A Study of Two Insect Pollinators Used for Plant Germplasm Increase

IntroductionWithin the Plant Introduction (PI) Station, we use six different types of pollinators, consisting of flies and bees. These are the honeybee, the alfalfa leafcutting bee, the osmia bee, the bumble bee, the blue bottle fly, and the housefly. Out of these six types of pollinators, my main focus is upon the alfalfa leafcutting bee (Megachile rotundata) and the honeybee (Apis Mellifera). These bees and other pollinators are used at this station to aid plant curatorial staff for controlled pollination of many plant accessions. My goal has been to determine if the alfalfa leafcutting bee (ALC) can be a good supplement for the honeybee (HB). The “Colony Collapse Disorder,” a disease, has been affecting the bees to decrease in numbers, making this a problem for keeping HB pollinators. The HB are our main pollinators at the station. Having a large number in quantity, it could easily decrease if they become part of this disease, causing the curatorial staff to have a huge loss in seed production. Replacing the HB will be difficult and very expensive. However, the ALC work just as hard as the honeybee, depending on the crop and working under the right temperature conditions. So, by committing to this experiment, we will determine if the ALC is a good supplement for the Honeybee.

MethodsIn order to find out if the ALC is a good supplement for the HB, cages containing a number of fly and bee species were observed (Figure 1). Observations included the number of insects on the following locations:

• cage screen• feeding on the flower• Insects domicile• flying around the cage idly

and were obtained with a hand held computer and a new tracking program called “the Pocket Pollinator” developed by NCRPIS personnel. Pollinator activities data are summarized in Table 1. The data collected were transferred to a Microsoft Excel file for manipulation.Also, my project included care and feeding of the insects. Nutrients were supplied for the HB, because the plants may have not supplied enough food.Data was also taken weekly on how many of the insects were requested, including the number of hives/containers that were started, stopped, ongoing, or active that week. Figure 2 presents the number of cages started with HB and ALC and that were active during the period June 10 through July 13, 2007

AcknowledgementsDr. Carolyn Lawrence, USDA-ARS, Dept. of Genetics/ Development/ Cell Biology, Ames, IA- Mentor Dr. Joan Peterson, Dept. of Agronomy, Ames, IA- AssistantDr. Candice Gardner, USDA-ARS, NCRPIS, Ames, IA – mentor

Thanks also to the National Science Foundation for funding to make this possible.

Jordan Shell Track1, Steve Hanlin2, Sharon McClurg2, Kristen Peterson2, Candice Gardner2

1Standing Rock Community High School, Ft. Yates, ND2USDA-ARS-PIRU and North Central Regional Plant Introduction Station and

Iowa State University, Ames, IA

HoneybeeThe social HB colony (Figure 3) is made up of three types of bee, which include the queen bee, the drones, and the workers. The queen is the commander, the mother of the bees. Her purpose is to populate the colony with new bees and order the bees to do their job. Without the queen the colony would eventually die. The drone’s only purpose is to mate with the queen. They help populate the colony, but will die soon after the mating is done. They can’t sting, because their stinger is designed only for mating.The workers are the muscle in the hive, doing all the work that needs to be done. They go out to collect nectar; they feed the drones, tend to the queen, feed the larvae, and are the main pollinators that help us with the seed increase. However, if they don’t like the former queen, they will force her to lay eggs in queen cells, which are unlike the normal cells. The queen cell hangs vertically, whereas the others are horizontal, or peanut shaped. After the queen lays the eggs, they will kill her.The new larvae within the queen cells are fed royal jelly. Different from the original nectar, royal jelly is rich in protein and reforms the new queen’s body structure, making her suitable for mating and laying eggs. After the feeding is done, they will cap the cells with a wax made from the body fat of young bees from eating nectar and pollen. It takes 10 to 14 days before the larvae emerge as adults. The first queen to emerge gets first right and goes around killing the other queens.Nationally, and perhaps world-wide, HB are undergoing a disease called, “colony collapse disorder.” This disease causes the bees to die or move.

