 fruits/tree and 34.7 - 54.8% of first class fruits). The damage level by all insect pests ranged from 7.8 - 13.8% in trees with weaver ants plus soft chemicals or with weaver ants only, but from 9.2 - 20.5% in trees protected by insecticides or in trees without weaver ants.

Weaver ants were effective in controlling the nine major mango insect pests compared to chemical insecticides and other ant species. These pest insects include the leaf hopper, the red-banded thrips, the fruit spotting bug, the mango leaf roller, the seed weevil, fruit flies, flower caterpillars, mango tip-borer and the dimpling bug. However, the ants have a mutual relationship with mealybugs.

One species of parasitoids (Hymenoptera: Encyrtidae) was common in mango orchards, and it is effective in parasitising egg rafts of the mango plant hopper, which is one of the main insect pests during the fruiting period. The parasitic level of the plant hopper was higher in trees with weaver ants plus soft chemicals than in trees protected by chemical insecticides.

In the selection of soft chemicals, Applaud (0.03%) and Potassium soap (1%) were effective in reducing mealybug populations and are safe to weaver ants. To stabilise weaver ant populations in mango orchards, two experiments have been continued since June 2001: the experiment on colony isolation and the experiment on transplantation of ant colonies with queen ants. These experiments are still on-going.

Based on the results obtained over the last two years, a preliminary IPM model is constructed, and it will be tested in 2003. Two extra activities were conducted in this reporting period: (1) the assessment of weaver ant formic acid on sugar contents in mango fruits and the shelf life of the fruits with weaver ant marks; (2) the effect of weaver ants on the dimpling bug damage. These two activities were unexpected at the time the project proposal was written, but they are crucial to judge the usefulness of weaver ants in mango orchards. Preliminary results from the two activities suggested that weaver ants have had additional benefits to mango growers.

The research group is actively involved in publications, communications, dissemination and extension activities. The project spending is well under control during the reporting period.

Thailand programs 1 and 2 started in August 2002, and the information about the research teams, study sites and experimental designs, research methods and the project progress is provided. Preliminary results obtained in Thailand program 1 suggested that weaver ants plus soft chemicals appeared to be either similar to or better than insecticides in controlling the main mango insect pests, including thrips, elephant beetles, stem borers, leaf hoppers and scales. However, mealybug populations seemed to be higher in the treatment with weaver ants plus soft chemicals than in the insecticide treatment. These results generally agree with the results obtained in Australian program.

Year 3 (01/01/2003-31/12/2003)
All the identified outputs in this reporting period have been successfully achieved. The data obtained in the field monitoring and field experiments in 2003 in the Australian program demonstrated that similar yields and better quality of fruits were achieved from trees with weaver ants plus soft chemicals (51.8 fruits/tree and 62.6% of first class fruits) compared to trees protected by chemical insecticides (42.6 fruits/tree and 40.9% of first class fruits). Higher yields and better or similar quality of fruits were produced in trees with abundant weaver ants (45.8-61.4 fruits/tree and 58.4-68.5% of first class fruits) than in trees without weaver ants (51.5 fruits/tree and 39.8% of first class fruits). Sugar levels are higher in fruits from the weaver ant plus soft chemical treatment than in fruits of the insecticide treatment. Similar results were also obtained in the Prince of Songkla University program.
Weaver ants were effective in controlling the major mango insect pests compared to chemical insecticides and other ant species. However, the ants have a mutual relationship with scales and mealy bugs. The parasitic level of the plant hopper was higher in trees with weaver ants plus soft chemicals than in trees protected by chemical insecticides, which agree with the data obtained in 2002.
The soft chemicals, Applaud (0.03%), Potassium soap (1%) and White oil (2%) were effective in reducing mealy bug populations and are safe to weaver ants. A pure water spray at a rate of 2000 L/ha can reduce weaver ant activity by more than 70% for 50 minutes, which greatly reduces ant disturbance to people picking fruits. In Thailand, a long handle picking pole or net used with a shaking action reduces ant aggressiveness.
To stabilise weaver ant populations in mango orchards, data obtained by the collaborators at the Prince of Songkla University suggested that weaver ant populations have been more stable in the mixed cropping orchard than in the monoculture orchard. Field experiments in the Australian component of the project were completed in November 2003, and the data analysis is in progress.
A preliminary integrated pest management (IPM) model constructed in 2002 has been tested in 2003, and a final model for Australian mango growers has been developed. Based on two years of data and on-going study, two preliminary models have been constructed for Thailand and Vietnam respectively.
The group is actively involved in publications, communications, dissemination and extension activities. A video for Australian mango growers has been made. Videos in Vietnamese and Thai are under preparation. Posters and booklets are also under preparation.

