Fruit quality of Elstar en Santana in the Netherlands

The growth of the market for Dutch organic apples is disappointing. Especially the large-scale introduction in the supermarket channel is not happening as fast as many hoped. One of the explanations given is that there is a gap between the quality as produced and the quality as expected by the retailers. In a three year project the Louis Bolk Institute together with many other partners in the sector have tried to facilitate talks on apple quality between actual partners in the different chains from producer till retailer. During this period we monitored the quality of Elstar and Santana on many farms and on the shelf in the different outlets. This has given us detailed information about the current quality of Dutch organic apples. Presented here are some preliminary results of the monitoring at the farms. The project will end mid 2004, final results will be published by the end of the year. Progress of the project can be followed through the website www. louisbolk. nl/projects/fruit/’classy apples’

Conference pears; work on system changes to enable better scab control in organic orchards in the Netherlands

Scab control in Conference pears is the bottleneck in organic growing. A group of growers, advisers and researchers in the Netherlands is working on new approaches to organic pear growing. Central to this approach is a reliable and good scab control. Changes in the system of cultivation are sought which will enable this scab control with less fungicide. This has become even more urgent since copper was banned as a fungicide in the Netherlands. First results from trials on vigour control show that there is potency for system changes that will enable a better scab control in organic growing. Scab incidence was reduced in three trials with 34, 58 and 82% respectively. The project, in which also other cultivation measures are being tested, will be continued

Fast temporal adaptation of on-off units in the first optic chiasm of the blowfly

We recorded from spiking units in the first optic chiasm between lamina and medulla in the brain of the blowfly (Calliphora vicina). Both previously characterized neuron types, on-off units and sustaining units, were encountered. On-off units had a temporal frequency response with a lower cut-off frequency than blowfly photoreceptors. This low cut-off frequency is related to a fast temporal adaptation of the on-off units to trains of short light pulses. Temporal adaptation occurred independently for short on- and off-pulses. On-off units only responded to stimuli of relatively large contrast. Contrasts of less than 10% gave little or no response.

Annual report 2002 LBI organic fruit growing research

Overview of projects, project results, funding bodies and partners in 2002 and plans for 2003 Including: SOIL MANAGEMENT * Evaluation of leaf analysis in organic fruit growing as a tool for measuring the uptake of nutrients: Consultants and researchers exchanged practical experiences and the LBI hopes to work with target values. * Impact of sulphur stress: The fruit quality seemed to be better in the reduced sulphur treatment (27 kg /ha instead of 60 kg /ha after flowering). * Fertilisation: In a late summer fertilisation trial with Elstar, trees fertilised late summer/autumn have a higher nitrogen content in the bud the following spring. And fertilising just before winter leads to increased growth of weeds in the next season. * Ground cover: The key to white clover undergrowth is to ‘do it properly or not at all’. It is difficult for an organic grower to restore undergrowth which has been invaded by grasses to bare earth. Undergrowth is definitely not the answer for fruit growers who have any difficulty with mechanical weeding. The management of ground cover requires at least as much mechanisation as the bare tree strip. REGULATING GROWTH AND CROP * Steps to counter biennialism in Elstar: A trial was set up at three orchards combining various measures: thinning or not thinning with two or three applications of lime sulphur, adapted pruning, 3 levels of fruit bearing (30, 40, 50 tonne/ha) and early or late manual thinning. This trial should demonstrate the relative significance of the various measures. Flowering will be evaluated in the spring of 2003. * Fruiting spur pruning in Elstar: To obtain better insight into the effect of different pruning methods three pruning treatments were used: standard pruning, removal of an extra large amount of fruiting spurs, and removal of extra fruiting spurs but sparing smooth one-year-old shoots. The production of the trees has been estimated and the blossom will be evaluated in the spring of 2003. * Effect of thinning times, fertilisation and bearing on regularity of production and fruit quality in Elstar: Ripening was delayed by the high nitrogen dose and associated higher acid content. Despite the late ripening the firmness was still lower, the calcium content lower and the nitrogen content higher. All three factors pro- duce a clear deterioration in quality. On the other hand, the sugar and acidity were higher in this case, but both these values fall within the target band. The trial will continue in 2003 CANKER * Administering calcium hydroxide against Cancer through the sprinkler irrigation system: Despite its effectiveness, sprinkling with calcium hydroxide cannot as yet be generally recommended for practical application. All the difficulties stem from the fact that the agent does not really dissolve, and the suspension formed very rapidly settles out. FRUIT QUALITY * Optimum picking time for Santana: Santana is a relatively new variety, and further investigation is required into optimising cultivation and storage. The apples only developed their full flavour when picked some time after the point of physiological ripeness. * Sprinkling to combat sunscald: By sprinkling under specific conditions an average of 1.38 fruits per tree was protected from sunscald. Per hectare sprinkling on these three days yielded around € 621 per ha. (Assuming: 3000 trees/ha, 6 fruits/kg, price € 1.10 or € 0.20 for industrial use). * Rot resistance test: The Louis Bolk Instituut is attempting to develop a test for the evaluation of the natural resistance of the fruit. This demonstrates, for example that apples with a high nitrogen content have more and larger areas of rot than apples with a lower nitrogen content. * Prospects offered by calcium chloride (CaCl2 ) before or after harvest: A pilot experiment was carried out on a farm to look into the prospects of spraying with CaCl2 before the harvest or rinsing with CaCl2 after harvest to reduce fruit rot. Neither treatment led to a reduction in fruit rot, but rather to an increase. * International association for ‘Organic Food, Quality and Health’ (FQH): The purpose of the group of researchers and traders brought together under the FQH banner is to develop a new concept of quality based on life processes and to select and further develop relevant methods of measurement

