Survey of Spilocaea oleagina, causal agent of olive leaf spot, in North of Iran

Survey of Spilocaea oleagina, causal agent of olive leaf spot, in North of Iran

S. J. Sanei and S. E. Razavi | View Article Olive leaf spot or peacock spot, caused by the fungal pathogen Spilocaea oleagina, can cause reduced growth and yield in olive trees (Olea eurapaea). Investigations were carried out during 2007-2010 to measure the prevalence and severity of olive leaf spot in the northern olive growing regions of Iran. The susceptibility of ten cultivars (Amygdalifolia, Blaidy, Koronakei, Mary, Manzanillo, Mission, Rooghany, Valatolina, Wild olive, Zard) to the disease was assessed. Olive scab was found in all study areas and with the worst affected in high relative humidity (Y= -21.058 + 0.794X,...
Effect of climate on olives

Effect of climate on olives

Vera Sergeeva | View Article Climate change has the potential to significantly impact Australia’s agricultural production. The predicted results of climate change – increased temperature, moisture and CO2 – can impact all three elements of the plant disease triangle (host, pathogen and environment) in various ways. Changes in temperature, rainfall, and extreme events will affect water availability, soil quality, fire risk, and the incidence of known and new diseases, pests, weeds, and disorders. Decreased soil and air moisture increases the incidence and impact of frost, while the frequency and severity of floods and drought are also expected to...
Diseases and Disorders Associated with Environmental Stress in Sustainable Olive Orchards in Australia

Diseases and Disorders Associated with Environmental Stress in Sustainable Olive Orchards in Australia

V. Sergeeva and R. Spooner-Hart | View Article The main aim of our research is to contribute to the knowledge on diseases and disorders of olives in Australia. Based on our diagnostic and field research work we report several new records of fruit rots and of fungi associated with foliage, trunk and root diseases. As well as being affected by a range of pathogenic diseases, olives are also subject to non-pathogenic disorders, such as damage by heat and sun, wind, fire and other weather conditions, water-logging and irregular watering or nutrient imbalances, all of which interfere with the normal physiological processes in trees. As a result, reduced crop set and fruit size as well as a range of other symptoms such as frost, chilling, hail injuries, and sunburn can be directly caused by environmental conditions. Moisture, temperature, sunlight, nutrition and soil characteristics can all affect plant growth. If one of these factors is out of balance it may lead to environmental stress which may, in turn, result in a greater tendency to become...
Colletotrichum clavatum sp. nov. identified as the causal agent of olive anthracnose in Italy

Colletotrichum clavatum sp. nov. identified as the causal agent of olive anthracnose in Italy

Roberto Faedda, Giovanni Enrico Agosteo, Leonardo Schena, Saveria Mosca, Salvatore Frisullo. Gaetano Magnano Di San Lio and Santa Olga Cacciola | View Article Molecular analyses of a large population of isolates, previously identified as group B or genetic group A4 of the Colletotrichum acutatum species complex, mainly of Italian origin from olive, but also from other hosts collected since 1992, confi rmed a well-resolved phylogenetic lineage with distinctive phenotypic characters which can be recognized as a separate species. Based on RAPD genomic fi ngerprinting, ITS and β-tubulin DNA sequences, this species was clearly distinct from C. acutatum sensu stricto, C. fi oriniae and C. simmondsii as well as from the genetic groups A1, A6, A7 and A8, all previously referred to as C. acutatum sensu lato. Group A4 is widespread in Europe, being responsible for olive anthracnose epidemics in some Mediterranean countries, including Greece, Italy, Montenegro, Portugal and Spain; moreover, it causes anthracnose diseases on a wide range of other hosts including about 20 different genera of woody and herbaceous plants, ornamentals and fruit trees. This new anamorphic taxon is described as Colletotrichum clavatum sp....
Colonization of Olive Inflorescences by Verticillium dahliae

Colonization of Olive Inflorescences by Verticillium dahliae

Carlos Trapero, Luis F. Roca, Esteban Alca´ntara and Francisco J. Lo´ pez-Escudero | View Article Verticillium wilt of olive, caused by Verticillium dahliae Kleb., is the most severe disease affecting this crop in most olive growing countries. In this study, the presence of viable structures of V. dahliae in dried inflorescences from wilted olive shoots was investigated. The pathogen was found inside peduncles and flowers, by assessing the number of typical star-shaped microsclerotial colonies formed onto the modified sodium polypectate agar medium. Microsclerotia of V. dahliae were observed inside the peduncles under the stereoscopic microscope. The presence of microsclerotia in these easily decomposable olive tissues shows that infected inflorescences can act as a source of inoculum for Verticillium wilt...
A stem canker disease of olive (Olea europaea) in New Zealand

