Lady bug fights Galapagos invasive pest


Adult lady bug attack adult cottony cushion scale

From the University of California in the USA:

Control of invasive insect in Galapagos called a success

Date: 2010-04-22
Contact: Iqbal Pittalwala
Phone: (951) 827-6050
Email: iqbal@ucr.edu

RIVERSIDE — The Galapagos Islands, made famous by Charles Darwin, have a unique biota now highly threatened by invasive species because of increased tourism and population growth.

Indeed, alien or exotic insects today constitute 23 percent of the Galapagos insect fauna. One of these insect invaders is the cottony cushion scale, a sap sucking bug native to Australia.

Capable of infesting many woody ornamentals and crops, the cottony cushion scale decreases the vitality of its host by sucking phloem sap from the leaves, twigs, branches, and trunk. But natural enemies, such as the lady bug beetle, Rodolia cardinalis, can bring the cottony cushion scale under control in a short time — a form of pest suppression called biocontrol.

In fall 2009, entomologist Mark Hoddle, the director of the Center for Invasive Species at the University of California, Riverside, and colleagues visited the Galapagos Islands to assess the impact and safety of the lady bug beetle that had been released in 2002 to suppress the cottony cushion scale.

“Populations of cottony cushion scale in 2002 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,” said Hoddle, also a biocontrol specialist in the Department of Entomology.

Combating the cottony cushion scale was a joint effort between the Charles Darwin Research Foundation and the Galapagos Islands National Park Service, which neighbors the foundation on the island of Santa Cruz in the Galapagos.

“Soon after release, the lady bug beetle readily established and spread,” Hoddle said. “Subsequent monitoring indicated that it was having the desired effect on the cottony cushion scale populations, which were collapsing because of feeding by larval and adult lady bug beetles. Our project was to follow up to see whether the lady bug beetle in 2009 was still exerting high levels of control over the cottony cushion scale and whether the project was safe as predicted by lab studies.”

After about three months of survey work Hoddle, along with Christina Hoddle (UC Riverside), Charlotte Causton (Charles Darwin Research Station) and Roy Van Driesche (University of Massachusetts, Amherst), concluded that the cottony cushion scale populations were very low in most areas on the Galapagos Islands.

“Pest numbers have been reduced by more than 99 percent on some native plants like mangroves, which were very susceptible to attack by cottony cushion scale,” Hoddle said. “While from other rarer native plants, like Darwiniothamnus tenuifolius, the pest appears to have been completely removed.”

To assess the impact of the beetle on the cottony cushion scale, Hoddle’s team surveyed native plants across five different islands – Santa Cruz, Isabela, Espanola, San Cristobal, and Santiago – and recorded the presence and absence of cottony cushion scale and the lady bug beetle, and their densities. The team then compared the data to similar data from the same areas – and in many instances, from the very same trees – that had been collected before the lady bug beetle was released into the Galapagos.

“We also found no evidence that the lady bug beetle was attacking non-target species,” Hoddle said. “The bug was never seen feeding on other insects in the Galapagos even when the cottony cushion scale and the non-target species were side by side on the same twig.”

The cottony cushion scale project with the beetle was born in Southern California in 1888-1889 and saved California’s then fledging citrus industry.

“The project in the Galapagos is an extension of the California success story,” Hoddle said. “But in the Galapagos the biocontrol agent is protecting native plants instead of agricultural crops. The project has gone full circle – from 1880’s citrus protection in Southern California to, in 2010, conservation of endangered plants in the Galapagos. A pretty incredible progression that would have been inconceivable by California entomologists and citrus workers back in 1888!

Non-native plant species are extending the growing season in eastern US forests by an average of four weeks, a study has suggested: here.

3 thoughts on “Lady bug fights Galapagos invasive pest

  1. Are invasives bad? Not always, say Brown researchers

    Science Centric | 18 May 2010 20:12 GMT

    In 1988, a mysterious invader washed upon the New Jersey shore. The Asian shore crab likely arrived in ballast from commercial ships, and it found its new home to be quite agreeable. More than two decades later, the crab, Hemigrapsus sanguineus, has expanded its range along the Atlantic coast northward to Maine and southward to North Carolina. Its numbers continue to expand, and wildlife biologists have found them in greater densities along New England’s cobbled shores.

    Another tale of an invasive species conquering a native ecosystem? Not so fast, says Andrew Altieri, a marine ecologist at Brown University and the author of a new paper in Ecology that scrutinizes the crabs’ success. Altieri and colleagues have found that the Asian shore crab has found a hospitable niche in its new environs and in fact gets along just fine with native species. While the crab has exploited the conditions set up by the native cordgrass and ribbed mussels that dominate the cobbled beach ecosystem, it does not appear to do so at the expense of other species that call the shoreline home.

    ‘Usually, when you think of invasions,’ Altieri said, ‘you think it will be bad. Yet we found here a situation where that doesn’t occur. We’ve found a place where the natives and invasives get along quite well.’

    Altieri and team members Bregje van Wesenbeeck, a visiting scholar at Brown from the Dutch environmental research institute Deltares, and Mark Bertness, chair of the Department of Ecology and Evolutionary Biology at Brown and Altieri’s adviser, counted crabs, which measure about 1 1/2 inches wide, at four sites on Narragansett and Mount Hope bays in Rhode Island in summer 2003-2004. They found crab density (an indicator of their numbers) to be highest where cordgrass and ribbed mussels proliferated. Crab density was more than 100 times higher in those areas compared to spots along the beaches where cordgrass or mussels were missing. The crabs have found their transplanted home so inviting that their populations are denser in North America than in their native range in Asia.

    From the field observations, the team, which also included Brian Silliman from the University of Florida, determined the Asian shore crab took advantage of the moist, shady environment created by the cordgrass and the mussels. In ecological terms, the researchers found a ‘facilitation cascade.’ The cordgrass attracts ribbed mussels by giving the molluscs something to attach themselves to as well as a shady spot; the mussels, in turn, give the crabs crevices in which to avoid predators as well as the harsh sun. The cordgrass also provides valuable shade for the crabs.

    ‘It’s a moist, stable environment in an otherwise harsh environment,’ Altieri said. ‘It’s the key to their success, the reason why they’re so abundant.’

    The team found that the crabs’ exploitation of their habitat did not crowd out native species, such as the common periwinkle, small crustaceans, blue mussels and barnacles. Indeed, the field studies showed the more invasive crabs, the greater the number of native species.

    In other words, the cordgrass-ribbed mussel environment has enough room to accommodate another tenant. ‘They may be promoting co-existence,’ Altieri said, ‘allowing for this ecosystem to absorb a new species.’

    Previous research suggests the crabs do prey upon juvenile American lobsters, and the Brown scientists also want to study whether the crabs eat other crab species.

    The research also seems to highlight the importance of cordgrass to provide shade, a service to species that may grow even more important with warming air and water temperatures forecast to accompany changes in the climate.

    Source: Brown University

    http://www.sciencecentric.com/news/article.php?q=10051858-are-invasives-bad-not-always-say-brown-researchers

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  2. Pingback: Galapagos frigatebirds, a distinct species? | Dear Kitty. Some blog

  3. Pingback: California island native plants recovery | Dear Kitty. Some blog

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