A successful summer harvest of peaches and nectarines starts in winter. General clean up, pruning, and dormant spraying will help prevent disease and keep your trees in good health.

Remove and destroy all mummified fruit hanging on tree branches or littering the ground. Although they look harmless mummies can harbor spores, fungus, and diseases which can ruin crops. Stop the cycle of infection by removing these mummies and destroying them, not composting them.

Once the tree is dormant (no leaves) you can prune out any dead, diseased or broken branches. Do not seal or paint pruning cuts, leave them open to the air to heal naturally. Sealing or painting these cuts traps moisture and leads to disease. Once all dead, diseased and broken branches are removed prune up to 50 percent of last year's wood. Pruning your tree produces new growth and opens up the tree to sunlight to produce quality fruit.

To prevent leaf curl (fungus) spray before bud swell, which typically occurs after Feb. 14 or Valentine's Day. Signs of leaf curl are detected on new spring leaves but by then it is too late to control the disease. By planning ahead, you can reduce the likelihood of leaf curl and mitigate its effects on tree growth and fruit production. Some effective fungicide spray materials that are registered for backyard use are bordeaux mixture, fixed copper and chlorothalonil. Always wear proper protective clothing and follow the label when applying any pesticides.

For more information on winter, spring and summer care of your peach and nectarine trees see the University of California Agriculture and Natural Resources (UC ANR) Publication 7261: Peaches and Nectarines: Calendar of Operation for Home Gardeners.

For further assistance contact your local UC Master Gardener Program.

Sources:

http://homeorchard.ucanr.edu/Fruits_&_Nuts/Peach/
http://anrcatalog.ucanr.edu/pdf/8057.pdf
http://www.ipm.ucdavis.edu/PDF/PESTNOTES/pnleafcurl.pdf (Pest note7426)
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7481.html