The Birds and The Beesand Vegetables

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Jim ShreflerExtension Horticulturist

Oklahoma Cooperative Extension

Vegetable PollinationImportance

Leafy greens, lettuce, carrot, onions etc. – needed for seed production

Sweet corn – needed to produce the edible seeds

Melons, squash and cucumbers – important for fruit set, fruit size, fruit shape and normal development

Broccoli, cauliflower, squash blossoms – flower generally used before pollination

Pollination and Fruiting Crops – A Quick Overview

What is pollination?– The transfer of pollen from an anther to the

stigma – Merriam Webster

Growers often refer to pollination in terms of the overall degree to which this pollen transfer occurs in a crop

For successful pollination the pollen must germinate and the pollen tube “travels” to the ovary.

Okra Pollination

Perfect flowers open sunrise until noon

Pollen released 15 – 20 minutes after opening and contact the stigma

Bees help, but not required

Wind not important

Plants are self-fruitful, but can also cross

Eggplant Pollination

Flowers are perfect– Remain open 3 days

Plants not self fruitful

Insect pollinators needed– Wind not effective– Vibration not effective

In one study, bumble bees were more effective than honeybees

Squash Pollination

Separate male and female flowers

Flowers open daylight – mid morning– Wither earlier when hot

Bees the main pollinator but other insects present

Bee colony number determines yield

Result of Poor Pollination

No fruit set

Low yields

Reduced quality seems less common

Muskmelon Pollination

Two flower types on same plant in most American cultivars– Staminate = male flower– Perfect flowers

1 pollen grain is needed per seed– 400 seeds needed for fruit to be useable– 400+ pollen grains must be transferred

Without bees there is no pollination– Other insects often present, but not effective

as pollinators

Muskmelon Pollination

If pollination does not occur, and no fruit is set, the plant may shift toward more production of perfect flowers

Flowers open at sun up– Close in the afternoon the same day– However, the effective pollination time is from

15 minutes to a few hours

Crown fruit set can be heavy if bee activity is high early in the blossom stage

Melons Sizing

Size 1

Size 7

Size # Range (inches)

1 <4

2 4 – 4 ¾

3 4 ¾ - 5 ½

4 5 ½ - 6

5 6 – 6 3/8

6 6 3/8 – 6 ½

7 > 6 ½

Cucumber Pollination

Separate staminate and pistillate flowers

Staminate may emerge 10 days earlier

In gynoecious types flowers are mostly pistillate.– Seed are sold with some

that will produce male flowers

Cucumber Pollination

Insect pollination is essential– Mainly by

honeybees– At least 8 – 10 bee

visits to a female flower needed

– One bee colony needed per acre; 2-3 is better

Tomato Pollination

Perfect flowers

Most pollination occurs with a given flower– Insects may cause some

cross pollination

Shaking causes pollen to fall from anthers to stigma– Air movement outdoors– Mechanical vibration is

used in greenhouses

Vegetable Pollination Problems

Lack of flowers– Immature plants– Environmental conditions– Excess vegetative growth– Season / daylength

Fruit not setting– Immature plants?– Lack of pollinators– Staminate flowers not

present

Pollination Problems

Can be heat related– Stigma may become unreceptive to pollen– Pollen may be killed– Pollen tube may not form

We may observe– Flowers and fruits abort– Low number of female flowers

Tomato Pollination ProblemsBlossom drop caused by temperature – with several days exposure– Daytime highs above 85oF– Nighttime highs above 70oF– Nighttime lows below 55oF

Blossom drop caused by short term temperature exposure– 104oF for 4 hours

May cause various flower and pollen abnormalities

Summary

For crops that require insect pollination– Yield depends on pollinator numbers– Quality may depends on pollinator numbers– Fruit size may depend on pollinator numbers

Environmental conditions may interfere with fruit set– Excessively high or low temperatures can

injure flowers or interfere with pollination– Duration of the temperature extreme matters