Pollinators critical to success of vegetable, fruit crops

posted April 18, 2016 10:40 a.m. (CDT)
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by / Jim Massey, Editor | jimmassey@mhtc.net

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PRAIRIE DU SAC — Fruit and vegetable growers can’t underestimate the importance of pollinators to the success of their crops, a UW-Madison entomology specialist told members of the Wisconsin Fresh Market Vegetable Growers Association at the organization’s field day.

Kat Prince, a graduate student working on a joint degree in entomology and agroecology, talked about the importance of bees to the crops WFMVGA members are producing. More than half of the crops currently grown require insect-mediated pollination to allow the crops to reach their potential size and quality.

Pollination is defined as the transfer of pollen grains, the male sex cells of a flower, from the anther, where they are produced, to the receptive surface, or stigma, of the female organ of a flower.

Prince said yield increases can vary from 30 to 400 percent with the presence of bees, depending on the crop. In some fruits, such as watermelon, the quality of the crop is dependent on bees, while in others, such as cucumbers, the crop is bitter when not properly pollinated. 

The reduction in the number of native pollinators has prompted some growers to bring in hives of honeybees as pollinators, she said, at a considerable expense. Rental of a honeybee hive can cost between $55 and $80, and some plants, such as cucumbers, require as many as two hives of honeybees per acre. 

For growers who rent or own hives of honeybees, Prince said the bees need open water to perform well and prefer a south-facing slope to warm the hive. A windbreak is also a good idea to protect a hive, she said. 

Wild pollinators are more efficient than captive bees, she said, as they are often active earlier in the day. However, wild pollinators face the same risks as hives of honeybees, and farmers can’t control the location of their visits.

“You’re not sure where they’re coming from or where they’re going to go,” she said.

Some small bees have a limited flight range — often as limited as the length of a football field. Bumblebees, on the other hand, can travel up to three miles between pollination stops.

Bumblebees are especially good cucurbit pollinators, Prince said, for squash, pumpkins, zucchinis and gourds. They can be six times more effective than honeybees, and are also commercially available, she said.

Certain chemicals that kill beetles, aphids and other fruit and vegetable pests also kill beneficial insects, Prince said, so growers should limit insecticide treatments when pollinators are active.

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