A mite attacking bees might be doing more than just affecting the local honey supply. Pumpkins, watermelons and cucumbers could also be affected by a drop in the bee population.

Local extension offices have been receiving more calls about poor fruit set in these crops, all of which are members of the cucurbit family. While there could be many possible reasons, many callers are convinced the lack of bees is the culprit.

Garden cucurbits like pumpkins, squashes, watermelons and cucumbers are most affected, primarily because they require honeybees for pollination. Crops such as cucurbits require multiple visits by bees for successful pollination.

Where have all the bees gone? In 2007, the varroa mite, known to attack honeybees, was detected on O'ahu in commercial and wild hives. In Mainland studies, this pest has caused losses as high as 95 percent in wild colonies, and has forced some commercial bee keepers out of business.

According to communications with Ethel Villalobos and Scott Nikaido, of the University of Hawai'i College of Tropical Agriculture and Human Resources, there are many similarities between the bee situation here and on the Mainland. Villalobos and Nikaido, along with the state Department of Agriculture, are educating beekeepers and growers in effective management strategies to suppress mite populations, minimize their distribution and revitalize bee colonies throughout O'ahu.

During the interim, gardeners can assist bees in pollinating fruits and vegetables by hand. Cucumbers, squashes, pumpkins and other cucurbit crops are monoecious plants, which mean they have separate male and female flowers on the same plant. The easiest way to differentiate between a male and a female flower is to look behind the flower petals. Female flowers have a small swollen fruit behind the petals, whereas male flowers do not. Male flowers develop on long, thin stalks and emerge earlier than female flowers. At the center of male flowers is a stamen, and at the center of the female flower is a stigma.

To enhance fruit development, remove the petals from the male flower. Pollen from the stamen (the orange powdery substance) can be rubbed onto the stigma of the female flower directly or be applied with a soft brush or cotton swab. The best time to pollinate crops is early morning.

When successful, the fruit behind the female flower will continue to develop. Unsuccessful pollination often results in aborted or distorted fruits which may turn yellow and drop off the vine.

To avoid killing bees, Villalobos and Nikaido suggest applying pest management sprays during the late evening. Pollination takes practice. Keep in mind that we can never pollinate a crop as well as bees, our natural pollinators.

Steve Fukuda contributed to this column. Jari Sugano and Fukuda are extension agents with the University of Hawai'i-Manoa College of Tropical Agriculture and Human Resources. Reach Sugano at suganoj@ctahr.hawaii.edu.