The Birds and The Bees and Vegetables Jim Shrefler Extension Horticulturist Oklahoma Cooperative Extension

Vegetable Pollination Importance 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 24 – 4 ¾ 34 ¾ - 5 ½ 45 ½ – 6 3/8 66 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 Problems Blossom drop caused by temperature – with several days exposure –Daytime highs above 85 o F –Nighttime highs above 70 o F –Nighttime lows below 55 o F Blossom drop caused by short term temperature exposure –104 o F 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