Another palm puzzle

The ACDI oil palm plantations (totaling about 12 hectares or about 30 acres) serve three purposes in the extension program. First, they are a somewhat more controlled production trial of the ASD Costa Rica varieties that we have promoted in the central Kwilu River region. Second, they provide a living laboratory and practice plantation for teaching practical plantation management to cooperating farmers. Third, they generate some income for the extension program, though not yet as much as we would like. So when a block of palms begins to show signs of distress our anxiety levels go up.

Last week I described a more generalized problem in the 8-year-old planting of Ghana x Deli palms.

In the same block the technicians have run across another problem, apparently affecting four palms. A fifth palm was removed last year, exhibiting similar symptoms. The following pictures and descriptions show what we found in dissecting the palms.

Photo 1 - partial cross-section of the trunk about 60cm below the growing point. A cylinder-shaped portion of the trunk, about 5-6cm in diameter, appears to have rotted, turning a light brown. The brownish section runs parallel to the trunk axis a bit off center. The fibers remain intact, but the supporting matrix seems to have been digested. There is no disagreeable smell associated with the brownish fibers.


Photo 2 - peeling off the leave sheaths and bases we find an undeveloped flower rotting. It is not clear where this is related to the central stem rot or not. Stripping off the tissue under the flower bud we find no indication that the rot from inside extends to the bud tissue here.

Photo 3 - a full section of stem through the base of the growing point, shows that the rot ceases before reaching the growing point.


Photo 4 - a close up of the fibers at the upper limit of the rotten area. Two red nematode-like larva can be seen just to the left of center and in the lower right hand quadrant. The palm with similar symptoms last year was heavily infested with these creatures feeding on the fermenting stem tissue.


Photo 5 - 90cm below the growing point, the rotted area seems to be larger.


Photo 6 - cutting off a corner of the base of the palm bole, we find a small circle of partially digested tissue oozing copiously, as if all the fluid in the rotted section of the trunk runs out through this drain. The rest of the bole tissue looks healthy, normal.


Photo 7 - slicing out a vertical section of the trunk, we find that the small soft circle near the base of the bole is connected to the rotting center of the trunk. The coarse, fibrous tissue has completely lost the whitish matrix that normally holds it together.


Photo 8 - this final closeup shows the broom-straw like fiber mass. There is a near brownish transition zone between the central rotted tissue and the whitish-yellowish healthy tissue.

There are no obvious signs of mycelium in the dissociated fiber of the rotted portions of the trunk.

My theory is that a careful dissection would uncover insect bore holes somewhere in the central trunk behind the incompletely trimmed frond bases, giving access to an organism able to digest the sugar-rich portions of the stem tissue. But my experience is limited. We could use some help diagnosing this.

e-mail: renoyes@gmail.com or our visiting soils specialist, Patricia Lazicki, patricia.lazicki@gmail.com