Growing public concern about Harmonia axyridis (multicoloured Asian ladybird or ladybeetle) in Europe reflects deep-seated and long-held misgivings within the biological control community about the inadequacy of regulation of natural enemy introductions. The latest media attention has come from the UK, where the identification of a single specimen from a garden in the southeastern county of Essex led to alarming press headlines, e.g. "The ladybird killers fly in" (Daily Telegraph, 5 October 2004).
Harmonia axyridis is a well-known aphid predator, attacking numerous species in its extensive native range in Asia. It is a voracious feeder, preying on not only aphids but also soft-bodied insects like psyllids, butterfly eggs and many groups of aphid predators including other ladybirds - and cannibalism is an important factor in its population dynamics. Studies in the USA suggest that it may displace native fauna by predation, competition and other indirect mechanisms1.
Harmonia axyridis was introduced to France for the biological control of various aphid species in 1982. Ten years ago it was commercialized for the control of aphids in greenhouses and field crops in northwestern Europe. Established wild populations were first found in Germany in 2000 (Frankfurt am Main) and in Belgium and the Netherlands at the end of 2002. Large populations have since been found in all three countries, together with evidence of its dispersal to new locations. Currently, scientists in these countries are conducting surveys to monitor its presence, abundance and spread. There is considerable concern about its possible effects on native competitors, but at present it is impossible to predict what its impact might be.
The ladybird has a far longer history in North America1. The first record of its introduction was in California in 1916. It has been introduced, both deliberately and accidentally, many times since, particularly to many eastern US states between 1978 and 1982. It is credited with contributing to control of pests in a wide variety of field and tree crops. It was not recorded as established in the wild until 1988, when it was collected in the southern US state of Louisiana (not near any known release site). Since then it has spread rapidly and is now found in most US states and in southern Canada. On top of the nontarget effects outlined above, it has been identified as a potential pest in the fruit industry as aggregations can occur on fruit. These are particularly difficult to remove from grapes and can lead to tainted wine. While there are scientific concerns about its nontarget effects, there is also regular public outcry: perennial complaints arise in autumn when its habit of aggregating in high numbers to over-winter in crevices in light-coloured substrates leads it to enter buildings. The sight of massed ladybirds, smell (emitted when stressed), occasional bites and allergies, and even the noise of the massed ranks crawling around contribute to its nuisance status.
In 2003, a paper in BioControl2 highlighted H. axyridis as having a high risk of nontarget impact (second only to another polyphagous ladybird, Hippodamia convergens) in Europe. The paper was an output of the ERBIC (Evaluating Environmental Risks of Biological Control Introductions into Europe) project, funded under the European Union (EU) 4th Framework Programme. It developed a proposed risk assessment method for biological control agents, and applied this to 31 exotic agents commercially available in the EU. Briefly, it calculated a risk index for each species based on the likelihood and magnitude of nontarget effects from dispersal, establishment, host specificity, direct effects and indirect effects. It is notable that most of the seven predatory insects assessed were given high-risk indices (three of the five top-scoring species were predatory insects, and only one was outside the top ten).
Despite mounting evidence of its nontarget impacts, H. axyridis is still available commercially in Europe, described as an excellent aphid predator. Alarmingly, in the context of this article, it is also noted as seeming to be very tolerant to pesticides. Can and should anything be done? It is probably too late. Given the spread and abundance of the ladybird, eradication in Europe is not an option. With the size of the populations that have built up on the continent this autumn, its establishment in the UK seems inevitable if not already reality. Harmonia axyridis has now been confirmed from other locations in the southeastern UK and evidence of breeding recorded in south London3. Only with the passage of time will it be possible to assess whether the introductions are a disaster, by weighing up the benefits of control against the nontarget impacts.
A prime reason why such apparently high-risk species are marketed lies in the need for biological control producers to make money. There is more economic sustainability (profit) in a treatment with wide-spectrum application, and this applies as much to biological control agents as to chemical pesticides. Thus, while biological control theory dictates that the best agent, for both efficacy and safety, is a highly host-specific one, economics dictates that voracious generalist species with broad host ranges are more attractive to the commercial producer. The BioControl paper notes, however, that generalist tendencies do not by themselves rule out a species as a biological control agent: "The likelihood of adverse ecological effects may be high, but the conditions in which they are released (e.g. greenhouse in temperate climates) may strongly limit the realization of these adverse effects." In other words, each introduction needs to be considered on its merits. Yet how far European countries do or do not regulate the introduction of invertebrate biological control agents varies, in practice, from strictly to not at all.
The issue of lack of regulation was recognized many years ago, ironically when the fledgling 'green movement' began to throw doubts on the sustainability of widespread use of pesticides, which led to the growth of integrated pest management (IPM) with biological control as a cornerstone. The advent of IPM meant that people and countries with no experience of biological control were beginning to make, or want to make, species introductions, either as natural enemies or formulated as biopesticides. Action by international biological control organizations and FAO (Food and Agriculture Organization of the UN) led to the drafting of the IPPC (International Plant Protection Convention) 'Code of conduct for import and release of exotic biological control agents' (International Standards for Phytosanitary Measures (ISPM) No. 3)4, which was adopted in 1996. Although primarily aimed at protecting crops, it is regarded as the general international protocol for countries implementing biological control. Nonetheless, it is not international law at this time (see below). The revision of ISPM No. 3, as regular readers will know, began in late 2002 and is currently at the country consultation stage. EPPO (European and Mediterranean Plant Protection Organization) has also developed standards (PM6)5 to provide guidelines for assessing and reducing risks associated with biological control agents and, in some cases, for comparing their efficacy. OECD (Organisation for Economic Co-operation and Development) has developed guidance on information requirements for ecological risk analysis6. However, although both these focus on commercial invertebrate biological control agents, they are advisory, not regulatory, documents.
