Managing scale outbreaks in the Capricornia Cays conserving biodiversity through pest management

Since 1993, infestations of scale have Using a variety of methods — primarily release affected pisonia forests on three of Central of native ladybirds, a scale predator, and baiting Queensland’s coral cays in the Capricornia Cays of introduced which interfere with the scale National Park. First affected was Tryon Island, predators — QPWS brought both infestations where most of the pisonia forest was ultimately under control, and the forests recovered. Today, destroyed, as natural predators failed to a revegetation program is underway on Tryon overcome the as expected. When Island, and research and monitoring are ongoing John Augusteyn scale outbreaks occurred in 2006 on Wilson across the cays. QPWS’s work has implications and Heron islands, the Queensland Parks and for coral cays and atolls elsewhere in the world, Wildlife Service (QPWS) actively managed them, where pisonia forests, already dramatically armed with the lessons from Tryon Island. reduced by clearing, are further threatened by scale insect outbreaks.

Why our pisonia forests matter Threats to pisonia Signifi cant and vulnerable Across the world, pisonia forests are threatened Pisonia grandis, a large-leafed woody shrub or by a variety of factors. Outside Australia, pisonia tree is found almost exclusively on Indo-Pacifi c is frequently cleared for plantation agriculture, islands broadly between the Tropics of Cancer development, and the mining of guano (bird and Capricorn, and as far away as islands of droppings used for fertiliser). the Seychelles, Hawaii and eastern Polynesia. In Australia, climate change — possibly increased John Augusteyn In Australia only a little over 190ha of pisonia El Nino (drought) events and rising sea levels grows — and most is on the islands of the Great — may be affecting some forests. Scale insect Barrier Reef. outbreaks have also wiped out or affected a number of pisonia forests in Australia and elsewhere. • At the southern end of the is Australia’s pisonia stronghold — More than forests at stake the Capricornia Cays — where large pisonia Damage to the pisonia forests of the Capricornia forests total about 135ha. Cays has far-reaching consequences. The forests • Other Australian islands where pisonia grows themselves are of international signifi cance, are Christmas, Cocos, Cobourg Peninsula and and permanent loss may threaten survival of Torres Strait islands and Coringa-Herald cays the Pisonia grandis species. Forest decline may in the National Nature Reserve. also affect the stability of the coral cays, and the Pisonia is critical to the ecology of the Capricornia survival of cay-dependant wildlife such as nesting Cays. Developed pisonia forests help stabilise the turtles and seabirds. Pisonia is critical for black cays, protecting them during cyclones. Pisonia noddy populations which nest almost exclusively in Mark Coombe Mark trees provide shelter and breeding habitat for a pisonia, while dense pisonia canopies create open variety of birds. In the Capricornia Cays, pisonia ground for wedge-tailed shearwaters to burrow. supports 75% of all nesting seabirds in the Great People are also affected by pisonia decline: forest Barrier Reef World Heritage Area. The cays are die-offs can limit recreational use, with visitors also important breeding grounds for endangered unable to walk or camp in affected or unsafe areas. sea turtles. The aesthetic impacts of dying or dead forests can dramatically affect tourist enjoyment of what are Australia’s pisonia forests are internationally usually extraordinarily beautiful coral cays. signifi cant as the majority are in protected areas. Pisonia forests in the Capricornia Cays provide About 70-80 percent of our pisonia forests are on island resorts and campgrounds with valuable the islands of the Capricornia Cays National Park protection from the sun and potentially and National Park (Scientifi c). destructive force of cyclonic winds. John Augusteyn

Queensland Parks and Wildlife Service Department of Environment and Resource Management as nativeladybirds natural factors, especia numbers appear tobeheldin check by scale toaleaf. For their themost part, lownumbersvery —less than oneortwo throughout healthy pisonia forests in Scale insects seemtooccur naturally balanced situation. between scale andants is anormal, this mutually benefi sites. Ourcurrent understanding is that they may evenmove scale tonew interfere and often attracted by honeydewwill farm scale for many common species. Ants ‘honeydew’, which is afoodsource a sweet,sticky substance called plant tosurvive. They alsoproduce Scale insects suck sap fromtheirhost usually absent. covers, althoughin‘soft’scales this is get theirname fromtheirscaly protective plants, includingpisonia. ‘Scale’ insects that lives ontheleaves of anumberof is atiny insect (around 2–3mmlong) The soft scale insect, A balanced relationship Scale insect andpisonia and inoutbreak you can see lots ofwhite Soft scale appear as greenish-brown blisters woolly-like eggmasses. with theirpredators; cial relationship and parasiticwasps. Pulvinaria urbicola, lly predators such

