Fungal or bacterial canker disease, root injury, and the wood-boring insect Peachtree Borer are all fairly common potential causes for major branch dieback in peaches. While not necessarily the only risk factor, if the tree was planted too deeply or over-mulched, that can stress the plant and contribute to root health problems. Root competition with some of the perennials and lawn near its base is not helping, though is probably a fairly minor issue compared to the rest. Under-watering/drought or over-watering tends to be one precursor to tree decline, but it's hard to tell once it's this advanced what began the tree's struggles. Much of Maryland experienced a drought last year, so depending on if/how the tree was irrigated, that might have caused some stress. (Borers tend to target trees under stress, even if the tree doesn't look stressed yet.)

Since we doubt the tree can recover and it has an awkward shape, it's probably best to replace it. You can put in a new tree this autumn if you want to enjoy whatever crop this tree can produce this year, and early fall is a great time to plant trees in general, though the availability of fruit varieties is probably higher late winter into spring.

Peaches and their kin are vulnerable to an array of pests and diseases, even setting aside branch-killing situations, so preventative pesticide use is usually needed to protect tree health and the harvest itself. Such measures are preventative only (especially fungicides) and not curative, so need to be applied before the pest or disease in question is present. The information on our Growing Stone Fruits page and its link to the Virginia Tech Pest Management Guide will provide more information about what conditions to monitor for and when (and what) treatments need to be applied. It's a long document, but you can search it for "peach" to find the relevant entries.

Insecticide sprays should not be used until a particular pest is identified, since you won't know if the spray chosen will work on the culprit causing damage, and it might harm pollinators or other beneficial insects in the meantime. Sometimes a minor pest or harmless insect may be present when the tree is inspected, but it won't be the primary cause of damage that you are trying to treat for. Many pesticides must directly contact the pest to be effective, though some are absorbed by the plant. At the very least, make sure the spray is labeled for use on a fruit tree from which you intend to harvest.

Miri