New young leaves on my lemon tree are curling up. What can I do?

probably the wrong fertilizer
Talk with a horticulturist as to what citrus trees prefer and the ph of the soil that they thrive in

This will happen, - if the Tree needs feeding, you may find it needs an acid type of Feed +Soil - also where you are keeping the potted tree usually better at this time of year under cover eg greenhouse, also check the leaves for bug infections.

Magnesium deficiency more than likely

To treat, remove all infected leaves and dropped fruit from the ground. Prune the lower branches from the tree, those that are more than 2 feet from the ground. Then spray with a fungicide such as Agri-Fos orCaptan. Botrytis fungus - Botrytis rot is yet anotherfungal infection which may afflict lemon trees.10 Jan 2016

Lemon Tree Problems: Treating Common Lemon Tree Diseases

https://www.gardeningknowhow.com/edible/.../lemons/common-lemon-tree-diseases.ht.. What is the Treatment for diseases of lemon trees Google Search

the leaf curl is from a grub ( very small that is inside the leaf and eating the leaf structure)
as you do not believe in pesticides
it will require a lot of google research as to natural compositions that will kill the pest or talk with organic organizations to get help

short on a mineral in the soil
read google pages on citrus fruit problems
could be lack of iron or manganese mineral

http://homeguides.sfgate.com/leaf-curl-citrus-tree-37359.html

The leaf-curl maggot. Spray the tree with Roundup (glyphosate)

This can happen for a few reasons, all involving water in one form or another. A rubber tree that is underwatered or overwatered will curl its leaves. As will a rubber tree that is in too low of a humidity or in poor soil.
When watering water when the soil is dry to the touch about 1 inch down and then water with enough water to that water runs out the holes each time. This helps remove any build up of soluable salts. IF the tree has recently been moved and lost leaves, the tree should put out new leaves but they will not be in the quantity that they were when the plant was brought in. Fertilizer should not be used at this time of adjustment. Only after the plant gets settled into the new location and then about once a month or so.
Information About Rubber Trees

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