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Patzek L.J.,Northwestern Washington Research and Extension Center | Du Toit L.J.,Washington State University | Paulitz T.C.,Washington State University | Jones S.S.,Washington State University
Plant Disease | Year: 2013

During 2009 and 2010, 45 isolates of Rhizoctonia spp. were recovered from onion bulb crops in the semiarid Columbia Basin of Oregon and Washington, in which patches of severely stunted onion plants developed following rotation with winter cereal cover crops. Characterization of isolates recovered from naturally infested soil and roots was performed by sequence analysis of the ribosomal DNA (rDNA) internal transcribed spacer region, with the majority of isolates (64%) identified as Rhizoctonia solani. In steam-pasteurized field soil, stunting of onion was caused by isolates of R. solani anastamosis groups (AGs) 2-1, 3, 4, and 8, as well as Waitea circinata var. circinata and binucleate Rhizoctonia AG E evaluated at 13 and 8 or 15 and 15°C day and night temperatures, respectively, typical of spring planting conditions in the Columbia Basin. Isolates of R. solani AG 5 as well as binucleate AG A and I were nonpathogenic. The most virulent isolates belonged to AG 8, although an AG 3 and an AG E isolate were also highly virulent. Isolates of AG 2-1 and 3 caused moderate levels of disease, while isolates of AG 4 and W. circinata var. circinata caused low levels of disease. Emergence was reduced by isolates of AG 2-1, 3, and E. When the various AGs were grown at temperatures of 5 to 30°C, the relative growth rate of the Rhizoctonia isolates was not positively correlated with virulence on onion within an AG. © 2013 The American Phytopathological Society. Source


News Article
Site: http://phys.org/biology-news/

One of the authors of a new study is shown harvesting baby-leaf greens in a field in Washington. Field experiments revealed ways growers can lengthen production seasons for popular salad greens. Credit: Carol Ann Miles. Ready-to-eat salad mixes have experienced a tremendous increase in popularity and sales over the last 20 years. A study in HortScience reports that supermarket sales of the produce increased from $197 million in 1993 to $2.7 billion in 2008 in the U.S. Looking for ways to meet consumer demand and extend the production season of popular baby-leaf salad greens in the Pacific Northwest, scientists in Washington evaluated salad cultivars for suitability as spring and fall crops. "There is strong demand in northwest Washington for locally grown baby-leaf salad greens," said Carol Miles, from the Department of Horticulture at Washington State University, corresponding author of the study. "While the market is well supplied throughout the summer in this region, growers require production information to enable them to extend the season as much as possible in the spring and fall." Miles and researchers Charlene Grahn, Chris Benedict, and Tom Thornton evaluated nine salad crop cultivars for suitability as baby-leaf salad greens in the spring (April-June) and six cultivars for the fall (September-November) growing seasons in northwest Washington. Trials were conducted at Cloud Mountain Farm Center in Everson, and Washington State University's Northwestern Washington Research and Extension Center in Mount Vernon. The scientists found interactions between year, season, location, planting date, and cultivar for all crop parameters recorded (marketable crop weight, days to harvest, and ability to compete with weeds). They said that these results suggest that "environmental conditions and phenotypic plasticity play an important role in the performance of baby-leaf salad crops." In the spring growing season, cultivars had higher marketable weight and shorter days to harvest than in the fall season. Overall, pak choi 'Joi Choi' had a high marketable weight, a relatively quick time to harvest, and high weed competitiveness. Mustard 'Komatsuna' also had one of the highest marketable weights, as well as the lowest days to harvest and highest weed competitiveness. Beet 'Bull's Blood' showed a consistently low weight, relatively long days to harvest, and poor weed competitiveness. 'Brown Goldring', a romaine-type lettuce commonly grown for baby-leaf salad, had the longest overall days to harvest. "Because lettuce is one of the most desirable crops for salad mix, there is a need to identify cultivars that are well suited to extended season production," the authors said. The report recommends that growers in the region plant a diverse array of crops for baby-leaf salad to protect from crop loss and realize overall yield stability. More information: The complete study and abstract are available on the ASHS HortScience electronic journal web site: hortsci.ashspublications.org/content/50/10/1467.abstract


Miller T.W.,Northwestern Washington Research and Extension Center | Libbey C.R.,Northwestern Washington Research and Extension Center
Acta Horticulturae | Year: 2012

Two studies were conducted in northwestern Washington, USA, testing several herbicides known to aid in the control of perennial weed species often infesting red raspberries in the Pacific Northwest. These species include Canada thistle (Cirsium arvense), horsetail (Equisetum spp.), broadleaf dock (Rumex obtusifolius), creeping buttercup (Ranunculus repens), field bindweed (Convolvulus arvensis), quackgrass (Elymus repens), and yellow nutsedge (Cyperus esculentus). Trial 1 examined effects of clopyralid and granular or liquid diclobenil applied postemergence (POST) in 2007 and 2008; Trial 2 examined effects of halosulfuron and rimsulfuron applied POST in 2009 and 2010. By applying these products after weeds are visible, growers can treat portions of fields where infestations are heaviest, resulting in cost savings compared to broadcast preemergence applications, and perhaps with greater efficacy to weeds. In Trial 1, primocane injury was noted both years. The greatest injury in 2007 resulted from diclobenil, ranging from 18 to 36%. Liquid diclobenil caused a similar level of injury from early postemergence (EPOST) application as did granular diclobenil applied either EPOST or late postemergence (LPOST), but injury from LPOST liquid diclobenil was only half as severe. In 2008, LPOST diclobenil caused the greatest primocane injury, with the liquid diclobenil at either timing caused a similar level of primocane injury as granular diclobenil, ranging from 11 to 19%. Clopyralid applied EPOST or LPOST caused only slight injury to primocanes, ranging from 0 to 8% in 2007 and 10 to 13% in 2008, statistically similar to non-treated raspberry. Floricanes were not significantly injured by either herbicide either year, and berry yield was also not significantly affected. In Trial 2, neither rimsulfuron nor halosulfuron caused a reduction in berry yield in 2009, nor significant injury to primocanes or floricanes. In 2010, however, rimsulfuron and halosulfuron caused 63 and 55% primocane injury, respectively. Berry yield that year was reduced by rimsulfuron compared to nontreated raspberries, although yield in this older planting was low. Source

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