Fire blight of pears in Israel: infection, prevalence, intensity and efficacy of management actions

The pear production area in Israel is 1500 ha, most of which(ca 1200 ha) is located in the northern part of the country. Fire blight (caused by the bacteriumErwinia amylovora (Burrill) Winslowet al.) was first observed in Israel in that region (in 1985) and the disease has prevailed there since then. In a comprehensive survey conducted in Israel in 1996–1999, data were collected and observations were made yearly in one-third to one-half of the pear production area. The aim was to document the prevalence and intensity of fire blight in commercial orchards and to use the data to evaluate the efficacy of management measures employed for its suppression. Regionwise, a severe fire blight epidemic developed in 1996, moderate epidemics developed in 1998 and 1999, and a mild epidemic developed in 1997. The intensity of fire blight in the preceding season in a specific orchard was more influential on current season severity in a season with a mild epidemic than in a season with a moderate epidemic. Analysis of disease onset records and weather data revealed that only a few (1– 3) infection episodes occurred in individual orchards each year. Comparison of fire blight intensity in orchard-plots treated before green tip with copper hydroxide with nontreated plots revealed that the treatment had no effect on disease intensity during bloom. The efficacy of bactericide sprays applied during bloom was not related to the number of sprays applied but to the timing of spraying. Adequate control was achieved in orchard-plots sprayed soon before or after the occurrence of infection episodes. Contribution no. 508/00 from the Inst. of Plant Protection, ARO, Bet Dagan, Israel.     

Official survey,in 2002, for detection of Erwinia amylovora in a proposed protected zone in Jihomoravsky region (Czech Republic)1

Inspectors of the Czech NPPO surveyed the occurrence of fireblight Erwinia amylovora in an area of Jihomoravsky region (South Moravia) proposed as an EU protected zone, including 16 designated buffer zones around nurseries. The disease was not detected in communes where fireblight hosts are grown (nurseries, variety testing stations, orchards) or in buffer zones around nurseries. In 902 communes where fireblight hosts are grown only in orchards or not at all, wild host plants were inspected at 2.629 observation points (2137 located by GARMIN GPS). In Vy?kov district, suspected fireblight was confirmed at one observation point on Crataegus, growing by a railway in Rousínov commune and, in the course of a delimiting survey outside observation points, in four other communes (Drnovice, Habrovany, Komo?any and Vy?kov).     

Fireblight in Poland

Fireblight ( Erwinia amylovom ) was first detected in Poland in 1966 and then occurred irregularly, in isolated foci mainly along the northern coast of the country, until 1975. During this period, radical measures were taken for localization and elimination of the disease. Since 1976, the disease has become established in numerous areas across northern Poland, and since 1985 has spread towards the centre of the country. Pear, apple and wild hawthorn are affected. In recent years, damage in affected areas has been only at a moderate level. A Ministerial Decree makes fireblight control compulsory. Inspections are carried out throughout the country and any outbreaks must be notified. Complete elimination of infected and adjacent host plants is recommended in areas of low incidence. In heavily affected areas, it is recommended to prune away all infected parts. Severe restrictions apply to nurseries. General preventive measures are also recommended.     

Regulatory measures against Erwinia amylovora in Switzerland*

Switzerland joined the list of fireblight‐affected European countries in 1989. Vigorous and systematic steps were taken to limit the impact of the disease on fruit production and amenity plants. These efforts are codified in a Swiss law detailing prevention, eradication, control measures and issues of compensation. As with many Swiss legal directives, there is a defined coordination of federal and cantonal responsibilities and, in the case of fireblight, there is also an emphasis at all levels on personal responsibility of owners of susceptible objects (e.g. nurseries, orchards, host plants). Extension activities have been a key component in achieving compliance with disease management regulations and in obtained public support for control efforts. Agroscope FAW Wädenswil has taken a leading role in this respect through its website http://www.feuerbrand.ch .     