Colony Collapse Disorder

The colony collapse disorder is a disease in which the adult worker bees disappear. There are theories stating many causes of this disorder. One of these theories includes the use of pesticides, but researchers say it is near difficult to test for the pesticide at the same time. Many commercial beekeeping operations transport their hives to many different areas, exposing them to different kinds of pesticides in each area. This disorder is only affecting the adult bees, so it is possible that pesticides are the cause, contaminating the nectar. The broods are not fed honey, and the adult bees consume very little pollen, causing them to take more honey. Also, because of the long-term storage of the pollen and honey, there is no determination of when the pesticide has been ingested within the bee. Other theories include poor nutrition, electromagnetic radiation, weather changes, genetically modified crops, and parasitic mites such as the varroa mite. The varroa mite (see figure 4) is a tiny crab-shaped bug about 1mm long and 2 mm wide. They will lay two eggs within the cell of a newly laid HB egg, usually male and female. When the eggs hatch, the male mates with the female and then soon dies. The female will stay in the cell, pregnant, until its host, the HB, emerges. When this happens, she will find another cell to continue the cycle. These mites feed off of haemolymph they get from the host. Haemolymph is a circulatory fluid that contains water, amino acids, sugars, salts, and white cells like the contents inside of blood, which are circulated by a pumping heart. No one knows the exact reason for this disorder, but there are more theories added to the results of the colony collapse disorder.

Alfalfa Leafcutting Bee

The alfalfa leafcutting bee is a little smaller than the honeybee, about 1 to 2cm in length (Fig. 5). ALC are black with silvery hairs and their top abdomen may have bands of white hair. The underside of a female has hairs used for carrying pollen. Males are usually smaller and have hairier faces than females.The leafcutting bees cut leaf discs to construct their nests. Each female uses about 15 discs to build a brood cell. She then stocks the cell with pollen and nectar, lays her egg in it, and then caps it, leaving the larva to grow and change into an adult bee. The nests usually are made in the spring, but young bees won’t emerge until the following year. Each female may produce up to 40 eggs, but usually they lay about 16.

My main goal has been to help determine if the alfalfa leafcutting bee (ALC) is a good supplement for the honeybee (HB). The reasons for this are due to the current concern about the “Colony Collapse Disorder” (CCD) which is now affecting the honeybees, as well as understanding which insect does a better job of pollinating. CCD affects the pollination process by resulting in a lack of older bees which do the pollination. We have a large number of honeybees at the station which are our main pollinators. If the HB were to suffer a significant disease problem, it would cause the curatorial staff a great loss of seed increase. If this should happen, the HB would be more difficult and expensive to replace. The ALC, however, work just as hard as the honeybee, depending on the crop and under appropriate temperature conditions. Thus, we need to know if the ALC can pollinate the same plants as the honeybee.

Abstract

Results

Due to the short amount of time for this project, there are no conclusive results yet to report. However, a preliminary comparison between the HB and ALC can be drawn regarding average overall time spent on flowers for the two week period which was 32% for ALC, 28% for blue bottle fly, 50% bumble bee, 10% for HB, and 20% for house fly. These results point out the nature of each type of pollinator. Bumble bees work long hours and are very good general pollinators but are not used as much because of the cost of the commercial colonies. Also of note is the comparative time spent by the pollinators on Cucumis, which was 6% for HB and 20% for ALC, which again underscores a difference in preferences between the two pollinators. These data were collected with the new pocket pollinator program which has been a good resource for the collection of data and will be used for future data collections.

ConclusionsBased on a two week observation time limit, there is not enough information to determine whether the ALC is a good alternative/supplement for the HB for all plant species and cage conditions used at NCRPIS. However, based on past observations and seed production, NCRPIS staff reports higher ALC bee activity and seed set in some crops and cage conditions than HB activity provided. Thus, they will continue to evaluate the use of ALC bee in more plant species, but will also continue to rely on the HB as the primary insect pollinator used at the station. In addition they will continue to closely monitor the health of the HB colonies maintained at the station.

Fig. 3- HoneybeesFig. 3- Honeybees

Fig. 1- Cage observationsFig. 1- Cage observations

Fig. 5- Alfalfa leafcutting beeFig. 5- Alfalfa leafcutting bee

Fig. 2- Number of cages of ALC or HB started and active over 6 week period.

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20

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Num

ber

of C

ages

ALC

ALC

ALC

ALC

ALC

ALC

ALC

HB

HB

HB

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1 2 3 4 5 6 AVG 1 2 3 4 5 6 AVG

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Started

Total Active

Fig. 4- Varroa mite

Table 1