Studies of the Clove Tree I. Sudden‐death Disease and Its Epidemiology

Abstract

Extensive root disorganization is associatedwithall recognizable stages of the suddendeath disease of cloves, the final symptoms being those of a rapid wilt. In the early stages of the disease, however, the water status of an affected plant is more favourable than that of a healthy one, in spite of the root disorganization. In the diseased plant, the transpiring power and assimilation rate of the leaves are greatly lowered, probably because of partial closing of the stomata. The consequent reduction in transpiration appears to account for the smaller water deficit found in the earlier stages of the disease.These results are considered to furnish additional evidence in favour of the hypothesis that the disease is caused by a pathogen.

The Relationship between certain Ant Species with particular Reference to Biological Control of the Coreid, Theraptus sp.

“…A. longipes has been in Zanzibar for over fifty years (Nutman & Sheffield, 1949), but A. custodiens was introduced or has become abundant only in the last fifteen years. The spread of A. longipes was noticed by local plantation owners, and Nutman and Sheffield (1949) observed that it attacked and exterminated the indigenous 0. longinoda.…”

Studies of the Clove Tree

“…That poles grafted to diseased trees die, whilst similarly situated but ungrafted poles do not, therefore affords overwhelming evidence of the pathogenic nature of sudden-death disease. There was already much circumstantial evidence to suggest this, and the various forms of pathogen which might be concerned have been discussed (Nutman & Sheffield, 1949; Sheffield, 1950). Sheffield (1950) was able to eliminate all possibilities except a virus or a fungus.…”

“…In previous papers of this series (Nutman, 1950;Nutman & Sheffield, 1949;Sheffield, 1950) it has been deduced that sudden-death disease of cloves is caused by a pathogen but no conclusive proof has been offered. Microscopic examination enabled all types of pathogen except a virus or a fungus to be eliminated (Sheffield, 1950), and physiological studies led Nutman (1950) to conclude that the causal agent must be either a toxin-producing fungus or a virus. If sudden-death disease is due to a fungus, the fact should be susceptible to direct proof, but the intractability of the only known host plant renders application of many of the recognized virus techniques impossible.…”

A low‐pressure trunk injection system for the chemotherapy of clove trees

“…Clove trees in the East African islands of Zanzibar and Pemba have suffered from sudden-death disease for many years (Nutman and Roberts, 1971;Nutman and Sheffield, 1949). The disease remains of unproven aetiology although in the past physiological causes, insect damage to the roots, fungal pathogens and viral infection (Nutman and Roberts, 1954;Nutman and Sheffield, 1949) have all been postulated as possible causes of the disease.…”

“…The disease remains of unproven aetiology although in the past physiological causes, insect damage to the roots, fungal pathogens and viral infection (Nutman and Roberts, 1954;Nutman and Sheffield, 1949) have all been postulated as possible causes of the disease. In the Malagasy Republic a similar disease of clove trees, apoplexie (Heim and Bouriquet, 1937) is also of unknown aetiology.…”