Fireblight in the Po valley (Italy): the monitoring programmes of Emilia‐Romagna and Veneto regions1

Erwinia amylovora, causing fireblight, is a very important quarantine pest for Italy. Since the beginning of the 1980s, import of host plants from countries where the disease occurs has been limited and subjected to laboratory analyses. Fireblight was found for the first time in Puglia (southern Italy) in 1990. Following this finding, a national monitoring network was set up in order to find new cases as rapidly as possible. In 1994, the first outbreaks of fireblight were found in Emilia‐Romagna. In 1997, a severe epidemic spread throughout this region and the first cases were reported in the bordering regions Veneto and Lombardia. To face this new situation, additional specific local monitoring was set up. This article describes the operational and legislative measures taken in Emilia‐Romagna and Veneto to contain the disease in orchards, to allow marketing of healthy plants for planting and to regulate the movement of beehives.     

Present status of fireblight in the Federal Republic of Germany1

The three phases of spread of fireblight in FRG are described, from its first appearance in 1971 to the present day. The disease is now well established in Schleswig-Holstein and Niedersachsen and scattered outbreaks have occurred over the whole of the rest of the country (but only one in Bayern). The control strategy now centres on destruction of diseased plants within 500 m of any outbreak found in an orchard or nursery (object protection).     

Ten years of experience with fireblight in Austria1

In 1993, fireblight (Erwinia amylovora) was detected for the first time in Austria, in the most westerly part of the country (Vorarlberg). During the following years, especially since 1998, a stepwise migration from west to east was observed. For control, mechanical measures are mostly used. As these measures require early recognition of symptoms, broad information campaigns for the public and extensive surveys of host plants have been set up. Suspicious plant samples are sent to the central laboratory for diagnosis. Regional plant protection services are assisted by trained volunteers. Eradication and pruning measures are performed by trained working teams. Infected plant material is burned. In all pome‐fruit production areas, the disease forecasting system Maryblyt has been established. Regulations concerning the movement of beehives have been adopted, together with prohibition of the planting of certain ornamental host plants (Crataegus, Cotoneaster). Chemical treatments are limited to one copper oxychloride product. In 2003, temporary application of Prohexadione‐Ca for the prevention of shoot infections was authorized. In some areas, the rigorous application of control measures has reduced the incidence of fireblight and possibly slowed down its progress. However these measures are not sufficient to protect against new, unexpected outbreaks.     

Fireblight Inoculum: Sources and Dissemination1

Understanding the disease cycle of fireblight requires knowledge of the sources of inoculum and means of dissemination. In regions where the disease is endemic, hold–over cankers are the most important source of primary inoculum. Dissemination of primary inoculum occurs by rain or by crawling or flying insects. Often, blossoms infested with Erwinia atnylovora (Burrill) Winslow et al. provide secondary inoculum that is disseminated by pollinating insects or by rain. Later in the growing season, secondary inoculum produced in infected tissues may be disseminated by rain or by sucking and biting insects. Relatively rare sources of inoculum and inefficient means of dissemination may be responsible for introducing the pathogen to areas where fireblight has not been found previously. E. amylovora may be carried to new locations in intimate association with host tissues (infected nursery stock), in association with vectors (insects, birds or man), or by wind as “strands” or in airborne water drops. Every effort should be made to prevent introduction of E. amylovora into areas now thought to be free of fireblight. Attempts to eradicate the disease from several new areas in northern Europe have been unsuccessful. Because weather conditions and the host plants present in southern Europe are especially conducive to severe damage from fireblight, plant protection personnel are advised to prepare now for the possible introduction of disease. Personnel should be trained to recognize the disease and plans should be drawn to contain it or to manage host plants to minimize disease losses.     

Using weather records and available models to predict the severity of fireblight should it enter and establish in Australia1

Australia is free from fireblight, a serious apple and pear disease. Published models and weather data from all major apple and pear-producing areas of Australia were used to predict the possible severity of the disease and losses in production should the disease enter and establish in Australia. The results suggest that fireblight could be severe in most areas in most seasons. In the worst case, with every area affected, this could result in up to 20% losses in apple production and up to 50% losses in pear production.     

