Mila Grahovac

Genus Monilinia on pome and stone fruit species.

Different species of the genus Monilinia are common plant pathogens that endanger pome and stone fruit production worldwide. In Serbia, two species of this genus are widely distributed - M. laxa and M. fructigena, while M. fructicola, which is officially on the A2 EPPO List of quarantine pest organisms in Europe and on the 1A part I List of quarantine pest organisms in Serbia, has so far been detected only on stored apple and nectarine fruits. The most important control measures against these pathogens include chemical control in combination with adequate cultural practices, particularly under favourable conditions for disease development. Concerning that species of this genus can cause significant economic losses, knowledge of the pathogen biology, disease epidemiology and pathogen-host interactions is a necessary prerequisite for stable and profitable production of pome and stone fruits. [Projekat Ministarstva nauke Republike Srbije, br. III46008 and br. III43001]

Monilinia spp. Causing Brown Rot of Stone Fruit in Serbia

Brown rot is one of the most important pre- and postharvest fungal diseases of stone fruit worldwide. In Serbia, where production of stone fruit is economically important, Monilinia laxa and M. fructigena are widely distributed. In surveys from 2011 to 2013, 288 isolates of Monilinia spp. were collected from 131 localities in 16 districts and from six hosts in Serbia. Using multiplex polymerase chain reaction, phylogenetic analysis, and morphological characterization, three species of Monilinia were identified as the causal agents of brown rot of stone fruit: M. laxa (89% of isolates), M. fructigena (3%), and M. fructicola (8%). In 2011, M. fructicola was reported for the first time on stone fruit in Serbia, with only one isolate detected. More isolates of M. fructicola were detected in 2012 (2 isolates) and 2013 (20 isolates). The presence of M. fructicola, as well as its increased frequency of detection during the survey, may indicate a change in the population structure of these pathogens, which could have an important impact on brown rot disease management in Serbia.

Molecular detection of Monilinia fructigena as causal agent of brown rot on quince

SUMMARy Species of the genus Monilinia are important causal agents of fruit rot on pome and stone fruits in Serbia. The pathogen is very harmful, especially on small properties and cottage plantations where intensive control measures are not applied. Quince is important host for the pathogens of this genus. During spring 2010, intensive occurrence of mummified fruits overwintering on branches of the quince was observed. The pathogen was isolated using standard phytopathological methods. Pathogenicity of eight obtained isolates was tested by artificial inoculation of injured apple fruits. Identification was performed according to pathogenic, morphological and ecological properties, and was confirmed by Multiplex polimeraze chain reaction, PCR. All the isolates studied caused brown rot on inoculated apple fruits. The isolates form light yellow colonies with lobate margins, with single-celled, transparent, elliptical or oval conidia in chains, regardless temperature or light presence. Sclerotia are observed in 14 days old cultures. The highest growth rate of most of the isolates is at 27°C and in dark. Based on studied pathogenic, morphological and ecological characteristics, it was found that the Monilinia fructigena is causal agent of brown rot of quince. Using specific primers (MO368-5, MO368-8R, MO368-10R, Laxa-R2) for detection of Monilinia species in Multiplex PCR reaction, the expected fragment 402 bp in size was amplified, which confirmed that the studied isolates belonged to the species M. fructigena.

Development of a thyme essential oil formulation and its effect on Monilinia ructigena

Antifungal activity of thyme essential oil against Monilinia fructigena and development of an effective and stable oil formulation for agricultural use were studied in this paper. Bioactivity of the oil itself and its developed formulation, an emulsifiable concentrate (EC), was tested in vitro and in vivo. In vitro experiments, using a slightly modified agar overlay technique, showed that the initially emulsified thyme essential oil, as well as the developed formulation, significantly inhibited mycelial growth of M. fructigena in vitro. Experiments in vivo, performed on inoculated apple fruits, revealed that the formulation successfully decreased oil evaporation from the treated area and provided a significant level of M. fructigena suppression, 64.7-72.1% compared to the control. To our knowledge, an EC formulation of thyme essential oil for agricultural uses had never been developed before. The presented results are initial findings and evaluation of product activity should be continued in the field to determine its efficacy and activity spectrum, and to estimate the economic aspect of its use. [Projekat Ministarstva nauke Republike Srbije, br. III 46008]

