Honey Bees in Self Pollinating Almonds
Abbas Edun
Globally, pollinators are on the decline; several factors have contributed to this dramatic and disturbing trend. They include the use of pesticides, climate change, and habitat fragmentation. The spread of pathogens, parasites and predators has also added to the dilemma. And, the number of managed honey bee colonies is not keeping pace with the agricultural demands for pollination.1 Because of these trends in availability, the breeding programs of many crops which are dependent on honey bees have concentrated on reducing the need for so many of them.
Almond is the name applied to the fruit as well as the tree of Prunus amygdalus.2 Americans consume more almonds than any other nut. 3Their per capita use grew 200 per cent from 0.8 pounds in the season August 2000 – July 2001 to 2.5 pounds in 2020/2021. Production in the U.S. has grown steadily as demand, both domestic and foreign, has risen. California is the world’s leading producer of the nut; it grows more than three quarters of the world’s supply. In 2020, production was over 3.1 billion pounds, valued at $5.6 billion.
Nonpareil, one of the top ten standard varieties, is the cultivar that is most widely planted in the state.4 It is one of many self-incompatible5 crops that cause commercial orchards to include a pollenizer.6 However, there are some types of trees that do not require pollen from others; they are self-fertile.
There has been much interest in recent years in the planting of self-compatible almond varieties. They are seen as a way to decrease pollination and other production expenses. Dr. Craig Ledbetter, in collaboration with the Almond Board of California (ABC), has been working on the development of a new line of such trees.7 It provides growers with an alternative to traditional bee-pollinated ones.
Although self-pollinating almond trees can produce a crop with only wind pollination, they are not entirely independent of pollinators. The conclusion of a study published recently is that pollination by honey bees significantly increases the fruit set and yield of self-fertile almond varieties.8 Farmers who are planning to grow any one of such varieties, are therefore advised to continue using honey bees in the pollination of their orchards.
The ability of a new cultivar to produce an abundant harvest without the need of a pollinizer makes it very important to California’s almond industry. It is the most important crop in the state; the blooming period of its flowers is the earliest and one of the shortest. It begins early in February and continues until the middle of March.
The total amount of hives permanently located in the state is about half a million,9 but there are nearly 250,000 orchards.10 Such a large number requires at least two million hives, two-thirds of the nation’s commercial supply. Almond farmers therefore have to rely on the help of migratory beekeepers for pollination services.11
The arrival of the itinerant beekeepers–mainly in five counties of the Central Valley (C.V.)–marks the start of a brief spell of turbulent activity.12 It is the world’ s largest annual pollination event,13 and the main one in the beekeeping industry of the state.
Self-fertile varieties require fewer pollinators in the orchard because the pollen has to move only a short distance from one blossom to another on the same tree rather than from that of adjacent pollenizers.14 Such cultivars may be grown in blocks of the same variety, allowing for more efficiency at harvest time. They are also part of the almond industry’s efforts in dust reduction. The equipment does not have to go through the orchard twice in order to harvest the nuts.
Self-fertile almonds are not new; a variety called Tuono has been around for a very long time.15 But it has few of the other characteristics that have made California almonds so popular. The main problem is that, unlike Nonpareil, Tuono’s outside seed coat has a hairy texture, and it has a very thick shell, making only 32% of the kernel edible, compared to 65% for Nonpareil.
Tuono is reliably self-fertile, so it was imported from Spain and used as the pollen-donating parent when Ledbetter began to breed a new almond in 1996; he crossed it with California-adapted almond cultivars and selections.16
One selection was eventually named Yorizane.17 It was very successful; it has Tuono’s genes for self-fertility along with almost all of the traits of Nonpareil. With a high yield in production, excellent vigor and quality, it is the top contender for purchase by farmers who wish to increase the size of their orchards.
Therefore, some growers will have a reduced number of hives in their orchards.
Farmers who are planning to grow any one of such varieties, are therefore advised to continue using honey bees in the pollination of their orchards.
Editor’s note: Because pollination is so incredibly important for almonds, in general, and so many colonies are brought in (approx. two million +) many almond growers of ‘self-fertile’ almond trees get ‘free pollination’ that enhances their yield as honey bees forage widely in many areas.
Honey Bee Pollinating Almond
References
1Pollination is the transfer of pollen from the male part of a flower, the stamen, to the female part, the pistil.
2For a description of the tree, see Edun, A. 2008. Herbal Remedies. Bee Culture. 136(12): 33 & 34. It was brought to California from Spain in the 18th century by Franciscan priests.
3They are very nutritious, have a lot of health benefits, and are used for a wide variety of food ingredients and consumer goods. See Herbwisdom.com, a website that provides articles on many plants.
4It was first introduced in the 1880s. There are approximately 7,600 growers and the majority of their farms are family-owned. About 40 per cent of them have Nonpareil; it ripens in September.
5Self-incompatibility is the general name for several genetic mechanisms by which certain plants recognize and reject their own pollen, thus forcing out-breeding.
6See van Wyk, B. 2019. Food plants of the world. CABI. A pollinizer is a tree with different genetic characteristics. It provides abundant, compatible, and viable pollen at the same flowering time as the plant to be pollinated. The best ones for Nonpareil are the Ne Plus and the All-In-One trees.
7Craig is a scientist in the Crop Diseases, Pests and Genetics Research Unit of the Agricultural Research Service (ARS). The latter is the U.S. Department of Agriculture’s chief scientific in-house research agency. Plant breeding is a branch of applied genetics. New cultivars can only result from a genetic re-organization that causes improvements to the existing varieties in particular characteristics.
8Sáez, A. et al. 2020. Bees increase crop yield in an alleged pollinator-independent almond variety. Scientific Reports. 10(1):3177.
9California’s coastal, desert, foothill, and mountain areas can only support about a half million colonies on a year-round basis.
10In the middle of the nineties, California almond trees covered less than 500,000 acres. In 2020, their orchards cover more than one and a quarter million acres.
11Migratory beekeepers are those who move their hives around the country to pollinate two or more different crops during the year. They are subject to the Department of Food and Agriculture quarantine regulations of California that prevent the entry of colonies contaminated with varroa or tracheal mites harmful to bees.
12The C.V. is a broad, elongated, flat valley that dominates the interior of California. Fresno, Kern, Madera, Merced, and Stanislaus are its leading almond-producing counties. They accounted for 73% of the total bearing acreage in 2020. Their Mediterranean weather and ideal soil are excellent conditions for the trees.
13Bjerga, A. et al. 2019. California Almonds Are Back After Four Years of Brutal Drought. Bloomberg.
14The yield potential of orchards with self-fertile trees old enough to produce fruit is maximized by stocking them with one colony per acre. However, two colonies are the average for traditional varieties.
15Flores, A. 2010. Self-Pollinating Almonds Key to Bountiful Harvests. Agricultural Research. Tuono is the classic variety that is productive without a pollinizer. Many home gardeners have sought a tree that produces nuts when grown alone.
16The basis of all plant breeding is selection, or the choice of plants with the best combination of agricultural and quality characteristics from populations with a variety of genetic constitutions.
17It is the surname of those who originally owned orchards on 138 acres that is now home of the ARS San Joaquin Valley Agricultural Sciences Center. It wanted to honor the persons who maintained the property. Yorizane is identified as Y116-161-99 in the ABC report. It is a public self-fertile variety released by the USDA as of January 2021, and has no royalties or other fees; any nursery is able to propagate and sell it.
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