34 Pantorhytes [EIF

__________________________________________________________________________

This leaflet is produced by the Ministry of Agriculture & Livestock, Solomon Islands, with support from IPPSI:
Improved Plant Protection in Solomon Islands, a project financed by ACIAR, the Australian Centre for
International Agricultural Research, Canberra. Authors: Helen Tsatsia, MAL & Grahame Jackson, TerraCircle
Inc. The photos of the adult and larvae are from The World’s Worst Cocoa Problems:

http://www.dropdata.org/cocoa/cocoa_prob.htm.

The photo of the crazy ant is taken from the Japanese Ant

Image Database:

http://ant.edb.miyakyo-u.ac.jp/E/P/PCD1050/43.html

Extension Fact Sheet 61:

Pantorhytes Weevils

Common name: Cocoa weevil borer

Scientific name: Pantorhytes species.
P biplagiatus is a serious pest of cocoa in Solomon Islands.

Hosts: Cocoa and several commercial forest trees, e.g., Eucalyptus and Terminalia.

Damage

The larvae do the damage. They bore into the sapwood of trunks and branches, making
tunnels 1-3 cm deep (photo, right). Often the tunnels are made at or near the jorquette, the
junction of branches and trunk. Damage at the jorquette has the potential to do considerable
harm. The overall effect of the damage is to weaken the trees, causing tip dieback, death of
branches due to ring barking, and even death of the tree if splits occur at the jorquette.
Consequently, pod yields may be reduced considerably.

The wounds made by larvae may allow entry of the bark canker fungus, Phytophthora
palmivora (see Fact Sheet no. 6), and also termites.

Biology and Life Cycle

The white, oval eggs, about 2 mm long, are laid singly in crevices in the trunk and main
branches, particularly near the jorquette. They hatch after 2-3 weeks. The larvae bore into the
wood, feeding for 3-9 months through nine instars, and then pupate beneath the bark for
about 2 weeks.

__________________________________________________________________________

http://www.dropdata.org/cocoa/cocoa_prob.htm.

The photo of the crazy ant is taken from the Japanese Ant

Image Database:

http://ant.edb.miyakyo-u.ac.jp/E/P/PCD1050/43.html

The adults are black and red (photo, above left), wingless weevils about 1.5 cm long. They
feed for 4-6 weeks before mating; afterwards, the female lays about two eggs a day
throughout a life of 1-2 years. Adults feed on the bark of young cocoa shoots, flowers and,
occasionally, pods, but the damage is not sufficient to affect pod production.

Detection and Inspection

Look for holes in the trunk and branches, particularly at the jorquette; look for the jelly-like
substance that exudes from the holes where the larvae feed. Look for the adult beetles, that
have a red abdomen with white spots, and are relatively slow moving, sufficient to be
handpicked.

Management

Natural enemies:

Biocontrol of Pantorhytes is possible using the crazy ant,
Anoplolepis gracilipes, or Oecophylla smaragdina. The ants make
colonies in soursop trees, so these should be planted between
cocoa trees to encourage the ants to colonise them. The Little fire
ant, Wasmannia auropunctata, too, may be antagonistic to
Pantorytes.

The yellow-brown crazy ant has remarkably long legs and antennae (photo, above). Its total
length is about 4 mm. It kills its prey by spraying formic acid. Wasmannia is smaller.

Cultural control:

• Hand pick Pantorhytes adults (they do not have wings) during the middle of the day when

they come down from the canopy to find cooler places;

• In severely infested plantations, find the larvae by looking for frass pushed out of the

entrance of the larval tunnel and/or the jelly-like substance. Remove the frass with a stiff
brush and apply a solution of Dichlorvos, white oil, Ridomil and water with a small 2 cm
brush onto the bark around the entrance hole. (Ridomil is added to control Phytophthora).
Repeat every 2 weeks;

• For smallholders, find the tunnels made by the larvae, and kill them with a piece of wire;
• If possible, plant cocoa beneath coconuts as Pantorhytes numbers are less than under

forest trees, Leucaena or Gliricidia; possibly, the lower numbers are associated with
higher ant populations under coconuts.

Chemical control:

The use of insecticides – other than as ‘paints’ to kill larvae - are not recommended. The
difficulty of bringing the chemical into contact with the larvae inside their tunnels, and the
low populations of beetles makes their use uneconomical.