Potential hemlock hybrids tolerant to invasive hemlock woolly adelgid

Nov 10, 2010

New hemlock hybrids that are tolerant to the invasive insect known as hemlock woolly adelgid have been created by U.S. Department of Agriculture (USDA) scientists.

Geneticist Richard Olsen and horticulturist Sue Bentz of USDA's Agricultural Research Service (ARS) teamed up with Forest Service entomologist Mike Montgomery to breed and select these tolerant hybrids. Olsen and Bentz work in the U.S. National Arboretum's Floral and Nursery Plants Research Unit in Beltsville, Md. The arboretum is located in Washington, D.C., and is operated by ARS, the principal intramural scientific research agency of USDA.

Over the past few decades, two hemlocks native to the United States-Tsuga canadensis and Tsuga caroliniana-have been under attack by the small sucking insect Adelges tsugae, also known as the hemlock woolly adelgid (HWA). Originally from Asia, this aphid relative has spread to forests and backyards in 17 eastern states, killing hemlock trees and devastating .

Under the direction of ARS geneticist Denny Townsend (now retired), the arboretum began a breeding program in the 1990s to develop hemlock hybrids tolerant to HWA. The scientists crossed hemlock species native to the United States with germplasm-collected in Asia-of hemlocks that have shown tolerance to the insect. Now, 10 years later, Olsen and Bentz have developed 140 hemlock hybrids, 108 of which are suitable for testing.

In 2006, Olsen and his colleagues began a multi-year field trial to test each hybrid's degree of tolerance to HWA. Testing more than 170 trees, the researchers artificially infested the hybrids by attaching HWA-infested branches to the hybrids' lower branches and securing them with mesh bags to prevent the insects from escaping. They found the species T. chinensis and its hybrids to be most tolerant to HWA.

Details of the scientists' studies have been published in the Journal of Economic Entomology, the Journal of Arboriculture and the Journal of the American Society for Horticultural Science.

The hybrids are appealing not only due to their tolerance, but because they have good vigor and shape. Still, the researchers have several years of testing to complete before they can release these hybrids.

Explore further: No walk in the park for S. Africa's embattled game rangers

More information: Read more about this research in the November/December 2010 issue of Agricultural Research magazine.

Provided by United States Department of Agriculture

not rated yet
add to favorites email to friend print save as pdf

Related Stories

Japanese beetle may help fight hemlock-killing insect

Sep 10, 2007

The eastern hemlock, a tall, long-lived coniferous tree that shelters river and streamside ecosystems throughout the eastern United States and Canada, is in serious danger of extinction because a tiny, non-native ...

Preserving the Hemlock

Mar 04, 2008

As part of an ongoing effort to preserve the imperiled eastern hemlock tree species, researchers from North Carolina State University have successfully located the most genetically diverse populations of the species in the ...

Scientists Find Evidence of Casuarina Hybrids

Sep 14, 2009

(PhysOrg.com) -- Hybrids of the invasive Australian plant species Casuarina exist in Florida, Agricultural Research Service (ARS) scientists and university cooperators have found.

Recommended for you

Invasive lionfish likely safe to eat after all

1 hour ago

Scientists have learned that recent fears of invasive lionfish causing fish poisoning may be unfounded. If so, current efforts to control lionfish by fishing derbies and targeted fisheries may remain the ...

Brother of Hibiscus is found alive and well on Maui

17 hours ago

Most people are familiar with Hibiscus flowers- they are an iconic symbol of tropical resorts worldwide where they are commonly planted in the landscape. Some, like Hawaii's State Flower- Hibiscus brackenridgei- are en ...

Boat noise impacts development and survival of sea hares

19 hours ago

While previous studies have shown that marine noise can affect animal movement and communication, with unknown ecological consequences, scientists from the Universities of Bristol and Exeter and the École Pratique des Hautes ...

User comments : 0