First, it's important to understand the different parts of a palm.
Newer leaves emerge closer to the spear (the structure of tightly bundled un-emerged leaves) and new fronds and inflorescences generally emerge on a monthly basis. When damage is observed, it indicates that CRB fed at some point in the past. It's important to note what part of the crown the damage is occurring in (newer or older fronds) to determine when CRB may have been feeding in the area.
The coconut rhinoceros beetle (CRB)'s preferred food sources are coconut, royal, date, and fan palm. They are not host-specific and if their primary food sources are unavailable, can shift to feed on other palms and tropical crops (e.g. banana, sugarcane, kalo).
CRB feed on the inner spear or heart of palm. Using their strong arms and horn, they burrow in and use their sucking mouthparts to feed on the juices they extract. The damage left behind can look different depending on the plant species.
Bore Holes
When feeding, CRB leave an oval-shaped hole about 2” inches across as it burrows through the innermost spear. This is called a bore hole and it can appear at the base of palm fronds or in leaves of other host plants. Similar damage can be caused by rats or other pests nibbling at the frond, but a bore hole is distinct in its clean oval shape. Bore holes are one piece of evidence that CRB have been feeding in the area.
V-Cuts
If the beetle burrows into an un-emerged leaf, the damaged fronds will grow out of the crown in a v-shape with a scalloped edge. These distinct cuts form at a 45-degree angle.
Scalloped Edges
Because the beetles are creating holes as they feed, the unfurled leaves will exhibit scalloped edges. This is most obvious in fan palm damage, which can also translate to a snowflake pattern as the leaves emerge.
To learn more, watch this video on How CRB Damage Palms.
Take a photo and report suspicious damage using our online reporting form.