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Invasive Species in the Galapagos Islands


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Invasive Species in the Galapagos Islands

By Mark Hoddle | December 24, 2009

I have just returned from an eight week research trip to the Galapagos Islands. The purpose of the work that was done was to assess the impact and safety of Rodolia cardinalis, a biocontrol agent, which was released for the suppression of an invasive insect pest, the cottony cushion scale, Icerya purchasi. Cottony cushion scale is a sap sucking bug native to Australia and it has been transported globally on plants.

Icerya purchasi, the cottony cushion scale (i.e., pulgon)

Uncontrolled population growth results in high density pest populations that weaken trees, bushes, and vines because they suck sap from their hosts. The sugary waste these insects excrete, honeydew, coats the leaves of plants which provides a rich carbohydrate source for black sooty molds. Populations of cottony cushion scale (locally referred to as pulgon [Spanish for flea]) were so high and spread across so many islands that

several endemic and native plant populations were thought to be going into decline because of heavy infestations. Loss of these plants could have serious consequences for the native animals that rely on them for food and shelter. Control options were limited, pesticides were not to be used, and hand removal of pulgones from infested plants was not practical.

To combat the pulgon, the first classical biological control program to be run in the Galapagos Islands was initiated. This project was a joint effort between the Charles Darwin Research Foundation in

An adult Rodolia cardinalis attacking an adult cottony cushion scale

PuertoAyora on the Island of Santa Cruz, and the National Park Service which neighbors the Charles Darwin Research Foundation. The natural enemy selected for use in this program

to fight the pulgon, was the lady bug beetle, Rodolia cardinalis. This lady bug (a.k.a mariquita) is native to Australia and evolved with cottony cushion scale.

It was first used against cottony cushion scale in California in 1888-1889 to control this pest on citrus. This first ever biocontrol program was a spectacular success. Consequently, Rodolia has been used in many countries around the world to suppress pulgon populations.

The Insectary and Quarantine Facility at the Charles Darwin Research Foundation, Puerto Ayora, Santa Cruz, Galapagos Islands

In 2002, after extensive safety testing in quarantine in the Charles Darwin Research Station Insectary and Quarantine Facility, Rodolia was released into the Galapagos Islands. The beetle readily established, spread, and subsequent monitoring indicated that it was having the desired effect on pulgon populations, they were collapsing because of feeding by larval and adult Rodolia.

Our project (i.e., Mark and Christina Hoddle, Charlotte Causton, and Roy Van Driesche) was to follow up to see whether Rodolia was still exerting high levels of control over pulgon, and whether there was any evidence suggesting that this natural enemy was causing problems to non-target organisms, especially other insect species.

After about three months of survey work we have concluded that pulgon populations are very low in most areas on Islas Santa Cruz, San Cristobal, Floreana, and Isabela.

Large walk in cages were used to study the feeding of behavior of rodolia in the presence of plugon and non target prey species

Occasional isolated outbreaks were observed on some young palo verdes (Isla Champion), white mangrove (1 plant at Playa de los Alemanes), and more commonly on uva de mar at Tortuga Bay on Santa Cruz.

Safety evaluations were conducted by running visual observation experiments in large walk-in-cages that held native plants infested with pulgon and non-target species of scales, mealybugs, mites, and aphids.

Into these cages adult Rodolia were released and they were observed for about 30-60 minutes. During this time their foraging behaviors were observed. In more than 30 hours of observations with around 30 beetles, no attacks on non-target species were observed. Rodolia only attacked and fed on pulgon. These large field cage studies confirmed the results of earlier studies that had been conducted in Petri dishes in quarantine. Our work so far indicates that Rodolia poses zero threat to other insect species in the Galapagos. To confirm these preliminary conclusions, we will be repeating these studies in 2010.

Walk in cages had native plants infested with pulgon, aphids, mealy-bugs, spider mites, and two different scale species (coccus viridis and ceroplastes sp.)

In addition to pulgon, the Galapagos Islands have suffered invasions by other insect pests. These include fire ants, polistes paper wasps, fruit flies, and Stenoma catenifer, a moth that has completely destroyed avocado production in the Galapagos. SICGAL (The Galapagos Islands Quarantine and Inspection Service) is running a fruit fly (these pests destroy fruit that people eat) control program using monitoring traps and poison baits.

The National Park Service is running fire ant eradication and monitoring programs. This is especially critical on islands where endangered native birds breed (e.g., Espanola has no fire ant or pest rodent populations) as fire ants have a devastating effect on young chicks, they eat them alive in nests!

