The intensive agricultural practices required to produce almonds place immense and cumulative stress on the honeybee colonies rented for pollination. Almonds are a unique crop in that their entire yield depends on honeybee pollination, demanding a level of logistics and hive density that is severely taxing on the bees’ health. This necessary agricultural process subjects the colonies to a combination of physical trauma, chemical exposure, and nutritional deficiencies. The annual movement of millions of managed colonies into California’s Central Valley exposes the bees to conditions that compromise their immune systems and overall survival.
The Scale of Almond Pollination
Almond production is uniquely dependent on the European honeybee (Apis mellifera), requiring near 100% cross-pollination to set a commercial crop. This biological requirement necessitates a massive logistical operation, as the almond bloom occurs early in the year, before local bee populations can meet the demand. Roughly 70 to 80% of all commercially managed honeybee colonies in the United States—about two to three million hives—are temporarily shipped to California’s almond orchards each February.
This sheer concentration of hives in a single geographic area is unparalleled in agriculture. The required stocking rate for many almond varieties is two strong colonies per acre to ensure maximum nut set. This mass migration and density set the stage for the subsequent challenges of disease transmission, chemical exposure, and inadequate nutrition.
Chemical and Nutritional Stressors
Chemical Exposure
Honeybees in almond orchards are simultaneously challenged by chemical exposure and a poor-quality diet. The almond bloom’s timing coincides with the need for growers to apply fungicides to prevent fungal diseases like brown rot. While insecticides are acutely toxic, the heavy use of fungicides during bloom creates a subtle but damaging problem. Fungicides weaken a bee’s immune system, interfere with metabolism, and disrupt the gut microbiome, making the bees more vulnerable to parasites like Nosema and various viruses. Furthermore, fungicides are often applied in a ‘tank mix’ with other chemicals, which can create a synergistic effect that dramatically increases toxicity, sometimes causing acute mortality.
Nutritional Deficiencies
The second major stressor is the nutritional inadequacy of the monoculture environment. Almond pollen is abundant during the bloom, providing the colony’s first major natural food source of the year. However, this single-source diet lacks the necessary diversity of pollen sources—amino acids, lipids, and micronutrients—that a healthy colony requires. A diet consisting only of almond pollen leads to nutritional stress, reducing the quality of the royal jelly fed to the queen and larvae. Colonies fed a monofloral diet have shown lower brood and adult bee populations and higher infection levels of pathogens. Since well-nourished bees are better equipped to withstand other stressors, this lack of diverse forage is a compounding factor in colony decline.
The Physical Toll of Commercial Transport
The necessity of bringing millions of colonies to California requires a system of migratory beekeeping that imposes significant physical stress on the bees. Hives are loaded onto flatbed trucks and transported hundreds or even thousands of miles from states as far away as Florida. This long-distance hauling subjects the colonies to constant vibration, temperature fluctuations, and air turbulence for days at a time.
The transportation process can lead to temperature stress within the hive, with smaller colonies being susceptible to chilling. This physical trauma triggers a biological stress response, altering gene expression related to immune activity. Following pollination, the colonies are often kept in crowded, temporary holding yards, which increases the likelihood of disease transmission and parasite spread, such as the Varroa mite.
Mitigating the Impact on Honeybees
The almond industry and beekeepers are actively implementing strategies to reduce the harm caused by these combined stressors. A primary focus is on improving the nutritional environment for the bees by diversifying the forage available in the orchards. Many growers are now planting flowering cover crops between the tree rows to provide a polyfloral diet, with programs like Seeds for Bees assisting in creating these pollinator habitats.
Growers are also adopting Integrated Pest Management (IPM) practices to minimize chemical exposure. These practices include avoiding insecticide application during bloom and ensuring necessary fungicide applications occur in the late afternoon, after the bees have returned to the hive. Ongoing research also focuses on improving hive inspection and treatment protocols for mites and pathogens before colonies are shipped to California.