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UCR entomologist develops electronic tool to identify California’s thrips

If you encountered an unfamiliar-looking insect, how would you identify it by name and learn more about its behavior and impact?

That difficulty has now been significantly eased for identifying California’s thrips — small insects, each measuring about one-fiftieth of an inch, that feed on the sap of plants. Many thrips are important pests of agriculture and urban landscape plants.

UC Riverside’s Mark Hoddle, a biological control specialist in the Department of Entomology and the director of the Center for Invasive Species Research, has created, with colleagues in Australia, an interactive computer-driven tool that quickly helps classify a thrips by its scientific name.

Available on CD-ROM for $52, the electronic tool or “key” summarizes all information available on 207 species of native and exotic (non-native) Californian thrips including 12 species that are considered potential invaders.

Users of the key answer a series of simple questions illustrated with high-quality photographs pertaining to the external appearance — or morphology — of the thrips in question. Each response narrows the number of choices needed to determine the identity of the thrips being studied, until, finally, the user is left with just one scientific name. Once the species is identified by name, the user clicks on the name to open up a fact sheet on the thrips, photographs and other pertinent information.

“Essentially, we have 1,500 high-quality photographs of several entire museum slide collections of thrips of importance to California on a CD-ROM that is highly portable and will be Web-accessible, too, on Sept. 1 at no charge,” Hoddle said. “Also included is a novel interactive glossary of technical terms concerning thrips morphology. It works either by selecting a body part name, or by clicking on the body part of a ‘cartoon’ thrips to get the name and definition of that particular body part structure.”

When young, thrips larvae are white, orange or yellow. As they age, they turn dark yellow, brown, or black. Many species develop wings and can fly. Upon infesting orchards, thrips can feed on leaves, young fruit, and the pollen in flowers. Some species can spread viruses which kill plants.

The avocado thrips cost California avocado growers tens of millions of dollars a year because of control costs and down-graded fruit which is damaged by feeding thrips larvae and adults. Citrus and tomato growers face similar problems from pest thrips.

“Until now, there existed few tools for identifying California thrips, and of available tools many are in excess of 40 years of age,” Hoddle said.

He explained that the vast majority of thrips native to California typically cause few problems, but there are one or two notable exceptions. On the other hand, the majority of exotic thrips species in California pose enormous economic and management challenges.

“In most cases the vast majority of native California thrips are closely associated with native California plants and they don’t feed on to any significant extent important crop plants,” Hoddle said. “Two notable exceptions are the western flower thrips, Frankliniella occidentalis, and the citrus thrips, Scirtothrips citri, both of which are native to California.

“Exotic invasive thrips on the other hand almost always turn out to be important pest species. This occurs because in most cases they have arrived on exotic plants that are of some economic value to California — either agriculturally or for beautifying the landscape. With vast monocultures to attack, no natural enemies or significant competition for resources, great year round climate, especially in coastal areas, the small invading populations explode, spread rapidly, and do immense damage.”

Hoddle feels assured that a taxonomical tool like his CD-ROM can help identify many of the thrips species present in California. “Knowing their identity will help greatly in predicting how that species may behave,” he said. “Additionally, the CD-ROM can identify serious pest species not yet in California, and early detection and accurate identification is key to successful management of an invasive species.”

“The thrips of California are highly diverse,” he said. “The state’s fauna is extremely unique because of the high diversity of native plants here — plants found on beaches, deserts to mountain tops and everything in between. We have an immense amount of agriculture in California and a baffling variety of exotic plants in urban areas.”

Next, Hoddle will work on getting a molecular fingerprint of all the thrips in California. These will include native species, exotic invasive species, as well as potential invaders from overseas.

“This second phase of the CD-ROM will allow users to identify fragments of thrips as well as the thrips’ larvae and eggs,” he said. “This will be very valuable for border inspection officials who may find only immature stages of thrips infesting plants. Molecular tools are extremely useful in this instance because traditional morphological approaches cannot identify immature thrips to species.”

The CD-ROM, is commercially available either through UCR or the Centre for Biological Information Technology at the University of Queensland, Australia.

Hoddle is the principal investigator of the two-year project that developed the CD-ROM. Besides developing the key, he participated in specimen photography and fact sheet development that discuss the biology, ecology, distribution, and taxonomy of California thrips.

He was joined in the project by Laurence Mound of the Australia National Insect Collection, Commonwealth Scientific and Industrial Research Organization in Canberra, Australia, who helped in the development of the key, photographed slide mounted specimens and writing of fact sheets of all the thrips species in the key.

Dena Paris of Dparis Design developed the final CD-ROM package in HTML format. Vincent D’Amico and Geoff Attardo of Key Point Graphics developed the interactive thrips glossary in Flash.

Funding of $35,000 for the project was provided for one year through a competitive grant by UC-ANR (University of California - Agriculture and Natural Resources) Core Issues.

Hoddle will use the new CD-ROM to run an identification workshop to be held Sept. 8-11, 2008, at UCR.

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