Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
We have had questions on the potential for using bee attractants in watermelons to improve yields or to make up for pollenizer losses. Bee attractants come in several forms. The most effective have been pheromone based products such as Bee-Scent or FruitBoost. Research on use of bee attractants in watermelons has been very mixed. North Carolina and Georgia research has shown no benefit. However, research in Florida did show some benefit. In work by Elmstrom and Maynard they found that when two applications of Bee-Scent, a bee attractant, were made to watermelon on five farms in central and southwest Florida, only on a few occasions was increased honey bee activity noted. However, application of bee attractant increased total yield in one field in central Florida and resulted in an increase in early yield at all three locations in southwest Florida. This work was done in the 90s with seeded watermelons but should transfer to triploids.
If bee attractants increase bee visits, this should result in improved fruit set and increased fruit weights in a healthy field with good pollen sources. However, it will not fully make up for a lack of pollen where pollenizers were lost. In this case more bee activity can transfer more pollen but fewer pollenizers will limit the pollen that the bees will come in contact with. Attractants will also not increase bee flights in poor weather or compensate for poor plant heath or plant vigor.
Another factor with honey bees is flower preference. Watermelons and other cucurbits such as cucumbers are not particularly attractive to honey bees. Other, more attractive sources of nectar can draw honey bees away from watermelon and cucumber fields. This is why we do not recommend placing bees in fields until some flowers are present. In Georgia research where watermelons were planted next to sunflowers, bee attractants sprayed on watermelons did not compensate for the preferential attraction of honey bees to the sunflowers.