Studies on the etiology of the crown disease / spear rot syndrome in oil palm

Abstract

The crown disease/common spear rot (CD/CSR) syndrome is the most common disorder in young oil palm plantations worldwide. Diseased and healthy plants were compared in their nutrient content, water status and type of soil in which they were growing. Disease progress curves were adjusted to either the monomolecular or Gompertz equations. The most frequently isolated microorganisms from necrotic lesions on leaves and rachises were species of Erwinia spp and Fusarium spp. These are probably common inhabitants of the phylloplane. Attempts to reproduce the CSR symptoms through the inoculation of isolated microorganisms normally failed. Typical CSR symptoms were reproduced only once, with at least three isolates of Erwinia sp. in 19 months-old nursery palms. The Gompertz equation was adequate to describe the disease progress curve for several of the most susceptible progenies. However, disease progress tended to follow the monomolecular equation for the more resistant progenies. Plants with the CD/CSR symptoms usually had higher nutrient contents in their younger leaves than healthy plants. The genotype showed to be the main determinant of susceptibility to the disorder. However, conditions that favor a vigorous growth could make more susceptible the plant by causing abnormal lignification of young tissues and allowing opportunistic microorganisms enter.