‘Red ring disease’ in the Paricatuba oilpalm estate, Para, Brazil

Abstract

AbstractStudies on ‘red ring disease’ (RRD) in the young oilpalm estate at Paricatuba concentrated on its symptoms, the rôle of the palm weevil Rhynchophorus palmarum as vector of the red ring nematode, the search for alternative host plants of the nematode as a source of weevil contamination, and its control.A detailed survey system, registering external symptoms, was carried out from 1974–1979. The palms were sectioned to arrive at a definite diagnosis. It was found that palms become vulnerable to RRD when they are about 5 years old.Nematode infection of the palm seems to occur exclusively via the adult palm weevil, dominantly by nematodes being carried externally. Injection of nematodes by internally contaminated weevils during oviposition apparently did not play an important rôle.Seasonal fluctuation in weevil abundance showed an increased population level largely within the dry season; an increase in the percentage of weevils contamined was also noticed in this period. Incidence of RRD was related to the abundance of contaminated weevils. Of 5,338 weevils examined for nematodes 1.7% were contaminated externally, 2.6% were contaminated internally and 3.3% proved contaminated both externally and internally.The wild palm Oenocarpus distichus Mart. turned out to be a natural host of the RRD nematode and the palm weevil and a potential infection source for the estate.Phytosanitation, comprising prevention of wounding of the palms and early elimination of palms showing distinct growth disorders, proved effective in keeping RRD incidence low. The system of felling, transport of the trunk to the oil factory, sawing the trunk in blocks and steam sterilization of the blocks at 130 °C for 1 hour, was carried out. Palm losses amounted to a total of 1.14% of the palms in the susceptible age group during the survey period.Relevant literature on RRD of the coconut palm is discussed in comparison with the results of the present study.ZusammenfassungUntersuchungen über die “Rote Ring‐Krankheit” (Red Ring Disease, RRD) in den Ölpalmanlagen Paricatuba, Para, BrasilienIn den Jahren 1974–1979 wurde besonders dem Schadbild, der Rolle des Rüsselkäfers Rhynchophorus palmarum als Vektor der Roten Ring‐Nematode, dem Aufspüren von alternativen Wirtspflanzen der Nematode als Infektionsherd für den Rüsselkäfer und der Bekämpfung Aufmerksamkeit geschenkt.Das Auftreten der “Roten Ring‐Krankheit”blieb beschränkt, wenn die Palmen während der Blattentfernung und Ernte so wenig wie möglich verwundet und die als krankhaft angemerkten Palmen konsequent und zeitig eliminiert wurden.Die wilde Palme Oenocarpus distichus Mart. zeigt sich als eine natürliche Wirtspflanze sowohl für die Rote Ring‐Nematode als für den Rüsselkäfer.Die Ergebnisse werden mit Literaturangaben über die “Rote Ring‐Krankheit”bei der Kokospalme verglichen.