Honey bees (Apis mellifera), as we have discussed many times before, are an extremely important pollinator for many of the crop plants that make up our agricultural ecosystems. One third of the food we consume depends on honey bees for its pollination! The need for honey bee pollinators, often at a very specific time in the development of a crop and often for just a few short weeks, has increased right along with increased productivity of our industrial agricultural systems!
This growing need for honey bees has led to the development of an industry in which billions of hived honey bees are trucked about on flatbed trailers from one end of the country to the other in order to accomplish each region’s and each crops’ essential pollination. Along this yearly circuit of bee transportation the bees are also taken to areas where they can rest, recover and reproduce. According to the non-profit “Bee Informed Partnership,” though, about forty percent of these industrial bee colonies die each and every calendar year.
The causes of the bee colony deaths are varied: the stress of transport, the exposure to high load of pesticides and herbicides in the agricultural fields, infections with viruses and infestations with mites probably interact synergistically to kill off the colonies. The cost of this colony death rate is staggering, and this cost gets passed on to everyone who contracts with the bee industries for assisted pollination.
Beekeepers are developing ingenious ways to deal with mites and viruses and even transportation stresses, but they can do very little about the ever increasing levels of agricultural chemicals in the environment or about the shrinking reserves of natural vegetation upon where they formerly rested and refueled their colonies. Honey bees may be approaching the upper limits of what they can accomplish in our agricultural systems!
Wild bees and other insect pollinators have been shown in a number of published studies to be much more effective pollinators of crop plants than the “industrial” honey bees both in terms of numbers of flowers visited and amount of fruit or seed set. Also, when a crop is pollinated by both honey bees and some other bee species, there seems to be a synergistic impact on the efficiency of the pollination. This has been observed in almond orchards in California. Orchards with surrounding flowering plants supported a wild bee population that helped the “industrial” honey bees pollinate the almonds. It has also been observed in cherry orchards in Washington State. Orchards produced twice as many cherries as they had in previous years after populations of native, blue orchard bees were established to augment the pollination work of the “industrial” honey bees.
Wild and alternative bee species gather and transport pollen in slightly different ways than honey bees, and the combination of these different types of pollen transport may make the overall crop pollination effort more efficient. These non-honey bee types of bees also have different flight patterns and activity levels within the branches of the nut and fruit trees and, thus, pollinate different flowers in different parts of the tree crowns. Wild and many alternative bees also readily work at temperatures that are too cool for honey bee activity.
A recent article in the New York Times (“Honey Bees Are Hurting,” August 21, 2018) listed four commercially available, alternative bees in the United States: the blue orchard bee, the bumble bee, the alfalfa leafcutter bee, and the ground nesting alkali bee.
The blue orchard bee (Osmia lignaria) is a type of mason bee and displays many of the life cycle features that we have discussed before (see Signs of Spring 8, April 19, 2018). These bees are native to North America and readily pollinate fruit and nut trees during their month or two of spring activity. Females build their mud partitioned nests in a variety of types of holes and readily use artificial paper tubes just like their eastern, mason bee relatives. Populations of these bees and the timing of their emergence can be controlled by the manager of the orchard crop. The blue orchard bees used in the Washington State cherry orchard cost the cherry grower fifty cents each! Realizing that this cost could be avoided by providing the bees a safe place to construct their nests within or near the orchard, the cherry farmer took on the task of nurturing the bees. “If I double my cherries, I’ll do the extra work,” he said.
Bumblebees are any one of 250 species of bees all in the genus Bombus. Forty six of these Bombus species are native to North America. Bumblebees are robust pollinators that form small colonies (50 to 400 individuals). They are capable of traveling between one to two kilometers from their nests to find flowers. Bumblebees are important pollinators of tomatoes, pumpkins, squash, watermelons, blueberries and cranberries.
The alfalfa leafcutter bee (Megachile rotundata) is a European bee species brought to the United States specifically for the pollination of alfalfa. Alfalfa flowers are not easily pollinated by honey bees. The leafcutters are solitary bees that make tubular nests that they line with cut-up leaves. Within the nests eggs and balls of gathered pollen and nectar are sealed up in chambers formed by the leaves. These bees are now found all across the United States in both managed and feral populations. In addition to pollinating alfalfa they also pollinate both fruit and nut trees.
The ground nesting alkali bee (Nomia melanderi) is a native North American species. Primarily found in the west and southwest, this solitary bee prefers to nest in soils enriched with salts. Alfalfa farmers, decades ago, found that if they disturbed or plowed up the surrounding salt flats near their alfalfa fields, productivity of their alfalfa crop greatly declined. These bees now are widely managed and encouraged through careful cultivation of their salty-soil habitats.
“Integrated Crop Pollination” is a public-private program funded in part by the Department of Agriculture. An important paper published in Basic and Applied Ecology in 2017 describes the objectives and structures of this new system of crop pollination. This program is exploring ways by which the presence of wild bees in our agricultural systems can be augmented. Logically, this will involve the establishment of wild, flowering plant areas in and around the agricultural fields. Providing a nursery and a refuge for wild pollinators may also result in improved habitats for the industrial honey bees! The program also wants to determine the best alternative bees for particular crops in different regions of the country. They are also planning to conduct experiments to try to determine the basis for the observed pollination synergies between honey bees and alternative bee species, and to better understand the interspecific interactions between the honey bee and the myriad of wild and alternative bees.