If you haven't had any diseases or pests attack the trees, there is no need to spray anything. If you would add your state to your zone, others may be able to give you more specific advice on the pests or diseases to watch for. If you do have a problem develop, be sure to identify it, then use the appropriate treatments for that problem. Otherwise, you are just wasting time and money applying cures that will do no good. Apple trees will usually start to bloom 3 to 7 years after planting. It varies with the variety and rootstock and growing conditions. So, if the trees have grown well but not excessively vigorously, they may bloom, but they could easily take a few more years to mature enough.

I'd watch for fireblight on the pears. Pears seem to not require a whole lot of spraying. I haven't touch mine and it looks great. I just spray for Cedar rust on my apples, which Immunox has worked well for. Other then that i'm bagging my apples this year so i got that part of it covered. I also have a bad case of Rose Chafers, but that is very dependent on location (sandy soils) and i've been spraying Sevin for that, but i might switch to Imidacloprid and buy some traps. You might want to think about thinning really soon, if you haven't done it yet.

Small caterpillars are very easy to control with spray or dust, if that is OK with you. I had some caterpillars in one of my small trees, defoliating the branches, I hit them with a bit of permethrin dust and that ended their destruction. Obviously in the top of the tree, spray would be a better choice. Ted

I've had aphid infest my artichokes so bad that water wouldn't work. The stupid buggers were so thick that in order to knock them off with water, I had to spray so hard that it broke the leaves. Not to mention the angry ants crawling up my boots. That's when I went to the insecticidal soap. I would think in your situation, that may work best since your apple tree is just a seedling... you don't want to rip its leaves off with water blasting. You can get a spray bottle of it at the garden store (or hardware store) for around 5 bucks. Just remember that when dealing with aphids, they are persistent, so you must be too. Check it every day and spray it every other till they're gone, then at the first sign of reinfestation, you can get away with mechanical methods... water, q-tips, whatever works. Oh and honeydew is just a sweet name for aphid poop.