With invasive species now climbing the European agenda, classical biological control, as successfully implemented by governments in many other parts of the world, offers perhaps the best hope for containing at least some of them. Biological control, properly implemented, has a good track record of safety. A few high profile, largely historical, cases have given it an unnecessarily accident-prone public image, but the emerging problem with H. axyridis does little to help promote modern biological control as a safe option.
Once revised and approved, ISPM No. 3 will have legal, international status, but at the moment there is no uniform regulation within Europe. Initiatives are, however, gaining pace. A workshop held in Engelberg, Switzerland in June 2004, reported on later in this issue7, reviewed methods for assessing environmental risks from invertebrate biological control agents and a book based on the meeting will be published next year. Another workshop in Zurich, Switzerland in July 2004 marked the establishment of the IOBC/WPRS (International Organization for Biological and Integrated Control of Noxious Animals and Plants - West Palaearctic Regional Section) Commission on Harmonization of IBCAs (CHIBCA) to harmonize the regulation of invertebrate biological control agents in the EU and other European countries.
Many biological control producers view the implementation of a regulatory procedure for biological control agents with considerable alarm. They fear that lengthy, cumbersome processes will increase costs and may prevent useful agents from reaching the market. However, without buy-in by the commercial sector to the importance of safety, the future of biological control is far from assured. For the moment, perhaps the best we can hope is that the high profile achieved by H. axyridis may help foster the message that safety must come first for all in the biological control sector.
1Koch, R.L. (2003) The
multicolored Asian lady beetle, Harmonia
axyridis: a review of its biology, uses in biological control,
and non-target impacts. Journal of Insect
Science 3, 1-16.
2Van Lenteren, J.C.; Babendreier, D.; Bigler, F.; Burgio, G.; Hokkanen, H.M.T.; Kuske, S.; Loomans, A.J.M.; Menzler-Hokkanen, I.; Van Rijn, P.C.J.; Thomas, M.B.; Tommasini, M.G. and Zeng, Q.Q. (2003) Environmental risk assessment of exotic natural enemies used in inundative biological control. BioControl 48, 3-38.
3Ladybird survey, Harmonia
4ISPM No. 3, original and
6OECD (2004) Guidance for
information requirements for regulation of invertebrates as
biological control agents (IBCAs). Series on Pesticides, No. 21.
7Menzler-Hokkanen, I., Babendreier, D., Bigler, F., Hokkanen, H. & Kuhlmann, U. (2004) Environmental impact of invertebrates for biological control of arthropods: methods and risk assessment. BNI 25 (4) [Conference reports, this issue].
Classical Biocontrol Introduced to Timor-Leste
The release of the coccinellid Chilocorus politus against coconut scale, Aspidiotus destructor, in the Democratic Republic of Timor-Leste (East Timor) in July 2004 was the first official release of a biocontrol predator in this small island country.
Aspidiotus destructor is a widespread and serious pest of coconut, and also infests bananas and a wide range of other crops. On coconut, it has been a frequent target around the world for biological control. Severe infestations cause characteristic complete yellowing of older coconut fronds, which is visible from a distance and even from the air. In the worst cases the trees die. Yellowing symptoms were first noticed in Timor-Leste in May 2001 around the town of Baucau, but the pest may have been present for some time by then. By 2003 the outbreak was affecting most trees in the area. Anecdotal evidence suggests that it was having serious consequences on the livelihoods of Baucau farmers. It is possible that the pest outbreak was associated with potassium deficiency in the trees. The area is characterized by coral limestone, which is mineral deficient, especially in potassium. The infestation has spread beyond Baucau and it is anticipated that it will spread elsewhere in Timor-Leste as a result of air currents and movement of infested coconut and banana plant material.
Three management options were considered by the Timor-Leste Ministry of Agriculture, Forestry and Fisheries (MAFF) in consultation with CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement, France):
The coconut scale biocontrol project has received generous financial support from USAID (US Agency for International Development) and German Technical Cooperation (GTZ, Deutsche Gesellschaft für Technische Zusammenarbeit). Advice from CIRAD and Gadjahmada University (Jogyakarta, Indonesia) led to C. politus being selected for introduction. Collections were made in Jogyakarta in September 2003 and a culture was established in Triloca, west of Baucau. Aspidiotus destructor colonies were established on pumpkins. The coccinellids were reared on these, supplemented with cut, scale-infested palm fronds, inside locally made wood and cloth cages. Other adaptations were devised by experimenting with ways to maintain a healthy colony:
Even so, predator numbers were slow to increase. The first releases were not made until May 2004, when 100 adults (40 males and 60 females) were released at each of four sites. The releases featured a novel bamboo release cage, lined with banana leaves covered in scales, which was suspended in the palm canopy by plastic cable clips. By October 2004 some 1800 ladybirds had been released at 23 locations.
Local people have also been trained in how to collect the ladybirds, and how to carry them and release them at sites of infestation where the predators appear to be absent. As A. destructor inevitably spreads further in Timor-Leste, new releases are likely to be necessary, but providing such training will allow the predator to be redistributed on a local level.
