Currently the Danish organic fruit & berry production area is 502 ha with the main crop being apples at 282 ha. FruitGrowth will address the main barriers identified by the ‘Working Group report, 2009’, by focussing on robust cultivars in apples, new innovative weeding methods and extending the fruit season & thereby product availability for consumers we will introduce new cultivars & technologies in storage.

We work on short and long time solutions of the key pests and diseases (codling moth, apple sawfly and apple scab in apples), natural beneficial’s in flower strips, and natural compound to control key pest.

FruitGrowth includes research, development, demonstration & dissemination of the results to fruit growers. Outcomes are expected to contribute to a market-driven growth of unique, high value fresh organic apples from local sustainable and profitable production systems, through increasing grower, industry and consumer confidence in Danish grown organic apples.

2013: Progress and activities:

Robust apple cultivars
Thirty new apple cultivars have been planted in connection with the project; the majority of these are new crosses that have not previously been tested under Danish conditions. After the 2013 season it will be possible to divide the cultivars into three categories. The majority will fall into the category of ’limited future perspectives’ due to inferior fruit quality, a significant number will fall into the category of ’ too early to pass judgement’ and a limited number
belong to the ’looking promising’ category. For the two latter catagories more experiment years are needed to assess quality and disease susceptibility more thoroughly.

New innovative methods to control weed
It is now succeed to bring the generated hot air in the weed burner approx. 25-30 cm outside the burner. This allows controlling the weed 60 cm beside the trees and between the trees. The speed is 3 km/h and the energy consumption is 96 kW/h. A test has been carried out on a lawn where the weed burner had significant impact on the grass, both beside and between the trees. The temperature dipstick (acting tree trunk) was approx. 168.5 ° C in 0.6 seconds.
The prototype is now ready for a field trial.

Field experiment focusing on organic weed treatments
The experiments with organic weed treatments show clearly that mechanical cleaning is the best solution in organic apple orchards. Alternatives to mechanical cleaning include rapeseed straw, biodegradable ground cover or weeds. All alternative solutions suffered large damage during the winter of 2012/13. Trees planted in rapeseed straw were severely damaged by mice that ate the bark off the tree trunks, the same happened to the trees in biodegradable ground cover, though to a lesser degree. Trees in permanent weeds suffered from frost cracking of the bark on the south facing side of the trees. Only tree growing in mechanical
cleaned trees-strips remained largely free of damage.

New storage techniques
Organic “Elstar” apples were harvested in October and stored from November to April under 1) Dynamic controlled atmosphere (DCA) with decreasing O2 concentration or under 2) Controlled atmosphere (CA) with low O2 concentration. The results show that it is possible to store apples under very low oxygen with good results concerning firmness for a rather long period until late March, but shelf life is reduced. Consumers expect a higher quality of organic apples compared to the cheaper conventional apples. In the future it is therefore important to focus more on possible causalities between quality loss during shelf life and cultivation
factors in the apple orchard.

Flower strips and predators
The field trials in 2012/13 confirm the favorable effect of flower stripes growing near apple trees concerning surviving codling moth larvae and the activity of predators in the spring and summer. The field trial in the summer 2013 with mass-release of two different species of Trichogramma show that one species was more efficient, but at a moderate level.

Natural substances against apple sawflies
Plant extracts Quassia (MD Quassin) azadiracthin (NeemAzal T / S) and spinosad (Trasources), which is a fermentation product from a bacterium have been tested in field trials according to GEP and EPPO standards. The trials were located at growers where apple sawfly is a problem. The trials confirmed that both MD-Quassin and Tracer are able to control apple sawfly with approx. 80%, while the effect of NeemAzal T / S was significantly lower by approx. 40% effect. At present, none of the compounds are approved for use in Denmark.

Mechanical protection against scab
Strategic irrigation is one of the initiatives being tested for prevention of apple scab. Unfortunately, the irrigation trials in 2012 and 2013 did not result in reduced scab infection in the majority of the experiments conducted. Ascospore release was studied in relation to irrigation. Ascospore activities in 2012 clearly showed that natural rain triggers far more spore release than sprinkling water.
Rain roofs over unsprayed apples have yielded astonishing results in terms of disease control. In 2012 scab was reduced from 72% in unsprayed ’Red Elstar’ to only 2% when grown under roof. Similarly, storage rots (after appropriate storage and shelf life) was reduced from 40% to only 2% when grown under roof. Other diseases also showed similar decline while it was not possible to detect any differences in fruit quality in the first year of the experiment.

