Improving Pollination through bumblebee habitation; Evaluation of nest box types in bumblebee colonization

Note to the reader: Diagrams and other resources referenced in this report are available on request from Northeast SARE. Call 802-656-0471 or send e-mail to nesare@uvm.edu and request final report materials for ONE08-079.

One of the most challenging issues for present day commercial agriculture is the recent dramatic loss of honeybee colonies, which are currently used as the main source of pollination for horticultural crops in the United States. A solution to this problem is encouraging farmers to shift their reliance from honeybees to native pollinators. One of the most efficient species of wild bee, the bumblebee (Bombus spp.), has many advantages.

This project is based upon the premise found commonly in research relating to bumblebees that only a small number of overwintering, fertilized queens, create successful nests. Although the numbers vary somewhat, it is estimated that only 1% of emerging queens develop new colonies. Mice and ant depradation as well as loss of habitat are considered to be the primary culprits impacting colony success.

In this project, we will examine various bumblebee nest box designs along with other variables relating to nest success in order to develop recommendations and plans for growers. This work should result in specific practices that growers can adopt in order to increase their native bumblebee pollinators, thus improving their overall fruit quality.

Introduction:

One of the most challenging issues for present day commercial agriculture is the recent dramatic loss of honeybee colonies, which are currently used as the main source of pollination for agricultural and horticultural crops in the United States. The problem is compounded by the fact that it is a risky endeavor to overly rely upon on a single species of bee, Apis mellifera (honeybee), to pollinate and insure the continuation of much of the nation’s food. The honeybee's crucial role for American farms is illustrated by a Cornell University study showing that honeybees pollinate more than $14 billion worth of seeds and crops in United States. Furthermore, approximately one third of the food consumed in the U.S. is produced through honeybee pollination, according to the Vice President of the American Beekeeping Federation, Zac Browning.

A solution to this problem is encouraging farmers to shift their reliance from the non-native honeybees to the native pollinators. One of the most efficient species of wild bee, which can pollinate a variety of commercially important crops including vegetables, fruit, berries, fodder and medicinal plants, is the bumblebee (Bombus spp.), which presents the following advantages:

-They are active earlier in the spring than honeybees.

-They grab the anthers of flowers and shake them (an important action for freeing the pollen in some blossoms).

-They work on cool overcast days, when honeybees remain in their hives.

-They tend to stay in one crop rather than flying between crops, thus insuring higher success in pollination.

-They stimulate the honeybee to work more efficiently when are in competition, etc.

We propose that a fresh evaluation of how to build and install nesting boxes for bumblebees is necessary to prevent further decline in the number of bumblebee colonies, which are dwindling due to a lack of suitable nesting sites and the very low survival rate of the queen over winter. Additionally, the bumblebee's rising potential in commercial value makes new information on how to provide nesting boxes that will nurture colonies on farms essential for creating a symbiotic relationship between farmer and bumblebee.

Even though many studies have been conducted on bumblebees, information on how to establish and maintain colonies for the agricultural industry is incomplete, inconsistent or contradictory. We are prepared to investigate the benefits of bumblebee colonies over the floundering system of honeybee colonies for commercial purposes as we believe that meaningful knowledge in the field will be of vital importance in developing and maintaining local agricultural business.

For greenhouses crops, several commercial bumblebee breeding companies presently rear bumblebee colonies to sell to plant growers. Considering that the hives for sale have a life span ranging from four weeks to three months, at a price of $700-$1000 for the multiple colonies necessary to pollinate a acre of crop, we believe that a more capable and inexpensive way of introducing long-term bumblebee colonies for the pollination of outdoor crops would be welcomed.

Some of the publicized research concerning methods of establishing bumblebee colonies, such as through the construction of nest boxes, includes the following: Frison, T.H. 1926, Fye, R.E. and J.T. Medler. 1954, Hobbs, G.A., Virostek, J.F., and W.O. Nummi. 1960, Prys-Jones & Corbert 1991, Munn 1998, Kearns & Thomson 2001.

Two main options for bumblebee nest box construction were gleaned from the research: one opinion is that the ideal nest box should have two chambers (one as a nest and the other as a vestibule where food can be provided and the bees can defecate), while the other opinion is that a one chamber box being perfectly sufficient.
Preceding research also tell us that bumblebees utilize their sense of smell and sight to hone in on ideal nesting places. Because of this, some researchers suggest that positioning the man-made nests near obvious land marks such as trees, posts, stumps, rocks, etc. will yield better results. Other studies have shown that drawing some type of pattern at the entrance helps the bees to locate their nest faster. For our project, we have taken into account the bumblebee’s perception of color as indicated by the research. Earlier studies have found that bumblebees can detect colors in the blue range (blue, indigo, violet and purple), and yellow range (yellow, red-yellow, green-yellow, yellow-green), and are most sensitive to hue-discrimination in the violet range and the blue-green to green spectral range, and cannot distinction between black and red.

One of the unresolved issues in the literature is if the nesting height is of any significance to the bumblebee, and if so, what is the optimal height for above ground domiciles. The earlier research presents three main possibilities: 1) the best height for nest boxes is at least 15 inches above the ground, 2) height should be four feet above the ground, and 3) the height of the nest is not important as long the nest is protected from flooding, excessive humidity, wind and heat.

As there is no general consensus in previous research in standards for bumblebee nest boxes, and there is scant information on the success rate of different types of nests, we will test several models based on variations in design, color, and height to determine the most suitable conditions for a robust bumblebee colony. We also recognize that the previous research on bumblebees is not readily available to farmers and therefore, as extension educators, it is our duty to share with our cooperating farmers proven, practical, and user-friendly guidelines in how to install man-made nest boxes with the express purpose of creating and maintaining a system of crop pollination with the bumblebee population.

Our goal is to determine what the most desirable habitat conditions are to encourage bumblebees with man-made domiciles. From this work we will develop a set of recommendations with construction plans and practices that growers can use to increase their on-farm success with bumblebees.

We will experiment with two types of wooden bumblebee nest boxes: one type will have just one chamber (for more details we have provided diagram B1), while the other will be comprised of two chambers (one as a vestibule and the other as a nest; diagram B2). Both types of the two nest boxes will be distinguished in the following ways: 20 will be painted yellow, 20 painted purple, and 20 left natural. The total of the 120 nest boxes will be installed at the following two heights: 16 inches above the ground and four feet above the ground. We have attached diagram D1 to the back of the application to help illustrate the nesting box categories.

By doing that, we hope to determine what type of box, and in what setting, attracted and housed the most populous and successful bumblebee colonies. We will also identify which species of bumblebees formed the colonies by capturing an individual and submitting it to an entomologist for Identification. Knowledge of the specific species will help to identify which bombus spp. are using these nests in order to assist in further refining of any final project recommendations.

To protect the colony against stress we will make observations biweekly, which will allow sufficient time to get a good idea of the growth rate of the colony by measuring the hives or counting the individuals. We aim for low-intrusive methods of observing and gathering data on the colonies through the usage of infrared or light amplifier equipment during the night. Each nest box will be constructed with a hinged panel over a transparent panel to allow these observations.

Results from the 2008 program will be used to refine similar projects in future years. We expect that the initial 120 bumblebee domiciles on 5 farms will provide us with significant results that will be useful in not only beginning the development of specific recommendations, but in increased numbers of bumblebees pollinating cooperators crops.