Current honey bee and bumble bee stocking information

Benjamin Phillips<benp@msu.edu>, Michigan State University Extension - April 12, 2019

Honey bees and bumble bees can be rented or purchased for crop pollination at appropriate stocking densities.

Current pollinator recommendations

Honey bees have long been the bee of choice for fruit and vegetable crops in the United States. They have traditionally been easy to manage in man-made environments, forage gregariously and can be coaxed into pollinating nutrient-deficient flowers such as those of cucurbit and solanaceous crops. Michigan State University Extension has reviewed the most up-to-date research literature on honey bee hive recommendations and rental fees in Table 1.

Beekeeper rental fees depend on the amount of travel required, hive count and the nutrition of the nectar and pollen of the crops they will be pollinating. Additionally, some cropping systems have a wide variety of recommendations dependent on the presence of existing pollinators, crop flower attractiveness, planting densities and harvest timing.

In general, if your business model requires high densities of a uniform fruit size on large acreage within a short window of time, your best bet is introducing a high density of bees shortly after the first viable flowers bloom and then removing them after a couple of weeks. If you hope to make multiple harvests on a small scale, then often you will find that crops will require a smaller hive density for a longer time, or no hives at all in cases where native wild bees are present and healthy.

Table 1. Recommended honey bee hives per acre. Denotes a general price for uncategorized produce crops in the Midwest Region. -Denotes that honey bees are not required for the pollination of these crops, but may improve fruit set.*
Crop	Published recommended hives per acre: range (avg)	USDA NASS 2017
Tomatoes, eggplants, peppers	-	86.20*
Beans, peas	-	86.20*
Squashes, zucchini	0.04 – 3 (1.5)	67.80
Cucumbers	0.1 – 4 (2.2)	67.00
Watermelons	0.2 – 5 (1.8)	77.70
Muskmelons, cantaloupes	0.2 – 5 (1.8)	86.20*
Pumpkins	0.04 – 3 (1.5)	76.20
Blackberries	1 – 4 (2.7)	86.20*
Raspberries	0.2 – 1 (0.8)	86.20*
Strawberry	0.5 – 10 (3.5)	86.20*
Blueberries	0.5 – 10 (3)	77.30
Cranberries	0.2 – 10 (3)	78.00
Apples	0.25 – 5 (1.5)	70.90
Pears	0.4 – 2 (1.5)	86.20*
Plums, prunes	1 – 2 (1.3)	86.20*
Peaches, nectarines, apricots	0.08 – 2 (0.8)	86.20*
Cherries	0.5 – 5 (1)	56.60

Table 1 information was aggregated from Crop Pollination by Bees and Insect Pollination of Crops. Costs per rental hive are based on USDA NASS data from 2017 in the Midwest Region.

The current recommendation for stocking density of commercial bumble bees in field produced vegetables and fruit is 0.5 to three colonies per acre. A Quad is a unit sold by Koppert with four individual colonies packaged together, and the Multi-Hive is a unit sold by BioBest with three individual colonies packaged together. Additionally, colonies should be spaced out in the fields, and not on the edges.

Research has shown that stocking commercial bumble bee colonies in open field-grown vine crops and blueberries results in similar yield and fruit quality performance as fields stocked with honey bees, or with high natural pollinator populations. However, bumble bees increase yields of greenhouse crops with their ability to orient themselves to the missing UV spectrum from glass and plastic coverings better than honey bees, and their more docile nature. Additionally, with the increasing likelihood that spotted wing Drosophila will force some small plantings of caneberries and blueberries under netting, bumble bees could be an effective pollinator for these as well.

Current recommendations are one to three bumble bee colonies per quarter acre of enclosed space. For a 30-feet by 48-feet, up to a 30-feet by 192-feet greenhouse, one standard bumble bee hive size is actually too many bees for the size of most tomato, pepper or vine crop hoop houses in Michigan, which could possibly factor into over-pollination and blossom drop if you can rule out other environmental conditions that cause similar problems. Whenever possible, ask about the starting number of bumble bees in a colony, choose whichever is smallest for your hoop house and shut bumble bees inside their colony if you begin noticing deeply bruised flowers. Bumble bees can live off supplemental sugar water and honey bee pollen in their colonies until plants are ready for them.

Lifecycle differences between honey bees and bumble bees

Interconnected factors, including sublethal pesticide accumulations, diseases, parasites, transportation stresses and flower availability, have been observed to increase winterkill and rental costs in the United States. This has fanned the flames of research on the commercial viability of other pollinators. Fortunately, through laboratory research on bumble bees in the 1950s, methods were developed to maintain colonies in man-made settings.

By 1980, a small commercial industry started growing around Large Earth bumble bees (Bombus terrestris) in Europe and Common Eastern bumble bees (Bombus impatiens) in North America. Important life history differences affect their applicability in crop systems and their cost (Table 2), but these species were found to be especially adept at pollinating blueberries, cranberries, tomatoes, eggplants and peppers. Current recommendations for bumble bees are extrapolated from research in the aforementioned crops, until more trials have been performed in other crops.

Table 2. Differences between bumble bees and honey bees regarding applicability in crop systems and costs.
Factors	Bumble bee	Honey bee
Wild nest habitat	Old mammal burrows, holes, thickets of grass	Trees, ledges, internal walls of buildings
Overwintering habits	Queens abandon workers and overwinter alone	Queens and workers overwinter as entire colony
Lifespan	6-12 week lifespan	Perennial
Pollen and nectar affinity	Nectar and pollen collectors	Primarily nectar seekers
Greenhouse applicability	Successful indoor applications	Best in the field
Forage activity	Active above 50 degrees Fahrenheit, can forage in wet, dark, windy weather	Active above 60 F, prefers clear, sunny, placid weather
Hive climate preferences	Hive maintained at 86 F	Hive maintained at 95 F
Hive population	~75-200 bees per colony	~20,000-60,000 bees per colony
Hive cost	~$135-$175 per colony	~$56-$86 per colony*

Information was aggregated from Insect Pollination of Crops and Best Management Practices for Using Commercial Bumble Bees on Horticultural Crops in Delaware. *Hive cost range does not include the cost of renting to almond growers, as that is an outlier.

Full list of references mentioned in tables:

Delaplane, K.S. & Mayer, D. Crop Pollination by Bees. (CABI Publishing, 2000).
USDA National Agricultural Statistics Service. Cost of Pollination. (December 2017).
Free, J.B. Insect Pollination of Crops. (Academic Press, 1970)
Marchese, J. Delaney D. & Johnson, G. Best Management Practices for Using Commercial Bumble Bees on Horticultural Crops in Delaware. (Cooperative Extension Delaware, 2013).
Morandin, L., T.M. Laverty, Peter Kevan. Bumble Bee (Hymenoptera: Apidae) Activity and Pollination Levels in Commercial Tomato Greenhouses. (Journal of Economic Entomology 94(2):462-7, May 2001).

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).