Though many gardeners value ants as pollinating insects, peach tree owners dread them. Ants may help peach trees grow fruit by transferring pollen from one flower to another while they feed, but once the fruit forms, ants spell disaster. The tiny insects burrow and feed on the fruit, causing it to die or rot on the tree. Not only is this unsightly, it makes the fruit inedible and can cause great harm to the tree if it loses too many fruits.
Of course, you can kill the ants with pesticides, but these can be as harmful to humans and plants as the insects themselves. Organic pesticides may work, but many of them are hit and miss. One sure way to repel ants from your peach trees is to use companion planting, planting helpful herbs that ants avoid.
Plant onions and garlic around your peach trees in mid-winter, just before Christmas. This gives them time to germinate in the cold and grow underground roots that will be able to support new growth in the spring. The scent of both of these plants will repel ants and prevent leaf curl in your peach trees.
Dig a hole about 5 inches deep and wide for each onion bulb and 3 inches deep and wide for each garlic bulb. Slip each bulb into its appropriate hole and mix a handful of mature compost with the soil from the hole to give the plants nutrients. Cover the bulbs completely with soil and pack it down gently. If you had to move aside snow to get to the soil, push it back over the holes. It will insulate the plants.
Watch for sprouts around your peach trees in the spring. When garlic and onion sprouts form, cover them with fabric screen to keep birds from taking your plants. The sprouts should emit a scent that prevents harmful insects from infesting your trees.