Issue link: http://read.dmtmag.com/i/561374
5 8 V I N E YA R D & W I N E RY M A N A G E M E N T | S e p t - O c t 2 015 w w w. v w m m e d i a . c o m tions and penalties for poor fruit quality. In the winery, fruit from infected plants has reduced soluble solids and increased titratable acid- ity, which impacts wine quality. Research data has shown leafroll- related yield reductions of 50%, and sugar-level reductions up to 20%, compared with healthy vines at the same sites. Leafroll-affected grapes tend not to fully ripen and the result- v i r a l s c o u r g e h a s b e e n s t a l k i n g t h e grapegrowing regions of the world: the virus that causes grape lea- froll disease, or GLD. Symptoms of GLD in grapevines were first described in 19th-cen- tury Europe; however, it was not until 1979 that a specific type of filamen- tous virus was identified in leafroll-infected vines. Nine different grapevine leafroll-associated virus- es (GLRaVs) have been identified, with GLRaV-3 the most common and widespread. F o r t h e g r o w e r, the virus causes yield reductions, poor fruit quality and reduced vine vigor. Managing the dis- ease begins with plant- ing certified, virus-free vines followed by vigilant roguing, or removing infected vines. Since the virus cannot be confirmed without laboratory testing, a new technique that combines hyper- spectral imaging with aerial map- ping can aid the management of GLD in the vineyard. The estimated economic impact of leafroll disease in wine grapes varies, depending on yield reduc- BY JAMES GIESE ing wine can have color loss, high acidity and reduced complexity. A recent survey in California, published by a team of researchers from Cornell University and the University of Cal- ifornia, indicates that the costs of grape leafroll disease in red varieties can range from $20,000 to more than $200,000 per hectare (1 hectare = 2.47 acres), if entire vine- yard blocks need to be removed and replanted. Due to its economic importance, scientists from UC Berkeley, UC D a v i s , U C R i v e r s i d e a n d U C C o o p e r a t i v e E x t e n s i o n h a v e b e e n researching leafroll dis- ease solutions in Cali- fornia for many years. In 2009, vineyard con- sultant Dr. Phillip Freese of Wine- Grow approached Drs. Matthew and Melissa Staid of VineView Sci- entific Aerial Imaging in Angwin, Calif., to ask if they could develop a method to remotely detect leafroll. After discussing the possibilities and some preliminary field work, Freese introduced the Staids to Dr. Monica Cooper, UCCE farm advisor for viticulture. Detecting Grapevine Leafroll from the Air New technique combines hyperspectral imaging with aerial mapping Leafroll disease in red varieties can cost many thousands of dol- lars per acre if entire vineyard blocks need to be replanted.