Midwest Vegetable Guide - 2022 - 31

Pollination
Pollination
Reviewed by Ben Phillips - Sept 2021
Pollination is the transfer of pollen from the male portions of
the flower (stamens) to the female portions of the flower
(pistils). This process is vital to the production of many
vegetable crops, including cucumber, cantaloupe, pumpkin,
squash, and watermelon. Some crops (such as tomato) are
self-fertile, but wind or bees must vibrate the flowers to
release pollen for fertilization.
Honey bees are often thought of as the most prevalent
pollinator for vegetable crops, but studies show that many
species of native bees - including bumble bees and squash
bees - play a vital role in pollinating many vegetable crops.
Tomato, for example, benefit from the " buzz pollination " that
bumble bees can provide. Honey bees are unable to buzz
pollinate, and therefore do not play a role in tomato
pollination. The squash bee, a North American native, is an
important pollinator of pumpkins and other squash crops.
Native bees are often active earlier in the day and at cooler
temperatures than honey bees.
To ensure pollination, many vegetable growers rent honey
bee hives rather than manage their own hives. Since honey
bee colonies are occasionally in short supply, growers should
communicate frequently with their bee providers.
In addition to renting honey bee hives, growers can improve
the pollination services of native and non-native bees by
increasing on-farm habitats. The Xerces Society for
Invertebrate Conservation (xerces.org) and Pollinator
Partnership (pollinator.org) offer guides, plant lists, and other
resources about building on-farm bee habitats.
At least 90 crops grown in the United States depend to some
extent upon bees as pollinators, either for seed or fruit
production. The exact number of honey bee hives needed to
pollinate a crop depends on a number of factors, including the
strength and condition of colonies, magnitude of the natural
pollinator community, amount of wild flower material
competing with the crop, attractiveness of the crop to bees,
projected yield, and weather.
The following are guidelines for the number of hives to use
when supplemental pollination is desired:
cantaloupe
cucumber
pumpkin
squash
watermelon
(2 to 3 colonies per acre)
(2 to 3 colonies per acre)
(1 colony per acre)
(1 colony per acre)
(1 to 5 colonies per acre - the pollination
requirements of seedless varieties are generally greater than
seeded)
The following vegetables will set fruit without bees, but bee
activity has been shown to increase yields:
eggplant
okra
lima bean
pepper
Honey bees do not assist in the pollination of the following
crops, but will collect pollen and/or nectar from them:
pea
snap bean
sweet corn
tomato
Do not place hives in a field until the crop's flowers are
available to visit. If the hives are placed before the flowers
are available, the bees will forage to surrounding areas and
may not forage sufficiently in the crop that needs pollination.
Bees forage best within about 100 yards of the colony.
Therefore, if the field is large, the bees should be distributed
in clusters around the field.
Bees also require a source of clean water. If not available
nearby, set out a shallow container with fresh water.
Approximate Time from Pollination
to Market Maturity Under Warm
Growing Conditions
Vegetable
Bean
Cantaloupe
Corn, fresh market1
Corn, processing1
Cucumber, pickling
(3/4 to 1-1/8 inch diameter)
Cucumber, slicing
Eggplant (2/3 maximum size)
Okra
Pepper, green stage (max size)
Pepper, red stage
Pumpkin, jack-o-lantern
Pumpkin, baking
Squash, summer, zucchini2
Squash, winter, butternut
Squash, winter, hubbard
Squash, winter, acorn
Tomato, mature green stage
Tomato, red ripe stage
Watermelon
1From 50% silking.
2For a weight of 0.25-0.5 lbs.
Bees and Pesticides
When foraging for pollen and nectar in flowering plants,
honey bees, as well as bumble bees and native bees (solitary
bees), may be exposed to a variety of different pesticides
(insecticides and miticides) that can cause direct or indirect
toxic effects. Direct toxicity occurs when honey bees are
immediately killed after exposure to wet sprays or dried
pesticide residues on leaves or flowers. Indirect toxicity is
Midwest Veg Guide 2022
31
Days to Market
Maturity
7-18
40-50
18-23
21-27
4-5
15-18
25-40
4-6
45-55
60-70
60-90
65-75
3-4
60-70
80-90
55-60
34-45
45-60
40-50
http://www.xerces.org/ http://www.pollinator.org/
Midwest Vegetable Guide - 2022

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