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A four year old pear may not be quite mature enough to fully fruit. It is able to flower and start a pear but not finish the job. Depending on the cultivar, pear trees start fruiting when 5-10 years old. Another potential issue is pollination. Many pears are not self-pollinating. They need another tree to cross-pollinate for fruit to succeed. There is more information at this link: http://treefruit.wsu.edu/orchard-management/pollination/

Is it actually holes or is it black spots? Black spot disease is a possibility. I don't really have enough information here or a photo, but you can call your local extension agent and I'm sure he/she can help. You might consider using a combo insect/fungal spray next year.

https://www.gardeningknowhow.com/edible/fruits/pear/pear-tree-diseases.htm

https://www.uaex.edu/publications/PDF/FSA-6059.pdf

I can't seem to find the article in reference, however, the National Center for Home Food Preservation has recommendations for such a task. They can be found here: https://nchfp.uga.edu/how/can_07/pear_preserves.html

We don't recommend certain products but here is information about when and what to spray:

https://www.gardeningknowhow.com/edible/fruits/fegen/fruit-tree-spraying.htm

https://www.gardeningknowhow.com/edible/fruits/pear/fixing-pear-tree-problems.htm

https://www.gardeningknowhow.com/edible/fruits/pear/growing-pear-trees.htm

Half the battle with insect pests is enhancing natural resistance through good soil fertility and water management. Fertilize with a complete organic fertilizer, mulch and water appropriately and you will not have such stressed and susceptible trees.

If the pear trees and others are still dormant (no flowers or foliage), then use a dormant spray with a 2% solution of horticultural oil (2.5 ounce in 1 gallon of water). If in flower, then wait until flower drop to avoid spraying pollinators, then use the same oil but in a "delayed dormancy" 1% concentration (1.25 ounce per gallon).

Or begin spraying every two weeks with 70% neem oil.

For the pears and fireblight prevention, you can add a biological fungicide-bactericide to the tank mix now and weekly until flower buds open.

Inspect the pears weekly for fireblight infected tips (dried foliage with blackened "shepherd's crook" tips of woody stems. Prune those out below the blackened lesions before the infections advance downward into larger branches.

https://www.gardeningknowhow.com/edible/fruits/pear/fixing-pear-tree-problems.htm

https://www.gardeningknowhow.com/edible/fruits/fegen/fruit-tree-spraying.htm

Spring or early summer will give you the most time to get the cutting rooted and growing well before winter cold sets in. Use cuttings from spring or early summer.