The aim our research was to develop effective methods for organic apple farming, based on the use of plant extracts to control the asexual reproduction of Venturia inaequalis. Plant extracts of artemisinin, chelidonine, thymol, and populin tested in vitro under laboratory conditions significantly slowed down the germination of V. inaequalis conidia. During a 2-year study under field conditions, the effect of 1% populin, an extract from black poplar buds, on apple scab was tested in parallel with synthetic fungicides and a nopesticide regime on Golden Delicious and Jonathan apples. Populin significantly reduced the number of scabbed leaves and fruits on Golden during the first year of the field evaluation compared to synthetic fungicides and had a similar effect as synthetic fungicides in the second year of application. The mean number of scabbed leaves on Jonathan was reduced significantly by both synthetic fungicide and populin applications in both years; however, while synthetic treatments did not reduce the number of scabbed fruits in the first year, populin significantly reduced the number of lesions on fruits. According to these results, we concluded that the severity of apple scab on commercial apple cultivars can be reduced using 1% populin plant extract as a cheap, alternative, and highly available method of reducing the conidial spores. The estimated costs of spraying populin per hector on apple plantations were much lower than costs for synthetic fungicides. Populin application may allow elimination or reduction of synthetic fungicide use and enable efficient organic apple farming.

In Romania, walnut Juglans regia L. is an important fruit crop, although most of the fruit production comes from non-grafted walnut trees, which are natural hybrids. Breeding programs have been launched during last 30 years to develop new cultivars with uniform fruit quality. In addition, foreign cultivars have been introduced and tested to establish a valuable walnut genepool. To improve the present assortment of generative rootstocks in walnut and to examine the infestation level, a long term survey was carried out in Eastern Transylvania. The main physical characteristics of fruits and its variation to the infestation level were considered. The cumulative distribution of Xanthomonas arboricola pv. juglandis and Gnomonia leptostyla were relatively low and the maximum value was around 15%. The highest infestation of husk with X. arboricola pv. juglandis was observed for roundish forms and differences were statistically significant comparing with other phenotypes. Infestation with G. leptostyla was similar for roundish, elliptic and thwarting egg-shaped phenotypes, while the husk infestation for egg-shaped phenotypes was not observed. The walnut population studied in our experiment can be considered as a genetically valuable population. More than 20% of them have upper class quality fruits with at least or more than 50% of nutmeat. Do to the large scale climate variation in Eastern Transylvania and the high humidity favourable for pathogen infestations, these population can be considered resistant and well adapted to abiotic and biotic factors.

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During the survey we studied traditional old apple cultivars in order to test disease resistance, as part of an apple breeding program. Diseases and pests assessments were made throughout the two growing season in 2008 and 2009 in traditional apple cultivars ('Batul' , 'Pónyik' , and 'Sóvári') from stray and commercial ('Golden Delicious' and 'Starkrimson') apple orchards. Our data add to a body of evidence indicating that traditional apple cultivars under natural selection and without pesticide regime are highly and/or moderately resistant to fire blight, apple powdery mildew and apple scab. High resistance was observed for green apple aphid ('Sóvári') and rosy leafcurling aphid (all cultivars, except 'Sóvári') throughout the assessment. Susceptibility from mediate to high level was observed for fruit peel moth and pear-leaf blister moth, while resistance and/or moderate resistance for spotted tentiform leafminer and codling moth. The codling moth damages were significantly correlated with seed number in fruits throughout the whole vegetation period. We can conclude that old apple cultivars sustained in their original regions could be a significant source of genes for apple breeding programs.