Fungicide sensitivity, growth rate, aggressiveness and frost hardiness of Monilinia fructicola and Monilinia laxa isolates

Monilinia fructicola, the most destructive pathogen of the genus Monilinia, has recently been introduced into Serbia and many other European countries. Since then, many studies have been conducted to evaluate the characteristics of Monilinia species that have a role in the establishment and survival of the pathogen in new areas. The present study assessed the capacity of M. fructicola to repress and replace Monilinia laxa in Serbia based on: fungicide sensitivity, growth rate and aggressiveness at different temperatures, as well as frost hardiness of the isolates of both species. The results showed that the isolates of M. fructicola, compared to M. laxa, were significantly less sensitive to the following fungicides: iprodione, tebucanozole, chlorothalonil, azoxystrobin, fluopyram, and boscalid. In addition, M. laxa isolates exhibited little variation in sensitivity to all of the tested fungicides, whereas M. fructicola isolates displayed a wide range of sensitivity. The temperature of 5°C favored M. laxa growth and aggressiveness, while at 30°C M. fructicola grew faster and had higher lesion expansion rate. These results support an assumption that M. fructicola will continue to spread in Serbian orchards in coming years, particularly on stone fruits harvested during hot summer weather.

Screening test for detection of Leptinotarsa decemlineata (Say) sensitivity to insecticides.

SUMMARy In 2009, the sensitivity of 15 field populations of Colorado potato beetle (Leptinotarsa decemlineata Say.) - CPB was assessed to chlorpyrifos, cypermethrin, thiamethoxam and fipronil, four insecticides which are mostly used for its control in Serbia. Screening test that allows rapid assessment of sensitivity of overwintered adults to insecticides was performed. Insecticides were applied at label rates, and two, five and 10 fold higher rates by soaking method (5 sec). Mortality was assessed after 72h. From 15 monitored populations of CPB, two were sensitive to label rate of chlorpyrifos, one was slightly resistant, 11 were resistant and one population was highly resistant. Concerning cypermethrin, two populations were sensitive, two slightly resistant, five were resistant and six highly resistant. Highly sensitive to thiamethoxam label rate were 12 populations, while three were sensitive. In the case of fipronil applied at label rate, two populations were highly sensitive, six sensitive, one slightly resistant and six were resistant. The application of insecticides at higher rates (2, 5 and 10 fold), that is justified only in bioassays, provided a rapid insight into sensitivity of field populations of CPB to insecticides.

Integrated management of causal agents of postharvest fruit rot of apple.

One of the major causes of poor quality and fruit loss (during storage and transport) are diseases caused by phytopathogenic fungi. Economic losses which are the consequence of the phytopathogenic fungus activity after harvest exceed the losses in the field. The most important postharvest fungal pathogens of apple fruits are: Botrytis cinerea Pers. ex Fr., Penicillium expansum (Lk.) Thom., Cryptosporiopsis curvispora (Peck.) Grem., Colletotrichum gloeosporioides (Penz.) Sacc., Monilinia sp., Gloeosporium album Osterw, Alternaria alternata (Fr.) Keissler, Cladosporium herbarium Link., Cylindrocarpon mali (Alles.) Wollenw., Stemphylium botryosum Wallr. The use of available protection technologies can significantly reduce losses caused by pathogens in storage. The concept of integrated pest management (IPM) in apple fruits i.e. sustainable approach in control of causal agents of postharvest fruit rot, using cultural, physical, biological and chemical measures, to minimize economic, health and risks to consumers and environment, is presented in the paper.

