In Utah, commercial raspberry production has succeeded in the northern part of the state, alongside tourism. Otherwise, production is limited to a handful of growers scattered around the state. A raspberry variety trial was planted in 2006 at five locations ranging from the northeast to the southwest corners of Utah. The plan for this project was to evaluate production in these five locations during the 2007 and 2008 seasons. The 2007 crop was destroyed by spring frost. Data on winter survival, yields, fruit size and production season were collected in 2008 and 2009 and are currently underway for the 2010 season.
Brambles, including raspberries and blackberries, are a high-value crop with a short shelf life, making them well-suited to local production and consumption. In Utah, raspberries have succeeded in the northern part of the state, alongside tourism. Otherwise, production is limited to a handful of growers scattered around the state.
Raspberry production in northern Utah has been devastated by an outbreak of Raspberry Bushy Dwarf (RBDV), a pollen-borne virus, largely because growers had relied on a virus-susceptible variety, Canby. Meanwhile, a number of new varieties, some resistant to RBDV, have been developed that offer adaptability to a wide range of climates.
Population growth in recent years has pushed development in Utah and other Intermountain areas onto what had been the best farmland, often leaving small parcels (1-20 acres) typically underutilized and infested with weeds. Properly managed, these small parcels could produce a rich variety of high-value crops, including brambles, sold directly to consumers at the farm gate, farmers markets or Community Supported Agriculture subscriptions.
- Conduct bramble trials on farmer fields and at one university research station, representing five climate zones in Utah.
Using trial results, develop lists of appropriate cultivars and cultural practices for the various climate zones.
Conduct field days and develop fact sheets and articles to disseminate research results to growers in Utah and other Intermountain states.
Conduct follow-up surveys of field day attendees to assess what information was important to them and what varieties or practices they may have adopted.
A raspberry variety trial was planted in 2006 at five locations ranging from the northeast to the southwest corners of Utah (Table 1). Cooperating locations included an Agriculture Experiment Station research farm (Kaysville) and four commercial farms. Two of these farms (Utah and Washington counties) had not previously grown raspberries and were seeking to identify suitable cultivars to include in diversification plans, whereas the other two were existing raspberry farms interested in new varieties.
A wide range of raspberry varieties was selected to include in the trial, consisting of both summer- and fall-bearing types (Table 2). Some varieties were included for potential heat tolerance at the southerly locations only, while cultivars believed to be more cold-hardy were included only in northern locations. A sub-set of seven varieties (three summer-bearing and four fall-bearing) were included at all five sites to facilitate comparison across locations.
Each location had four replicate plots of the varieties selected for that location, with plots arranged in a randomized complete block design, with blocking by location in the field. Plots consisted of a 12-foot bed of raspberries, with an 8-foot buffer between plots to prevent different varieties from growing together. At the commercial farms, space between rows was maintained with clean cultivation, whereas the row middles at the experimental farm consisted of a grass-clover cover crop that was mowed periodically.
Fertility, irrigation and pest management were as per each grower’s typical practices. The Washington County location was on certified organic ground, and the remaining locations were managed conventionally. Irrigation was supplied by a combination of overhead microsprinklers and drip irrigation at the Kaysville location and by drip irrigation at the remaining locations.
Observations and evaluations were made by participating farm managers, as well as by the ag Professional and technical advisors. Detailed yield, fruit size and quality data were also collected at the Kaysville location by research staff.
Winter injury from both the 2006-07 and the 2007-08 seasons was more severe than normal. The 2007 season should have been the first significant harvest of the summer bearers, but the degree of cane damage was such that harvest was not practical. Significant cane damage was also apparent in the spring of 2008, with noticeable variation among varieties. Although these incidents have made it difficult to fully assess the fruiting potential of the varieties, they have provided good “test winters” for determining cold hardiness. The 2008-09 winter was unusually mild with better yields in 2009 across all cultivars compared to 2008. Winter injury resulting in 2009-2010 was intermediate to the previous two seasons.
Results from these observations have indicated that several varieties including ‘Coho’, ‘Encore’, ‘Lauren’ and ‘Tulameen’ are clearly not hardy to Utah’s conditions. Interestingly, the industry standard variety ‘Canby’ has also shown higher than average winter injury at multiple locations, indicating that some of the newer varieties will provide better winter hardiness than the current industry standard. Some varieties showing better than average winter survival include ‘Cascade Bounty’, ‘Cowichan’, ‘Royalty’, ‘Latham’, ‘Killarney’, and ‘Nova’.
Irrigation management was a serious problem at three of the five locations during the 2006 season and in early 2007, with irrigation intervals being too long and/or insufficient water supplied during each irrigation event. To help cooperators improve irrigation practices, resistance block sensors and hand-held readers were purchased with grant funds and distributed to each of the five cooperating sites. Instruction was provided to each cooperator on proper sensor installation and operation. A fact sheet on proper raspberry irrigation management was developed to reinforce the instruction provided.
Poor irrigation management severely affected stand establishment at the Cache, Utah and Washington county locations. Implementing improved irrigation management technology has resulted in marked improvement in plant growth and stand establishment, with the most dramatic effect at the Utah County location.
Irrigation at the Cache location continues to be a problem, as the grower is transitioning from a pressurized secondary surface water system to an on-farm well. Water availability and pressure continue to limit proper irrigation.
