Western Plant Diagnostic Network Newsletter

WPDN – First Detector Dear WPDN First Detectors, Two new pest problems Network News have been found in the WPDN region. The first, the fruit- piercing moth, has been found in Hawaii. It is a destructive moth with a broad host range. The second is a The newsletter for the disease called thousand cankers disease of walnut, which WPDN is caused by a fungus vectored by the walnut twig beetle. First Detector Community This disease has been found throughout the western U.S. Read more about these in the following articles. February 2010

Volume 3, Number 1 We now have over 3,750 First Detectors in the WPDN,

achieved with several training sessions in Guam, Oregon, Contact us at the WPDN and California. Congratulations to all our WPDN First Regional Center: Detector Educators. Dr. Amanda Hodges, the NPDN Training and Education Chair, informs us that there is a Phone: 530 754 2255 new online Chilli Thrips module on the Online Training Fax: 530 754 7998 site. Chilli Thrips Email:

[email protected] To access this new module, log on to the NPDN home page at: http://www.npdn.org/ Websites:

https://www.wpdn.org

https://www.npdn.org

Published by the

WPDN Regional Center

Department of Plant Pathology

A Fruit-Piercing Moth found in Hawaii

Lepidoptera: Noctuidae Oraesia excavata Butler Personal Communication from Bernarr Kumashiro, entomologist with HDOA

On December 28, 2009, William Haines, University of Hawaii, notified Hawaii Department of Agriculture (HDOA) of a new fruit-piercing moth in Hawaii. The moth was identified as Oraesia excavata by Michael Pogue, USDA Systematic Entomology Laboratory. The biology of this moth is not well known. The moth (1" long) is orange colored and is very distinctive- like a dead leaf. The worldwide distribution includes Japan, Korea, China, Thailand, and Taiwan. The first known specimen was observed in a student's collection for an entomology class. It was collected at Kula, Maui, on November 24, 2009. Subsequently, 7 specimens were collected on Maui and Oahu. Young larvae may have been possible collected by F. Starr at Olinda, Maui on Cocculus orbiculatus A literature search indicated that C. orbiculatus (Family Menispermaceae ) may be a preferred host for the larva. This species is indigenous to Hawaii and is known as "huehue". It is found in open areas such as grasslands and in mesic to dry forests. Other possible hosts are Lepisanthes rubiginosa (Family Sapindaceae) and

Stephania japonica. These are not common ornamentals, and are found in a few botanical gardens. Some of the botanical gardens operated by the City and County of Honolulu have been alerted of this potential pest. Fruits recorded in literature as hosts for the moths include prune, citrus, grape, peach, pear, apple, guava, papaya, mango, banana, and loquat. The sudden appearance of several moth specimens and the widespread distribution in a short period of time may indicate a potential seriousness of this pest.

Larva on Huehue leaf

Kawakita Insect Library Takagi Tentiki

Starr Plants Adult Fruit-Piercing Moth

(note leaf-like appearance)

Update on Thousand Cankers Disease of Walnut Richard Bostock – UC Davis Plant Pathology and WPDN Director, Ned Tisserat – Colorado State University, Whitney Cranshaw – Colorado State University, Janine Hasey – UC Cooperative Extension, and Steven Seybold – US Forest Service

Thousand cankers of walnut of eastern black walnut (Juglans nigra) and related Juglans spp. has emerged as a disease of significant concern in the western U.S. The disease is caused by a newly described fungal pathogen, with a proposed name of Geosmithia morbida . Spores of the fungus are carried from tree to tree by tiny walnut twig beetles (Pityophthorus juglandis) that attack susceptible trees, creating numerous entry wounds and galleries for the pathogen to establish and colonize the bark. The fungus destroys the surrounding phloem tissue and the cankers that form eventually coalesce to girdle the stems and branches. Plant pathologist Ned Tisserat and entomologist Whitney Cranshaw from Colorado State University first identified the pathogen and characterized its association with the beetle in declining black walnut trees in central Colorado (Tisserat et al., 2009). In some areas of the state, eastern black walnut trees in landscapes and urban settings have been decimated by thousand cankers disease. In addition to Colorado, the disease is contributing to the decline and death of eastern black and native walnuts in California, Idaho, New Mexico, Oregon, Utah, and Washington. In the summer of 2008, thousand cankers disease was first confirmed in declining northern California black walnut trees ( J. hindsii) near Davis, CA by University of California and US Forest Service researchers (Graves et al., 2010). Since then and with collaboration from the Colorado team, researchers have found the disease throughout the state on native black walnuts ( J. hindsii and J. californica), as well as on English walnuts (J. regia ) in a number of commercial orchards. Research is underway to assess the relative susceptibility of various Juglans species and the host colonization preferences of the beetle. J. nigra appears to be the most susceptible to beetle attack and to the pathogen. Nonetheless, there is a growing concern of the potential susceptibility of black and hybrid walnut rootstocks and the possible impact of the disease on English walnut production. The walnut twig beetle, which is thought to be native to northern Mexico, New Mexico, Arizona, and California, was first collected in California over 50 years ago in Los Angeles County. As of this writing, the disease and its beetle vector have been confirmed in urban, native/riparian, or agricultural settings in nine counties in the state. There is

considerable concern that the beetle and the disease may spread to the eastern U.S. and into the native range of J. nigra.

Jim LaBonte – Oregon Dept. of Agric.

Symptoms of thousand cankers disease include staining of the outer bark tissue that extends into the cambium, yellowing and thinning of the upper crown, wilting of leaves, flagging branches, and die back and eventual death of the tree (Graves et al., 2009). The beetles are very small and may or may not be present in the cankered tissue. However, characteristic beetle entry/exit holes about 0.5 mm in diameter may be apparent in symptomatic branches. There are presently no effective controls for the disease. Rapid detection is a primary management option, but what to do after this depends on the host species and region. In Colorado, it is recommended that J. nigra trees be cut as soon as possible after symptoms are observed and the disease confirmed, then removed to a safe site (one where the disease is already present) and all wood material chipped. Chipping does not kill the beetles, 4 but will shorten the period that the wood can support breeding. In California, management strategies are being explored, but removal of infected branches to green wood or tree removal where the whole tree has declined are recommended. Infected wood should be burned in accordance with local air quality restrictions. What is unclear is why thousand cankers disease has emerged on such a wide scale to create a situation of concern. Surveys are underway to assess the distribution and extent of damage of the disease in walnut growing regions.

see Colorado State thousand cankers Pest Alert

For more detailed information see:

Graves, A.D., Coleman, T.W., Flint, M.L., and Seybold, S.J. 2009. Walnut twig beetle and thousand cankers disease: Field identification guide, UC- IPM Website Publication, 2 pp., Nov. 21, 2009, http://www.ipm.ucdavis.edu/PDF/MISC/thousand_cankers_field_guide.pdf

Graves, A.D., Flint, M.L., Coleman, T.W., and Seybold, S.J. 2010. Thousand cankers disease of walnuts: A new disease in California, UC-IPM Website Publication, 4 pp., http://www.ipm.ucdavis.edu/EXOTIC/thousandcankers.html

Tisserat, N., Cranshaw, W., Leatherman, D., Utley, C., and Alexander, K. 2009. Black Walnut mortality in Colorado caused by the walnut twig beetle and thousand cankers disease. Online. Plant Health Progress doi: 10.1094/PHP-2009-0811-01-RS.