Taking a harvest sample for orchard IPM check-up

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 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 2-3 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 orange worm (NOW) (Picture 1-2), ants (Picture 3), oriental fruit moth (OFM) (Picture 4), and peach twig borer (PTB) (Picture 5), and leaffooted plant bug (Picture 6). 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, causing shallow grooves on the kernel. The only difference is that OFM leaves behind small amounts of reddish brown frass. Damage by the leafooted pant bug is noted by dark spots on the kernels.

Picture 1: Navel Orange Worm Damage to a mature almond.

Picture 2: Webbing and excessive frass left by navel orange worms.

Picture 3: “Sawdust-like” frass left by ants.

Picture 4: Damage by Oriental Fruit Moth. Note the reddish frass left behind.

Picture 5: Peach Twig Borer damage found on almond kernels. Note the lack of frass and shallow grooves.


Picture 6: Darkened spots caused by the leaf-footed plant bug.

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3 thoughts on “Taking a harvest sample for orchard IPM check-up

  1. David, There are a couple items that I would like to bring to your attention. First, although it has been long believed that once almonds were on the ground, they are immune to attack by NOW, recent studies have shown that this is not entirely true. Second, OFM damage can look much like NOW in terms of the depth of feeding in the kernel (I believe this is the correct spelling, rather than kernals)and often looks similar to PTB but deeper


  2. Thanks Brad for the comments. Below is a bit of follow up:

    You are correct that NOW damage can occur to almonds that are on the orchard floor. Damage, however, doesn’t appear to be as great as if those same nuts were left in the tree. Thank you for catching my oversight. I may be under-estimating the damage caused by NOW to grounded nuts, but I will try and dig up more info on this subject.

    Usually, early harvesting suggests a longer drying time on the orchard floor. While on the floor, the nuts are susceptible to pests – this includes NOW – but the point I was trying to make in the articles is that ants can be unexpectedly problematic if the population density is high enough. Research has shown that a moderate ant population can inflict a 3.2% rejection rate within 10 days of the almonds being on the ground. This is why it is critical to know the pests and densities present in the orchard.

    The second point about OFM is correct as well. If samples were brought to the office and I was asked to identify if it was either OFM or PTB, I don’t think I would be able to tell you for sure. The other aspect is that PTB and OFM damage is often masked by NOW damage. NOW seems to be “attracted” to the nuts previously damaged by the other worm pests. The reasoning for this is not fully understood, but it may be due to an easier entrance in previously damaged nuts.

    Thanks for the correct spelling. I will fix that in my entries. I hope it is alright, but I am going to re-post this comment on the 2010 Harvest entry as well.


  3. Pingback: Almond Board: Importance of Harvest Sampling | AgNetWest

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