Wilco J.M.M. Liebregts*
The incursion of B. longissima into Southeast Asia exemplifies the invasion of a new area by invasive alien species where no or few natural enemies exist. Quarantine and surveillance are the best prevention methods. If incursion occurs, the distribution of the pest and the feasibility of eradication should be determined and measures, such as sourcing natural enemies, should be studied. Collaboration with pesticide lobby members should remain close and the community should be kept abreast with the activities of the control programme. Lessons learned from regional projects are provided.
The incursion of the coconut hispine (leaf) beetle, B. longissima, into Southeast Asia is a typical example of what can happen when an exotic pest arrives into a new area where no or few natural enemies exist. The damage inflicted by the pest is dramatic, as it initially affects the central crown and slowly, as the leaves become older and young emerging leaves continue to display damage symptoms, progresses to include all of the tree leaves.
In the absence of natural antagonists in the region where it is endemic, the pest can multiply very rapidly. This has led to high damage levels, and death of trees at an estimated 5 percent per annum. The pattern of the outbreaks displayed over Southeast Asia is very similar to the one experienced in Samoa in the early 1980s.
The assistance provided by FAO to help affected countries achieve control of the beetle has been progressively fine-tuned to incorporate the results of projects in other countries. During this process, a number of lessons have been learned from the Brontispa incursion into Southeast Asia; these are briefly described hereunder. Accurate identification of the pest is of key importance and information on control measures should be studied.
Quarantine is the first step in blocking a pest. On the Asian mainland, this is not so much a national responsibility, but rather a regional responsibility. If a pest becomes established in one tropical Southeast Asian country, it is highly likely that it will eventually spread to others, where it will in turn necessitate control efforts.
Surveillance not only depends on surveys for pests and diseases in areas at risk, it also should involve extension agents and farmers. Information on known pests in the region and abroad should be made available and should include good photographs of the adults, immature life stages and damage symptoms.
Accurate identification of the pest is of key importance. Taxonomic capacity should be on hand, or rapidly available. This, of course, requires the availability of and access to up-to-date taxonomic information. However no single taxonomist can identify every arthropod/insect pest. Thus, a wide range of taxonomic skills is required, necessitating regional cooperation.
The distribution of the pest and the feasibility of eradication should be determined. For example, a case occurred in April 2004 at Hulhule Island, the location of Maldives’ international airport. Surveys showed that the beetle infestation appeared limited to some 6 - 8 trees near the jetty. An immediate campaign was started to eradicate the beetle. Regular monitoring has failed to detect any signs of the beetle to date, and it is now assumed that the eradication has been successful.
A literature study and web search on the pest and related specimens should be conducted to obtain information on control measures that can be applied if the pest becomes established.
It should not be assumed that all published information is up to date. Whilst preparing the project document for FAO support to Viet Nam in 2001 and 2002, we assumed that there were three parasitoids and one predator in Samoa, where B. longissima was recorded about 20 years earlier. Work on Brontispa stopped in 1985/1986, when it was decided that classical biological control of the pest had been achieved, and no further studies or surveys were conducted. We therefore assumed that at least two parasitoid species would be found that we could consider for introduction into Viet Nam, as well as a predatory mite, but field surveys only found one species of parasitoid.
Once it is determined that the pest is present in a certain area, measures should be taken to reduce its spread. This may include restrictions on the movement of plant hosts from the infested area. However, this should always include a major effort to increase community awareness about the pest and how it spreads, and seeking help from the public to prevent this. The smaller the infested area, the easier it will be to achieve biological control more quickly.
Classical biological control often takes considerable time (5 - 10 years), and in many cases any significant result should not be expected during the initial years. For Brontispa, we were lucky to have expertise in Brontispa control and sources of parasites. The pest had spread earlier in the Pacific, and in particular in Samoa it has remained an insignificant pest since it was brought under sustainable control more than 20 years ago.
Capacity requirements for classical biological control projects involving arthropods should, besides extensive skills and experience in entomology and plant protection, also include population ecology, population dynamics and integrated pest management (IPM). Knowledge of pesticide application is useful, but often less necessary.
