Why is preharvest important in an IPM program?

Early split nuts

Early split nuts.

Mature pistachio nuts beginning to split

Mature pistachio nuts beginning to split.

In the weeks before harvest, give special attention to irrigation, early splits, timing and preparing for harvest, and monitoring especially for navel orangeworm. Using an IPM program at this time can prevent substantial nut damage and yield loss.


Budget irrigation from August through early September to maintain adequate soil moisture, reduce early splitting, and keep orchard rows dry enough to support harvest machinery. Early shell splitting increases nut infestation by navel orangeworm. Infestations are unsightly and they increase nut susceptibility to fruit mold infections and, therefore, to subsequent aflatoxin contamination.

Harvest planning

Harvest in a timely manner to preserve nut quality. Later harvests increase the risk of damage from fourth flight of navel orangeworm, bird feeding, hull deterioration, and early rains. Preharvest rains halt harvest, increasing the rate of hull deterioration, fruit mold infections, and aflatoxin contamination. Before harvest, prepare the orchard floor by managing weeds. Pay attention to the recommended pre-harvest interval label for treating weeds in tree rows. Mow middles to facilitate the movement of harvest equipment.

Early splits (navel orangeworm), Alternaria late bight, birds, Botryosphaeria panicle and shoot blight, Citrus flat mite, and mealybugs

During the weeks before harvest these pests are monitored, and if needed, managed according to the Pistachio Pest Management Guidelines.

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2016 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/C605/m605prharvestwhy.html revised: June 24, 2016. Contact webmaster.