John Augusteyn

dying if theoutbreak continues. a couple of years, beforeeventually defoliations, over several months or trees can go throughanumberof recolonised by scale andants.Pisonia and formnewleaf buds,but aresoon trees. The original trees start torecover or beblown orcarried ontoother their highly mobilela leaves. Scale eggs areplentiful and if drought-stressed anddroptheir of scale, pisonia trees respondas Under thestress of such large numbers in theCapricornia Cays. big-head ant particularly theintroduced African an explosion inthenumberof ants – outbreaks arealsoaccompanied by response totheincreased foodsupply, explodes, creating an‘outbreak’. In of scale insects inapisonia forest Sometimes, however, thenumber When the balance goes wrong megacephala rvae willrvae move,

John Augusteyn Palmyra Atoll inHawaii. Bird Island inthe Seychelles and severely damaged pisonia forests on insect during byscale destroyed was completely Coringa Island inAustralia’s Coral Sea elsewhere. The pisonia forest on have alsoaffectedpisonia forests During thesame period,scale outbreaks National Park: Tryon, Wilson andHeron. of theislands of theCapricornia Cays are knowntohave occurred onthree Since theearly 1990s,scale outbreaks A globalproblem acrossworld. the islands, but for cays andatolls for the protection ofQueensland’s the Capricornia Cays is vital not just work ofQPWSinmanaging scale on to pisoniaforests worldwide. The Scale insect outbreaks are a threat ants scale insect Pisonia grandis Pheidole megacephala, the 1990s. Scal DERM Pulvinaria urbicola. leaf, African big-head ecological diversity. of extraordinary a critical role in Capricornia Cays, which are places the ecology of the Pisonia forests play beauty and e has and soft also

John Olds Legend Managing outbreaks in Capricornia Cays North Reef Reef the Capricornia Cays Shoal edge Tryon Island Tryon Island — growing Capricornia Cays National Park North West Island Broomfield Cay a new pisonia forest Capricornia Cays National Park Wilson Island (Scientific) – no access In August 1993, an outbreak of the scale insect was detected in Tryon Island’s pisonia forest. At this time, Tryon’s Sykes Reef Great Barrier Reef World Heritage Area pisonia covered nearly half the island. Tropic of Capricorn Heron Island This was the fi rst known scale outbreak in a pisonia forest of the Capricornia Tropic of Capricorn Wistari Reef Gladstone Cays, and one of the world’s earliest Irving Reef One Tree Island Capricorn Cays National Park records. Expectations were that natural Polmaise Reef predators — ladybirds and parasitic Lamont Reef Scale wasps — would bring the outbreak Fitzroy 0 5 10 Reef under control. At various points the Wilson Island — managing an nautical miles forests appeared to be recovering, Llewellyn 0 51510 outbreak through ants and ladybirds Reef with previously affected trees showing kilometres In May 2006, QPWS rangers discovered new growth. Ultimately the repeated a scale insect outbreak on Wilson Island. Boult Reef scale infestations killed many pisonia, The island’s 2.4ha pisonia forest was in taking 7–8 years before scale numbers Hoskyn Islands the early stages of infestation. subsided. Even after the outbreak had Fairfax Islands ended, the forest did not regenerate as Armed with the lessons from Tryon might have been expected. Today, 90 Island and the previous successful percent of Tryon Island’s original pisonia predator and parasite releases in the forest has gone. Coral Sea, QPWS responded quickly. In early June ant bait was used to almost All is not lost, however. Once it became eliminate the introduced ants on the clear that the forest could not recover Island. Two weeks later, 5000 native naturally, QPWS began a revegetation ladybirds (Cryptolaemus montrouzieri) program. Trial plantings in 2004 were released. Ladybirds are natural and 2005 indicated a need for more scale predators, frequently seen in low detailed investigations, and a more numbers on the Capricornia Cays. John Olds comprehensive trial began in July 2006. Surprisingly, however, by early August, QPWS staff and a team of volunteers are Native ladybirds Cryptolaemus montrouzieri working to determine the most effective the outbreak had continued to spread, are natural predators of scale, and central to techniques for regenerating pisonia. and 90 percent of Wilson Island’s forest managing outbreaks. was affected. Unusually cold winter A successful ant-baiting program has Heron Island — early detection also signifi cantly reduced Tryon Island’s temperatures might have prevented and success introduced ant population, with no the ladybirds from reproducing. In visible effects on native species. August, 2500 more ladybirds were Also in May 2006, staff from Heron released, this time successfully Island resort contacted QPWS regarding Tryon Island (along with Coringa Island in reproducing in September’s warmer a suspected scale outbreak on a small the Coral Sea) also gave QPWS important spring temperatures. By early October, group of pisonia trees within the resort insights into effective management of scale numbers had started to fall under area (most of the island’s 13.6ha forest scale outbreaks. The main lesson was pressure from the now several hundred was unaffected). Pruning and ant baiting that like a wildfi re, once underway, thousand ladybird larvae and adults. By immediately controlled the outbreak on outbreaks of this kind apparently will early December 2006, the outbreak was the lower leaves of affected trees and not subside before most, if not all, the over and the forest was in recovery. Heron Island’s parasitic wasps did the rest. island’s pisonia is gone.