2012: Progress and activities:

Robust apple cultivars:
The cultivar experiment with fruit from an earlier unsprayed planting (45 cultivars) is now evaluated. Promising cultivars, suitable for organic cultivation with good fruit quality are Nanna and Collina. The Belgian Zonga is also an interesting cultivar for organic farming, and is of good fruit quality with ripeness after the early cultivars (Discovery, Collina, etc.). In a new experiment, 32 promising cultivars of apples from different countries have been planted, and the first four cultivars are now ready for evaluation.

New innovative methods to control weed:
The development of a self-propelled gas burner to control weeds under the apple trees is underway. The weed burner is expected to be developed in the summer 2013. The robot to control the weed burner in orchards is developed and waits for testing with the gas burner.

Flower strips and predators:
The field trial with flower strips growing near apple trees in 5 orchards demonstrated favorable effects on surviving codling moth larvae and the activity of predators in the spring. The field trial with mass-release of two different species of Trichogramma to control codling moth will be repeated in 2013. The damage by codling moth was very low in 2012, because of a very cold and wet summer.

Natural substances against apple sawflies:
Plant extracts Quassia (MD Quassin) azadiracthin (NeemAzal T / S) and spinosad (Trasources), which is a fermentation product from a bacterium have been tested in field trials according to GEP and EPPO standards. The trials were located at growers where apple sawfly is a problem. The trials confirmed that both MD-Quassin and Tracer are able to control apple sawfly with approx. 80%, while the effect of NeemAzal T / S was significantly lower by approx. 40% effect. At present, none of the compounds are approved for use in Denmark.

Protected production:
A strategic irrigation trial aimed at triggering ascospore release in periodes of dry weather has been carried out for 2 years in the apple cultivar “Elstar”.
Ascospore release was studied in relation to different irrigation strategies using variable quantity of water, different size of droplets and accompanying deep sounds. All resulted in release of spores, however, the largest release of spores was observed by natural rain. The different irrigation strategies showed no overall effect on apple scab infections.
In 2013 additional irrigation trials with rainwater will be carried out.
Rain roofs as means of scab protection has been tested in another study in 2012 using two very scab sensitive apple cultivars. The effect of rain roof was studied with and without use of approved organic fungicides (sulfur and potassium). The final results are not yet available as the fruits are stored until February 2013. However, at present it can be concluded that the
rain roof has had a significant effect on the occurrence of scab in the orchard. Despite a challenging scab season with many infection periods during the summer, it was possible to produce almost scab free fruits of the cultivars Elshof and Rubens without spraying. The occurrence of sooty blotch and russeting was also significantly reduced, giving hopes that also rot diseases can be reduced; this will be further investigated in 2013.

2011: Progress and activities:

In FruitGrowth the goal is to increase the production of high quality apple fruit. It is important to overcome risks from poor cultivar productivity, pest and disease threats and to find long term sustainable production solutions to increase profitability. Overcoming these production risks would improve yield,
profitability, fruit quality, seasonality and consumer confidence in Danish organic products, as consumers would be provided with a more reliable supply of quality organic fruit over a longer market window. An increased and reliable Danish based production would become more competitive against imported organic apples and provide future export opportunities. The project is designed to resolve current risks to the organic apple industry by focusing on delivering a robust production system for apples. 
The project is well underway with the following ongoing activities:

• Evaluation of the existing apple cultivar collection for their suitability for organic cultivation and planting of new promising cultivars for organic cultivar trials
• Gas burner for weed control in development
• Storage Experiments with DCA (Dynamic Controlled Atmosphere) in order to extend the apple season
• Field trials with floral stripes, with the aim of creating better environment for the pests' natural enemies
• Knowledge exchange with other research institutions and companies working with natural regulation of pests
• Experiments with natural chemicals against apple sawflies
• Preliminary study with mechanical protection in order to protect against apple scab 

Project leader

Michelle Williams
Aarhus University
Kirstinebjergvej 10
DK-5792  Aarslev

Tel: (+45) 87 15 83 35
E-mail: Michelle.Williams@agrsci.dk

 Find publications from the project in Organic Eprints