By Elaine Applebaum, UC Master Gardeners of Placer County
Q: I have a lot of nectarines on my tree this year but most have ugly brown and yellow scabby-looking scars on them. They’re also much smaller than the ones in the grocery store. Some of the leaves are curled and distorted, too. What am I doing wrong?
A: It sounds like you have damage from thrips. These are tiny, slender insects, (less than 1/20 of an inch long) which often go unnoticed, but can do a lot of damage. Thrips puncture plant tissue and suck out plant juices, leaving the scars and leaf distortions you describe. The damage most likely occurred earlier this year, and the thrips may already be gone.
Thrips are difficult to control, so an integrated approach is best. To prevent the problem next year, keep your tree healthy by practicing proper cultural control. Don’t overwater or apply too much nitrogen fertilizer. Maintain natural parasites and predators by avoiding broad spectrum, persistent pesticides. Remove injured and infested parts of the tree. Next year, monitor closely for the presence of thrips during and after bloom. If large populations are present, horticultural or neem oil, insecticidal soap or pyrethrins can help reduce numbers. Find more information at UCANR Pest Note, Thrips.
As for the size of your nectarines, having small fruit is a common complaint of backyard growers. The solution is to thin out the fruit when it is about an inch in diameter, leaving only one fruit every 6” to 8”. With good pollination, a tree routinely sets much more fruit than it can adequately support. These fruits compete with each other for limited amounts of carbohydrates produced by the leaves, so remain small.
Excess fruit can also drain energy from the tree itself, weakening it and leaving it open to disease and attack from pests. Additionally, branches can break under the heavy load of too many fruits. With more room between fruit, sunlight can penetrate, producing better color and flavor. The increased air circulation will help prevent diseases. Whether it is nectarines, other stone fruits, apples, or pears, thinning fruit early in the season may be the single best thing a homeowner can do to produce a quality crop.