The climatic conditions in the region where Brontispa is endemic parallel those in Samoa and southern Viet Nam. In Hainan, the climate is significantly different, and prolonged cold spells are experienced during the winter season, which may have an effect on the survival and effectiveness of the parasitoids there.
Although we anticipated finding three parasitoids and one predatory mite in Samoa, we could only find one species of parasitoid during surveys from April to June 2003. Moreover, T. brontispae, a pupal parasitoid of Brontispa that was imported and released in large numbers in Samoa in the early 1980s was not found at all.
Monitoring of damage and pest abundance is important to help demonstrate the impact of natural enemies. It should be noted that when commencing releases of parasites in the field, there is little time to study decreases in host abundance and damage, particularly if the parasite is highly effective.
There is a very strong pesticide lobby in most countries of Southeast Asia. Although this lobby inevitably is oriented towards profitability, it has provided short-term relief of the pest in several cases. Lobby members should be viewed as partners, and collaboration should remain close where possible.
Keeping the community abreast with the control programme is essential to ensure continuous support for activities. This should be done at any opportunity, and include the press, TV and radio. Whenever possible, community leaders and policy-makers should be informed about a project and its progress.
In Tables 1 and 2, additional information on lessons learned from regional projects and the effect of release of parasitoids on Brontispa beetle (2 possible scenarios) are given.
Table 1. Lessons learned from regional projects
|
The problems |
The solutions |
The moral |
|
Increasingly strong pressure from civil society and policy-makers at national, provincial and town levels to control the pest immediately, asking for wide-scale pesticide applications, and proposals that offer “quick fix” solutions. |
This is the most difficult issue. Pesticides generally do not work well and if they appear to provide some cosmetic relief, this is not sustainable owing to costs, environmental impacts and the scale of the problem. Moreover, the application of pesticides will impede the successful establishment and effectiveness of natural enemies. Classical biological control is no quick fix – but once established, it is a lasting one. We have worked with government authorities to increase awareness on biological control. Indeed, for some of us it was a leap of faith to put trust in a small animal that is hardly visible. Some provinces – initially those that were the most desperate – had few other alternatives but to trust us. In particular it was difficult to convince some clients that time was needed before any signs of improvement could be seen. |
Work with policy-makers and civil society – keep them updated on progress, and provide details and examples of classical biological control projects in the country and abroad. |
|
Following extensive surveys for Brontispa and parasitoids, we only found one parasitoid species – one that had never been recorded from Samoa before. The other species, and the mite, could not be found. |
Out of necessity, we imported the parasitoid to Viet Nam – particularly because the parasite was doing a very good job in Samoa: Brontispa was maintained at very low population densities – damage to palm trees was very low, and tree infestation rates were perhaps 0.5 - 0.1 percent. Also, the climate in both countries (Samoa and Viet Nam) was quite similar. This made our work easier, since we could dedicate all our efforts to the rearing of a single species. In fact, it facilitated everything….for Viet Nam at least. |
You cannot comfortably assume that the same situations that existed (more or less) 20 years ago are still the same – especially when no recent data are available. It is highly recommended that a visit is made to (1) assess the extent of the problem; and (2) determine the current status of the pest and its natural enemies. |
|
The FAO TCP project facility has quite a rigid structure – and some forms of support are kept to a minimum (e.g. international specialist and vehicles). |
We were fortunate to have very good support from officers and offices (national, regional and headquarters) and partner organizations which allowed us to have considerable flexibility in the planning and implementation of the project. |
