Harvest Sampling Provides Valuable Feedback for Orchard's IPM Program

By: David Doll, UCCE Merced County

The collection and crack-out of a harvest sample is often forgotten during the bustle of the harvest. It is, however, one of the most important practices to employ as it provides a "progress report" of your season's IPM program. A representative sampling of 500 nuts from orchard blocks that underwent differing pest management practices should be collected after shaking but before sweeping. These nuts can be stored in a refrigerator for two to three weeks until time is available to shell the kernels and inspect for insect damage. This sample will indicate what pests are in the orchard to help determine the management activities for the next year. Furthermore, it will serve as a record to compare with the huller/processor grade sheet.

Insects that cause economic damage to almond kernels include navel orangeworm (NOW), ants, leaffooted plant bug, oriental fruit moth (OFM), and peach twig borer (PTB). NOW actively chews and bores through kernels, often leaving behind webbing and excessive white frass. Ants feed on the kernel skin and can hollow out kernels, leaving behind piles of sawdust-like frass. The OFM and PTB cause similar damage on almonds, creating shallow grooves on the kernel. The only difference is that OFM leaves behind small amounts of reddish brown frass and PTB often does not. Damage by the leaffooted plant bug is noted by dark spots on the kernels.

Click here for pictures of the damage caused by the different insects.