7th ICPP: reports on new pests
During the 7th International Congress of Plant Pathology (Edinburgh, GB, 1998-08-09/16) several papers were presented on 'new pests', a selection of these is presented below. References only mention the names of the authors and the number of the abstract in the proceedings.
Abutilon yellows virus. Abutilon yellows virus had been found for the first time in Abutilon theophrasti (weed) in Illinois (US) in 1977 and has recently been characterized as a closterovirus. This virus is transmitted by Trialeurodes abutilonea in a semi-persistent manner and is retained by the vector for 4 days. It has apparently a narrow host range (Abutilon theophrasti). No indication is given on the damage this virus may cause (Liu, H.Y.; Wisler, G.C.; Duffus, J.E. - 1.11.8).
Bacterial apical necrosis of mango. A new bacterial disease of mango (Mangifera indica) causing necrosis of buds, leaves and stems was observed in Southern Europe (no details given), with a high incidence during winter dormancy. The causal agent of this bacterial apical necrosis of mango has been identified as Pseudomonas syringae pv. syringae (Cazorla, F.M.; Duran, V.E.; Arrebola, E.; Hermoso, J.M.; Tores, J.A.; de Vincente, D.E. - 3.7.58).
Bacterial shoot blight of oak. Dieback of evergreen oaks was observed in nurseries in Japan in Kagoshima and Miyazaki prefectures, 10 years ago. In recent years, similar diseases occurred in other Japanese oaks (including deciduous oaks) in nurseries, artificial and natural forests. Symptoms are characterized by brown to black necrotic lesions on young shoots and petioles which may develop into cankers. At the beginning of the disease, discoloration or bacterial ooze often appear on the young shoot. The causal agent was identified as a Xanthomonas campestris, and the disease has been called bacterial shoot blight (Ishihara, M.; Kawabe, Y.; Akiba, M. - 3.7.77).
Citrus seed-borne virus. In the mid-80s, soon after the establishment of satsumas (Citrus unshiu) orchards in New Zealand, symptoms of a virus-like disease were observed. Affected plants showed boat and spoon-shaped leaves, dwarfing and small fruit size. Electron microscopy of purified preparations showed the presence of two different types of filamentous particles, one virus was identified as being citrus tristeza closterovirus (EPPO A2 quarantine pest). The other virus was also found in a range of other citrus species, and in citrus seedlings growing in an insect-free glasshouse. It was provisionally called citrus seed-borne virus. So far, citrus seed-borne virus does not appear to be related to citrus tristeza closterovirus, citrus tatter leaf capillovirus, or to US strains of citrus ringspot virus but it is serologically related to an Indian virus isolate also referred to as citrus ringspot virus (Pearson, M.N.; Aftab, M.; Mooney, P. - 3.7.8).
Lettuce necrotic spot nepovirus. A new virus tentatively called lettuce necrotic spot nepovirus has recently been found in glasshouse lettuce crops, in the north of Portugal. Affected plants showed necrotic spots. This virus appears to be related to arabis mosaic nepovirus (Cortes, I.; Moura, L.; Peters, D.; Pereira, A.M. - ;1.11.30).
Oak disease. High mortality of Quercus serrata and Q. crispula has been observed during summer months in Japan. Prior to wilting, massive attacks by Platypus quercivorus and xylem discoloration are observed. An unidentified fungus has been detected on the beetle and also in wilting oak xylem. Healthy oaks were killed when inoculated with this unknown fungus (Kuroda, K. - 3.7.16).
Potato latent carlavirus. A new potato virus tentatively called potato latent carlavirus has been found in asymptomatic potatoes (Solanum tuberosum cv. Red La Soda) imported from USA as in vitro plants. It is also noted that two more carlaviruses have been recently discovered: potato rough dwarf carlavirus from Argentina and potato virus P from Brazil. More studies are needed on the possible relationships between these carlaviruses (Brattey, C.; George, E.; Burns, R.; Goodfellow, H.A.; Jeffries, C.J.; McDonald, J.G.; Badge, J;L.; Foster, G.D. - 1.11.33).
Soybean severe stunt virus. A new soilborne virus disease affecting soybean (Glycine max) has been found in Delaware, USA. At present, approximately 60 ha are affected by this viral disease called soybean severe stunt. Affected plants show shortened internodes resulting in severe stunting, thickened, dark-green mottled leaves and a reduced number of flowers, pods and seeds. Plants may be killed. Soybean severe stunt virus is transmitted through soil, and Xiphinema americanum is consistently associated with infected plants in the field (Evans, T.A.; Mulrooney, R.P.; Carroll, R.B. - 1.11.37).
Abstracts of papers presented at the 7th International Congress of Plant Pathology, Edinburgh, GB, 1998-08-09/16.