BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Wipe out coconut rhinoceros
by Mary Charlotte O. Fresco

January-March 2002
Volume 4 No. 1

Sawdust and other wood excesses may mean waste for some. But for coconut farmers, sawdust can be a primary weapon against ruthless pests such as coconut rhinoceros beetles.

The rhinoceros beetle (Oryctes rhinoceros) is common in Southeast Asia and has long been one of the most serious problems among coconut growers worldwide. In fact, almost all studies conducted and published about pest management in coconut deal with this pest. The extent of damage by the rhinoceros beetle is almost incalculable. The threat starts when the beetle reaches its adult stage (two months) and feeds on the palm shoot or ubod. Subsequently, the new leaves that are about to open are damaged. The beetle also attacks young palms in nurseries. When not regularly monitored and no control measures are employed, damaged young plants eventually die.

What's in the sawdust?
Problems are best solved when one considers their root cause. Researchers of the study worked with this principle by considering the breeding habit of the insect. Rhinoceros beetles normally breed and lay their eggs in rotten wood, compost and other decaying organic matter. Experts preferred the use of decaying sawdust as best alternative to lure the beetles. The decaying sawdust normally emits an aroma that attracts the beetles.

In a study conducted by a group of experts from the Philippine Coconut Authority (PCA) Zamboanga Research Center led by Mr. Emmanuel Eterrado, 116 trap boxes (150cm X 150cm X 50cm) were linearly installed (50 to 75 meters apart) along the perimeters of a 300 ha experimental coconut farm. Each trap box contained approximately 10 to 15 bags of coconut sawdust. To determine if other factors such as bio-insecticides would affect the "annihilation" process, a half kilogram of Metarhizium anisopliae was incorporated in each sawdust trap box. Metarhizium anisopliae, also known as green muscardine fungus (GMF), is a beneficial fungus that attacks various insect pests. Half of the amount was spread over a three-inch sawdust lining at the bottom of the box while the remaining was thoroughly mixed with the rest of the sawdust, which served as breeding media.

The result
The efficiency of sawdust trap boxes was thoroughly observed for almost a year. Based on the data gathered, a total of 20, 402 beetles of different life stages were collected from the trap boxes.

Collected beetles and their eggs were destroyed right away to avoid any chance of escape.

The researchers also monitored the level of fungal infection using GMF. Based on the data collected, the level of GMF infection reached 1.7% during the initial stage of the insect life. According to the researchers, these results indicate that newly hatched beetles are the most susceptible to infection since their integuments (hard covering of insect's body) are still soft, and thus, can easily be penetrated by fungus.

The rhinoceros beetle (Oryctes rhinoceros) is common in Southeast Asia and has long been one of the most serious problems among coconut growers worldwide.

However, at the end of the study, the level of infection increased to 4.1% in the 12th month of traps installation. Researchers attributed this to the fungi that have developed on the surface of the insects' carcass that initiated a new round of infection.

The rhinoceros beetle (Oryctes rhinoceros) is common in Southeast Asia and has long been one of the most serious problems among coconut growers worldwide.

Practicality of using trap boxes
Researchers confirmed that trap boxes remain attractive to beetles and are still suitable for breeding even after 11 months of use. The level of sawdust in the boxes significantly decreases through time especially when it starts to rot. This, however, serves as additional attractant to insects. At this point, it is necessary to replenish the traps with additional sawdust to meet the required volume (50 cm thick).

The study further revealed that the application of bio-insecticides like GMF may no longer be necessary since sawdust alone is effective enough to trap the beetles. Bio-insecticides can be used to control beetle population development during its early age.

For more information, please contact, Mr. Emmanuel Aterrado, Philippine Coconut Authority Davao Research Center at Tel. No. (082) 2930016.