DISCOVERY OF A FACTOR LIMITING YIELDS IN A COCONUT PLANTATION ON PEAT: THE INSECT PEST SUFETULA SPP

Abstract

On a large coconut plantation planted on a deep peat soil in Sumatra, Indonesia, hybrid coconut yields are stabilizing at values well below their potential, even in plots where known production factors have been mastered since the outset: land preparation, water control, and mineral fertilization. To explain this situation, five hypotheses have been proposed. They were tested one by one in field trials. The authors have demonstrated that the main reason for stabilized yields was the Lepidoptera root pest Sufetula spp. and conclude by considering lines of research for controlling this pest in the context of rehabilitation and replanting.

CONTROLLING SUFETULA SPP.: A COCONUT INSECT PEST ON PEAT SOILS

“…These were the same as those described previously (Bonneau et al, 2004). The study was carried out on a coconut estate (18 000 ha) belonging to Riau Sakti United Plantations (RSUP) and planted on deep peat on the east coast of the island of Sumatra (Indonesia, Riau province).…”

“…We are continuing here with a trial already described in Bonneau et al (2004) (Trial 3) and we also refer to two other experiments, Trial 4 and Trial 5, which did not feature in the earlier article. Different variables were observed: fruit setting, yield as ‡Corresponding author: xavier.bonneau@cirad.fr 290 X .…”

“…Trial 3 (Bonneau et al, 2004) was continued under the same conditions, i.e. by comparing two cultural practices: -Interrow covered by ferns, weeded planting row and a weeded circle with a radius of 2 m around the coconut palms.…”

“…We have demonstrated once again that the depressive effect of fern cover works via strong pest pressure on coconut palm roots. A correlation existed between the type of soil cover, the frequency of pest attacks on coconut roots, the existence of the dry bunches and leaves and defective fruit-setting (DBL) symptom (as described by Bonneau et al, 2004) in the aerial organs of the coconut palms (although the difference between treatments is less striking for this variable), and depressed yields (Table 1). It was thus by encouraging the presence of Sufetula spp.…”

“…In an earlier paper (Bonneau et al, 2004), we reported the discovery of a factor limiting yields in a coconut plantation on a peat soil, namely the root-mining insect Sufetula spp. Since then, the depressive effect of the pest has been assessed, and control methods have been proposed to limit its impact.…”