David Doll0 commentsNovember 29, 2020General, Horticulture

Factors to Consider when Determining Honeybee Hive Needs for Almond Orchards

Determining the number of hives to rent for an almond orchard can be challenging. With a strong reliance on honeybees for pollination, placing too low of number of hives and bees can reduce crop potential, especially in inclement weather, while placing too many increases operational expenses. To determine the proper hive strength for the almond orchard, the following factors should be considered: Varieties present within the orchard Age of the orchard Strength of the hives contracted Crop insurance requirements Anticipated weather for the orchard’s production area; Presence of other pollinators. Almond Varieties within the orchard. All almond varieties benefit from having pollinators present during bloom. In California and Australia, the primary varieties planted are ‘Nonpareil’ and the selected compatible, pollinating varieties. Since these varieties, as well as others (e.g.’Butte’/’Padre’), require cross-pollination to set a nut, bees are required to maximize orchard yields. Due to the requirement for cross-pollination, the recommendation by the University of California has been to place two 6-8 frame hives per acre (5 hives per ha) to maximize pollination (Micke, 1996). In Europe and more recently in California and Australia, self-pollinating almond varieties are present. These varieties do not require pollen from a compatible variety to fertilize the flower. In these orchards, bees are not required to set a commercial crop, but they have shown to increase yields. In Europe, studies have shown yield increases between 5-20% amongst European varieties. In California, the presence of honeybees has shown to increase yield by 20% or more within ‘Independence’ (Saez, et al, 2020).  These studies indicate that bees should be placed to optimize pollination, but suggest that the number of hives per acre can be fewer. In Europe, 1-1.25 hives/acre (2-3 hives/ha) are common stocking rates within orchards that utilize bees. This may be a reasonable range to consider

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David Doll0 commentsJanuary 10, 2016Horticulture

Can mechanically-applied pollen either supplement bees, or ensure an almond crop in the event of bee inefficacy or unavailability?

Written by Elizabeth J. Fichtner, Farm Advisor, UCCE Tulare County and Katherine Wilson, Staff Research Associate, UCCE Tulare County Each year during almond bloom, a fraction of growers try artificial pollination as either a supplement to bee pollination or an insurance policy against bee-inefficacy.  Several factors may impact the availability and efficacy of bees as pollinators for California’s (CA) almond crop. Increasing almond acreage has increased the overall demand for hives while chronic honey bee health issues limit hive supply.  Additionally, bee efficacy for pollination may be challenged by adverse weather conditions during bloom.  In an effort to either supplement bee pollination or provide an insurance policy against inefficient bee-pollination, growers have utilized two different approaches to artificial pollination:  1) mechanical application of pollen to trees by blowers or airplanes, and 2) insertion of pollen dispensers (‘inserts’) into hives. Conceptually, the application of pollen to trees by blowers relies on bee activity to redistribute pollen within the orchard; only a small amount of the blown pollen would be deposited directly on receptive stigmas. Several research studies, however, have demonstrated that techniques involving “blowing” pollen onto trees have no benefit as a supplement to bee pollination on fruit set or yield (ie. Schupp, 1997). A published 1966 almond research trial similarly demonstrates a lack of benefit of supplemental, mechanically-blown pollen on Nonpareil nut set and yield in a 2:1 block of Nonpareil and Mission (Thorp et al., 1967).  Conversely, a study in 1978 demonstrated a value of mechanically-blown pollen on nut set (Thorp, 1978), but replication of the study in 1979 did not demonstrate any effect of artificial pollination (Thorp, et al. 1979). The orchard housing the 1978 and 1979 trials was chosen due to its unfavorable varietal combination (1:4:1, with 4 contiguous rows of Nonpareil) –a combination not utilized by

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David Doll0 commentsFebruary 5, 2011Horticulture

Supplemental Pollination – What we (don’t really) know

I had a few questions this week about supplemental pollination to increase the amount of compatible pollen available for almonds. Mainly, the growers were asking about the feasibility of increasing compatible pollen in orchards with only one pollinator variety or in orchards with greater than 50% Nonpareil. Here was what I was able to dig up: Research: – Work conducted by Robbin Thorp determined that application of supplemental pollen by modified ground rig, helicopters and beehive inserts did not increase fruit set or yields in orchards with adequate cross pollinating varieties; – However, a 2006 study by Tom Gradziel indicates there may be benefit when using hexane washed pollen (removes sticky pollenkit and the pollen does not clump) dispensed at the hive entrance. In this experiment, trees were caged and pollen parentage was tracked. They found that 6% of the almonds were pollinated with the washed pollen. Comments: In many of the older trials, pollen sourced for the experiment had questionable viability. It is important to know if the pollen is viable and able to germinate, form a strong pollen tube, and fertilize the almond embryo. Pollen viability is not the only limiting factor; stigma receptivity also affects nut set. This is why flowers are the most receptive to pollen within the first few days after opening and explains why an extended bloom usually means a reduce crop. It may be reasonable to try to provide extra pollen, delivered by honey bees, when there is no other variety providing overlapping bloom. It is important to note that it is extremely difficult to determine if the extra pollen improves crop production. Studies (paternity tests) have demonstrated that supplemental pollen is able to fertilize the embryo in orchards where they have been applied. Then again, how can you prove that those nuts

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