Weed control has been problematic at two locations and has further limited stand establishment. The site of the Cache planting had a pre-existing problem with persistent perennial weeds such as curly dock and field bindweed that have been difficult to control. The Washington location is under organic certification, which has also presented unique challenges to controlling perennial grasses. Weed control at the remaining three locations has been much less problematic.
Insect damage at the organic site has also been a problem, where late-season grass hoppers and other leaf-feeding insects have been problematic.
Fall-bearing varieties have generally out-performed the summer-bearing types at all locations, except Bear Lake. At the three southern most locations (Washington, Utah and Davis), this confirmed impressions that fall-bearers are better suited to production where hot summer climates push the limits of raspberry growth and productivity. In 2008, the fall-bearing cultivars such as ‘Caroline’ did surprisingly well at the northernmost location (Rich). The elevation of this location provides a particularly short growing season, where the peak of the summer raspberry season does not occur until late July to early August. Typically, the freeze-free season in Laketown is considered too short for fall raspberries. Despite mowing off the floricanes to push a primocane crop, the cooperator reported commercially acceptable yields of high quality fruit from the basal floricane regrowth and the primocanes in 2008, with particularly low floricane production due to a harsh winter. However, after these initially promising results, cool late springs in both 2009 and 2010 severely limited productivity of fall-bearing varieties, and this cooperator has since abandoned efforts to grow fall-bearing types for Bear Lake.
Serious attempts at commercial production have been tried by two growers in Washington County. In both cases these growers recognized the potential for marketing fresh berries at local farmers markets and possibly restaurants. The two areas, New Harmony and Enterprise, located at the northern boundary of Washington county have significantly cooler summer temperatures (an average of 10-15 degrees) than the St. George area. Although, summertime highs are typically in the mid-nineties, this only lasts until around August 1-15 and then temperatures begin to cool off, especially at night. These temperature trends caused us to focus attention on “Primocane” or fall-bearing varieties. We projected that fall-bearing types would begin to ripen just about the time when temperatures were cooling off, and this would allow for good berry size and flavor.
A concern which emerged as a bit of a surprise to us in these southern growing areas was the effect of winter time low temperatures on summer bearing varieties. It is not unusual for low temperatures to drop into the teens and in some cases near zero, particularly at the Enterprise site. These conditions seemed to repeat both winters 2008-09 and 2009-10. “Floricane” damage on summer-bearing varieties was estimated at around 70% during the 2008-09 season. The following winter of 2009-10, damage was higher at nearly 100% and was observed on all summer varieties. Snowfall was unusually high (December 2009 through April 2010) but did not seem to provide additional protection. We observed this damage on both raspberries and blackberries.
As we begin to write our recommendations regarding variety selection, these observations will play a critical role. Our concern about mid-summer heat and its affect on “Floricane” varieties has been overshadowed by heavy losses we experienced both winters on these plants. There is some interest by growers in using polymer type products on overwintering canes to prevent damage. This has been shown be helpful in locations where wind is a major factor, but it is doubtful that much protection will be afforded where the main obstacle to production is low temperature.
Educational & Outreach Activities
As a result of the difficulties in helping cooperators understand proper irrigation management for these plantings, we developed an extension fact sheet outlining proper irrigation strategies for cane fruit including raspberry and blackberry. This fact sheet has been peer reviewed, distributed to field day participants and is now available online.
During the 2007 season, the UBGA held one of their annual summer farm tours in Rich County, with half of the tour centered at the variety trial at that state. Participants toured the plots where each plot was prominently labeled. The grower-cooperator shared his impressions of these varieties with tour participants. Irrigation scheduling techniques were also explained. The field day was attended by 24 participants from across Utah and southern Idaho. In 2009, the UBGA had a variety showcase at the Kaysville site on July 16, with approximately 27 participants.
In both 2008 and 2010, the UBGA co-sponsored a field day at the Kaysville research farm, which featured tours of the tree fruit, berry crop and vegetable crop research at the farm. The prominent feature of the berry crop tours was the variety trial at that location. The field days were held in August, at the end of the harvest season for summer bearers, and at the beginning of the fall-bearer harvest. Approximately 90 participants attended both years. These represented large- and small-scale commercial growers, market gardeners and serious hobbyists from across Utah and southeastern Idaho.
The UBGA publishes a quarterly newsletter and articles regarding both summer tours were published in the newsletter. This newsletter is sent out both in hard copy and electronically to over 900 addresses and is also posted online (extension.usu.edu/publications, under the “Horticulture” heading). These newsletter articles have resulted in a number of telephone and email inquiries for more details on the results of this trial.
(http://extension.usu.edu/files/publications/newsletter/pub__5544137.pdf, see page 2).
During the 2009 and 2010 seasons, in addition to collecting yield data, USU Extension Entomologist Dr. Diane Alston has been observing several of these plantings to study insect damage patterns. Raspberry horntail, a clear-wing moth whose larvae bore into and destroy developing primocanes, is proving to be a significant insect pest in the region. Dr. Alston has been studying feeding patterns in several of these trial plantings to determine whether horntail preferentially feed on specific raspberry varieties and whether or not cultivar selection could be a management tool in controlling horntail. Results from the two seasons are indicating that there appears to be some preferential feeding, but more research is needed to develop specific recommendations or control strategies.