Because the introduction of coccinellids against A. destructor has had mixed results elsewhere, signs of establishment were awaited with some anxiety. However, early signs in Timor-Leste gave reason to be optimistic. Numerous larvae were detected at the first sites within 2 weeks of the adults being released. Several months on, the predators seem to be thriving in the field. Where releases have taken place, it is now common to find dense aggregations of the black pupae (up to 300 on a single frond), often clustered towards the base of the frond. This is being used as one of the indices of establishment in the post-release surveys that began in November, 6 months after the first releases. Thus, although it is still very early days, signs are promising that Timor-Leste's first foray into classical biological control may be a successful one. If so, it will doubtless make biological control an option to be seriously considered for other pests in this country.
By: J. Mark Ritchie,
Americo Brito, Head, Plant Protection
Lourenço Fontes, Director,
Coconut Community Highlights Hispine Beetle Pest
The coconut hispine beetle (Brontispa longissima) is proving a devastating pest as it spreads to new parts of Asia and the Pacific. IPM specialists from the Asian and Pacific Coconut Community (APCC) warn that it could threaten coconut production in some of the world's major coconut growing countries if the spread continues unchecked. They point out that the pest has been successfully controlled in the past by the introduction and enhancement of natural enemies, and call for new surveys in the area of origin of the pest.
APCC is an intergovernmental organization of 15 member countries (Federated States of Micronesia, Fiji, India, Indonesia, Kiribati, Malaysia, Marshall Islands, Papua New Guinea, Philippines, Samoa, Solomon Islands, Sri Lanka, Thailand, Vanuatu and Vietnam). Established in 1969 as the first commodity-based organization in the region, the APCC is tasked to promote, coordinate and harmonize all activities in the coconut industry which sustains the lives of millions of coconut farmers as well as those engaged in the processing, marketing and other sectors of the industry. The coconut IPM programme, currently concentrating on coconut mite and rhinoceros beetle, is working in four countries (Papua New Guinea, Philippines, India and Sri Lanka) with another five set to join next year (Malaysia, Tanzania, Samoa, Thailand and Indonesia).
Brontispa longissima was originally described from the Aru Islands (Maluku Province) of Indonesia. The chrysomelid is native to Indonesia (Aru Islands and possibly Papua Province, formerly known as Irian Jaya) and Papua New Guinea (including the Bismarck Archipelago), where it seldom causes serious problems. It has now spread widely in Asia, Australasia and the Pacific Islands attacking not only coconut palm but also several other cultivated and wild palms. In recent times it has spread to Singapore, Vietnam, Nauru, Thailand, the Maldives and Hainan Island (China) and possibly to Cambodia and Laos. In the absence of natural antagonists it has become a very serious and devastating pest in its new areas of spread. Furthermore, it is feared that B. longissima will find its way from the Maldives to Sri Lanka and the southern parts of India to derail the economy of these important coconut-growing regions. Emergency operations are thus necessary to try and substantially reduce its population in the Maldives. Similarly, its control in South East Asia is necessary to prevent its entry into Myanmar and Bangladesh.
The pest prefers young palms, and both larval and adult beetles are usually found in the still-folded heart leaf. They feed on the mesophyll tissue, the damage visible as long white streaks. Heavy infestations reduce photosynthetic activity to zero. Loss of eight or more leaves per tree impacts on production and prolonged attack can even kill the trees.
The first pest outbreaks of B. longissima, in South Sulawesi and Java, began to be reported in 1919 and continued until the pest was brought under biological control in the mid 1930s. In this first programme, control was achieved with the eulophid pupal parasitoid, Tetrastichus brontispae. As the pest spread through Indonesia, further outbreaks were brought under control by redistributing the parasitoid. Since then, it has been successful in several Pacific island countries. A eulophid larval parasitoid, Aescodes hispinarum, from Western Samoa has been successfully introduced to a number of countries. Spraying with the fungus Metarhizium anisopliae, isolated from B. longissima in Western Samoa, has also shown promise in Western Samoa and Taiwan. A number of other promising natural enemies have been recorded in the region, including egg parasitoids (the trichogrammatids Hispidophila (= Haeckeliania) brontispae and Trichogrammatoidea nana and the encyrtid Ooencyrtus podontiae), another fungus (Beauveria bassiana) and an unidentified bacteria. Predators have also been recorded, including the dermapteran Chelisoches morio and the ant Oecophylla smaragdina, together with geckoes, skinks and tree frogs. Mites (Anoplocelaeno sp. and Celaenopsis sp.) have been recorded on adult beetles.
Biological control will take some time to implement in the new areas of spread. Alternative measures are needed to replace chemical control as most of the insecticides that were recommended have been phased out owing to their harmful side effects. Although difficult to implement, an integrated approach including the use of tolerant cultivars, the adoption of phytosanitary measures, and the imposition of strict quarantine measures is recommended. In addition, relatively safer pesticides could be used to knock down the pest until biological control becomes operative and effective.
There is an urgent need to initiate an international project to provide training to coconut entomologists and create awareness in the affected countries and the countries to where the hispine beetle may spread.
By: Dr S.P. Singh, Project
First Release against Mile-a-Minute in the USA
Polygonum perfoliatum or mile-a-minute weed (MAM) is an annual vine with sharp, reflexed prickly spines on the stem and petioles that adhere to and climb over native species. MAM infests roadsides, disturbed forest sites, stream banks, and old field and tree plantations in invaded habitats in the USA. The release of a weevil from China is an important milestone in the control programme against this weed.
