The dark but small spots on your avocado leaf look like a fungal infection but it could also be scab disease. In both cases you can remove the infected leaves and also add a fresh mulch to the soil so the spores that have fallen off the leaves are less likely to reinfect the new growth. You may want to spray with a fungicide but know that this will not reverse the spots on the trunk and leaves. A fungicide spray could help to prevent the disease from spreading to the new growth. Try to keep the foliage dry and give the plant good air circulation by mot crowding other plants around it. Sometimes it is the weather we can blame for the fungus among but in most cases the plant will not die and the fruit is still edible. Do a good fall clean up and here is hoping for a fresh start next year. Keep growing, Marianne Binetti