Home Industry News Enology Early Season 2023 Oregon Vineyard Update

Early Season 2023 Oregon Vineyard Update

Members of the Oregon State University Viticulture and Enology Extension Working Group meet monthly to discuss season progression and program updates across the state. Here OSU Extension Specialist Patty Skinkis provides a summary of vineyard growth and topics of interest in each of the areas represented by regional or county Extension faculty who directly serve wine grape growers in Oregon. She also provides the statewide summary here while also providing an update for counties in the Willamette Valley where there is no dedicated county-level Extension support.

Statewide – The 2023 growing season had a late start with a cool April that prevented bud break, which most growers welcomed after last year’s spring frost. Vines across the state started bud break with the abrupt warm temperatures in late April (~April 28 to May 1, Figure 1). The warm May led to some of the most rapid grapevine growth that I have seen in my 16 years in Oregon. As a result, most of the state’s growing regions started bloom by early June, as sufficient heat units were reached (Table 1). Some cooler vineyard sites or later cultivars were wrapping up bloom as of mid-month (June).

Umatilla County (Walla Walla Valley) – Cody Copp, Extension Horticulturist and Assistant Professor of Practice located in Umatilla County, reported 90% bloom in warm sites as of June 1. Precipitation was below average for the water year (since October 2022). Due to the very rapid growth and warm temperatures shoot thinning operations were behind. With good weather conditions, the first preventative fungicide sprays for powdery mildew went on as planned.

Douglas County (Umpqua Valley) – We welcome Logan Bennett, OSU Extension – Douglas County Small Farms Program Coordinator, to our Wine Grape Extension Team. He replaces Steve Renquist, former OSU Extension Horticulturist, as the local contact in Roseburg and has been working in his position for the past year. He has been addressing emergency vineyard situations to date. Logan visited as many vineyards as he could last year and will be working with the NRCS this summer to visit all farms to do a needs assessment. If you are a grower or winery in Douglas County, please reach out to Logan for vineyard and farm related questions. Logan reported that vineyards in the region were progressing with growth similar to the Willamette Valley. Lower fruitfulness was noted in some vineyards.

Figure 1. Mean daily air temperature reported by Agrimet locations throughout Oregon from April 1 to June 15, 2023.
Table 1. Heat accumulation in growing degree days (GDD50) of wine grape growing regions in Oregon as represented by Agrimet weather station locations. Summation is shown by month of the growing season 2023.

Jackson and Josephine Counties (Rogue, Applegate, and Illinois Valleys) – Alec Levin, Associate Professor and OSU-SOREC Director, reported that bud break was late for their region but on par with the rest of the state (starting April 27-28). They had no frost issues this spring and had very low mildew pressure. They had 0.87” of rain in May, which was the most precipitation reported across the state’s wine growing regions (Table 2). The water situation is improving, as all reservoirs are over 50% and some are full. However, the region is behind in rainfall for the water year. The vineyards are looking good with high fruitfulness and inflorescences look large. As of June 1, bloom was just starting in the earliest cultivars.

Willamette Valley (from Lane to Washington Counties) – This region had a very wet April with ~6” of rainfall, similar to April 2022. However, May’s rainfall was less than 1” (Table 2), which was 66% lower than the long-term average for May. Heat accumulation was rapid from late April to mid-June, and vines grew at a pace not often observed for this region. Shoot thinning operations were behind as a result. With the ample soil water content, vineyard cover crops and resident vegetation/weeds grew a lot of biomass. Undervine management was a challenge given the rapid growth. Vines are looking healthy with good fruitfulness. There were no issues with growth observed in vineyards that experienced the worst of last year’s spring frost event.

Although the weather was great for plant growth across most vineyards, some had vines failing to break bud and significant stunted growth, particularly at distal nodes. In some cases, the buds never grew while others broke bud weeks later and had stunted shoots of not more than 6-8 compressed nodes and sometimes had multiple shoots per node. There was stronger, more normal growth, at the head of the vine and from suckers lower on the trunks. The cause of this is unknown. Potential causes, including bud mites, rust mites, fall/winter cold damage, boron deficiency, trunk disease, crown gall, carbohydrate shortage, time of pruning, pruning severity, and hormone imbalances were all discussed, but none seem to be the single cause of the blind nodes and stunting. Furthermore, some causes are nearly impossible to prove. Eriophyid mites (bud and rust) were ruled out in some cases as they were rarely found when tissue washes were performed (by consultants, agronomists or the OSU Plant Clinic). However, it is hard to find bud mites in this way since the damage is already done before the bud breaks. Tissue damage did not look similar to that of boron deficiency when examining shoots, and cold damage was rarely found by examining phloem and buds. By late May/early June, leaf deformation was apparent on otherwise healthy leaves, and the symptoms looked like potential herbicide exposure. It is likely that the deformed leaf symptom later in May/early June is a separate issue than the delayed/failed bud break and stunting noticed earlier. These combined observations were noted from the north to south Willamette Valley and into the Umpqua. With the wide geographical spread, it may include an abiotic factor, such as weather conditions and possible drift, but this is not clear given that there are also healthy, unaffected vineyards across that area. If you have vineyard blocks with these symptoms, monitor them closely and maintain management practices for good plant health. Be sure to quantify fruitfulness and fruit set early on, as yield might be reduced in affected blocks. Also, be sure to work through our stunted shoot app to help diagnose the problem further.

Entomology Update – Rick Hilton, OSU-SOREC Entomologist, gave an update on mealybugs in southern Oregon. Gills Mealybug (adult females) were observed by growers during shoot thinning. The range of observed Gills Mealybug has spread; however, there is good biocontrol in vineyards already and often the populations will decline on their own. Insecticide applications are not necessary. Vine Mealybug (VMB) is a greater concern for southern Oregon since it was identified in the Rogue Valley in 2021. Rick and Vaughn Walton, Horticultural Entomologist and Professor, were able to get enough mating disruption products donated by Pacific Biocontrol to use in all quarantined vineyards with known VMB infestations. Movento applications will be used according to Oregon Department of Agriculture (ODA) quarantine treatment rules. Rick and others at OSU-SOREC are working with ODA to maintain pheromone traps. No males were found in traps as of June 1. The OSU-SOREC team is also actively searching the quarantine sites for crawlers and females, but only Gills Mealybug were found to date. We are encouraging growers to be aware of the two types of mealybugs and consider putting in pheromone traps to determine presence and future control. Be sure to check out our VMB Resources at OSU Extension. — By Dr. Patty Skinkis, Professor & Viticulture Extension Specialist, Oregon State University

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