Primary scab control using a "during-infection" spray timing and the effect on fruit quality and yield in organic apple production

Organic apple production in Europe depends to a great extent on the use of copper fungicides for scab control (Venturia inaequalis). The objective of this 6-year study (2003-2008) conducted in Belgium was to determine measures for reducing the use of copper fungicides in organic apple production. The effectiveness of a 'during-infection' spray strategy using wettable sulphur (with or without copper), lime sulphur, potassium bicarbonate, silicon and five natural plant extracts (orange peel, soapbark, tea seed, quinoa seed and grapefruit seed) for controlling primary scab was investigated in a split-plot field experiment. Four apple cultivars that express a gradient of partial scab resistance were included: a high scab-susceptible cultivar (cv. 'Pinova'), a medium scab-susceptible cultivar (cv. 'Pirouette') and two old cultivars expressing low to very low scab susceptibility (cvs. 'Reinette Hernaut' and 'Reinette des Capucins'). Apart from these cultivars, four monogenic Vf scab-resistant cultivars (cvs. 'Initial', 'Topaz', 'Zvatava' and 'JN 20/33/58') were also included in the experimental orchard. In order to reduce the amount of fungicide required, two strategies were used: a specific spray timing involving spraying during the infection processes, before fungal penetration, determined by the RIMpro software warning system, and a tunnel sprayer machine for optimal treatment applications. Depending on the year, a total of 8-12 applications were made annually. Under field conditions that were highly conducive disease, low rates of elemental sulphur (≤ 40 kg.ha-1 per year) combined with low rates of copper (≤ 2.1 kg.ha-1 per year) provided the best scab control and reduced scab severity on the leaves and fruits by 85-100%, depending on the year and cultivar, compared with the untreated control. In most cases, the lime sulphur spray treatment, which used more elemental sulphur but did not use copper, provided a similar level of scab control to the combined wettable sulphur and copper spray treatment. Sulphur, potassium bicarbonate and all plant extracts significantly reduced scab severity on leaves and fruits. In general, the treatments increased the yield of the high and medium scab-susceptible cultivars as well as that of the low and very low scab-susceptible cultivars. Under these experimental conditions, none of the treatments caused phytotoxicity, increased fruit russet or led to undesirable soil and fruit residues at harvest. The potential and limitations of "during-infection" spraying as a protection strategy against apple scab in organic farming are discussed

Local European cultivars as sources of durable scab resistance in apple

The Vf resistance gene has been widely used in apple breeding programmes to control Venturia inaequalis, the causal agent of scab, the major apple disease. Since the appearance of new strains that are able to overcome this major gene, research in Europe has been focused on durable resistance. The objective of one task of the European DARE project was to find cultivars which show a broad spectrum of resistance to the different scab races. This collaborative work involved 6 partners who tested 36 cultivars with various local scab inocula collected in the participating countries and with 8 monoconidial strains belonging to known races or isolated and characterized in the frame of the DARE project. Tests were performed each year from 1998 to 2001. Symptoms were assessed using macroscopic scoring scales. Some microscopic observations were performed; these resulted in a better knowledge of the host/pathogen interaction. Very diverse and complex resistance behaviours were found: the cultivars which showed the widest range of resistance were mostly local cultivars and some newly selected hybrids combining major genes and partial resistance. It would be worthwhile to include these individuals as parents in apple breeding programmes to improve the durability of scab resistance. Some methodologies and strategies to reach this goal will be proposed

Co-Design and set-up of innovative fruit-based agroforestry cropping system in Belgium

Multiple options exist to set up agroforestry systems that combine pome fruit trees and vegetables. Proposals for different spatial arrangements and prototypes have been developed and evaluated through participative discussions involving scientists, advisors and farmers. Key challenges will be to optimize economic/technical constraints and ecological principles that stimulate natural regulation processes against pests and diseases in a temperate climate. In 2014, an experimental agroforestry orchard was planted in Gembloux, Belgium, on a surface of one hectare. The aim was to test the following three hypotheses: (i) a mixture of selected robust fruit and vegetable cultivars creates a functional biodiversity that significantly reduces the risk of pests and diseases; (ii) annual crops and tree canopies may have an impact on soil functioning, biological interactions and regulations; and (iii) in our optimized ratio and distances between vegetables and trees in intensified and organized alley-cropping systems, the tree shading does not reduce light levels below the threshold of light saturation. Two other on-farm fruitbased agroforestry cropping prototypes in Belgium are under evaluation on two pilot farms according to the farmer’s production objectives, including: (i) adaptation to mechanization, which may limit plant interactions with perennial and/or annual crops; and (ii) the need for a diversified income per surface unit that would allow the economic viability of farms in a capital-intensive economic system

