THIS week NAREI in Focus will begin a series on growing lemons. In Guyana, lemons (Citrus limon) are produced mostly for the domestic fresh fruit and juice markets. Grafted trees begin bearing fruit within three years after transplanting. The lemon fruit has a relatively long postharvest life in comparison with other types of citrus.

Harvest Maturity Indices
The most commonly used non-destructive indices of harvest maturity are peel colour and size. Lemons may be picked either at the dark green colour stage or when the peel has started to turn yellow. Fruit picked at the dark-green stage have the longest postharvest life, but generally, have not reached their maximum juice content. Fruit left on the tree to turn slightly yellow will have higher juice content, but a shorter market life.

Export market lemons should have at least some yellow colouration of the rind at harvest. Fruit size may also be used to determine harvest maturity. Lemon fruit with a diameter less than 5 cm (two inches) are generally not sufficiently developed and have less than the desired juice content. Fruit intended for export should meet or exceed the minimal diameter of 5 cm and pickers should carry a wire ring of this diameter as a reference guide to avoid harvesting undesirably small fruit.

Juice volume is the most commonly used internal index for determining harvest maturity. Random samples of fruit of similar size are harvested and the juice content is measured. The generally accepted standard for proper harvest maturity is a minimum juice content of 28Vo by volume. Lemon fruit from the size categories meeting the minimum juice content should be harvested.

Harvest Methods
Lemons should be harvested by carefully twisting and pulling the fruit from the tree. The button (calyx and disk) needs to remain attached to the fruit. Protruding stems left attached to the fruit should be removed with a pair of clippers to avoid puncture damage of adjacent fruit in the harvest container. Careless picking that results in plugging, i.e., part of the rind pulls loose from the fruit, is unacceptable. Avoid rough harvesting practices which result in fruit bruising. Never shake the tree to harvest the fruit. Any fruit which falls to the ground is likely to be severely bruised and subject to postharvest decay.

The harvested fruit should be carefully put into padded field crates, well ventilated plastic containers, or picking bags. Ladders may be needed to facilitate harvesting of fruit borne on tall trees. Lemons should be put in a shaded area as soon as possible after harvest.
The use of large non-ventilated synthetic sacks as harvest containers should be discouraged.

These sacks do not provide protection to the fruit against compression injury, particularly if they are stacked on top of each other. They also do not allow for dissipation of heat and the lemons inside will be more susceptible to decay, especially if the fruit remains in the sack for several days.