Some specific questions:

- fertilizer recommendations - fruit tree spikes, or granular fertilizer, or compost, or manure?

- frequency/timing of fertilizer - is it too late in the spring?

- mulch on top of fertilizer?

- trees are not close to a water source - how important to water weekly?

- when/how to prune?

- we think we have peach leaf curl - how to treat?

- should we be spraying for pests/fungus?

- can you hire an arborist specializing in fruit trees to come for a consultation?

Growing tree fruit is a rewarding experience and it does not come without challenges. Pest management for these trees relies on identifying the pest and then choosing management options that minimize pest-caused damage without harming beneficial insects like predators and pollinators. There is no one-size-fits-all approach and you will have to come up with a program that works well for you. To help get you started, I am going to give you a list of resources for information that will help you keep the trees at their best and minimize pest damage (see below).

Here are some answers to your specific questions:

fertilizer recommendations - fruit tree spikes, or granular fertilizer, or compost, or manure?

Base all of your fertilizer needs on a soil test: https://www.canr.msu.edu/news/soil-testing-returns-through-msu-extension

The formulation that you choose is up to you. Generally slow release fertilizers (e.g. compost, composted manure, synthetic slow release granules) are better for annual maintenance of soil nutrient levels. Water soluble fertilizers will impact the plant more quickly and can be helpful in situations where they need to be rescued from acute deficiency symptoms. 

Here is an article from MSU Extension that provides some additional information about fertilizing fruit trees: https://www.canr.msu.edu/news/spring_fertilization_of_garden_fruits

trees are not close to a water source - how important to water weekly?

Frequency of watering will depend on the soil type, the tree species, and when it was planted. Newly planted trees will need more water than established trees. Some tree species might need irrigation throughout their lives to produce good quality fruit, especially if they are growing in sandy soils. You will have to get to know your fruit trees and work with your soil type to come up with an irrigation plan that works for your site. 

when/how to prune?

More cold hardy fruit trees (e.g. apples, pears) can be pruned in the winter. More tender fruit species (e.g. cherries, peaches, apricots) are best pruned in late winter/early spring. Young fruit trees of all types should be pruned later in winter because they are less tolerant of cold temperatures following pruning. 

we think we have peach leaf curl - how to treat?

Peach Leaf Curl is a disease caused by a fungus that overwinters as spores on the bud scales. It can be managed with fungicide applications in the fall after the leaves drop and/or spring at bud swell. This year we are seeing a lot of it, which I think is related to weather conditions last fall and this spring being conducive to propagation of the fungus. Now that it is in the leaves, there is nothing that can be done. The trees will not die and the leaves that remain will continue to perform photosynthesis.

can you hire an arborist specializing in fruit trees to come for a consultation?

Some certified arborists have expertise in fruit tree care. You can find a list of certified arborists by Zip Code on the website for the International Society of Arboriculture here: https://www.treesaregood.org/findanarborist

General tree fruit care and culture:

Considerations for growing backyard tree fruit http://msue.anr.msu.edu/news/considerations_for_growing_backyard_tree_fruit

Pdf: https://www.canr.msu.edu/uploads/resources/pdfs/backyard%20tree%20fruit%20-%20web.pdf

Pruning and training backyard fruit trees: https://www.canr.msu.edu/resources/smart-gardening-pruning-and-training-backyard-apple-and-pear-trees

Pdf: https://www.canr.msu.edu/home_gardening/uploads/files/smartgardening-pruningfruit-web.pdf

Renovating old fruit trees:

Oregon State University

https://extension.oregonstate.edu/gardening/berries-fruit/restore-those-old-fruit-trees

University of Wisconsin Extension Bulletins:

Growing Apples in Wisconsin: https://learningstore.uwex.edu/Assets/pdfs/A3565.pdf

Growing Pears in Wisconsin (A2072): https://learningstore.uwex.edu/Assets/pdfs/A2072.pdf

Growing Apricots, Cherries, Peaches & Plums in Wisconsin (A3639): https://learningstore.uwex.edu/Assets/pdfs/A3639.pdf

Good Fruit Grower article on Cherry training systems: http://www.goodfruit.com/the-seven-cherry-training-systems/

Michigan Fresh Bulletin (E3173) ”Growing Tree Fruits at Home”: http://msue.anr.msu.edu/uploads/resources/pdfs/Growing_Tree_Fruits_(E3173).pdf

Good Fruit Grower article on proper spreading of shoots and branches: http://www.goodfruit.com/spreading-shoots-of-young-apple-trees/

Washington State University page for fruit tree Pruning and Training systems: http://treefruit.wsu.edu/orchard-management/pruning-and-training-systems/

Pest Management Resources:

Minimizing pesticide risk to bees in fruit crops (MSU E3245): http://msue.anr.msu.edu/uploads/resources/pdfs/Minimizing_Pesticide_Risk_to_Bees_in_Fruit_Crops_(E3245).pdf

Michigan Fruit Management Guide (for commercial fruit growers) E154 available for purchase at local extension offices or at http://shop.msu.edu/product_p/bulletin-e0154.htm .

Home fruit spray schedule from University of New Hampshire Extension:

https://extension.unh.edu/resources/files/Resource005256_Rep7402.pdf

Managing pests in home fruit plantings (Purdue University Extension, ID-146-W):

https://www.extension.purdue.edu/extmedia/id/id-146-w.pdf

Bagging fruit to protect it from pests and diseases:

https://entomology.ca.uky.edu/ef218

https://www.clemson.edu/extension/peach/commercial/diseases/clemsonfruitbags.html