Any suggestions? I think the leaf damage was from slugs, and that is now under control, but the leaves are starting to turn yellow. I've applied an organic fertilizer near the base of the tree.

The damage you see is not from slugs, it is consistent with leafhopper's or beetles. Look on the under side of the leaves for insects as well, you can have more than one pest at a time. Most insects that damage leaves eat at night you can see them with a flashlight, take a picture to get a Identification. Once identified we can provide you with a recommendation, Normally I can give you several choices organic or not chemical or not etc.

Randy
Yamhill County Master Gardener

The yellowing on the leaves is consistent with micronutrient deficiency a common problem with organic growers. Micronutrients include: boron, copper, iron, manganese, molybdenum and zinc. Yes, these are organic materials and the margin between enough and too much is very small. Soil and or leaf analysis is the only way to be sure of what is needed or not.
Also, when applying fertilizer the roots extend out to and beyond the drip line the drip line is a good place to apply the fertilizer.

Randy
Yamhill County Master Gardener

Thank you Randy. I'll look into both of these issues, and appreciate your help!

Hi Jade,
I concur with Randy on the holes. I found one of those on mine. It was eating it pretty badly. It looked like a stink bug like creature. It hopped off. He then got scared and never came back to the Paw paw. I later killed one just like him. The same? All the new leaves are whole, with no holes.

The yellowing and drying of leaves I find commonly on pawpaws especially this time of year. Remember, the pawpaw is native to areas in which most of the rain occurs in summer. Midwest-South.I give the pawpaw an occasional bucket of extra water and he is happier. Over time, he will develop that tap root to go deeper, as long as its not frequent shallow watering. Then those yellow dry marks will go away. The deeper the tap root goes, the more he gets minerals, so it's like a combo thing.
John S
PDX OR

Thank you, John. That makes a lot of sense. I'm glad I'm not the only one who has noticed this on pawpaws. I will keep them moister than I have been.