The proliferation of the coconut bug (Pseudotheraptus wayi) in orchards, particularly those in low riverine areas and close to natural bush, is concerning as the pest is able to complete its entire life cycle on the macadamia, writes Dr Schalk Schoeman from Sonbesie Consulting.
By The Macadamia
The coconut bug is a serious sucking pest that attacks a wide range of fruit and nut crops. While it is best known for damaging coconuts, it has become a major concern for macadamia growers in parts of southern and eastern Africa. It can also feed on avocado, mango, guava, litchi, pecan, and several other plants.
What does it look like?
Adults: Reddish-brown in colour, about 15mm long. They have very long antennae – roughly equal to or slightly longer than their body length. Their mouthparts (rostrum) are medium long, measuring around 6.2mm.
Nymphs (immature stages): Smaller than adults and range from creamy white to brownish. Like the adults, they have noticeably long antennae.
The bug belongs to the family Coreidae (leaf-footed bugs). Both adults and nymphs use their needle-like mouthparts to pierce plant tissues and suck sap.
Host plants
The coconut bug feeds on many crops, including:
Coconut palm (Cocos nucifera) – its primary host
Macadamia (Macadamia integrifolia and M. tetraphylla)
Mango, guava, avocado, litchi, pecan, loquat, cacao, cinnamon, and some wild plants, such as ebony diospyros and weeping bushwillow
It can complete its full life cycle on macadamia nuts, which makes it especially problematic in macadamia orchards.
When is it most active?
The bug is present throughout the year, but populations usually peak during autumn (March/April in the southern hemisphere). Numbers tend to build up when the developing fruit are plentiful.
Low-lying orchards near riverine vegetation or natural bush are often more heavily infested, providing alternative hosts and shelter.
How does it cause damage?
Both nymphs and adults feed by sucking sap from young stems, flowers (inflorescences) and developing fruit and nuts.
They inject toxic saliva during feeding, which causes:
Wilting and necrosis (death of tissue)
Flower and young fruit drop
Sunken, necrotic lesions or scars on fruit
Cracking or deformation of nuts
On macadamias, feeding often leads to premature nut drop. Nuts that survive may have damaged kernels or reduced quality. In severe cases on coconuts, it can cause high rates of nut abortion.
Economic losses can be significant, particularly in macadamia orchards where the pest is not uniformly distributed – some blocks may be badly affected while neighbouring ones remain relatively clean.
Monitoring and early detection
Good scouting is essential because the bugs are often not evenly spread across an orchard.
Practical monitoring tips:
Walk orchards regularly, especially from flowering through early nut/fruit development and again in autumn.
Look for premature drop of flowers or young fruit/nuts.
Check dropped nuts or fruit for feeding scars, gum, or lesions on the inside of the husk.
Shake branches early in the morning to dislodge bugs (they may drop to the ground).
Inspect trunks and lower branches for eggs (laid singly) during peak periods.
Pay extra attention to low-lying areas near bush or riverine vegetation.
Early detection allows you to act before populations increase.
Integrated management strategies
No single method will completely eliminate the coconut bug. The best approach combines several tactics:
Cultural practices
Remove or manage alternative host plants around the edges where possible.
Consider the location when planting new orchards – elevated or well-drained sites away from riverine bush may have lower risk.
Biological control
Encourage natural enemies. Predatory ants (such as weaver ants Oecophylla longinoda in suitable areas) can significantly reduce bug numbers by hunting nymphs and adults.
Egg parasitoids (tiny wasps) also attack the eggs and can help suppress populations naturally.
Avoid, whenever possible, broad-spectrum sprays that kill these beneficial insects.
Chemical control
Use insecticides only when monitoring shows economic damage levels.
Synthetic pyrethroids are commonly registered and effective against coreid bugs on macadamia and similar crops in many regions. Always follow label rates, observe withholding periods, and rotate chemical groups to prevent resistance.
Spray timing is critical – target young nymphs and adults when populations are building, usually around flowering/early fruit set and in autumn.
Spot-spray heavily infested areas rather than blanket-spraying the whole orchard, to protect beneficial insects.
Area-wide and orchard hygiene
Work with neighbouring farmers if possible, as the bug can move between orchards and alternative hosts.
Remove and destroy heavily infested dropped nuts as they are easy to spot and will influence total kernel recovery percentages.
Key points for macadamia growers
The coconut bug is regarded as a major pest in some macadamia regions, though not every orchard is equally affected. Orchards close to natural vegetation often suffer more. Regular monitoring combined with timely, targeted sprays and conservation of natural enemies offers the most sustainable long-term control.
Usually, coconut bug numbers are considered in relation to the presence of other bugs in an orchard before control decisions are made. Very infrequently they are exclusively responsible for all recorded bug damage.
By staying vigilant during the high-risk autumn period and integrating cultural, biological, and chemical methods, farmers can minimise losses and protect the quality of their crop.
If there is suspicion of a heavy infestation or a specific product recommendation is required, farmers are encouraged to consult their local agricultural extension officer or crop protection specialist for assistance.