Disease management in organic apple orchards is more than applying the right product at the correct time

The relative importance of diseases on apple is varying with cultivar, management, time, and climate. Many aspects of the cropping system influence the development of diseases. The choice of the variety determines the disease management during the lifetime of the orchard. Cultural practices improve the growth and nutrial status of the tree, and therewith influence the susceptibility of the plant and fruits to diseases directly. Prolonged growth can also have an indirect effect by causing a microclimate and growing pattern that favours infection of tree, leafs and fruits by various diseases. Sanitation measures are common practise for most organic fruit growers and help to make other measures more effective by reducing infection inoculums. Despite all preventive measures, disease control in organic orchards at an economically feasible level still largely depends on the application of fungicides. Measures that allow reduction of fungicidal applications on key diseases, lead to the development of a secondary disease complex that can cause severe losses when not managed effectively and make a well thought-out control strategy necessary. In research, advisory and practical decision making, disease management in organic orchards should always be seen in the perspective of the management of the total growing system. With all factors that contribute to disease management in organic orchards optimized, we are able to successfully implement new materials and methods that may not be as effective as common fungicides in themselves, but add to the effectiveness of the disease management system as a whole. This total system approach makes organic fruit growing what it is

Annual report 2003 LBI organic fruit growing research: including plans for 2004

Our objectives in soil management research combine a number of issues: soil fertility, production, fruit quality, growth regulation, prevention of night frost damage, leaf decomposition (scab) and practical feasibility. This will result in different regimes of weed control, fertilisation, foliar feeding and watering for each plot. The evaluation criteria remain particularly difficult to assess. The proposed revised edition of the soil book (LF39) is combined with the final publication of the regulation project which appeared in de winter of 2003 as a hand-book “Biologische Appels en Peren – teeltmaatregelen voor kwaliteitsfruit-” (Organic apples and pears – cultivation measures for quality fruit) (LF75, ed. Joke Bloksma). Time after time our research shows that good crop regulation is the basis for a quality crop. This applies to all varieties, but Elstar requires special attention because of its susceptibility to biennialism. This last year lime sulphur was available for controlling scab. This enabled us to benefit from the side effects of blossom thinning. Trials are still being run internationally on new thinning agents for organic growing. To date however there is no prospect of a more efficacious agent than lime sulphur without the undesirable side effects. This begs the question of how much more energy should be spent on this research. We take the view that there are other areas to be developed which are essential to good crop regulation. There is scope for further development of an adapted pruning method which very specifically anticipates the prospects for the coming year. Pruning also seems to be important for the new variety Topaz, while we still need to ensure that we get sufficient fruit on the tree. Many trials in which we monitor flowering and bearing rates show time and again that Elstar trees with slightly excessive growth levels have much poorer flowering rates in the following year, even where there is no excessive vigour. Thus much attention still needs to be paid to growth regulation. LaMi is running a project in Utrecht province in which demonstration trials are being carried out to encourage the use of calcium hydroxide in conventional fruit growing. As advisor the LBI contributed its experience from the projects in previous years. Infection of a fruit by fungi or disease depends among other things on the resistance of the fruit. The resistance of a product to fungi, pests and diseases is a parameter for the quality of the product. The Louis Bolk Institute is attempting to develop a test for the evaluation of the natural resistance of the fruit, in which the apple can demonstrate how well or poorly a fruit rot fungus (Botrytis c.) can spread in the flesh of the fruit. The LBI has previous experience with self-disintegration tests. The problems here were the replicability and the unknown sources of infection. Fruit quality is an increasingly important aspect of fruit production. The supermarkets in particular continually raise the standards required for (external) product quality. Using organic growing methods it may not always be possible to meet the high standards for external quality. This means that the internal quality will become increasingly important. LBI is currently running 2 projects on apple quality: “Classy Apples in the Chain” (2001-2004) which involves monitoring and working with partners in the chain to reduce the quality gap between supply and demand and also reduce the distance between the start and end of the chain. The second project, “Parameters for Fruit Quality” (2001-2003) addresses more fundamental issues about suitable quality parameters for organic production. (See also 2002 report)