QPWS has learned that detection of outbreaks at the earliest possible stages is essential. Detection must then be followed by intervention to bolster natural enemies of scale and reduce interference from ants to help pisonia Mark Coombe forests survive. This information was crucial Volunteers help with Tryon Island’s pisonia revegetation program. in managing an outbreak on Wilson Island. Scale outbreaks can devastate John Olds a pisonia forest. What causes outbreaks? Where to from here? How you can help Researching the cause An ongoing effort Report suspected infestations The causes of scale outbreaks are still Managing and researching scale insect If you fi nd an infestation of scale insects unclear. QPWS is exploring a range of outbreaks in the Capricornia Cays is an on any island of the Capricornia Cays possibilities. It is likely that a number of ongoing effort. National Park, please phone the QPWS factors combine to cause an outbreak. On Tryon Island, revegetation will Gladstone. Do not try to remove the insects or leaves from the trees. A natural phenomenon? require many more years of planting, sampling and monitoring. Across the Scale outbreaks could be caused by Support our work Capricornia Cays, QPWS is monitoring natural declines in the number of natural Organisations can support the important scale and ant populations to help predators, such as native ladybirds research, monitoring and revegetation detect and prevent further outbreaks. and parasitic wasps. This is most likely being conducted by QPWS by sponsoring Staff are also monitoring pisonia forest on smaller cays, where lower diversity our work, or joining us as partners. For distribution and any changes that may means there may be few or no hosts, more information on the benefi ts you can arise from past scale infestations. including scale, for natural predators share by working with us, call the pisonia Data collected from all this fi eldwork and parasites. project offi cer in QPWS Rockhampton. is then analysed and incorporated into Introduced ants? the research being carried out by QPWS Individuals can register to volunteer at the Capricornia Cays national parks by calling Introduced ants have been found at the scientists and its partners. the QPWS Gladstone. You will be contacted site of scale outbreaks in Australia and QPWS staff are also developing when a vacancy becomes available in our elsewhere. Their role in farming scale procedures and promotional campaigns volunteer programs for the cays. and interfering with natural parasites and to reduce the spread of pests between predators may be central to maintaining islands in the Capricornia Cays. Spread the word, not the problem an outbreak. In the Capricornia Cays, A collaborative effort Tell other people — for example, the African big-head ant Pheidole travellers, resort guests, local residents QPWS is collaborating with a range of megacephala is associated with all — about the importance of ‘biosecurity’ respected institutions in its work on outbreaks, whereas in the Coral Sea it is in protecting the future of our unique scale insect outbreaks. the guinea ant Tetramorium bicarinatum. island environments. It is very easy to The Queensland Herbarium is contributing Genetic variation? unintentionally spread a pest through information about cay soils and the health simple, day-to-day activities. Just Pisonia may have slightly different of pisonia forests, and reporting on cay one dirty boot can carry the seeds of genetic strains on different islands, vegetation communities. Queensland’s a problem from island to island in a which may be more or less resistant to Department of Primary Industries frighteningly short time. scale attack. There may also be different and Fisheries is providing expert Encourage anybody who is about to genetic strains of scale that are more or entomological advice, and assistance leave the mainland to visit an island, or less resistant to predators. in analysing, sorting and collecting data is moving between islands, to check their on ants and other invertebrate fauna. Seabird decline? clothing, especially footwear, for pests The Australian Government Department such as seeds or insects, and to remove Seabirds nourish pisonia forests by of the Environment and Water Resources any pests by brushing them off. Also providing large amounts of nutrients, is sharing its knowledge on managing ensure food, camping equipment, building nitrogen, phosphorous and calcium scale outbreaks on the pisonia in the materials and any other equipment being through their droppings. If seabirds are Coral Sea cays. absent or in decline, pisonia forests transported is free from vermin of any kind. may suffer nutrient stress, making them A global outcome more vulnerable to scale attack. Climate The QPWS research on scale outbreaks Together, we can safeguard the future change is likely to be a key factor in is of international signifi cance. Scale of Pisonia grandis and the coral cays. changes to seabird populations. insects are a global threat to pisonia. Drought? Research being carried out here will provide vital information on the best way During drought, plants are water to respond to an outbreak, including stressed. Stressed plants are more optimal methods of ant control and susceptible to insect attack and in predator release. In addition, Tryon some cases drought favours insects. Island’s revegetation work will determine the best methods for regenerating scale- ravaged pisonia forests. All QPWS fi ndings are being documented For further information © State of Queensland. Queensland Parks and Wildlife Service 2010. and shared as quickly as possible with Visit us online at www.derm.qld.gov.au BP1763 January 2010. Recycled paper saves energy and resources. the international scientifi c community. or phone on 1300 130 372.