The first established infestation of MAM in the USA was traced to a nursery in York County, Pennsylvania in the 1940s. It was suspected that MAM was introduced along with holly (Ilex spp.) seeds or rhododendron (Rhododendron spp.) plants from Japan. The infestation in York, Pennsylvania has been considered as the centre of spread in the eastern USA. However, MAM was also reported to be present in the Glenn Dale Introduction Garden in Maryland, where it was introduced with Meliosa seed from Nanjing, China in 1937. Since these first recorded introductions about 60 years ago, MAM has been recorded in ten states and continues to spread aggressively in various habitats. Fifteen additional states, all within Plant Hardiness Zones 6 and 7 have climates favourable for MAM.
The first biological control initiatives focused on potential natural enemies of MAM in the USA. One of the earliest surveys for these was conducted in the eastern USA (e.g. south-central Pennsylvania in 1981-83) by Wheeler and Mengel. They recovered 34 species that developed on MAM and 12 species that fed on it only as adults. However, none of them caused significant damage to the weed. In 1997, a survey was initiated by the US Department of Agriculture (USDA) Forest Service (USFS) for arthropods associated with MAM in four states (Pennsylvania, Maryland, Delaware and Virginia). By the end of the 2000 field season, specimens representing over 112 families and seven orders had been recovered from MAM; only ten showed potential as biological control agents but none had sufficient impact on MAM to reduce its damage or spread.
The search then switched to the weed's native range. In 1996, a collaborative project was initiated between the Institute of Biological Control, Chinese Academy of Agricultural Sciences (BCI-CAAS) and the USFS Forest Health Technology Enterprise Team (FHTET) to survey for and screen potential biological control agents in China for release against MAM in the USA. A team led by Ding Jianqing conducted surveys for phytophagous insects from 1996 to 2001 in 23 provinces including northeastern China, where the climate is similar to that of the eastern USA, and southwest China, which is considered the centre of origin of the family Polygonaceae. A total of 111 species of insects representing six orders and 29 families was collected during the surveys. Most of these were recovered from leaves, although several stem borers and fruit- and seed-feeders were found. No insects were recovered from roots.
There are about 40 genera and 800 species of Polygonaceae (buckwheat family) in the USA and Canada. They include 14 economically important plant species including those grown as human and animal food (e.g. Fagopyrum spp. - buckwheat and Rheum spp - rhubarb), so host specificity in candidate agents from China was of prime importance. Among the 111 species found associated with MAM in China, 11 were initially regarded as important because of either their severe damage to MAM or their narrow host range. Based on additional information from the literature and results from lab and field tests on host range, distribution, population density and severity of damage to MAM, one species emerged that appeared to have the greatest potential, the stem-boring weevil Rhinoncomimus latipes. Adult weevils eat young leaves of P. perfoliatum and lay eggs on leaves and stems. After hatching, larvae bore into the stem where they complete development, then exit the stem and drop to the soil for pupation. Development from egg to adult takes about 26 days under laboratory conditions. Damage to the plant occurs primarily from larval feeding, which kills the stem from the exit hole to the stem terminal.
No other plant species was found to be attacked by R. latipes during all the field surveys in China. Choice, no-choice, and open-field tests for the weevil were conducted with more than 50 plant species from 17 families in China from 1999 to 2002. No-choice tests showed both adult and larva fed on only a few plant species in the family Polygonaceae. Based on this information, R. latipes was introduced into quarantine in the USA in 1999. Further feeding and oviposition tests in US quarantine gave results favourable for its release. Rhinoncomimus latipes was recommended for release by TAG (Technical Advisory Group for Biological Control Agents of Weeds), and approved by USDA-APHIS (USDA Animal and Plant Health Inspection Service) and the states of Delaware and New Jersey. On 19 July 2004, R. latipes adults were released at two sites in White Clay Creek State Park in Delaware and on 29 July 2004 at one site in southern New Jersey. Protocols for monitoring the abundance of both MAM and the weevil and evaluating the weevil's long-term impact have been developed.
In 2005, further releases are planned in New Jersey and Delaware. Releases are also expected in Pennsylvania, West Virginia and Ohio as the biological control programme against mile-a-minute weed in the USA takes to the road.
Contact: Richard Reardon, FHTET,
First Rust Fungus Fully Approved for Biological Control of Yellow Starthistle in the USA
A rust fungus from Turkey has joined five introduced insect species in the battle against yellow starthistle (Centaurea solstitialis) in the USA. The first release of the rust, Puccinia jaceae var. solstitialis, was made in Napa Valley, California in July 2003 and successful infection in the field was confirmed later in the month. The fungus attacks the thistle's leaves and stem, forming rust-coloured pustules that rob the plant of nutrients. In sufficient numbers, these reduce root growth and seed production. The joint programme that released the P. jaceae var. solstitialis includes scientists from the US Department of Food and Agriculture - Agricultural Research Service (USDA-ARS) and the California Department of Food and Agriculture (CDFA).
The release marked the culmination of 25 years work on the pathogen, which included testing it against 65 species of plants in ten families, gaining permission to release from USDA-APHIS (USDA Animal and Plant Health Inspection Service), the State of California and the Napa County Agricultural Commissioner, and optimizing a release protocol which involves spraying the inoculum onto plants protected by a plastic tent.
Yellow starthistle is an invasive weed introduced from the Mediterranean region in the mid nineteenth century, probably in contaminated seed shipments. It has adapted to a wide range of habitats in the USA, aided by its ability to cope with both wet and dry conditions. It infests annual and perennial grasslands, pastures, shrub and open woodlands and disturbed habitats. It is now found in most of the USA apart from some southeastern states and is continuing to spread. The worst infestations are found in western states, where it infests some 7.3 million hectares of rangeland. California has the by far the largest infestations (5.8 million hectares) followed by Idaho, Oregon and Washington.
