That's a loaded question.

Are those trees bare root or potted? If bareroot, I won't worry about insecticide yet as they won't produce fruit. It'd take an average of 3 years for peach to bear fruit. Cherry could be 4, apple can be anywhere from 3-8 depending on what varieties and rootstocks they are. You can worry about that in the future.

Fruit trees are divided roughly into two groups, pome (apples, pears, etc) and stone fruit (cherry, peaches, nectarines, plums). They have some common problems and also have different ones. For now, you need to learn about common diseases.

Peach can easily get Peach Leaf Curl (PLC) and cherry gets cherry leaf spot. To prevent PLC , you need to spray copper during dormant. The one often suggested is Kocide 3000. Mix with water, follow the label and spray in early spring before trees leaf out. One spray should work. Copper helps with several other fungal and bacterial diseases.

Cherry left spot, you can use Captan or Myclobutanil. Myclobutanil is the ingredient in several fungicide. The common one is Immunox. Immunox should be spray when your cherry fully leaf out. Follow the label.

Apple: Immunox/myclobutanil will also help you with Cedar apple Rust, another common leaf issue on apples. The label will tell you when to spray and how often. You should only need 1-3 sprays.

Keep your trees healthy. Try not to whack the trunk with mowing your lawn. Injury brings more diseases. Canker is another issue with peach and cherry. Fire blight can be a serious issue with apples.

Hopefully, your trees are disease resistant varieties. Otherwise, they may get more diseases than you ask for.

Don't want to discourage you but if growing fruit trees is not that easy. Otherwise, everyone would do it. It needs some learning, patience and perseverance. As long as you are willing to commit to grow them, you'll be successful.

Thank you very much for all of the insite. So all of the trees were potted. The cherries are about 8-9ft tall the peaches around 7ft and the apples around 8ft. The apples were the only ones that had fruit on them and I removed all but one apple from each tree so that I can try them and so the trees focus more on establishing themselves than fruiting.

With that being said. Will it be likely that the apple trees will keep fruiting? or probably not next year while they establish themselves?. So far the apple and cherry trees have been growing like weeds. I pruned them when I first put them in and since have only removed new growth that has grown towards the center of the trees. The peach trees are growing a bit and seem happy just not as much as the apples and cherries.

Those trees are tall, too tall for potted trees, at least to me. You should look into pruning. All of them can be pruned in the summer. In fact, pruning them know will help control the size and stimulate fruit buds. Pruning during dormant will shape the trees and stimulate more growth. Many good pruning instructions on YouTube. Try ones posted by university extension services or Dave Wilson nursery.

What are the variety of each of your trees? One apple on each tree would not stunt the tree. For potted trees, by the time you bought them from a nursery, they are 2-3 years old, not a totally young tree like bare root trees.

Make sure you have room in your garage or shed to keep those trees in the winter. You will need it.

They were potted when I bought them. All in 10-15 gallon pails. They have all since been put into the ground. The apples are 2 Fuji and a Gala.

Fuji is susceptible to fire blight. Gala is susceptible to scab. Scab is easily controlled with myclobutanil. Fire blight is harder. Streptomycin can be used. Dormant copper spray is helpful.

Please read up on how to many those diseases with website like Cornell U. They have tons of good info and they are in NY state.