Pineapple - Crop Post-Harvest: Science and Technology - page 154

should not be sent to the fresh market, as they are unattractive
and also prone to disease, due to trimming. Knobby fruits
are best used for the canning industry (Pegg et al . 1995).

Control
Planting should be planned to avoid cold weather during
flowering and early fruit development. In southern and
central Queensland, fruits should not be induced in late
summer (March-April). If fruits are induced during this
period, prickly eye can be reduced by covering the fruit with
paper bags. However, this must be completed as soon as the
flowers appear and before the petals open (Pegg et al . 1995).
Sunburn
Sunburn, also called 'sunscald', is caused by high fruit
temperatures resulting in injury and death of fruit tissue
(Pegg et al . 1995). Sunburn can cause major losses, espe-
cially when fruit is maturing during hot months (> 35°C) of
the year (Keetch & Balldorf 1979), when the fruit is not
shaded by leaves and especially in ratoon crops, and is
more prevalent in the outer rows and when fruit is lodged
(Nakasone & Paull 1998). Ratoon fruit are especially
susceptible. Much of this fruit falls over (lodged), exposing
its sides to the full force of the sun. Plant crop is less
susceptible, as it is generally standing upright. However,
fruit shoulders can still be damaged during very hot
weather, especially on western slopes and around the edge
of the field (Pegg et al . 1995). The dark green skin of the
fruit contributes to the problem, as it absorbs a lot of heat
from the sun. Sunburn damage is much more likely to
occur on calm days (Pegg et al . 1995). Affected fruits soon
rot and become infested with pests.
Mild fruit sunburn simply shows as a bleached yellow
area on the exposed side of the fruit, which turns pale grey
and brown, with damage to the flesh underneath. More
severe injury causes the development of a sunken, spongy,
brown skin lesion in the centre of the bleached area.
Interfruitlet cracks in the brown area allow drying out of
fruit tissue, and entry of disease causing organisms. Tissue
underneath this area could be extensively damaged. These
damaged areas are more susceptible to disease organisms,
particularly yeasts and bacteria (Nakasone & Paull 1998).

Multiple crowns
Crown abnormalities occur frequently in pineapple. The
condition, multiple crowns, is a common condition of
pineapple, caused by a genetic aberration. When two or
more crowns develop on each fruit, there is a tendency for
fruit to flatten and fruit cores to thicken (Pegg et al . 1995).

Control
Careful selection of planting material is essential for its
control. Plants showing this disorder should be culled from
the field or separated from planting material. Multiple
crowns need to be trimmed if fruit are destined for the fresh
market. However, the appearance of the trimmed top
reduces the visual appeal of the fruit. The preferred (but
sometimes impractical) option is to send only single crown
fruit to the fresh market (Pegg et al . 1995).

Prickly eye
Prickly eye, a malformation, is caused by cold weather
during flowering and during the early stages of fruit
development (Pegg et al . 1995). Malformations, or
pineapple fruit with pronounced eyes or fruitlets, are
normally not acceptable in fancy grades of fruit, and the
thicker skin results in lower flesh recovery (Lim 1985).
The condition occurs when cold weather prevails during
flowering and early fruit development. Fruit harvested in
southern and central Queensland, Australia, during the
months of November and December often show typical
symptoms of prickly eye. Fruit harvested in north
Queensland rarely show this problem and command a fresh
market price premium at this time. The north Queensland
crop harvest schedule is aimed at taking advantage of this
(Pegg et al . 1995).
Pronounced fruitlets or 'eyes' appear instead of being
flat. Each eye is quite conical. Affected fruit are reported to
be more susceptible to fruit blemish. Internally the flesh is
not as juicy as normal and prominent cavities appear in the
fruitlets. Fruit size is smaller than normal. Apart from the
skin symptom, the fruit is quite edible. When processed,
affected fruit have a low flesh recovery, as a thick skin slice
is required to remove the defect (Pegg et al . 1995).
Some Spanish varieties are susceptible to broken core, in
which the central core has a transverse break leading to the
upper part of the fruit ripening ahead of the bottom resulting
in another form of malformation of pineapple (Lim 1985).

Control
Adjusting the ratoon crop cycle to ensure that the fruits do
not mature during hot summer months will provide some
control. Treating cannery fruit maturing during the hot
months with a reflective, clay-based sun screen is also
recommended. The unattractive residue of these treatments
precludes its use on fresh market pineapples. Some fresh
fruit consumers are aware of its nonharmful nature, but
treated fruit is generally in poor demand (Pegg et al . 1995).
Care should be taken to control lodging or leaning. Dry
grass, straw or brown paper sleeves may be placed over