An understanding of basic honeybee biology can help orchardists make the best use of bees for pollination, says a Michigan State University entomologist.
Honeybees are more important than other pollinating insects because they are efficient pollen foragers and help to pollinate millions of acres of fruit and vegetables. They have special characteristics that help them collect pollen and tend to focus on flowers of a single species, said Dr. Walter Pett, MSU entomologist and bee specialist. They also communicate with other bees to let them know about the pollen source, he added.
Nationally, the value of honeybees for pollination is estimated to be around $14.6 billion per year, according to Pett.
"The queen bee is the ‘mother of all,’ Pett said. Her only job is to lay eggs—around 2,000 eggs per day—and release a pheromone to let the worker bees know she is healthy.
The real workers
Sterile female workers do all the work and live 21 to 45 days. They do sting and do all the in-hive work and outside work, foraging for pollen, nectar, and water, and defending the colony.
The only job that drones do is mate with queens. Male drones are produced only during May through August, he explained.
Worker bees emerge as adults about 21 days after egg laying. When they first emerge, they serve as nurses, then hive housekeeper, and only start foraging when they are about three weeks old, Pett said. The average foraging tenure for the workers is about two weeks.
Both internal and external factors affect foraging behavior. Inside the hive, the health of the queen and hive determine its strength. The weaker colonies, with fewer bees, must concentrate more on brood rearing and, therefore, have fewer foragers.
Outside the hive, temperature, wind, and rain can affect bee foraging. "When the wind picks up in apples, bees typically drop to the ground and start foraging dandelions," Pett said. Honeybees don’t work in the rain and work less on cloudy days. They also slow down when it gets too hot.
"Foraging activity is positively related to temperatures, with a linear relationship from 60 to 90°F," he stated.
Sprinkler irrigation can also discourage foraging, as bees don’t like to get wet while in flight and avoid visiting flowers filled with water. He suggested sprinkling the crops at night or early in the morning or using drip irrigation.
Evaluate colony health
Growers need to check the colony to ensure they are getting strong hives. Pett recommended looking for chalkbrood, American foulbrood, and varroa mites, common bee ailments that can reduce strength and bee numbers. The bee frames should be full of bees.
He suggested that finding three to five frames of a solid brood of bees is an indicator of a fertile queen and healthy colony. Another way to gauge colony health is to count the number of foragers returning to the colony in a 15-second period to estimate the number or percentage of foraging bees. Colonies are considered to be strong if they have about 30 percent of the hive foraging, he noted. Weak colonies are those with less than 10 percent.
Placement of hives is critical, Pett explained during horticultural talks at the Great Lakes Expo in Grand Rapids, Michigan. Hives must be placed next to the orchard to disperse the colony within the targeted crop.
He said that for tree fruit, the early strategy—having bees working the flowers as soon as they open—usually works best. This helps improve the odds that fertilization occurs before the ovules lose vigor, and flowers are more likely to receive multiple visits.
Pett also recommended that growers unsure of the number of colonies they need for pollination should start heavy, with four to six per acre, and then reduce the number the following year if pollination was more than adequate. The average number of colonies used in tree fruit is from two to four per acre.
Growers should strive to develop a long-term relationship with their beekeeper, he advised. "Notify the beekeeper if you have to use pesticides so that colonies can be shut down and protected if toxic chemicals must be used." Avoid using dust or a granular form if possible and apply in early morning if application is necessary. Use compounds that are the least toxic to bees and pay attention to the pollinator restrictions on the label.
Orchard management techniques that help rented bees survive should also improve native bee populations. "Remember that if you are not hurting the contracted bees, it means you are helping your native bee populations," he said.
Studies have shown that for every $1 spent on bees and pollination for apples, growers receive $25 back.