Cooperation between and support from various departments in an organization, and with external partners, greatly helps the implementation of the project, and ultimately in achieving success. |
|
How to rear and distribute many parasites in as short a time as possible. |
Viet Nam established decentralized rearing centres in various provinces. Parasite releases were made according to a grid pattern based on observed dispersal rates, to optimize natural spread of the natural enemies. The grid pattern identifies large areas of coconut, and splits these into quadrants of approximately 10 x 10 km. Based on a natural dispersal rate of 5 - 8 km over 2 months, 1 (in the centre) to 4 (each 2.5 km from any 2 borders) releases are made of 5 - 6 mummies (approx. 250 parasitoids) in each of these quadrants – depending on production levels. |
If parasitoid production levels are limited (which they always are early in the project), it is better to make as quickly as possible – many releases of small numbers of parasitoids in many widely distributed sites, as opposed to few releases of large numbers in nearby sites. |
|
FAO TCP support is limited to amounts of US$500 000, and a duration of two years. In general, this is insufficient funding to seriously implement biocontrol projects, and the time is too short to obtain results. |
In the case of Viet Nam, it was fortunate that biocontrol agents were already known, and a source had been identified. This allowed the parasites to be introduced 4 -5 months after the start of the project, and field releases to commence after six months. However, at the conclusion of the project – 1½ years after the first releases – sound results were only available from the southern provinces The budget of US$400 000 was sufficient, as no exploratory surveys for additional natural enemies had to be made in countries where Brontispa is endemic. |
When planning a biological control project, one should take into account that they generally take many years and may appear costly – but the results are sustainable over the long term, and highly cost effective. When planning a biological control project, one should take into account that they generally take many years and may appear costly – but the results are sustainable over the long term, and highly cost effective. |
|
How can we reduce the rate of spread in Southeast Asia, and to nearby countries? |
We believe that by the time the project started the pest had already reached Lao PDR and Cambodia. Hence, any parasite releases were too late to reduce its spread there. However, the reaction time was considerably shorter when the pest was discovered in Thailand and Lao PDR, and parasites were released shortly thereafter. Information on the seriousness of the pest incursion in Cambodia only reached FAO in October 2004, and assistance is now being planned. The pest is also present in Myanmar, but so far no request for assistance has been received. A different approach was applied in Maldives where pest incursion was limited to a few islands in the south of Ari Atoll. Nationwide public awareness campaigns via the media (TV, newspaper, radio, posters, and stakeholder meetings) helped prevent the further spread of the pest to other atolls: Until now, the distribution of the pest remains limited to a chain of nearby islands in the south of the atoll; the nearest islands are some distance from the infestation, probably too far for the beetle to fly. A pest incursion on the airport island was detected early in April 2004 and it is now assumed that the eradication has been successful. The risk of spread of the beetle from Maldives to nearby countries has been recognized, and two awareness seminars were held in Sri Lanka for quarantine and plant protection staff. To date, the pest has not been recorded elsewhere in the region. |
A network of plant protection agencies, organizations and individual specialists will allow a rapid exchange of information on both the pest’s distribution and control methods. For those countries isolated by natural barriers (ocean, mountain ranges), quarantine is of the utmost importance to prevent the pest from entering. If the pest manages to enter, the implementation of an eradication campaign should commence. |
|
How to promote the benefits of biological control? |
