Stress factors and bunch development

Bunch production is affected by many factors:

• The number of bunches produced depends on the frond production rate (fronds/month). Frond production rate is reduced by environmental stress (e.g. water deficits) nutritional deficiencies and poor field upkeep. It is useful to measure the frond production rate in selected blocks. Mark Frond #1 at leaf sampling and identify the position of this frond at the next leaf sampling event and calculate the number of fronds produced per month.
• If the palm is under stress, a frond is produced, but there may be no inflorescence. Fronds pruned at present that do not contain an inflorescence are likely to have been produced under stressed conditions 40 months previously.
• The oil palm is monoecious (separate male and female inflorescences on the each palm) but heterogamous (cross pollination). Inflorescence sex is determined over the period 20–30 months before bunch harvest and 10–20 months after leaf initiation. If the palm is not affected by stress, inflorescences tend to develop into female flowers whilst, under more stressed conditions, inflorescences tend to develop into male flowers. Some male flowers are required to provide pollen to pollinated female flowers at anthesis. The ratio for female flowers to female plus male flowers is termed the sex ratio.
• If significant stress occurs, female flowers may be aborted at 10–12 months before harvest and 28–30 months after frond initiation.
• Female flowers undergo anthesis (flower opening) for a period of 2–3 days about 5 months before bunch harvest (and 35 months after frond initiation). Pollination may be poor or incomplete if there is a shortage of pollen (insufficient male flowers, high sex ratio), boron deficiency (poor pollen tube development), or low pollinating weevil activity due to very wet weather. Incomplete pollination leads to poor fruit set and reduced bunch weight.
• Successfully pollinated female flowers develop first into ‘clove’ bunches, then cinto ‘coffee’ bunches and then into black bunches. Stress during bunch development, however, may lead to bunch failure.
• Oil accumulation is completed when 5±2 loose fruit have become detached from the bunch and the bunch is then ready for harvest.

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