Yellow starthistle is a winter annual. Seeds germinate in autumn and grow into overwintering rosettes. Given sufficiently high temperatures and moisture, germination continues throughout the winter and into the early spring. Established seedlings are in a good position, come spring, to outcompete other plants. Long tap roots allow them to absorb soil moisture and nutrients, and they grow quickly to produce large plants whose multiple flower heads can produce as many as 100,000 seeds. Thorny spines around the flower head, often up to 2-3 times its width, interfere with livestock grazing, recreation, and wildlife management. The plant is toxic to horses, causing a chronic and potentially fatal neurological disorder, 'chewing disease'. Infestations also displace native vegetation. Biological control is one part of a long-term management strategy, which also includes cultivation, hand weeding and mowing, herbicides, burning, managed grazing and other practices to suppress the weed and enhance competition by desirable species. Under the biological control programme, three weevils and two flies, each for impact on seed production, have been released at various sites over the last 20 years. The rust is the first field release of a pathogen against yellow starthistle in the USA, and it can attack all aboveground plant parts throughout the growing season.
Although infection was observed soon after the pathogen was released in the field, immediate secondary spread was not expected and not observed. Neither were new infections detected in spring 2004, indicating it had not over-wintered at the release site. Nonetheless, the winter provided an opportunity to build up inoculum in the laboratory and this year has seen more releases of the fungus. These have led to infections being established at 24 sites in 20 counties. Little secondary spread has yet been observed despite very good infections at a number of locations, but the team anticipate that dispersal of the pathogen will gather pace over the next year. Plans for 2005 include monitoring release sites for infection and spread of the fungus, and making more releases in other areas of yellow starthistle infestation in California. The team hope that eventually the rust will complement the impact of the established insect agents and allow other plant species to begin to outcompete yellow starthistle.
Information/contact: William Bruckart,
Wilson, L.M., Jette, C., Connett, J.
& McCaffrey, J.P. (2003) Biology and biological control of
yellow starthistle. USDA Forest Service FHTET-1998-17, 2nd Ed.
Suskiw, J. (2004) Fungus unleashed to
combat yellow starthistle. Agricultural
Research Magazine 52 (8), 20-22.
California Department of Food and
Agriculture, Biological Control Program:
Giant Salvinia Feels the Strain
A strain of Cyrtobagous salviniae imported from Australia has effected a dramatic decrease in giant salvinia (Salvinia molesta) populations at release sites in the USA. Some water bodies once completely covered by the weed are now mostly open water, a situation comparable with the best biological control achieved by the weevil against giant salvinia in other parts of the world.
Salvinia species native to South America, in common with many invasive weeds, have been transported around the globe as ornamental plants. Giant salvinia is now recognized as one of the world's most important invasive aquatic weeds.
Like so many invasive aquatic weeds, giant salvinia has a rapid growth rate and can regenerate from fragments; it can also tolerate a wide range of environments. The species was first recorded in the wild in the USA in 1995 in South Carolina where it was eradicated from a pond. It appeared again in 1998 (although it may have been there longer) in eastern Texas. It now creates havoc in slow-moving, freshwater systems in Texas and Louisiana. The dense mats have a negative impact on other aquatic species because they block out sunlight and use up oxygen. They make recreational activities such as boating, swimming and fishing impossible, which harms local economies. The weed also interferes with water use, clogging irrigation channels and hydroelectric turbines.
Classical biological control was first attempted during the 1960s in Africa, Asia and Australia, but taxonomic confusion over both the plant and its natural enemies dogged these early programmes. Once giant salvinia had been assigned species status as S. molesta and its native range identified, spectacular success followed. A weevil from Brazil in S. molesta's home range, then thought to be a strain of C. singularis, was introduced to Lake Moondarra in Australia in 1980. It destroyed 30,000 tonnes of the weed in less than a year. The 'before and after' photographs have illustrated various biological control textbooks. The weevil was later described as Cyrtobagous salviniae and has since provided control of the weed in many countries.
Reaction to news that the weed was present in the wild in the USA was rapid. A biological control programme was initiated by Ted Center and Phil Tipping from the USDA-ARS (US Department of Agriculture - Agricultural Research Service) Invasive Plant Research Laboratory at Fort Lauderdale, Florida. There were regulatory hurdles to be overcome before the population that had been used elsewhere could be imported into the USA. The first control attempt, in 1999, involved releasing C. salviniae collected from common salvinia (S. minima) in Florida. The weevil has been found on S. minima in Florida since the 1960s, presumably inadvertently imported on plants from South America at some time in the past. Hopes that the locally available weevil would provide a rapid solution were dashed because herbicides, floods and drought between them destroyed all the release sites.
As this sorry tale was unfolding, molecular evidence began to suggest that there were differences between the local 'Florida' population of the weevil and the 'tried and tested' Brazil population that had controlled the weed elsewhere. The latest, yet to be published, molecular evidence now indicates that the two populations of weevils are very close to each other, especially when compared to a different species, Cyrtobagous singularis. However, at the time interest was refocused on the Brazil population. A new release permit had to be obtained before it could be released in the USA, and this was not achieved until late 2001 [see BNI 23 (1), 1N (March 2002), Salvinia: USA begins round two]. Scientists at the USDA-ARS Australian Biological Control Laboratory in Indooroopilly, near Brisbane field-collected and shipped weevils to Fort Lauderdale. Once cultures had been established, releases were made at four sites. Regular surveys of these sites since then have shown a steady, sometimes spectacular, reduction in giant salvinia. By September 2003, it covered just 1% of the water's surface at sites where the imported weevils had been released, and at two sites (one in Texas, one in Louisiana) the mats have almost completely collapsed. In contrast, at control sites giant salvinia continues to cover the water surfaces completely.