Co-design and establishment of innovative fruit-based agroforestry cropping systems in Belgium

Multiple options exist to set up agroforestry systems that combine pome fruit trees and vegetables. Proposals for different spatial arrangements and prototypes have been developed and evaluated through participative discussions involving scientists, advisors and farmers. Key challenges will be to optimize economic/technical constraints and ecological principles that stimulate natural regulation processes against pests and diseases in a temperate climate. In 2014, an experimental agroforestry orchard was planted in Gembloux, Belgium, on a surface of one hectare. The aim was to test the following three hypotheses: (i) a mixture of selected robust fruit and vegetable cultivars creates a functional biodiversity that significantly reduces the risk of pests and diseases; (ii) annual crops and tree canopies may have an impact on soil functioning, biological interactions and regulations; and (iii) in our optimized ratio and distances between vegetables and trees in intensified and organized alley-cropping systems, the tree shading does not reduce light levels below the threshold of light saturation. Two other on-farm fruitbased agroforestry cropping prototypes in Belgium are under evaluation on two pilot farms according to the farmer’s production objectives, including: (i) adaptation to mechanization, which may limit plant interactions with perennial and/or annual crops; and (ii) the need for a diversified income per surface unit that would allow the economic viability of farms in a capital-intensive economic system

Co-design and establishment of innovative fruit-based agroforestry cropping systems in Belgium

Multiple options exist to set up agroforestry systems that combine pome fruit trees and vegetables. Proposals for different spatial arrangements and prototypes have been developed and evaluated through participative discussions involving scientists, advisors and farmers. Key challenges will be to optimize economic/technical constraints and ecological principles that stimulate natural regulation processes against pests and diseases in a temperate climate. In 2014, an experimental agroforestry orchard was planted in Gembloux, Belgium, on a surface of one hectare. The aim was to test the following three hypotheses: (i) a mixture of selected robust fruit and vegetable cultivars creates a functional biodiversity that significantly reduces the risk of pests and diseases; (ii) annual crops and tree canopies may have an impact on soil functioning, biological interactions and regulations; and (iii) in our optimized ratio and distances between vegetables and trees in intensified and organized alley-cropping systems, the tree shading does not reduce light levels below the threshold of light saturation. Two other on-farm fruit-based agroforestry cropping prototypes in Belgium are under evaluation on two pilot farms according to the farmers production objectives, including: (i) adaptation to mechanization, which may limit plant interactions with perennial and/or annual crops; and (ii) the need for a diversified income per surface unit that would allow the economic viability of farms in a capital-intensive economic system

Temporal dynamics of sexual dimorphism in a dioecious species

• Background and Aims Sexual dimorphism for floral traits is common in dioecious plant species. Beyond its significance for understanding how selection acts on plant traits through male vs. female reproductive function, sexual dimorphism has also been proposed as a possible risky characteristic for insect-pollinated plants, as it could drive pollinators to forage mostly on male plants. However, even though most flowering plant species spread their flowering across several weeks or months, the temporal variation of floral phenotypes and sexual dimorphism have rarely been investigated. • Methods We performed a survey of male and female plants from the dioecious generalist-pollinated Silene dioica (Caryophyllaceae) in a common garden experiment, over two consecutive flowering seasons. Flower number and floral size were measured each week, as well as pollen quantity and viability in male plants. • Key Results Sexual dimorphism was found for all investigated floral traits, with males showing an overall higher investment in flower production and flower size. Males and females showed a similar temporal decline in flower size. The temporal dynamics of daily flower number differed between sexes, with males showing a peak in the middle of their flowering season, whereas flower production by females was quite stable over time. At the scale of the experimental population, both individual and floral sex ratios appeared to vary across the flowering season. Moreover, because the onset of flowering varied among plants, the magnitude of sexual dimorphism in floral size also fluctuated strongly through time. • Conclusions Capturing male/female differences with only one temporal measurement per population may not be informative. This opens stimulating questions about how pollinator behaviour and resulting pollination efficiency may vary across the flowering season