Fireblight (Erwinia amylovora) of pome fruits in Hungary: national phytosanitary measures and management of the disease

After the first detection of Erwinia amylovora in Hungary, as a result of an intensive survey started in spring 1996, it was concluded that the incidence of fireblight was highest in a zone 10–30 km wide and 200–250 km long near the southern and south-eastern border. The disease was concentrated in the Békés, Bács-Kiskun and Csongrád counties. Isolated infection foci were, however, also found in Baranya county. In 1997, further spread of the disease was recorded. Only three of the 19 counties could be considered as free from the disease. The disease attacked nine major host plants, but the majority of infected plants were quince and pear. During the eradication campaign in 1996, more than 60 000 trees were uprooted and destroyed across the country. Eradication was performed partly by special work teams and partly with the participation of growers. The pathogen most probably entered Hungary by aerial drift from Romania or Yugoslavia during the previous 2 or 3 years. In the interior of the country, introduction through nursery stock and possibly infested tools, as well as wind and insect movement, cannot be excluded. Major measures to control the disease are discussed.     

Experiences with the control of fireblight in Norway during 1986/20031

Fireblight was detected for the first time in Norway in 1986, in a limited outbreak on ornamentals, in particular Cotoneaster. An organization for the eradication and containment of the disease was rapidly established, and given comprehensive statutory powers and resources to do surveys and to remove diseased plants and highly susceptible plants from infested areas. The activities have so far been successful. The disease has remained within a restricted area on the West Coast, and has not moved into important fruit‐growing areas or nurseries. Since 2000, fireblight has spread to some adjoining areas, mainly due to uncontrolled movement of beehives. New statutory powers prohibit movement of beehives out of infested areas from May to October.     

Biotype Q of<Emphasis Type="Italic">Bemisia tabaci</Emphasis> identified in Israel

The biotype status of samples of the whiteflyBemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) collected from several field and greenhouse sites in Israel during 1999–2000 was determined by polyacrylamide gel electrophoresis (PAGE) for general esterases, and by RAPD-PCR using primers of arbitrary sequence. Results of this survey provide the first published evidence for the occurrence of theB. tabaci Q biotype, alongside the more widely distributed B biotype. Based on the collected samples, it appears that both the B and Q biotypes are present in Israel, and that field populations consist of a mixture of the two biotypes. A possible link betweenB. tabaci biotypes and insecticide resistance is discussed. Contribution no. 508/02 from the Inst. of Plant Protection, ARO, The Volcani Center, Bet Dagan, Israel. http://www.phytoparasitica.org posting Dec. 5, 2002.     

A Review of Methods Used in the Laboratory Diagnosis of Fireblight1)

Most well–known laboratory methods which can be used in the diagnosis of fireblight, as well as more recent developments in identification, have been discussed. They vary from the use of simple culture media to the use of immunofluorescent microscopy. The use of any one method alone is not advised, but by combining methods, accurate and rapid diagnosis is possible. In order to minimize diagnostic errors, especially among less experienced workers, the use of 5 % sucrose–nutrient agar for bacterial isolation followed by serological control is recommended. For further information reference is given particularly to the procedures described by Lelliott at the first EPPO Conference on Fireblight held in 1967 at Canterbury.     

Status of pesticide resistance in arthropod pests in Israel

A complex of events and factors, pertinent to a specific insect and insecticide, governs the development of resistance to insecticides. In Israel, resistance to conventional and novel insecticides occurred in insect pests such asBemisia tabaci andSpodoptera littoralis (that damage agricultural crops),Tribolium castaneum and other flour beetles (that contaminate stored products), andPediculus humanus spp., house flies and mosquitoes (that threaten public health). In the mid-1980s an insecticide resistance management (IRM) strategy was established for all cotton grown in Israel and is being adjusted on a yearly basis as needed. At present, insect pest management and IRM strategies are being developed and implemented area-wide for three regions in Israel: Bet She’an Valley, western Galilee, and western Negev. There are several research groups now working in Israel on various aspects of resistance including occurrence, mechanisms, and management practices. This paper offers a tentative review of the status of insecticide and acaricide resistance in pests in Israel.     

