The identity and bionomics of insect vectors of tristeza and greening diseases of citrus in Ethiopia

Survey studies were carried out to determine the identity and bionomics of insect vectors of tristeza and greening diseases of citrus in citrus growing regions of Ethiopia between 1982 and 1985: Results of these studies revealed that three species of aphids: Aphis gossypii Glover, Toxoptera aurantii Boyer de Fonscolombe and T. citricidus (Kirkaldy), were implicated in tristeza, whereas the citrus psyllid, Trioza erytreae Del Guercio, was solely responsible for greening; the Asiatic psyllid, Diaphorina citri Kuwayama, was not found in this country. Among the aphids, A. gossypii was least common on citrus while T. aurantii was found in large numbers and was widely distributed throughout the country; T. citricidus was confined mainly to the middle Awash areas. Trioza erytrea was widely spread in the country above 1500 m and was more severe at higher altitudes. Host range studies indicated that A. gossypii, T. aurantii and T. erytreae are polyphagous while T. citricidus was found only on citrus. No parasitoid was reared from A. gossypii during the study while five and six species were identified from T. aurantii and T. erytreae respectively. The encyrtids, Psyllaephagus pulvinatus (Waterston) and Psyllaephagus sp. were the dominant and widely distributed primary parasitoids of T. erytreae. Eleven species of predators were recorded on one or more of the insect vectors.