Weevil

Pollination is critical in oil palm because it directly determines fruit set, bunch weight, and oil yield. Below is a clear, step-by-step explanation focusing on weevil-mediated pollination, mainly by Elaeidobius kamerunicus.

1. Oil Palm Flower Biology (Basic Understanding)

Oil palm (Elaeis guineensis) is monoecious:

Male flowers and female flowers are on the same palm

BUT they appear on separate inflorescences at different times

Flowering cycle

Male inflorescence: produces pollen

Female inflorescence: receives pollen

Anthesis (flower opening) lasts only 2–3 days

Timing between male and female flowering is crucial

➡️ This is why natural wind pollination is insufficient, and insects are essential.

2. The Weevil: Elaeidobius kamerunicus

This small beetle is the main pollinator in oil palm plantations worldwide.

Why this weevil is effective

Highly attracted to oil palm male flowers

Lives, feeds, mates, and breeds inside male inflorescences

Body size and hair structure allow pollen to stick easily

Naturally moves from male → female flowers

3. Step-by-Step Pollination Process by Weevil

Step 1: Attraction to Male Flowers

When male flowers reach anthesis, they release:

Strong aniseed-like scent (estragole)

Heat (thermogenesis)

This attracts thousands of weevils from nearby palms

Step 2: Pollen Collection

Weevils:

Feed on pollen

Mate and lay eggs in male flowers

Pollen grains stick to:

Legs

Thorax

Abdomen

One weevil can carry hundreds to thousands of pollen grains

Step 3: Movement to Female Flowers

Female flowers at anthesis emit:

A similar scent, but weaker

Weevils mistakenly visit female flowers

While crawling inside:

Pollen drops onto the stigmas

Step 4: Fertilization

Pollen germinates

Pollen tube grows

Ovule is fertilized

This must occur within 24–48 hours

4. Effect of Successful Pollination on Fruit Bunch Formation

A. High Pollination Efficiency → Good Fruit Set

When pollination is successful:

70–90% fruit set achievable

Fruits are:

Well-packed

Uniform in size

Properly filled with kernel and mesocarp

Resulting benefits:

Higher Fresh Fruit Bunch (FFB) weight

Higher Oil Extraction Rate (OER)

Lower loose fruits at harvest

B. Poor Pollination → Abnormal Bunches

If weevil population is low or pollination fails:

Common symptoms:

1. Parthenocarpic fruits

Fruit forms without fertilization

No kernel

Low oil content

2. Aborted flowers

Empty spikelets

Gaps in bunch

3. Small, loose bunches

Low bunch weight

High unpollinated flowers

Economic impact:

Lower yield per hectare

Reduced oil recovery

Higher cost per tonne production

5. Factors Affecting Weevil Pollination Efficiency

A. Plantation Practices

Excessive insecticide use ❌

Poor male flower availability

Over-pruning male inflorescences

B. Environmental Factors

Heavy rain during anthesis

Extended drought

Very high temperatures

C. Biological Balance

Optimal ratio:

~1 male inflorescence per 10–15 female inflorescences

Healthy weevil population density:

~20,000–30,000 weevils per hectare

6. Summary (Key Points)

Oil palm depends heavily on weevil pollination

Elaeidobius kamerunicus is the primary pollinator

Successful pollination leads to:

High fruit set

Heavy, compact bunches

High oil yield

Poor pollination causes:

Empty fruits

Low OER

Economic losses

#oilpalm #planter