By Forrest Scharf, PAg., Provincial Specialist, Fruit Crops
Last winter was tough on plants and bees. Raspberries suffered the most plant damage. Hardy varieties like SK Red Mammoth, SK Red Bounty only suffered tip-kill to roughly the top quarter of the canes, but some less-hardy varieties like Nova suffered more extensive damage.
Depending upon microclimatic factors, some susceptible varieties experienced floricane death and, in those patches, marked yield loss will be experienced in 2018. Luckily, in every site witnessed, primocanes are growing vigorously and the patches are overcoming last winter’s adversity. In addition, the varieties that only suffered some tip-kill were able to serve as hosts to high concentrations of bees (perhaps because canola and other flowering crops were somewhat late in many regions so bees had to source nectar and pollen from a limited number of sources). In regards to raspberries, despite the fact that over-winter bee mortality was reported to be extremely high, bees have provided ample pollination service.
In some areas of the province, early-flowering crops like haskap and strawberry reported low bee visitation rates in spring. Haskap is known to be extremely hardy, and those plants suffered very little plant damage. They also appeared to flower relatively profusely this year. This crop requires pollination for the fruit to set and, without it, yields drop precipitously. In pockets where wild bee populations successfully overwintered, pollination was strong and yields were reported to be average to above average. Unfortunately, in extensive areas where honey and wild bee populations succumbed to more loss, pollination was down and this had a significant negative impact on yield. In regard to strawberry, the standard June-bearing varieties overwintered relatively successfully where they were properly covered with straw and snow. In relatively few cases, the straw and snow were blown off, and then the plants appeared to have dried out and died. Plant loss was more pronounced in day-neutral and everbearing varieties. Those strawberry types are often bred in more southern locales, and they were typically selected in ideal soils for strawberries where pH is between six and seven. Many Saskatchewan soils have high pH, and this causes some varieties to experience micronutrient deficiencies. When micronutrient deficiency is combined with a harsh winter, it is difficult for strawberries to survive and produce high yield. In some areas, early flowering did not entice enough bees, and, due to lack of pollination and seed development (signalling for the fruit to develop below the seeds), “cat-facing” was evident. As the season progressed, the number of bees increased and the amount of pollination was sufficient (lack of pollination may have been more evident in areas of the province that were dry in 2017, and the poor conditions in those regions contributed to poorer production).
The fruit crop that appears to have succumbed to the greatest overall yield loss is dwarf sour cherry. The sour cherry plants did not suffer significant tissue death and most varieties displayed full blooms, but after the blossom stage, the vast majority of flowers and early developing fruit aborted. Frost damage can cause similar effects, but in 2018 most regions did not report frost during the bloom period. Inspection of vascular tissues did not show significant signs of winter damage, so it is suspected the low fruit-set resulted from more general poor plant physiological conditions. In many regions, fruit-set in 2017 was quite strong, so the plants may have exhausted their energy balance and set themselves up for a weakened yield in 2018. Cherries don’t fully ripen until mid-August, so fruit quality is not known at present. In any event, with fewer fruit, the cherries that are retained are likely to size larger and perhaps contain higher concentrations of sugar than previous years.
Dwarf sour cherries are self-pollinating, so pollination did not play as significant a role in yield potential as it did in many other fruit crops.
Most other fruit crops weathered the winter relatively unscathed, and obtained sufficient pollination to produce average yield potential. In general, fruit quality has been high with sugar accumulation being above average for the crops that have already ripened.
For growers interested in improving their stock of wild bees, and in learning how to better manage bees, a Pollinator Biosecurity Specialist has been hired at the Saskatchewan Ministry of Agriculture. Graham Parsons has taken on that role, and has been active in promoting better management in some orchards already. He joins the veteran Provincial Specialist (Apiculture), Geoff Wilson, whose role is more predominantly focused on honey bees. Graham has started experimenting with manufacturing bumble bee hives, and should be the first person to contact if pollination isn’t meeting long-term orchard goals.