Poor Fruit Production

Inquiries regarding fruit production usually involve either low number or poor quality.
Poor fruit production can be attributed to many factors depending on the type of plant
in question. Contributing factors may be environmental, cultural or pest related. Discussed
in detail are fruit trees, cucurbits, peppers and tomatoes.
Fruit Trees

Site selection is extremely important when planting fruit trees. Sandy loam to loamy,
well-drained soil is generally preferred as opposed to heavy clay soil. Plant the trees
on a slope, preferably facing northeast or east. Planting in low-lying areas can lead to
spring frost pockets and subsequent blossom injury. Early spring frost is a major
contributor to poor fruit production. If the flowers become damaged, fruit production
is inhibited. Both light intensity and duration are extremely important in fruit production.
Many fruit trees require at least six hours of full sun a day in order to yield a large
number of high quality fruits. Ensure that the trees receive adequate sunshine and are
not in the shade of larger trees, buildings, etc.

If the trees are producing a tremendous amount of green foliage but few flowers and
fruits, the likely cause is excess nitrogen in the soil. Also, applying nitrogen fertilizer
late in the growing season can lead to poor colour and quality of developing fruits.

Poor weather conditions during flowering can also lead to poor fruit production.
Most fruiting plants have specific temperature ranges in which pollen viability and
fertilization success are maximized. Deviation from such temperatures often results
in low fruit yields.

For trees that are cross-pollinating, insect vectors are often necessary for pollination
and subsequent fruit development. Cold, wet and windy conditions during bloom can
reduce insect activity in the area. In this situation, the tree will likely produce many
flowers but few fruits. Pesticide applications in the area will also reduce the number
of insect vectors available for pollination.

Pollination is a key concept in fruit production that must be understood in order to
maximize productivity and yield. Only pollinated flowers can bear fruit. Poor pollination,
for one reason or another, is often the most probable cause of poor fruit production.
Apple trees are cross-pollinators, meaning they require pollen from another apple
(of a different variety) in order to produce fruit. In a cross-pollinated system, insect
vectors (pollinators) such as honeybees or bumblebees control the transfer of pollen
from one plant to another. Pollen sources (pollinizers) can include many different types
of apple, or even crabapple. If there are no pollinizers within the recommended distance
and flowering at the same time, pollination does not take place and fruits are not formed.
Four-in-one apple trees are available that have several varieties of apple grafted onto a
single rootstock. This eliminates the need for a second apple or crabapple pollinizer.
Including flowering plants that bloom the same time as the fruit tree will help to attract
bees and other pollinators. Other cross-pollinating fruit trees include pears and plums.
Self-pollinating fruit plants include apricot, nectarine, peach, sour cherry, currant,
gooseberry, blueberry, strawberry, raspberry and saskatoon. These crops are self-fertile
and do not require an outside pollen source. Therefore, poor fruit production in these
crops is more likely attributed to factors such as injury, stress or unfavorable growing
conditions.

If fruit trees such as apples, plums, peaches and nectarines are improperly pruned, or
are not pruned at all, fruit yield and quality may be reduced. The result is often many,
small fruits instead of fewer, larger fruits. Most fruit trees have a particular frame or
structure that is most conducive to fruit production. Although maintaining a favorable
structure increases productivity, it is imperative that proper techniques are followed so
that the tree does not sustain unnecessary injury. This often requires a great deal of
knowledge and expertise. In some cases, poor fruit production simply results from
the removal of fruit-bearing wood during pruning.

Alternate flowering is a natural, biological phenomenon exhibited by some flowering
shrubs and fruit trees. Plants that exhibit an alternate flowering pattern will have alternating
"on" and "off" years. They will flower heavily during "on" years but then flower poorly
(if at all) during the following "off" year. Some plant species may actually have two
repeated "off" years before flowering again. Alternate flowering is especially common
in apple and crabapple trees. Basically, a heavy fruit crop in one year will consume a
significant proportion of the plant's food reserves at the expense of the next year's
flowers and fruit. It has been suggested that hand thinning excess fruits in an "on"
year will help to conserve the plant's resources and reduce the occurrence of
subsequent "off" years. Otherwise, the best thing to do is avoid varieties that are
particularly prone to alternate flowering patterns.