Controlling broad-leaved dock (Rumex obtusifolius) in grass clover mixtures

This article describes three experiments on the control of broad-leaved dock. Experiment 1: Dock seeds were ensiled in grass silages of different dry matter percentages; 23, 34 and 60% respectively. All silages showed a decline of seed vitality in time. Grass clover with dock seeds should be ensiled at a low dry matter percentage or remain in the silage bin for a longer period than 8 weeks. Experiment 2: In a potassium fertilisation trial on grass clover the development of dock was followed. After two years of potassium fertilisation, the number of dock and the root mass was not significant different between the fertilised and the unfertilised plots. It is concluded that potassium fertilisation at a low potassium status does not positively influence the dock development. Experiment 3: In a resown grass clover, dock seedlings were cut at three frequencies; 2, 4 and 6 weeks. After 3 months the number of seedlings had decreased the same in all treatments. However the root biomass of the seedlings was significantly affected. It is concluded that frequent cutting has a negative effect on root biomass but should be practised for a longer period than 12 weeks to have an effect on seedling numbers

Kali-vinasse tegen ascosporen vorming in conference blad : verslag van een éénjarig experiment

In a one year experiment under orchard conditions in an organic Conference orchard, a single treatment with 500 l/ha beetroot Vinasse was tested as a means to reduce the formation of ascospores in the over wintering leaves. Vinasse was applied with an orchard sprayer at the beginning of the leaf-fall period, diluted 1;1 with water. Directly after the completion of the leaf-fall large amounts of leaves were gathered in the orchard to be over wintered in wire mesh cages on the open ground. The fine wire mesh did not allow large earthworms to come in and take away the leaves. When ascospores were ripe in spring, samples were taken from these cages for the detection of ascospores. This was done using a water bath method after an incubation period in the laboratory. Vinasse applied in this way did not lead as expected to a reduction of the potential ascospore discharge but, on the contrary to an increase in ascospore discharge of 45%. This result differs from results in earlier trials. A satisfying explanation could not be found thus far. For the time being the leaf fall treatment with Vinasse against scab should be advised against

Parameters for apple quality - 2 - and the development of the ‘inner quality concept’ 2001-2003

We found clear correlations between management measures, tree characteristics and fruit characteristics. This means that growers can regulate apple quality during the growing season. On the basis of the two apple experiments, we can distinguish respective sets of growth and differentiation parameters and evaluate them in the light of conventional fruit cultivation science. Our results have little new value for fruit growing in practice, however. The value of our research lies in the approach developed to draw up a quality concept and the way in which we can apply this concept to crops about which little knowledge exists regarding the relationship between management measures, crop characteristics and product quality characteristics. Our research also offers a method to validate experimental parameters

Differences in leaf litter, ascospore production and infection of pear scab (Venturia pirina) in Dutch organic orchards

The last two years we measured the amounts of leaf litter and ascospore production per unit of leaf litter area in 7 organic pear orchards throughout the Netherlands. In one of the orchards, adapted managements strategies were implemented two years ago, being grass/clover that is grown as ground cover on the tree-strip, and organic cattle-manure that replaces chicken manure pellets, in order to stimulate the earthworm population and change the palatability of the leaf litter. First results indicate large differences between orchards in percentage of ground covered by dead leaves at the time of major ascospore infections, but also in number of ascospores per cm 2 leaf litter and in resulting potential ascospore dose. We used these data, together with weather data (temperature, rainfall), in a simple multivariate analysis to gain insight in the dynamics of the system. In 2010, 85 % of the variation in pear scab was explained with a model with rainfall during summer and the amount of asco sores per unit of leaf area. In 2011, 81 % of the variation was explained by a model with the amounts of ascospores per unit leaf area and the potential ascospore dose. In the adapted management experiment we measured no changes in leaf litter in the treatments yet. We discuss that our first results show that, to a limited degree, leaf litter was indeed important for the scab epidemic in 2011, whereas in 2010 the high amount of rainfall in the second part of the growing season must have led to a high conidial infection pressure. Surprisingly, in both years ascospore number per unit leaf area was of more importance than leaf litter area or potential ascospore dose. This raises questions on for example the correlation with branch-lesions that we did not measure, and whether the number of ascospores per unit of leaf litter is a direct or an indirect factor that steers the scab incidence in the orchards