A stem canker disease of olive (Olea europaea) in New Zealand

R. K. Taylor, C.N. Hale, W. F. T. Hartill | View Article A disease complex, with symptoms that include stem cankers and tip die-back, is reported in New Zealand olives (Olea europaea L.). Bacteria from stem cankers of olive were consistently isolated as pale lemon-yellow colonies on King’s medium B. On the basis of microbiological, molecular, and pathogenicity tests the bacterium isolated was identified as Xanthomonas sp. The bacterial isolates allowed verification of Koch’s postulates on young olive trees. As a result of our findings we suggest that the stem canker on olive is caused by Xanthomonas sp. In addition a fungus identified as Fusicoccum luteum was consistently isolated from stem cankers and tip die-back. In inoculated plants F. luteum occasionally formed cankerous symptoms though not as aggressively as Xanthomonas sp. At this stage it is not clear what role F. luteum has in primary...
Balanced plant nutrition may help reduce anthracnose

Balanced plant nutrition may help reduce anthracnose

Vera Sergeeva | View Article Some olive varieties are more susceptible to anthracnose than others. Warm and wet weather can further aggravate the problem, leading to infections of epidemic-like proportions. Wet weather makes the application of chemical treatments difficult, so it is important to consider the use of other cultural practices for controlling disease, such as selection of cultivar type, pruning, irrigation and fertilisation. Correct variety selection, planting density, irrigation scheduling and balancing the physical and biological properties of the soil are all crucial to producing a highyielding, quality crop. However, the proper nutritional management of olive trees is also very important. The essential nutrients extracted from the soil and required by the plant in relatively small amounts are called ‘minor...
First report of anthracnose and fruit mummification of olive fruit

First report of anthracnose and fruit mummification of olive fruit

H. S. S. Duartea, P. G. C. Cabrala, O. L. Pereiraa, L. Zambolima, E. D. Gonc¸alvesb, J. Vieira Netob, E. M. Zambolima and V. Sergeeva | View Article The olive tree is an arboreal species belonging to the family Oleaceae with recognized importance in the production of olive oils and olives. In December 2008, typical lesions of anthracnose, with mature fruit mummification were observed in olive tree fields in Maria da Fe´ , in the state of Minas Gerais, Brazil. A fungus was isolated directly on potato dextrose agar (PDA) from conidia collected from pink to orange masses on infected fruit. A typical fruit sample was deposited in the local herbarium (VIC 31209). The isolate showed a pink colony on PDA, producing sporodochia with a mass of hyaline amerospores with pointed ends. Based on these morphological characteristics the fungus was identified as Colletotrichum acutatum, which has been reported to cause anthracnose on olives trees in other countries and most recently in Australia (Sergeeva et al., 2008). In Brazil, C. acutatum is reported to cause disease on fruit of apple, citrus, strawberry, peach, plum, nectarine, medlar, and on yerba-mate (Kimati et al.,...
Verticillium wilt of olive

Verticillium wilt of olive

Francisco Javier López-Escudero & Jesús Mercado-Blanco | View Article Olive (Olea europaea L.) is one of the first domesticated and cultivated tree species and has historical, social and economical relevance. However, its future as a strategic commodity in Mediterranean agriculture is threatened by diverse biotic (traditional and new/emerging pests and diseases) and abiotic (erosion, climate change) menaces. These problems could also be of relevance for new geographical areas where olive cultivation is not traditional but is increasingly spreading (i.e., South America, Australia, etc). One of the major constraints for olive cultivation is Verticillium wilt, a vascular disease caused by the soil-borne fungus Verticillium dahliae Kleb. In this review we describe how Verticillium wilt of olive (VWO) has become a major problem for olive cultivation during the last two...
The influence of pruning methods on insect and disease control

The influence of pruning methods on insect and disease control

Vera Sergeeva and Michael Thomsett | View Article Insect pests and diseases in the olive grove have significant impacts on production and overall tree health, which if not managed with sound horticultural practices can result in significant economic loss to the grower. Olive trees are susceptible to a wide range of pests and diseases, including black scale, olive lace bug, peacock spot, cercosporiose and...