We propose to examine the feasibility of producing early season, floricane producing raspberries and blackberries in Colorado. Early season (late June or July) locally produced fruit is in high demand in Colorado. Fruit at this time of year sells at a premium price compared to late season fruit, and has the potential to drive sales of other early season produce at farm stands and farmers markets. Further, early season fruit ripens before spotted wing Drosophila (SWD), a new and now key berry pest, is most active in the field. Development of economically viable early season berry production techniques would both increase farm revenues and reduce management costs and losses from this pest. For producers that follow organic management practices (such as ourselves) there are few management options other than rigorous culling of damaged fruit that are effective in managing SWD damage. Shifting the majority of berry production to earlier in the season has the potential to be an environmentally and economically sustainable production strategy.
This project will determine if active management of tunnel temperatures allows for early season raspberry and blackberry production in Colorado. With the added protection of high tunnels and minimal supplemental heat, organic floricane raspberry production in this region may be very feasible. This project will compare results from of high tunnel raspberry production to field production with row covers. Further, the data we record on the efficacy of frost and freeze protection within tunnels would be useful for many other crops grown in Colorado and other cold weather locations.
1) Measure internal and external temperatures and determine the efficacy of fall and spring temperature management within high tunnels using a combination of:
a. Side and end wall ventilation for cooling b. Fans for frost protection c. Floating row cover for frost protection d. Portable heaters for freeze protection
2) Measure the effect of fall and spring temperature management on fruiting timing and yield for 7 raspberry and blackberry varieties.
3) Measure insect and disease pest pressure on these varieties and compare these to those seen on raspberries grown in the open.
4) Transfer the results of this project to small growers and the public using extension publications, YouTube or other social media videos and facebook posts and field days.
This is a progress report, and we have not yet finished collecting data. As the experiment progresses we will report our impacts and outcomes and transfer the results of this project to bramble growers in Colorado and other intermountain states.
In summer 2015 we planted a total of 98 Raspberry plants in two management blocks – open field (OF) and protected by a high tunnel (HT). In each of these treatment units we established 7 replicates of 7 varieties in a randomized block design. In April, 2016 we completed construction of the high tunnel. In June and July 2017 we counted the number of floricanes on each plant. At this time we also estimated damage from spider mites by visually assessing leaf condition. Plants were placed into 4 categories: 0 (no mite damage observed), 1 (feeding marks / leaf cupping on less than 10% of leaves) 2 (feeding marks /cupping on more than 10% but less than 50% of leaves), 3 (feeding marks / leaf cupping on more than 50% of leaves or 4 (stippling common, presence of webbing, evidence of leaf death).
Overwintering survival of floricanes. Although construction and covering of the high tunnel was not completed until April, 2016, there were differences between OF and HT berries for the number of floricanes that survived to produce fruit (Figure 1). For every variety, HT canes had more floricanes than open field canes. For one variety this effect was modest (Royalty) but for others this effect was much greater (Nova, Encore and Tulameen). These preliminary data suggest that HT do increase floricane survival, and that this effect is greater for some varieties than for other.
Pest densities. As of July, 2016, the only significant insect pest has been two spotted spider mites. In early June, we released 4,000 commercially produced Galendromus occidentalis in each treatment to try and stave off mite populations. This was not successful in the HT treatment. By the end of June, several of the varieties in the HT had extreme levels of mite damage (Figure 2). In contrast, mite densities never reached high enough densities to cause visible damage to the OF plants. IN the HT, not all varieties were equally damaged. Cowichan was particularly hard hit, with many of the brambles damaged to the point of webbed leaves and early leaf senescence. In early July all brambles were sprayed with a mixture of canola and soy oil to reduce mite infestations.
Future work. 1) Collect data on timing of fruit ripening for each variety in each treatment. Measure floricane overwintering success this winter, with a high tunnel in place for the entire winter. Collect detailed data on HT temperature management over next fall – winter – spring.
At this point in our project, several varieties of floricane fruiting brambles are established in a high tunnel and replicated outside in the field. The plants are vigorous and the canes are overwintering, however we have been unsuccessful at achieving a crop in the high tunnel brambles for 2 seasons. So far there is no significant advantage to growing the brambles in a high tunnel. The high tunnel may even be counterproductive compared to outside growing. The average daytime temperature increase of 15 degrees in the high tunnel is not providing enough nighttime protection in the spring. SWD pest pressure appeared earlier than ever on the few fruits that were present in the high tunnel. Unlike in 2016, spider mites numbers were low on all varieties in the high tunnel and were below detection levels in the field. Poor fruiting may be attributed to lack of chilling in the high tunnel environment, or too much temperature fluctuation. In 2017, bud break on high tunnel floricanes occurred 3 weeks earlier than outside. However, the high tunnel plants had very few flowers on floricanes. The lack of flowers may be due to a late freeze of 20 degrees on May 18.
In 2017 high tunnel temperatures averages 3.5 degrees warmer from February-May, and 1.7 degrees warmer from September-January. This winter we are experimenting with minimizing daytime heat in the high tunnel in order to ensure that the plants achieve appropriate chilling. Temperatures are being monitored closely.
Two winters of trials demonstrated that high tunnels do not offer a way to increase production of early season, floricane fruiting brambles. Both in both 2017 and 2018, canes in the high tunnel did not produce any early spring fruit, while fruit while canes growing outside did. In Colorado, high tunnels provide no significant advantage over open field production for floricane fruiting brambles. During winter, temperatures fluctuate too much in the high tunnel. Without supplemental nighttime heat the fruit buds freeze late in the spring. The high daytime temperature interferes with achieving adequate chilling. Unheated high tunnels are not recommended for floricane bramble production in Colorado.
Educational & Outreach Activities
Education and Outreach will take place in 2018.
Project outcomes will be shared in 2018