Finally, poor fruit production may simply be a function of the plant's age. For most
fruit trees, a certain amount of time is required to become established before fruit
production can commence. Some plants may not even flower within the first
couple of years. Conversely, older plantings may also exhibit a decline in fruit
production, especially if the trees have not been pruned regularly over the years.
A good pruning will sometimes revive an old, tired fruit tree. So, before jumping
to conclusions about why fruit production is poor, first consider the age of the tree.
The cause may simply be immaturity or old age.
 
Cucurbits

Cucurbits such as cucumber, squash, pumpkin and melons, are also cross-pollinators
. They require insect vectors, particularly honeybees, for pollination and subsequent fruit
set. Poor fruit production in these crops is commonly a result of inadequate pollination.
Cucurbit flowers only remain open for one day. As a result, there is only a small window
of opportunity for pollination to occur. If pollination does not occur, the flowers simply
drop off the plant. In this case, no fruit is produced. If only partial pollination occurs,
the resulting fruits are small and deformed. Successful pollination of some cucurbits
requires as many as twenty bee visits per flower. If the seeds inside the fruit are
underdeveloped, inadequate pollination is the probable cause. Many cucurbits, especially
newer varieties, produce far more male flowers than female flowers. Male flowers will
never produce fruit. Therefore, it is important to realize that an abundance of flowers
will not necessarily translate into an equivalent number of fruit. Some cucurbits produce
male flowers and combination flowers, in which case only the
combination flowers will produce fruit. Insect vectors, however, are still required
for pollen transfer even though combination flowers have both male and female
reproductive parts.

Environmental conditions can also affect fruit production in cucurbits. Like most fruit plants,
pollen viability and fertilization are influenced by temperature. Adverse temperatures during
critical periods can have a negative effect on pollination and fruit set. Cucurbits are also
sensitive to moisture availability. If drought conditions persist during flowering, fruit will be
deformed and yield will be reduced. Avoid overhead watering during daylight hours as
this may case a decrease in essential bee activity. Also avoid the use of insecticides,
especially during flowering.
 
Peppers and Tomatoes

Peppers and tomatoes are self-pollinating crops. Poor fruit set is usually associated with
adverse environmental conditions as opposed to poor pollination. Both of these crops are
sensitive to temperature extremes, especially during flowering. Low temperatures during
flowering (<10ºC) can inhibit pollen production and reduce pollen viability. Low
temperatures during fruit fill often result in adequately sized but poorly coloured fruit.
High temperatures during flowering (>30ºC) have a negative effect on pollination,
especially if accompanied by moisture stress. Moisture stress during any stage of
growth can have a negative affect on
the plant, but it is extremely perilous during flowering. Fruit production in pepper and
tomato tends to be especially sensitive to nighttime temperatures. Blossom drop is
a characteristic symptom of both temperature and moisture stress.

Soil fertility also plays a key role in fruit production. Excess soil nitrogen will delay or
inhibit fruit production, as it causes the plant to produce a flush of green, vegetative
growth at the expense of blossoms and fruits. In this situation, the plants, though healthy
and vigorous, will have few or no flowers. Be especially careful when applying manure
and nitrogen fertilizer early in the growing season. On the other side of the coin, excess
phosphorus and inadequate nitrogen can result in fruit with good colouration but poor
size. In this situation, the plant has essentially put more energy into producing the fruit
but not enough energy into producing the vegetative tissue required to fill the fruit.

Finally, shade can be a major contributor to poor fruit production in peppers and
tomatoes. If these plants don't receive at least six hours of direct sunlight per day,
they cannot accumulate enough energy to produce and fill fruit.

Poor fruit production, in any plant, can also be pest related. It may be a direct symptom
of an insect, virus or fungus, or it may be a secondary result of stress or injury caused
by these pests.  In any case, it is important to become familiar with the pests and
symptoms commonly associated with the respective plant in order to identify the
problem and implement an appropriate control measure. Apply pesticides only if a
disease or insect has been confirmed and always follow the manufacturer's label
carefully. Remember that most insecticides are toxic to pollinators and other
beneficial insects, a common cause of poor fruit production.

Keeping plants as healthy and vigorous as possible will help to increase their immunity
to pest invasion. This means administering a regimented watering plan and a balanced
fertilizer program. Ensuring that stress and injury are minimized throughout the growing
season promotes healthy, vigorous growth. Healthy and vigorous plants accumulate a
tremendous amount of energy throughout the growing season and are, therefore, better
equipped to produce larger quantities of high quality fruits.