Common salvinia, which has caused few problems since its arrival in Florida, is becoming a problem in Texas and Louisiana. Although not yet a weed on the scale of giant salvinia, it typically occurs in dense populations which show a tendency to expand. At the Jean Lafitte National Historic Park and Preserve near New Orleans, Louisiana, the results of an 8-year study show that common salvinia has completely displaced native duckweed species (Lemnaceae). This also threatens waterfowl populations for which duckweed, with its high protein content, is an important food source.
Tipping and team have been releasing and evaluating the effectiveness of weevils from the Florida population. Regular recoveries of weevils indicate that a viable population has been established. Although still early, indications are that this population of weevils will be able to suppress common salvinia in Louisiana as it does in Florida.
Source: Flores, A. (2004) Tiny weevil
beats back giant salvinia. USDA-ARS Agricultural
Research, September 2004.
Kenyan Efforts towards Integrated Biological Control of Water Hyacinth
Although water hyacinth (Eichhornia crassipes) was first recorded in Africa from the River Nile in Egypt in the 1890s, it did not reach Lake Victoria until the end of the 1980s. It is thought to have reached the lake through the Kagera River whose headwaters were invaded during the 1980s. It was reported in Lake Naivasha in the mid 1980s, in Lake Victoria (Ugandan waters) in 1990 and in the Kenyan waters of the same lake in 1992. It has since spread to many other water bodies in Kenya including rivers and ponds.
The water hyacinth cover in the Winam Gulf, a large inlet in the northeastern corner of Lake Victoria, occurred as both stationary and mobile fringes, but generally the plant was observed to form stationary fringes on shoreline environments that are sheltered from violent offshore winds and wave action. The plant preferred flat to gently sloping shores (rarely deeper than 5 metres) with a soft muddy bottom, rich in organic matter, such as found along the southeastern shoreline of the gulf, extending from Nyakach to Kendu Bay. At its peak infestation in 1998, coverage of 17,230 ha was recorded in the Winam Gulf through satellite imagery analysis by USGS (US Geological Survey).
In cooperation with relevant organizations in Uganda and Tanzania, and several international organizations (International Institute of Tropical Agriculture, IITA; South Africa's Plant Protection Research Institute, PPRI; Australia's Commonwealth Scientific and Industrial Research Organisation, CSIRO), the Kenya Agricultural Research Institute (KARI) implemented a biological control programme for water hyacinth. This involved importation, mass rearing and releases of exotic biological control agents. It imported 13,800 adult Neochetina eichhorniae and Neochetina bruchi weevils from Australia, Benin, Uganda and South Africa for mass rearing and releases and produced over 200,000 weevils, of which approximately 180,000 were released together with 40,000 weevil eggs at 40 littoral and riverine sites in Kenya. By 1999, a reduction of over 80% of water hyacinth was recorded in the Kenyan waters of the lake, and this was mainly attributed to action by the weevils.
However, in 2000 a resurgence of water hyacinth in the Winam Gulf was noted. Nyakach Bay, to the south, was the first to experience the weed's re-invasion between August and September 2000. The emergent plants were young, healthy and rapid growing, and were the result of the germination of seeds deposited in the sediment before the previous water hyacinth mats disintegrated. Seedling germination was stimulated by light penetration of the water column following the mats' collapse. Growth was enhanced by high levels of nitrates and phosphates in the water due to runoff from agriculture and to the release of nutrients from the decaying mats. By May 2001, the coverage was 1347 ha.
The resurgence necessitated a continued supply of the Neochetina weevils to the lake. To ensure this, community-based weevil rearing units were established and the community taught aspects of weevil rearing, harvesting and release. So far a total of 15 such units have been established, mainly in primary schools along the shoreline in areas with persistent mats of water hyacinth. A total of 28 teachers and youths from the beach management units have been trained.
Seven years after the Neochetina weevils were first released into Lake Victoria for the control of water hyacinth, the population of the weed is now down to less than 15% of the peak infestation levels. Satellite images taken in December 2003 show that the infestation on the Kenyan side of the lake stands at 384 ha as compared to the peak infestation of 17,230 ha recorded in November 1998.
Water hyacinth monitoring and surveillance over the past 5 years revealed the presence of persistent water hyacinth 'hot-spots' in the lake. In Kenya, these were at Sio Port/Bukoma (Berkeley Bay) to the North, Kisumu (Kisumu Bay) to the East and Sango Rota/Kusa (Nyakach Bay), Kendu Bay, Homa Bay, Luanda Konyango (Karungu Bay) and Rakwaro (Osodo Bay) to the South. Also noted are infestations at the mouths of certain rivers entering the lake, namely the Yala, Kisat, Lambwe, Sondu and Kuja rivers. Elsewhere in Kenya, many inland water bodies such as dams and ponds are also infested. Several factors contribute to the persistence of water hyacinth at these sites. These include land-use cover, shoreline topography, pollution, urban and industrial activities/centres and human population density and distribution.
