Almond Gumming – Insect Damage?

Posted by David Doll  /   April 26, 2014  /   Posted in Almond  /   11 Comments

I have noticed gumming coming from the hulls of almonds in several orchards. The gumming is clear, and can come from multiple points on the nuts. I have also been seeing it more on ‘Nonpareil’ than ‘Monterey’ or ‘Fritz.’


Initially suspected to be leaffooted plant bug, I think these issues are caused by another insect or are physiological. Once I cut into the nut, I do not find a small pin-hole from the bug’s proboscis, or feeding mouth part (Figure 2). Typically, if plant bug damage, a small pinhole can be observed from the surface to the shell (For an example of the pinhole, please see point 1:35 on this video). Even if it is leaffooted plant bug, the damage does not extend into the shell or kernel, and would have minimal effect on kernel development.almondgumming3

Gumming nuts should be checked to make sure that they have been damaged by leaffooted plant bug before spraying. There is more than one possibility to explain gumming nuts.

With that being said, perhaps I am missing something (or misdiagnosing). How much damage have you attributed to leaffooted plant bug?

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About David Doll

David Doll is a University of California Cooperative Extension nut crop pomology farm advisor for Merced County.


  1. Tom Zavesky April 26, 2014 1:09 pm Reply

    I’ve found live LFB and damage in Fresno and Madera Co. I’ve similar gumming on non-pareil but also found some conspurse stinkbug on nutlets.;

    • David Doll April 26, 2014 3:33 pm Reply

      Thanks Tom! I was wondering if the damage I am seeing is due to some minor feeding by other true bugs (i.e. stink bugs, elder bugs, etc). I will keep an eye out for possible culprits.

  2. Cris Wilk April 26, 2014 4:38 pm Reply

    We are seeing the same thing in Butte/Glenn/Tehama/Colusa Counties. In many cases, we have associated the damage with Boxelder Bug. We can find boxelder bug eggs on the nuts and leaves, and nearby grasses have adult boxelder bugs. The punctures are shallow and do not reach the meats. In the past, we have also attributed this type of damage to peach twig borer or oriental fruit moth first instar larvae attempting to feed on the nut, but unable to do so. We have still not found any LFB problems in our orchards up here, but are continuing to monitor very closely.

    • David Doll April 26, 2014 4:42 pm Reply

      Thanks for sharing, Cris! I was thinking that boxelder bugs might have been a culprit, but havent found many of them. I agree with your thought that they would cause minimal damage as I dont think their mouth parts could reach the kernel. I will keep an eye out for the moth pests.

  3. Ted Nix April 26, 2014 6:03 pm Reply

    We have seen similar damage and occasionally gum coming out of the suture only. Could this be NOW trying to get into the nut? Also the hulls have expanded early with an obvious suture formed and NOW may be laying eggs there?

    • David Doll April 26, 2014 6:34 pm Reply

      Thanks, Ted. I have seen gumming from the suture a few years ago – I think it is physiological. Perhaps the nut is developing too rapidly? I suspect that the early suture development may be problematic with NOW, especially if there is something to damage the nut. A year or so ago at a meeting, Joe Siegel (USDA-ARS) indicated that the NOW moth can not “see” the nut until it is damaged. With that said, I would keep an eye out for egg laying, but suspect it might be lower than our fear – only time will tell.


  4. Pingback: C.I.T FOODS – Commodities International Trading – California Almonds: Gumming? Don’t Jump To The Wrong Conclusion.

  5. Andrea Gjerde April 27, 2014 4:58 pm Reply

    I’ve seen the gumming too. I attribute it to shot hole as my Kern Co grower decided not to spray a fungicide this year as it (until recently!) as been very dry and he wants to save as much money as possible to buy water. There is some shot hole damage on the leaves.

  6. Mark Brady - Plant Food Systems April 29, 2014 3:07 am Reply

    Perhaps we can also entertain the possibility of Bacterial Spot, please refer to the picture which accompanied the following article I believe in June of 2013 in the Almond Doctor.

    Bacterial Spot – A New Disease of Almond in the San Joaquin Valley
    Written by: Roger Duncan, Brent Holtz, David Doll and Themis Michailides

    • David Doll April 29, 2014 4:40 am Reply

      Good thought! You are correct – bacterial spot (BS) may cause gumming, but I dont think this is it. The gumming is clear, and present on ‘Nonpareil’ and ‘Monterey,’ 2 varieties that have lower susceptibility to BS (minimal damage even in Australia on these 2 varieties). In the orchard I observed this, ‘Fritz’ was also planted, but no damaged was observed on this variety. ‘Fritz’ is one of the most susceptible varieties to BS.

      BS would have a lesion underneath the gumming. The gumming also tends to be amber in color.

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