People, and policy-makers in particular, tend to forget quickly about a pest once it has been brought under control. Production losses and costs of chemical controls become a thing of the past, until another pest arrives. After initial promising results from the biocontrol project, an economist was hired to conduct a study on the costs of the Brontispa incursion into Viet Nam, and to prepare a cost-benefit analysis. The study showed that damage by the pest to the coconut industry alone exceeded US$35 million per annum; as it is typical to measure such impact over a 30-year period, the total damage would amount to well over US$1 Billion. |
As early as possible in the control programme, conduct a financial analysis on the losses and the costs of conventional control with pesticides and eradication efforts. This will help support preventive measures (e.g. quarantine) and sustainable (biological) control activities. Classical biological control projects commonly have very high cost-benefit ratios. |
|
Stable
population density of Brontispa |
||||||||||
|
Parasite generations in field |
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
|
|
Days (development time = 20 days) |
0 |
20 |
40 |
60 |
80 |
100 |
120 |
140 |
160 |
|
|
SCENARIO ONE |
||||||||||
|
Total No. adult beetles per 10 by 10 km grid |
125000000 |
|||||||||
|
Brontispa abundance (120 days adult life) |
125000000 |
124995500 |
124950500 |
124545500 |
122115500 |
112395500 |
92955500 |
63795500 |
||
|
Brontispa immature abundance (30 days; 1/4 of adults) |
31250000 |
31248200 |
31230200 |
31068200 |
30096200 |
26208200 |
18432200 |
6768200 |
||
|
Of which potential hosts (L3 and L4) (0.5) |
15625000 |
15624100 |
15615100 |
15534100 |
15048100 |
13104100 |
9216100 |
3384100 |
||
|
L3 and L4 abundance per tree |
12.5 |
12.49928 |
12.49208 |
12.42728 |
12.03848 |
10.48328 |
7.37288 |
2.70728 |
||
|
Multiplier (females produced per female) |
10 x |
9 x | 6 x | 4 x |
2 x |
1.5 x | 1.2 x | 1.1 x | ||
|
Number of females released/in the field: |
||||||||||
|
initially - one |
1 |
15 |
150 |
1350 |
8100 |
32400 |
64800 |
97200 |
116640 |
128304 |
|
initially - one hundred (1 per sq km) |
100 |
1500 |
15000 |
135000 |
810000 |
3240000 |
6480000 |
9720000 |
11664000 |
12830400 |
|
initially - one thousand (10 per sq km) |
1000 |
15000 |
150000 |
1350000 |
8100000 |
32400000 |
64800000 |
97200000 |
116640000 |
128304000 |
|
initially - three hundred (20 mummies per sq km) |
300 |
4500 |
45000 |
405000 |
2430000 |
9720000 |
19440000 |
29160000 |
34992000 |
38491200 |
|
Number females released |
300 |
|||||||||
|
Eff. Parasitisation (ie. ratio that produces offspring) (%) |
20 |
|||||||||
|
Number of effective parasites (b29 * b30) |
60 |
900 |
9000 |
81000 |
486000 |
1944000 |
3888000 |
5832000 |
6998400 |
7698240 |
|
2nd release (30 mummies; +60) |
960 |
9600 |
86400 |
518400 |
2073600 |
4147200 |
6220800 |
7464960 |
8211456 |
|
|
3rd release (30 mummies; +60) |
9660 |
86940 |
521640 |
2086560 |
4173120 |
6259680 |
7511616 |
8262777.6 |
||
|
SCENARIO TWO |
||||||||||
|
Total No. adult beetles per 10 by 10 km grid |
125000000 |
|||||||||
|
Brontispa abundance (120 days adult life) |
125000000 |
124977500 |
124820000 |
124032500 |
121670000 |
116945000 |
110330000 |
103053500 |
||
|
Brontispa immature abundance (30 days; 1/4 of adults) |
31250000 |
31205000 |
30890000 |
29315000 |
24590000 |
15140000 |
1910000 |
-12643000 |
||
|
Of which potential hosts (L3 and L4) (0.5) |
15625000 |
15602500 |
15445000 |
14657500 |
12295000 |
7570000 |
955000 |
-6321500 |
||
|
L3 and L4 abundance per tree |
12.5 |
12.482 |
12.356 |
11.726 |
9.836 |
6.056 |
0.764 |
-5.0572 |
||
|
Multiplier (females produced per female) |
10 x |
7 x | 5 x | 3 x | 2 x |
1.4 x |
1.1 x | 1.1 x | 1.1 x | |
|
Number of females released/in the field |
||||||||||
|
Number females released (3000 mummies) |
45000 |
|||||||||
|
Eff. Parasitisation (ie. ratio that produces offspring) (%) |
5 |
|||||||||
|
Number of effective parasites (b45 * b46) |
2250 |
22500 |
157500 |
787500 |
2362500 |
4725000 |
6615000 |
7276500 |
8004150 |
8804565 |
|
2nd release (+1000) |
23500 |
164500 |
822500 |
2467500 |
4935000 |
6909000 |
7599900 |
8359890 |
9195879 |
|
|
3rd release (+1000) |
165500 |
827500 |
2482500 |
4965000 |
6951000 |
7646100 |
8410710 |
9251781 |
||
Table 2. Effect of release of parasitoids on Brontispa beetle (2 scenarios)
* Team Leader. FAO Projects TCP/VIE/2905; TCP/MDV/2904; TCP/NAU/2901; TCP/THA/3003
