PPFS-AG-SG-3



	<H1><CENTER>BARLEY YELLOW DWARF</CENTER>
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	<H3>Don Hershman and Paul Bachi</H3> (Revised 7-94)<BR>

					




	Barley Yellow Dwarf (BYD) is a virus disease which is transmitted to wheat and barley by various species of aphids.<BR>
 



<B>SYMPTOMS</B><BR>


	Affected plants show a yellowing and purpling of tips and margins of upper leaves. In most fields, this discoloration will be accompanied by stunting of some plants, evident as saucer-shaped depressions in fields about 2-10 feet in diameter. Plant discoloration and stunting is evidence of transmission of the virus in the fall to seedlings. This is most common in fields planted in late September to early/mid October. Plant discoloration, but no stunting, is evidence of spring transmission of BYDV by the aphid vectors. Spring infections usually become evident anytime from flag leaf emergence through head emergence. Fall infections, on the other hand, are frequently noted as early as crop greenup in the spring.<BR>




<B>YIELD EFFECTS</B><BR>


	Serious yield loss is likely to occur where stunted and discolored plants are widely distributed in a field. Plants showing these symptoms may yield about 25-50% less than their non-stunted counterparts. If plants are discolored, but not stunted, only minimal yield loss is likely to occur. Yield loss estimates for a field, thus, can be made by determining the area of a field comprised of stunted and discolored plants. If yield appears to have been substantially reduced, then you may want to consider abandoning the crop. Remember, there are other diseases which can be confused with BYD. If you are in doubt as to whether or not you are seeing BYD or a disease such as take-all, please submit a sample to one of the Plant Disease Diagnostic Laboratories for identification.<BR>




<B>CONTROL</B><BR>


	The best control of fall infections of BYDV is to avoid planting wheat before mid October, the so-call "fly free" date.  Delayed planting will have little effect on spring infections. Insecticide treatments aimed at controlling the aphids which transmit BYDV are inconsistent and unpredictable, and, generally, are not recommended. Aphidicide treatments made to wheat already showing symptoms of BYD will be of no value.