Our new growth in our young lemon tree has curly leaves…should we spray with eco oil or Yates copper fungicid

Thanks for your question, Mireille! Usually curling leaves in citrus is due an environmental response (ie: they're thirsty) or they have citrus leaf miner (which you can read more about here: https://www.yates.com.au/garden-hub/citrus-leaf-miner/). You absolutely can use eco-oil for citrus leaf miner, applying about every two weeks with the first flush of new growth, covering both top and bottom of the leaf until the point of run off. You can read more about the product here: https://www.ecoorganicgarden.com.au/products/pest-disease/eco-oil/

Finally, it may be a good time to give your citrus a bit of nutrition before winter sets in to help it along! Try 'Yates Thrive Natural Citrus & Fruit Organic Based Pelletised Plant Food' as a complete, soil-conditioning fertiliser for richer, juicier and more abundant fruit and healthy plant growth. Click here for more info on this product: https://www.yates.com.au/product/garden-fertilisers/organic-based/yates-thrive-natural-citrus-fruit-organic-based-pelletised-plant-food