For a successful harvest, start the season strong. A large crop at harvest requires good bee activity at bloom in the orchard. The current UC general recommendation for bee hive stocking rates is 1-3 strong hives per acre. A strong hive contains at least 8 frames covered with bees, an actively laying queen, and one to two frames of brood. Where cold, rainy and/or windy conditions limit bee flight (remember the 2019 bloom?), two to three strong hives may be needed to supply enough bees to set a decent crop when narrow windows of good bee weather open up. Less than two hives per acre may be sufficient to set a good crop in extended good bloom weather (2020 bloom). Good bee weather is at least 59oF, no rain and less than 10 mph wind speed. [In general, bees begin to forage when temperatures reach 55oF, winds less than 15 MPH and it’s not raining.]
Hive strength makes a difference in pollination activity (see graph below). The more frames covered with bees in a hive means more foraging bees and more flowers pollinated. The best possible start to the season begins with strong hives in the orchard at the start of bloom.
Average pollen collected per hive for a range of hive strengths based on frames of bees per hive over a 7 or 10 day period. Data from Sheesley and Bernard, Cal Ag, 1970
To ensure strong hives in the orchard as bloom starts, pollination contracts should include 1) language stating hive strength and 2) an inspection clause stating that some fraction of the hives will be opened and frames inspected by a third party at or soon after delivery to confirm if the contracted hive strength was delivered. The hive strength check should happen at or close to delivery because, as almond flowers are an excellent food source for honeybees, a four-frame hive at delivery to the orchard can become stronger as the pollination season progresses. Assessing colony strength at the end or close to the end of pollination season is not an accurate measure of the pollination activity at the start of the season when strong hives are most needed.
Growers using lower bee stocking rates (1-2 hives/acre) in an effort to save money are the most in need of contract language stating hive strength and a hive inspection. A single 8-frame hive collects 2.5x the pollen as a 4-frame hive.
Hive health. Where hives are located and bees treated in an orchard can impact hive health and potentially pollination performance. Hive location, availability of clean water and spray programs (materials and timings) all should be considered by growers and communicated with beekeepers. Hive placement plays a role in good bee activity across the orchard. Hives should be placed in locations where early morning sun will warm the hives and in groups in or around the orchard no more than a quarter of a mile apart.
Bees need water and will go find it (somewhere else) if not available in your orchard. Check-in with your beekeeper to decide on location and responsibility for providing watering stations for bees in your orchard. The water stations should be protected from pesticides by covering or moving the station or changing the water, or changing after spraying. Bees can’t drink while flying and can drown trying to get to water if there is no landing site at the water source. A 5 gallon bucket with clean water and an old towel or piece of burlap draped over the bucket lip and into the water works as a bee watering site. The Almond Board of California’s most recent Honey Bee Best Management Practices is available at almonds.com/sites/default/files/2020-12/BeeBPMs_12212020.pdf
Bees can be harmed by pesticides. Certain pesticides and practices can be particularly harmful. In particular, all/any insecticides (except B.t. products such as Dipel) should not be used at bloom. Adjuvants, particularly organosilicones, can harm bees directly and/or increase the impact of pesticides on bees and should be left out of bloom sprays. Foliar nutrients may also harm bees. Protect your bee investment; put only fungicide(s) in the spray tank at bloom.
While both bees and fungicides are needed during bloom in Sacramento Valley almond orchards in most years, the best practices for bee health and crop set require dividing the day between time for bee activity and time for spray activity; a split shift for bees and sprayers (on spray days). This approach lets bees work and then flowers can be protected. Here’s how that works.
The key to good hive health is keeping sprays off the daily pollen load that forager bees carry back to the hive and fed to the brood. Almond flowers release some pollen every morning as humidity drops after sunrise. This occurs for several days after the flower opens. In an orchard with good bee activity, pollen released that morning is stripped from flowers by early afternoon. Fungicide spraying shouldn’t start until then; when pollen available for the day is gone (collected by bees and flown back to the hive). There are a couple of ways to check if the pollen is gone from flowers. If the pollen gathering bees (the ones with yellow lumps of pollen on their hind legs) are just doing touch-n-go landing on flowers, those flowers don’t have pollen left and it’s OK to spray. Another method is to rub the flower anthers (the spikey structures in the center of the flower) between your thumb and fingers and then check for yellow pollen on your hands. If there is little to no pollen on your fingers, the bees have been there and gone. (Wash your “pollen– check” fingers before rubbing your eyes. Don’t ask me how I know.)
Almond flowers provide pollen (and nectar) that build strong hives while providing pollination leading to nut set and a good harvest for growers. The continued success of this annual win/win relationship relies on consideration of the needs of both partners. Growers need strong hives at the beginning of bloom and beekeepers need strong hives at the end of bloom.
Finally, hives should be removed once 90% of the flowers in the last pollinizer variety have shed their pollen. By this time, the colonies have done their job in the orchard and most bees working the flowers will be foraging for nectar, not pollen. The majority of the pollen gathering bees will be foraging off-site and not providing pollination services to the grower who rented the hives. — By Franz Niederholzer, UCCE Farm Advisor, Colusa & Sutter/Yuba Counties