Fireblight situation in Bulgaria and measures undertaken by the NPPO1

Fireblight disease, caused by Erwinia amylovora was first detected in Bulgaria on quince in the region of Plovdiv in 1989. The disease was initially localized in that area but, during 1995/1997, due to favourable climate conditions, it became epidemic. Infected trees were grubbed out and destroyed. The main hosts are quince and pear (over 40% of affected trees), then apple, medlar and Cotoneaster. Containment measures undertaken by the Bulgarian NPPO are laid down in the Plant Protection Law, in Phytosanitary Regulation no. 1 for phytosanitary control, and in Phytosanitary Regulation no. 5 of 1996 (amended 1997) for containment of fireblight. Phytosanitary control is mainly focused on fruit‐tree nurseries and on the distribution of healthy plants for planting. In 2003, 41 protected zones and 29 protected sectors within infested areas have been established.     

First occurrence of fireblight in Romania

Fireblight was first observed in Romania in 1992-08 near Braila, and shortly after in the pear collection of the Fruit Research Institute in Pitesti-Maracineni. Advanced symptoms indicated that the disease was present at least one year earlier. Symptomatology, fruit pathogenicity, selective culture media, hypersensitivity, agglutination and fatty acid class analysis confirmed the authenticity of the pathogen as Erwinia amylovora. Of the native Romanian fruit cultivars affected, apple cv. Delicios de Voinesti and pear cv. Aromat de Bistrita appear the most susceptible to fireblight.     

Techniques for the treatment, removal and disposal of host material during programmes for plant pathogen eradication

Eradication of plant pathogen incursions is very important for the protection of plant industries, managed gardens and natural environments worldwide. The consequence of a pathogen becoming endemic can be serious, in some cases having an impact on the national economy. The current strategy for eradication of a pathogen relies on techniques for the treatment, removal and disposal of affected host plants. There are many examples where these techniques have been successful but many where they have not. Success relies on a sound understanding of the biology and epidemiology of the pathogen and its interaction with the host. Removal and disposal of infected plant material for eradication and containment of plant and soil inhabiting fungal, bacterial and viral pathogens are reviewed by considering black Sigatoka of banana, apple scab, maize smut, fireblight, citrus canker and sharka disease of stone-fruit crops. In examining examples of dealing with plant pathogens and diseased host material around the world, particularly Australasia, various techniques including burning, burying, pruning, composting, soil- and biofumigation, solarization, steam sterilization and biological vector control are discussed. Gaps in the literature are identified and emphasize the insufficient detail of information available from past eradications. More effort is required to produce and publish scientific evidence to support the success or otherwise of techniques and suggestions for future research are proposed.     

Real-time PCR for detection and quantification of Erwinia amylovora, the causal agent of fireblight

Real-time PCR was used for quantitative detection of Erwinia amylovora , the causative agent of fireblight. Specific primers were created from a DNA fragment of the common plasmid pEA29, successfully used for standard PCR identification of the pathogen. The primers amplified DNA from various E. amylovora strains, but not from other plant-associated bacteria. DNA of E. amylovora was also amplified from field samples and from inoculated apple leaves or flowers. Neither the presence of other bacteria nor low amounts of tissue extracts from bark or leaves changed the signal threshold. Assays with SYBR Green I instead of the Taqman probe showed a similar sensitivity, detecting 50 cells per assay. Real-time PCR could be especially useful for mass screening of commercial products and for resistance studies of transgenic host plants, in breeding experiments and after treatments to control fireblight.     

Practice of applying streptomycin to control fireblight in Hungary1

The conditions under which streptomycin may be used for fireblight control in Hungary are described. Authorizations for individual limited treatment programmes are given to registered growers only.