A new, first-of-its-kind automated system could speed up identification of karnal bunt, a wheat fungus recently found in the southwestern United States.Some countries won't import the infected wheat containing karnal bunt-infected kernels. Currently, wheat samples are visually inspected for the presence of spores and infected kernels. The new system automatically identifies wheat classes and defects such as bunt-infected kernels or scab. In preliminary tests, the instrument correctly identified 93 percent of all bunt-infected kernels. The instrument sorts both common and karnal bunt from healthy kernels at the rate of two kernels per second. This system was designed by ARS researchers and engineers with Perten Instruments North America, Springfield, IL.

U.S. Grain Marketing Research Center, Manhattan, KS Floyd E. Dowell, (785) 776-2753,

fdowell@usgmrl.ksu.edu

Nurserymen and landscapers can help rein in a disease that is slowly dooming century-old trees near the historic Mall in the Nation's Capital.Nothing can be done to save these oak, elm and maple trees, but the spread of the bacterium Xylella fastidiosa by sap- sucking insects can be stemmed by growers' vigilance. X. fastidiosa's calling card is leaf browning that begins on outer edges and moves inward. As the disease progresses, branches fail to revive in spring and eventually die. To save neighboring trees, nursery staff should keep vigilant and remove the stricken tree in time before insects spread the bacteria. The disease is commonly known as leaf scorch. It kills by attacking the xylem tubes that carry water within the plant. Leaf scorch has been found throughout the U.S. and in Brazil, where it attacks coffee trees. There is no cure for leaf scorch, but some plants appear to have resistance. Scientists are exploring why. They have also narrowed the list of xylem-feeding insects that may be responsible for spreading the disease. Floral & Nursery Plants Research Unit, U.S. National Arboretum, Beltsville, MD Jo-Ann Bentz, (301)504-8260, jbentz@asrr.arsusda.gov

The microscopic wheat mite Aceria tosichella has been unmasked as the culprit behind an emerging corn and wheat virus in the western United States and three other countries.The mite is a carrier of High Plains Virus (HPV), which was first observed in western corn and wheat fields in 1993, hitting especially hard in northern Texas. It has now been confirmed in more than 100 counties and 11 states, as well as in Chile, Brazil and Israel. Symptoms of HPV infection include severe stunting, yellowing, reddening and death of the lower leaves. A. tosichella, also known as wheat curl mite, infects plants when it injects the virus into plant tissues as it feeds. The mite also carries wheat streak mosaic virus, another threat to crops. ARS researchers have teamed with scientists at the University of Nebraska to breed new mite-resistant corn and wheat varieties. Wheat, Sorghum, and Forage Research, Lincoln, NE Stanley Jenson, (402) 472-1526, sjensen@unlinfo.unl.edu

Last Updated: April 29, 1998
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