Study of Sufetula n. spp. (Lepidoptera, Crambidae, Spilomelinae) root mining caterpillars on the PB 121 coconut hybrid : coconut entomology mission, Riau Sakti United Plantations (RSUP), Pulau Burung, Sumatra (Indonesia), 27th February to 16th March 2002

This mission was used to take stock of the entomology trial results obtained since the last mission in February 2001. The halt to monthly insecticide treatments in trial HSF 11 does not yet reveal any depressive effect of Sufetula larva attacks on production. The Yields of coconut palms mulched with cocopeat alone (coconut husk debris) are still significantly higher than in the control. In the meantime the cocopeat totally disappeared from the base of the coconut palms more than a year ago (HSF 14). The new insecticide Imidachloprid has not effectively protected roots from Sufetula attacks. We can confirm that Sufetula does not infest a pineapple monoculture. Hence, it is possible to start up a young coconut planting after one or two cycles of pineapple. Planting coconut palms in an environment free from Sufetula (RSTM/RS CC 07) for several years (up to 3 years) enable the palms to develop very long primary roots (over 5 m on average at about 5 years old). That can thus engender a highly efficient absorbent root system (RII, RIII, and RIV). Subsequent severe attacks on RI might then hinder production less (to be confirmed). On the other hand, planting coconut palms in an environment invaded by Sufetula (RSUP/RS ES 74) leads to immediate attacks on the roots of the young palms. Cocopeat and coconut husks do not protect the roots from Sufetula attacks. Moreover, coconut husks prevent fertilizers from penetrating the soil, which can disrupt young plant development. The complete demonstration of the positive effect of "bare soil" on an estate level is not possible. That is due to a difficulty in carrying out durable weeding in the absence of herbicide, and in removing all dry fronds and coconut husks. The two priorities for the new Management at RSUP are chemical weeding at an appropriate frequency throughout the estate, i.e. around 17,000 ha - Standard application of fertilizers in line with recommendations after leaf analyses. (Résumé d'auteur