Why are the leaves curling lengthwise on my apricot tree?

Answer 1

With apricots, it seems like it's inevitably going to be aphids that cause leaves to curl. They're very tiny and live on the underside of the leaves. You may want to try the remedies in this article: https://www.gardeningknowhow.com/plant-problems/pests/insects/homemade-aphid-control.htm

If you've examined the leaves and find that this isn't the case, you may want to consult an arborist or your local extension service: http://cesantacruz.ucanr.edu/
Here are couple other articles that may help: https://www.gardeningknowhow.com/edible/fruits/apricots/apricot-tree-pests.htm
https://www.gardeningknowhow.com/edible/fruits/apricots/spraying-apricot-trees.htm