At these sites, particularly at the river mouths, the turbid and polluted conditions cannot sustain nor complete the growth cycle of the weevils. To enhance control in these areas, KARI has been undertaking studies on additional methods of control and looking into possibilities of integrated biological control strategies. Apart from the two weevil species a mite, Orthogalumna terebrantis, was also imported from South Africa and released in the lake in 1999. The mites have now established and damage to plants is visible in many parts of the lake. Also to this end, KARI recently imported the moth Niphograpta albiguttalis from IITA, Benin. The moths are currently contained under quarantine facilities at the KARI Centre, Muguga. The three East African partner states (Kenya, Tanzania and Uganda) have agreed to undertake host specificity tests on the moth before any releases can be made. As required by the Environmental Management Authorities and the East African Community Secretariat, an Environmental Impact Assessment will be undertaken before a release permit can be issued. The moths are expected to be more effective in the river mouths and ponds where the short-bulbous type of water hyacinth prevails.
The development of a fungal-based mycoherbicide to complement the action of the Neochetina weevils and the mites is also being undertaken at the KARI laboratories at Muguga. Surveys carried out in collaboration with CABI, under the International Mycoherbicide Programme for Eichhorniae crassipes Control in Africa (IMPECCA), revealed over 200 fungal isolates associated with diseased water hyacinth plants collected from infested water bodies. Among these were species that have been isolated elsewhere in the world and have been evaluated and found to have potential for the biological control of water hyacinth. These include Alternaria eichhorniae, Alternaria alternata, Acremonium zonatum, Cercospora rodmanii, Rhizoctonia solani and Myrothecium spp. Pathogenicity tests carried out under semi-controlled conditions have shown that Alternaria eichhorniae caused high incidence and severity of disease on water hyacinth. A host-range test was designed for A. eichhorniae and the fungus tested against ten food and cash crops growing around the lake region. These included cotton, rice, cassava, sweet potato, maize, beans, tomato, onion and cabbage. Water hyacinth was used as the control plant. The fungus was not found to cause disease on any test plant other than water hyacinth. The next step is to undertake formulation tests. Studies on the synergism of the various control agents will also be undertaken.
Water Hyacinth: Ugandan Postscript
The situation with water hyacinth (Eichhornia crassipes) on the Ugandan side of Lake Victoria has remained largely unchanged over the past 2 years - the resurgence in weed growth appears to have stabilized. [See BNI 23 (2) 40N-41N (June 2002), Resurgence in Lake Victoria: a case for optimism.] Neochetina weevils are found on the plants in varying numbers, and some pockets have no weevils at all. Although water hyacinth remains a problem in some places, which biological control agents might be beneficial is a matter for debate. Factors such as water quality, the growth form of the water hyacinth and the life cycle of the potential agent need to be considered, and it may be that the best choice turns out to be location-specific.
At Nakivubo Channel, where waste from Kampala empties into the lake, there remains, as there has always been, very healthy 'bull' water hyacinth (up to one metre tall). From the outset, the weevils failed to establish here because of pollution. Any new agent whose life cycle does not involve the roots (as is the case with Neochetina) and can therefore 'escape' the pollution would be very useful. Niphograpta albiguttalis (see preceding article) fits the bill in terms of a larval life cycle restricted to the leaves and petioles, but it is most effective against bulbous forms of water hyacinth. These are almost completely absent from the Nakivubo Channel, so on balance it is doubtful whether the moth would enhance control there.
By: Dr James A. Ogwang,
Hopper Hope for Water Hyacinth Control
South Africa understands only too well the complexities of effective water hyacinth (Eichhornia crassipes) control. The weed remains a problem in its dams and rivers despite attempts to control it using chemical, mechanical and biological methods. Five arthropod and one pathogen species have been released against water hyacinth in South Africa and although these agents do provide good control in some areas, they have been less effective in areas that are characterized by cold and a high level of nutrients. Recent efforts have focused on identifying suitable agents for habitats where water hyacinth has evaded control. An application for release has now been lodged for the grasshopper Cornops aquaticum. This article discusses why this agent, rejected elsewhere because of its polyphagous habit, is now seen as a good candidate to add to the suite of introduced agents already established in South Africa.
The grasshopper was identified by David Perkins in 1974 during surveys conducted by USDA (US Department of Agriculture) as one of the most damaging insects associated with water hyacinth in its region of origin in South America. Its initial promise faltered, however, as studies of its biology and host specificity progressed. Silveira-Guido and Perkins found that under laboratory starvation trial conditions C. aquaticum was able to feed and develop on species in the Pontederiaceae and limited feeding, but no development, was recorded on three species within the Commelinaceae and on rice and sugar cane. They concluded that C. aquaticum is an oligophagous species in the Pontederiaceae and that some feeding could be expected on pickerel weed (Pontederia cordata), which is native to the New World including the USA. As a consequence, the grasshopper was not introduced into the USA. It appears that concerns about the insect's host specificity have also prevented it from being considered as a biological control agent for the weed elsewhere.
As it became apparent that the available measures were not going to control water hyacinth in all the invaded habitats, South African scientists began to survey for new agents and re-examine those previously rejected to see whether biological control could provide something new. Given the fairly cool climate of its native range in Argentina, C. aquaticum has the potential to control water hyacinth in South Africa's colder habitats. In addition, it is heavily parasitized in Argentina and could potentially build up large populations, in the absence of its natural enemies, following an introduction. However, its release in South Africa could only be sanctioned if nontarget species could be shown not to be threatened. In recent years, an evaluation of C. aquaticum as a potential agent in South Africa has focused on this question.
