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Integrated organic practices in apple orchard management

Activity summary

Apple is one of the most important fruit crops in Canada with a yearly production of about 400,000 metric tonnes on more than 18,000 hectares, with a farm gate value of about $150 million (). The leading apple producing province is Ontario, followed by Quebec, British Columbia and Nova Scotia. With growing consumer-demand for organic foods, global markets for organic produce continue to expand. Organic apple growers are in a good position to capture this increasing trend, but only efficient organic apple production can meet these growing market demands. The challenges of providing adequate tree nutrition to maintain tree health and effective pest management practices to produce marketable organic apples are paramount. Four important issues which hamper organic apple production in our region are: tree nutrition, apple scab, black rot and the European apple sawfly.

Organic apple growers rely on compost and other organic materials as fertilizers, but these are often complicated by their slow nutrient release and unpredictable mineralization. Improving nitrogen (N) use efficiency, in particular providing N in a timely fashion, can be challenging in organic systems. The Swiss sandwich system is a relatively new concept for better N management of tree fruits, especially organic apples, and is gaining popularity. In this system, a strip of mainly legume ground cover is planted in the tree trunk line, with a tilled bare strip on each side. Biomass from the legume is incorporated into the bare strips. Alternatively, growing legume covers in the lane ways can offer two to three times more area than the trunk line for the cover crops and thus the outcome will ensure more biomass and N addition to the trees.

Good nutrition is essential to maintain tree health, which in turn helps to combat disease and insect pest attacks. A major impediment to conventional and organic apple production in eastern Canada is apple scab, which can result in a complete crop loss. In addition, summer diseases such as bitter rot, black rot, powdery mildew, sooty mould and fly speck are fungal diseases poorly controlled in organic orchards. Conventional and IPM growers apply 8 to 10 synthetic fungicide applications annually, while organic growers rely upon copper and sulphur, often making 14 applications per season. Biological control agents are becoming more readily available for a number of apple diseases, but not all diseases are adequately controlled. Also, considerable research has been directed toward inducing the natural disease resistance response mechanisms inherent in all plants to provide adequate disease control.

The European apple sawfly (EAS), an introduced pest of apples lacking indigenous natural predators, has recently emerged in Atlantic Canada and Ontario. The EAS has been reported to cause severe damage to some apple cultivars in an organic orchard of Nova Scotia. This pest emerges early in the spring and lays eggs in the flower receptacles when pollinators are active. Control of this pest is particularly difficult due to the need to protect pollinators. Currently in Canada there is no registered organic pest product for this pest, but organic growers in Europe have had some success in the control of EAS using a pollinator-friendly extract of Quassia wood.

Research efforts to develop novel integrated organic practices in apple orchard management aim to resolve the imminent issues facing organic apple production in our region. We propose to provide organic apple growers with effective management tools, such as new strategies to maximize N uptake by way of a modified Swiss sandwich system, precise timing of N application to minimize possible N losses from the orchard, and novel techniques for fungal disease pest management. In addition, registration of Quassia extract in Canada would allow organic apple growers an effective and organic-compliant pest control product to combat the newly emerged EAS insect pest. New knowledge gained will lend support to the long term development and sustainability of the organic apple sector.

Materials and Results to Date

• • HortScience (2016) 51: 1378-1383
• • Fruit and Vegetable Magazine. 2016

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