Puzzled over oil palm distress at Lusekele - suggestions?

posted by Ed

(Ed’s note: If your interests extend to the arcane details of small-holder oil palm growing, READ ON. If not, you may want to just skip this blog entry and wait for the next one.)

Drought stress? Potassium deficiency? Fusarium wilt of mature palms? Something else?

For over ten years ACDI Lusekele, the Baptist agriculture extension program, has been promoting high-yielding hybrid oil palms to renew small-holder palm plantations along the central Kwilu River. Over a thousand small farmers have benefited from the program. Altogether, between 850 and 1,000 acres of small, family-operated plantations have been established or renewed, generating enough extra income to cover simple health care, basic school fees for children and perhaps make simple household improvements, like a roof that doesn’t leak.

But a troubling development has hit the inaugural plantation at the Lusekele ag center itself. Last year, about 1.5 acres of the 2003 planting began to show signs of drought stress. The telltale signs of potassium deficiency (orange blotches progressing to leaflets dying and drying out) were widespread and sometimes quite marked. Older fronds dried out, leaving the plantation with an unusual open sunny aspect rather than its normal shade. Sometimes palm ribs would break midway along their length, even when still green.

Two years ago the palm canopy was closing nicely, creating almost continuous shade in the this portion of the plantation.

2008-2009 was a lean rainfall year with only 1233 mm of rain from July 1 to June 30. July 2009 to June 20010 had nearly 1600mm of rain, only to give way to an erratic 2010-2011 year ending with less than 25mm in May. From May 24 to August 26 only 4.6mm fell, all before June 15th, making this the hardest dry season in years.

In October 2010 we responded with a split dose of 178 kg / ha of muriate of potassium, followed by improved ring weeding and regular cutting of Chromolaena odorata competitors. No immediate change occurred in the vigor of the palms.

Broken and dessicated older palm branches. This is one of the worst affected palms.

This year, as the severe dry season continued week after week, stress symptoms began to spread across the rest of the 2003 planting and into the 2004 planting adjoining it. In searching through the literature we have on hand and on the internet, drought stress seems to be the primary candidate. Apparently potassium deficiency can exacerbate the stress by contributing to limited root uptake. Fusarium wilt seems to produce symptoms similar to drought stress and none of our varieties are specifically bred for resistance. Ganoderma could be implicated, but no palms display the characteristic skirt of drooping fronds.

The newly-affected areas of the plantation this year seem to coincide with the area over which we significantly improved weeding practices. Is it possible that clearing off heavy weeds (cutting not digging up) could create problems for superficial palm roots – something similar to removing shade from nursery seedlings? As you can see we are grasping a bit, trying to understand what is happening.

If you have any comments or suggestions about what this might be, how we might narrow down or confirm a diagnosis, and what we might do about it, please feel free to contact me ( renoyes@gmail.com ) or Patricia Lazicki, our visiting soil scientist, (patricia.lazicki@gmail.com )