Grasshoppers used in these studies came from material originally collected from water hyacinth in Manaus, Brazil in October 1995, from Trinidad and Venezuela in April 1996 and from Mexico in October 1996. Once the cultures derived from the collections had all been confirmed as C. aquaticum, they were combined into a single culture.
The laboratory host range of C. aquaticum was determined through studies of nymphal development, using no-choice trials on 65 plant species in 32 families selected on the basis of relatedness to water hyacinth, degree of similarity of habitat and economic importance. If plant species were found to support nymphal development, adult no-choice oviposition and feeding trials were conducted. No-choice trials are the most cautious of all specificity tests, prone to throw up the most 'false positives', yet complete nymphal development was recorded in only three species (apart from water hyacinth):
Three survey trips for new agents were made to South America between 1999 and 2001. During these visits, the host plants of C. aquaticum in its native habitat, besides water hyacinth, were found to be Eichhornia azurea, Pontederia rotundifolia and pickerel weed, which are either not present in or not native to South Africa.
Using the results, an evaluation could be made of the threat posed by C. aquaticum to nontarget species in South Africa. Of indigenous plants, only H. callifolia supports complete nymphal development but it does not attract oviposition, and only M. africana attracts oviposition but it does not support complete nymphal development. Pickerel weed and canna support both oviposition and complete nymphal development, but these are introduced species, and are either potentially or actually invasive in South Africa.
Thus, although C. aquaticum is an oligophagous species and capable of utilizing several species of Pontederiaceae, it is argued that the results provide sufficient evidence to suggest that no native African Pontederiaceae is at risk and that the insect is thus safe for release in South Africa. Despite the heightened awareness of the importance of considering nontarget effects on native biodiversity since the USDA assessment was made in the 1970s, some 11 biological control experts (both local and international) support the release of C. aquaticum in South Africa. A release application has been lodged with the National Department of Agriculture and the Department of Environmental Affairs and Tourism in South Africa. It is hoped that this very effective agent will be cleared for release for the Austral summer.
By: Martin Hill, Department of
Azolla Biocontrol Grows in the UK
The floating fairy fern, Azolla filiculoides, native to the New World, was first recorded in the UK in the 1840s. It has been imported ever since as a popular ornamental for garden ponds. It is now a major aquatic invasive in the UK, ranking third in terms of distribution. Yet despite warnings about this, and a ban on it at Royal Horticultural Society shows, it continues to be imported and sold.
Azolla can grow from tiny fragments and is often a contaminant of purchases of other aquatic plants at garden centres. From garden ponds it has escaped into freshwater ponds, lakes, rivers and canals throughout the UK, including areas of conservation importance such as Romney Marsh and the Nene Washes. During the winter the plants' growth slows significantly, although they can tolerate all but the most severe British winters and can even survive encasement in ice. Growth resumes the following spring from vegetative fragments or via germination of spores that are produced in millions during the autumn, and sink into the substrate. During the summer, Azolla can form mats up to 30 cm thick, which may double in surface area every 5 days in hot weather. Consequently the weed impedes flood defences, blocks irrigation pumps and interferes with recreational activities. It also blocks out light and reduces oxygen in the water, which kills other aquatic biota. Last but not least, it can be mistaken for solid ground by animals and children.
Controlling Azolla in the UK has become more difficult with the banning of diquat, leaving glyphosate as the only available chemical control option. Glyphosate, although it can be effective, is non-selective, and when mats are thick will kill only the surface layers. There is, however, strong public pressure to reduce pesticide use. Manual control is doomed to failure as the plants fragment easily and soon regrow. Biological control is therefore an attractive alternative, especially as a tried-and-tested control agent is already present in the UK, meaning the weevil would not have to attempt to breach its biocontrol-shy shores.
In South Africa, where classical biological control has long been a mainstream weed management tool, the frond-feeding weevil Stenopelmus rufinasus was introduced from the USA and released in 1997. It was a spectacular success, clearing even large water bodies within a year.
The same species was recorded in the UK as long ago as 1921, and has probably been inadvertently introduced many times since on imported plants. Its failure to effect natural control of infestations throughout the UK is ascribed to a number of reasons: although cold-tolerant, it does not over-winter well in the UK, especially in the north; it only begins to build up damaging populations late in the season; and it may have limited capacity to reach widely dispersed water bodies infested with the weed. Nonetheless, these limitations could potentially be overcome by an inundative biological control approach.
Over the last 3 years, scientists at CABI Bioscience's UK Centre have developed methods to over-winter the weevils and mass rear them. Releases could then be made early in the year so that populations built up in time to curtail Azolla's growth. Glasshouse studies indicated that the weevil, when released in large numbers, could be effective in UK summer conditions in as little as 3-4 weeks. The speed of control depends on the size of the infestation and number of weevils released. Typically a seed population of several thousand weevils are released, which rapidly multiply. Weevil densities of up to 6000 individuals per metre squared have been recorded prior to the weed disappearing. Trials at a number of sites last year showed that inundative releases were indeed effective. This year has seen an expansion of the initiative with the formation of Azolla control (www.Azollacontrol.com). With the permission of DEFRA (Department of Environment, Food and Rural Affairs) it is supplying weevils 'to order' from a maintained culture. Customers include English Nature, the Environment Agency and British Waterways, as well as local parish councils and homeowners. If the releases made so far continue to be successful, as anticipated, demand is likely to grow.
Contact: Rob Reeder or Richard Shaw,