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.

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

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.

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.

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.

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.

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