Apples, Squash and
Tomatoes: Feed Yourself and
the Bees
Pollinators Cubed
November 6, 2014
Karl Foord, Extension Educator & Professor, Horticulture
University of Minnesota Extension
Topics
• Introduction
– What factors influence pollination
• Tomatoes, squash, apples
• Flower characteristics
– Structure
– Floral biology
• Pollinators
WHAT AIDS GOOD
POLLINATION?
Healthy flowers as a function of
temperature & plant health
Pollinator presence as a function of:
temperature, wind, rain, & direct sun
Tomato (Solanum lycopersicum)
•
•
•
•
Heat-loving
Long, frost-free season
Full sun
Sensitive to low night temps &
extremely high daytime temps
• Relatively low attractiveness to
bees
www.flowerevery.com
Stigma
Ovary
Tube of
fused
anthers
Tomato – floral biology
• Hermaphroditic, self-pollinating, &
hangs from plant
• Flower does not produce nectar
• Stamens grow together to form a
closed tube around the shorter pistil
• The tube has longitudinal openings
• Stigma is surrounded by dehiscing
anthers
Pollination - Tomatoes
• Wind vibrates flower causing pollen
to fall onto the sigma & affect
maximum set
• Stigma receptive for relative long
time
• 1-2 days before anther dehiscence to
4-8 days after dehiscence
Pollinators - Tomato
• Honey bees do not
– Pollen difficult to access due to flower
structure
– No nectaries = no nectar
• Bumble bees are used in greenhouses
– “buzz” pollinate
TOMATO
https://www.youtube.com/watch?v=7HOEuqJUvPE
&feature=youtu.be
1000 fps – slowed by factor of 33
1 minute of viewing = 1.8 seconds real
time
Play till 2:32 = 4.5 seconds
Squash (Cucurbita pepo)
• Warm-season herbaceous annual
• Prefer higher temps & frost
sensitive
• Monoecious = Male (staminate) &
Female (pistillate)
FLOWER TYPES
Monoecious
Staminate Male flower
Pistillate Female flower
Image46 microscopy uk org
MALE TO FEMALE
FLOWER RATIOS
Flower production
• Male flowers produced first &
throughout the season
• Female appear @ 10-14 days after
first male flowers
• Male flowers outnumber female ones
by about 3.5 : 1 to 10 : 1
ATTRACTIVENESS OF
CUCURBIT FLOWERS
Nectar
• Nectaries located at base of the
corolla
• Female flowers produce a higher
volume of nectar than male flowers
• Sugar concentration is higher in
male flowers
Timing - flowering window
• Flowers open 1 to 2 hours after
sunrise
• Pistillate flower & staminate flower
just below it open the same day
• Stigma is most receptive to pollen in
morning
• Pollen foraging is highest before
10:00 a.m. decreases dramatically in
afternoon
Pollen viability
•
•
•
•
•
Decreases rapidly
Newly opened male flower @ 92%
Closing time that same morning @ 75%
Next day 10%
Important for a female flower to be
pollinated as early as possible on the day
it opens & while pollen is still viable
The KEY to Vine Pollination
Quality of fruit ~ # seeds ~ #
pollen grains deposited ~ # of
pollination visits ~ type of bee
pollinator
Pollination of squash
• Insect transfer of pollen - mandatory
• 1-2 bee visits – no fruit, poorly
shaped
• Pistillate flowers need 10-12 visits for
satisfactory fruit set
• Need some 350 pollen grains
deposited
Poor fruit set or misshapen fruit
• Weather stress (wind, rain or
cold)
• Reduced pollinator activity
• Poor pollination
Squash Pollinators
• Honey bees
• Native bees:
–Squash bees
–Bumble bees
–Solitary bees
Squash bees
• Peponapis
• Specialized pollinator of squash
– Solitary
– Early morning bees
• Prefers to nest in ground within crop
–16-30 cm beneath ground
–Possible negative tillage effects
POLLINATORS
Squash bee (Peponapis pruinosa)
Male squash bees on staminate flower
Male squash bees on staminate flower
Squash bees
Heritageharvestfestival
peponapis_hp_lg fs fed us
APPLES
Malus domestica
• Spring flowering small tree
• Apples are self-incompatible
–Must cross-pollinate to develop
fruit
• Flowering times must overlap
• Crabapples are good pollinizers
Urbanext.illinois.edu
Good flight weather = good
pollination
• Minimum:
– Temperatures >55oF
– Winds less than (11 mph)
– Not raining
• Preferred:
–Sun - cloudless sky
–Winds calm
–Temperatures >70oF
Apple Pollinators
• Honey bees
• Native bees:
–Bumble bee {Queens} (Bombus
spp.)
–Cellophane bees (Colletes spp.)
–Mining bees (Andrenid spp.)
Andrenid
male
attempts
to mate
with
Bumble
bee
queen.
BLUEBERRIES
RASPBERRIES
Author
•
•
•
Karl Foord Ph.D. MBA
Extension Educator &
Professor, Horticulture
[email protected]
A.
milwaukeensis
Andrena miserabilis male
Andrena carlini
Andrena dunningi
Andrena pruni
Andrena regularis
Andrena vicina
Andrena crataegi
Andrena imitatrix
Andrena
hippotes
Andrena forbesii
Andrena rugosa
Andrena perplexa
Colletes inaequalis
Colletes inaequalis, Unequal Cellophane Bee
Ceratina calcarata
Ceratina dupla