Based on the Outputs table of the project, all the identified outputs of this project have been successfully achieved.
In Vietnam and Thailand, the yield and the fruit quality produced in the treatment with weaver ants plus environmentally friendly soft chemicals (WPS) were similar to or higher than in the chemical insecticide treatment (CI), while in the Northern Territory, Australia, the profit from WPS or from trees with abundant weaver ants was increased by over 70% compared to the profit in CI or in trees without weaver ants.
Compared to chemical insecticides, weaver ants were effective in controlling the major mango insect pests. These include mango leafhoppers, thrips, fruit spotting bugs, flower caterpillars, seed weevils, fruit flies, elephant beetles, stem borers, planthoppers, leaf cutting weevils, web caterpillars and seed borers.
Although weaver ants have a mutual relationship with scales and mealy bugs, the soft chemicals such as white oil, D.C.Tron oil, Neem oil, potassium soap, Biobit, Beauveria or Applaud were effective in reducing the populations of these pests, and these soft chemicals are safe for weaver ants.
Weaver ant formic acid caused black spots on fruit skin mainly due to ant fights between colonies. Separation of weaver ant colonies is effective in reducing the levels of fruit damaged by the formic acid.
Weaver ants annoy people working in the orchard during the harvest. Water spray can greatly reduce the ant activity prior to harvest, and it does not cause fruit lenticels or post-harvest diseases. Mango growers are pleased with this method in Australia. In Thailand, farmers found a picking pole or net with a long handle plus shaking action after a few picks to be useful to reduce the disturbance from the ants. In Vietnam, two methods are useed to reduce ant disturbance: (1) to rub wood ash on the main branches of the relevant part of the tree to break ant trails when harvesting; and (2) to lure the ant away from the trees, which will then be harvested or pruned. Weaver ants do not have a detrimental impact on the level of parasitism of homopteran pests in mango orchards.
The mixed cropping orchards harbour more natural enemies of the insect pests compared to the monoculture orchards.
To stabilise weaver ant populations in mango orchards, it is essential to isolate the ant colonies, transplant ant colonies with queens and mix mango trees with other tree crops such as citrus. If mango orchards are monoculture, the provision of ant food is needed when trees are in dormancy.
Two types of IPM programs for both organic and conventional growers have been successfully developed for mango growers in Vietnam, Thailand and Australia. These IPM programs are friendly to the environment, and they allow mango growers to significantly cut chemical insecticide use and to produce insecticide-free or organic fruits.
The educational materials (Booklets, video (DVD and tapes) and a series of posters) in English, Vietnamese and Thai have been produced to describe how to use the IPM program step by step. They are easy for farmers to understand and to use.
Farmers in Vietnam, Thailand and Australia who are involved in this project are happy with the IPM programs, and they have adopted the methods. The Pest Management Center in Khon Khan Province, Thailand tried the IPM program in 2004, and they achieved better results than they expected. They will continue to use weaver ants for their oriental fruit fly research in Udorn Thani Province. The owner of the Supan Buri site, Department of Agricultural Extension of Thailand was happy with the yield, and the mango growers nearby expressed their willingness to use the ants in their orchards.
The research group is actively involved in publications, communications, dissemination and extension activities. Throughout this project, the project staff have produced 10 publications, 18 research presentations and 5 major research reports, and they have also conducted 8 major communication and extension activities.
Detailed future project plans have been made to implement the IPM programs developed in this project to a wide range of mango growers in Vietnam, Thailand and Australia.