Alternaria alternata, a new pathotype pathogenic to aphids

A fungus, identified as Alternaria alternata, was isolated from dying or de ad aphids and proved to be pathogenic. It was isolated from different parts of Greece from aphid specimens on cultivated plants, ornamentals and weeds . In the laboratory, disease development started with the germination of sp ores on the insect integument and the subsequent growth of mycelium. The fu ngus formed apical and intercalary, globose or lobate appressoria which wer e firmly attached onto the host exoskeleton and facilitated entrance of the mycelium into the insect body. Under favorable conditions of temperature ( 15-35 degreesC) and relative humidity (100%), infected aphids died in 2-4 d ays. A characteristic brown discoloration accompanied the death of the inse cts. Both mycelial growth and sporulation were profuse on dead specimens. T he pathogen infected all 26 aphid species tested but was unable to infect o ther insects (Drosophila melanogaster and Ceratitis capitata) or aphid host plants. There were significant differences in mortality rate among aphid s pecies only during the first two days after inoculation. It is suggested th at A. alternata may be a good candidate to be exploited for the biological control of aphids.