Leafhoppers (Homoptera: Cicadellidae) were surveyed in Western Oregon vineyards in 1999. Four sites were sampled for leafhoppers using a sticky trap method, and 29 vineyards were sampled for leafhoppers using a sweep net method in the summer of 1999. The sticky trap and sweep net methods were chosen based on cost, ease of use, and the fact that they are commonly used tools available for growers and IPM programs. Populations varied according to sample method, date, location, height, agricultural practices, and growing region. Each method resulted in the capture of different leafhopper species. Sticky traps attracted, and caught mobile insects such as the winged adults. The sweep net captured leafhoppers of all stadia from the vegetation. There was seasonal variation seen for each leafhopper group. Greatest numbers of leafhoppers were caught on the border and edges of the vineyard, presumably because of the surrounding vegetation providing refuge and food. The height of catch was dependent upon the preferred host plant of the leafhopper. Species that feed on the grapevine were generally found in the canopy from 90 to 150 cm above the soil surface. Vineyard management influenced abundance and diversity within the sites. Those vineyards using the least input had the highest diversity and lowest overall abundance of leafhoppers. Chemical use, irrigation, and cover crop choice influenced the species composition of the vineyard. The sites to the south of the Willamette Valley had a higher abundance of the species Psamotettix sp. The community structure of leafhoppers appeared to be more similar in the southern sites to California. The vineyards that had a diverse mix of plants in the cover crop had a more diverse population of leafhoppers. Most species found in this study feed on herbaceous plants that are common as vineyard ground cover. The cover crop that most low input management sites use may increase the number of leafhoppers that feed on the vine, but the presence of a cover crop has many advantages in the vineyard system. / Graduation date: 2001

Vineyard management strategies, including vineyard floor management and crop level management, can be used to influence vine vigor and fruit composition. Two studies were conducted to evaluate the impact of these practices on Pinot Noir in Oregon's Willamette Valley. Managing crop levels is common in cool climate vineyard production though it is a costly practice. With economic pressures, the premium winegrape industry is questioning whether they can reduce production costs and increase yields without compromising quality. A crop thinning trial was conducted in 2010 and 2011 to address these concerns and to better understand the role of vine balance on fruit composition. Crop levels were moderately (35% crop removed) or severely (65% crop removed) thinned at pre-bloom, fruit set, lag phase, or véraison and compared to full crop treatments. In both years, crop thinning reduced yields but had no effect on berry weight or cluster size. In 2010, poor fruit set reduced overall yields, and thinning treatments resulted in very few differences in vine growth, cluster architecture or fruit composition, including total soluble solids (TSS), pH, titratable acidity (TA), yeast assimilable nitrogen (YAN), anthocyanins, phenolics and tannins. In 2011, yields were much higher due to high fruit set and larger cluster size. No differences were found in vine growth (leaf areas or pruning weights) or fruit YAN, but thinned vines had higher TSS and pH and lower TA than full crop vines at harvest. Fruit thinned at lag phase and véraison had higher TSS and lower TA than fruit thinned pre-bloom. Intensity of thinning had a stronger influence on anthocyanin and tannin concentration than timing, while phenolics were not impacted by either factor. Ravaz index values (fruit yield/pruning weight) below 2.25 and leaf area to yield ratios of 2.25 to 3.25 m²/kg improved fruit composition in 2011 as did later season thinning, though data from the remaining years of this study will provide more insight into appropriate crop load metrics for cool climate Pinot Noir. A second study was implemented in 2011 to determine the impact of crop thinning in vines with different levels of vegetative vigor caused by three vineyard floor management techniques: permanent grass (Festuca rubra spp. rubra) cover (grass), alternating grass cover and tillage (grass & tilled), and tillage of every alleyway (tilled). Crop was thinned at the BB stage of berry development (EL stage 73) to one cluster per shoot (half crop) or not thinned (full crop); all cluster wings were removed at the time of thinning. Tillage treatments had been in place four years prior to the start of the study and competition for nitrogen in grass caused reduced early season vine growth, leaf chlorophyll and canopy size at both bloom and véraison while crop thinning increased canopy size at véraison. Yields were altered by tillage and crop thinning treatments, as grass had fewer clusters per shoot and berries per cluster, and crop thinning reduced yields to 64.7% of full crop across all tillage treatments. At harvest, grass had the lowest TA while TSS and pH were not affected by tillage. Crop thinning increased TSS but did not impact pH or TA. Anthocyanins were affected by both tillage and thinning and were found to be related to vine yield, YAN, leaf N, and leaf area index. Tannins were highest in grass but were not affected by crop thinning, and phenolics were not changed by either factor. Few interactions between tillage and crop thinning were found, but as variables such as yield per vine were impacted by both treatment factors, monitoring long term effects of crop / Graduation date: 2012