A decline in bee populations coupled with poor pollination performance is reducing agricultural yields. Two different solutions - one technical and the other biological - have been developed by TAU scientists.

The world's bee populations, crucial for the natural pollination of a majority of crop plants, are dwindling due to disease, the spread of the aggressive "africanized" bee from South America northwards, and the development of hybrid crops with sterile flowers. The North American bee-keeping and pollination industry, in particular, is under threat.

Crop plants reproduce by several types of pollination. While some plants, such as wheat and peas, are self-pollinators, and the banana plant is parthenocarpic - it bears fruit without fertilization - most crops are pollinated by wind or by various types of bees. The bees drink the flowers' nectar and collect the pollen to feed their larvae back in the hive; in the process, the pollen from one flower is transported to the stigma of another. Without adequate pollination, crop yields for both growers and seed breeders can decline drastically and even lead to food shortages - posing a challenge to scientists to find solutions.

An electrifying development

An innovative method of artificial pollination using electrostatic technology has been developed by TAU scientists Prof. Dan Isikowitch and doctoral student Yiftach Vaknin of the Department of Plant Sciences, George S. Wise Faculty of Life Sciences, in cooperation with researchers at Israel's Volcani Institute and at the University of Georgia in the US.

The technique involves the use of aerodynamic and electrostatic forces to increase the amount of pollen deposits on flower stigma. The pollen deposits are transported to the stigma using an electric charge. The technology has been tested over the past five years on almond and pistachio orchards in the US and date palm orchards in Israel with promising results, especially in pistachio orchards where the method yielded 19%-40% more fruit per tree, compared with crops pollinated naturally by wind.

Previous methods of artificial pollination have involved placing pollen dispensers at the entrance of hives, or dusting pure or diluted pollen manually or mechanically onto flowers. Another technique involves spraying flowers with pollen suspended in several aqueous solutions including pure water.

The use of electrostatic technology, which has numerous applications in industry, has introduced an entirely new direction for applied agricultural research, says head of the TAU research team Prof. Isikowitch. The project was supported by BARD (Binational Agricultural Research & Development Fund), and was carried out in cooperation with Professors Samuel Gan-Mor, Beni Ronen, Yoram Schwartz and Avital Bechar of the Volcani Institute; and world-renowned specialist in electrostatic engineering, Prof. Ed Law, and horticultural scientist Prof. Hazel Wetzstein, both of the University of Georgia at Athens, USA.

The technology is still in its initial stages and the team is examining new methods of boosting pollination in other crops such as apples and kiwis.

No more bumbling

A second approach to agriculture's pollination woes - based on chemical communication among insects - relies on "persuading" bumblebees to pollinate flowers they would ordinarily avoid. Basic research conducted in the laboratory of Prof. Abraham Hefetz at TAU's new Terry and Lawrence Bessner Building for Zoological Research, the I. Meier Segals Garden for Zoological Research, has led to the development of a new technique for increasing the yields of hybrid crops and seeds.

A custom beehive for a tomato greenhouse.

The problem began in Israel about 10-12 years ago, when tomato and eggplant growers moved their operations from open fields to greenhouses. Physical access to the crops by their natural pollinators was blocked. Moreover, certain flowers of the new, hybrid crop strains were engineered to be sterile and held no "reward" for bees - no nectar, no pollen. Farmers have since been forced to pollinate these crops by hand, which is costly and time-consuming.

In a search for an economical solution, Prof. Hefetz and his colleagues investigated the use of pheromones - odors that serve as a means of communication among social insects - as the foundation for manipulating bumblebee behavior. The pheromones are used to lure the bumblebees to visit "non-rewarding" flowers, particularly seed-producing ones, and pollinate them.

Bumblebees bring tomato pollen to their larvae in the hive.

"The results are highly promising," Prof. Hefetz says, "but there is still a long way to go until the system is completed and is suitable for commercial exploitation. When that happens, the Israeli hybrid seed industry will see millions of dollars in profits."

Prof. Hefetz points out that other crops such as avocado, peppers, and berries could potentially benefit from the new technology.