Is low efficacy of fungicides always a consequence of fungicide resistance development in pathogen populations

Efficacy of four fungicides with different modes of action (vinclozolin, pyrimethanil, benomyl and fenhexamid) in control of B. cinerea in raspberry, was investigated in the paper. The trials were conducted at two localities in commercial raspberry plantations. In the case of unsatisfactory fungicide efficacy, qualitative and/or quantitative test of the susceptibility of the isolates to particular fungicide was performed, to determine whether the low efficacy is a consequence of resistance development in the pathogen population. At both localities, pyrimethanil and fenhexamid demonstrated the highest efficacy (73.2-89.6%), while the efficacy of vinclozolin was statistically significantly lower (48.7-63.4%) at both localities. However, qualitative and quantitative test of susceptibility to vinclozolin showed that all the isolates were susceptible to vinclozolin and that the reason for unsatisfactory efficacy should be primarily sought in inadequate fungicide application.

The Status of Erwinia amylovora in the Former Yugoslav Republics over the Past Two Decades

SUMMARY Erwinia amylovora, the causal agent of fire blight (FB) on fruit trees and ornamental plants, rapidly spread across eastern Mediterranean countries in the early 1980s. This quarantine bacterium probably arrived in the southern parts of the former Yugoslavia (now FYR Macedonia) from Greece. Based on symptoms, and isolation and identification data, it was concluded that Erwinia amylovora was the causal agent of pear drying in Macedonia (1989). It was the first experimental confirmation of a presence of E. amylovora in the territory of the former Yugoslavia. The presence of E. amylovora was also proved in Serbia that same year. In Bosnia and Herzegovina, FB was detected during 1990. Based on an official report filed with the Federal Ministry of Agriculture in Belgrade, the presence of E. amylovora in Yugoslavia was confirmed (EPPO – Reporting Service, 1991). Therefore, the presence of the bacterium E. amylovora in the territory of Yugoslavia was officially confirmed in 1990. In Croatia, FB was first observed in villages near the border on Serbia in 1995. In Montenegro, FB was first detected in 1996. In Slovenia, FB appeared as late as in 2001. E. amylovora is now present on 10 hosts (pear, wild pear, apple, quince, medlar, mountainash, hawthorn, firethorn, cotoneaster and Japanese quince) in the territory of the former Yugoslav republics. Based on literature data, losses caused by FB in the former Yugoslav republics in the period 1989-1992 were estimated at about 12,000,000 DEM (mostly in Macedonia) and in the period 1992–1996 at 6,000,000 DEM. Total damage in a more recent epiphytotic year in Slovenia (2003) was estimated at

Antifeeding Activity of Several Plant Extracts Against Lymantria dispar L. (Lepidoptera: Lymantriidae) Larvae

SUMMARY Lymantria dispar L. is the most devastating polyphagous pest of deciduous forests, orchards and urban greenery. To prevent damages that L. dispar larvae cause in forestry, agriculture and horticulture, mechanical measures and the use of biological insecticides are the most frequently applied practices. However, the use of conventional insecticides is inevitable in crop protection and forest management on smaller areas, especially in gradation years. However, inadequate use of these chemicals has led to disturbance of biocoenotic balance, outbreaks of some previously less harmful organisms and pesticide residues in soil and watercourses in some regions. To mitigate these consequences it is necessary to harmonize L. dispar control with integrated management principles by applying selective and less toxic insecticides. Therefore, the potential of botanical insecticides and antifeeding substances is gaining in importance. The aim of this study was to assess the influence of ethanol extracts (1, 2 and 5%) of Ambrosia artemisiifolia L., Erigeron canadensis L., Daucus carota L., Morus alba L. and Aesculus hippocastanum L. on the feeding intensity of L. dispar larvae, i.e. to evaluate their antifeeding activity under the conditions of “no-choice” test. Ten larvae per repetition were placed in Petri dishes and offered oak leaf slices (2 x 9 cm 2 /repetition) previously dipped in plant extract or ethanol (1, 2, and 5%) for the control. Feeding intensity, expressed as a percentage of consumed leaf area (%), was measured after 48 h. For assessing the antifeeding activity of plant extracts AFI was calculated and the extracts were classified according to scale: no antifeeding activity, slight antifeeding activity, moderate antifeeding activity and strong antifeeding activity. Data were ana