The Galapagos Islands have severe problems with invasive weeds too. Amongst the most problematic are black berry (this weed may be the next target of a biocontrol program using a rust fungus. This has been very successful in Australia and New Zealand), elephant grass, Lantana, and guava.

Invasive mammal species have taken a huge toll on the native flora and fauna of the Galapagos. Introduced rats, mice, pigs, goats, donkeys, cats, and dogs either attack and feed on native birds, tortoises, iguanas, or lizards, or the herbivores kill plants by grazing and destroy the soil by walking on it with their hooves.

Native birds like this blue-footed booby are at risk from invasive species like rats, cats and dogs

None of the native plants and animals have evolved with these pests so they are particularly vulnerable to attacks and predation as they have no natural defenses against them.

The invasive species situation in the Galapagos is only going to worsen. There are now four plane flights per day from mainland South America to the Islands, and these large planes bring hundreds of people with luggage that likely bring unwanted organisms (either intentionally via smuggling or accidentally as hitchhikers.) Cruise ships frequent a lot of islands (in habited and uninhabited) which greatly increases the risk of unwanted marine aquatic pests being introduced into the Galapagos, and for rats to escape from boats and establish on islands that currently lack these pests. There are strong outreach efforts to educate people about the risk invasive species pose. There are educational posters at airports and docks, and SICGAL inspects luggage and freight moving between islands. The Charles Darwin Foundation runs educational programs on invasive species and information is peppered around the research center, a popular destination for tourists because of the giant tortoises on display there.

To read more from Mark Hoddle about the Biological Control of Icerya purchasi with Rodolia cardinalis in the Galapagos Islands, click here

To read more about this project from the UCR Newsroom, click here

Cruise ships, airplanes and small boats are constantly shuttling passengers and supplies to the islands. Theseare ideal situations for hitchhickers to migrate to the Galapagos Islands.

Black sooty mold growing on mangrove leaves

Invasive mammals like this feral cat on Isla Isabela are a major threat to native reptiles and birds in the Galapagos Islands

A larval Rodolia eating a cottony cushion scale while ignoring a potential non-target prey species, Ceroplastes

Icerya purchasi excreting sugary honey dew

Fresh avocados imported from South America are sold in local supermarkets. These fruit are infested with live Stenoma larvae (holes in fruit), the avocado seed moth. This pest has established in the Galapagos and has destroyed the local avocado industry. This scenario drives greater importation of fresh produce, which in turn increases the risk of more unwanted fruit pests establishing in the Islands

Fresh avocados imported from South America being sold at the farmers market each Saturday in Puerto Ayora, Santa Cruz

The National Park Service deploys monitoring traps for pest rodents on islands (e.g., Espanola) to detect early incursions of mice or rats onto these rodent free islands

Educational posters at airports help educate people on the threats invasive species pose to the Galapagos Islands

The Charles Darwin Research Foundation has research programs mitigating the adverse effects of invasive species in the Galapagos Islands

The Charles Darwin Research Foundation has educational programs on invasive species. This poster was displayed at the native plants nursery on the Foundation's campus

Dogs are used to inspect baggage and freight moving between islands to detect the illegal movement of plants and animals

SICGAL inspects luggage and freight moving between islands for illegal materials, including plants and animals that should not be moved between islands

Surveying for Icerya and Rodolia in natural areas in the Galapagos is extremely difficult because the vegetation is very thick and plants have sharp robust spines that shred your clothes and rip your skin!

After a 10 year campaign, the National Park Service eradicated goats on Isla Floreana. However, the program is plagued by the illegal introductions of goats back into recently cleared areas. People do this so they have goats to hunt and eat.

National Park Service workers baiting wooden sticks with peanut butter for fire ant monitoring on Isla Champion. The sticks are shoved into the ground and then examined several hours later for the presence of fire ants

Topics: Invasive Species, Mark Hoddle | 3 Comments »

3 Responses to “Invasive Species in the Galapagos Islands”

  1. Allie Says:
    July 26th, 2011 at 12:18 am

    wow! this looks like a very interesting trip.

  2. The Abacos Says:
    October 21st, 2011 at 8:19 am

    Loved the pictures you took. Almost makes me feel like I was there.

  3. creativediagnostics Says:
    May 28th, 2015 at 1:01 am

    Interesting trip! I really love what you do. There are so many new species i did not even notice about. The pictures are great too.

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