Ilex VS Zimmerman Pine Moth

Zimmerman pine moth's pitch tube on pine.

Zimmerman pine moth’s pitch tube on pine.

Last year’s drought caused Austrian, Scots, and red pines of the Midwest to be susceptible to the Zimmerman pine moth (Dioryctria zimmermani). White, tan, or rust colored resin flowing on the trunk could indicate the presence of the moth’s caterpillar like larva. Finding one or two boring points is usually of no concern. Heavier infestations could cause weakened trees that topple in strong winds, and the tree will act like a nursery for the moths infecting nearby, stressed trees. These heavier infested trees should be removed.

It is critical to understand the life cycle of the Zimmerman pine moth [ZPM] for proper management. The tiny caterpillar over-winters in a silken cocoon-like structure just under the bark. Now, in the early spring, the caterpillars feed on the bark for a week or two, then tunnel into the main trunk, usually in a whorl area. Resin is pushed out by the insect causing a ‘pitch tube’. Fresh pitch tubes are white to tan, the consistency of lard, and have a shiny appearance. Old tubes are yellow to grey, crystallized and hard, with a dull appearance. It is important not be confused by old tubes and new, which all together, may look like an infestation.

In mid summer, the caterpillars pupate either inside the external resin or within their tunnels. At this time, it may be possible to kill the pupa by hitting the resin with a rubber mallet. I love organic cures!

The adults emerge as small grey moths in mid to late August. These moths fly at night and are rarely seen. Females lay their eggs on the trunk under the bark, thus beginning the cycle.

Management of ZPM begins with tree care including proper mulching, watering, pruning, and fertilization. Healthy trees do not get attacked.

Insecticides should be applied during the two vulnerable times in the ZPM cycle. These times are late to mid-April, as the over wintering caterpillars become active, and in August, when the female moth has just laid her eggs and the caterpillars are searching for over wintering sites. Indicator plants for these spray times are when the saucer magnolia is in pink bud to early bloom, or in mid to late summer when panicle hydrangea is pink. Preventive insecticide sprays should be applied as a drenching spray to trunks in mid to late April.  Spraying branches and foliage is not necessary & wasteful.  Permethrin or bifenthrin are preventative sprays that are available for use by homeowners. Spraying at any other time is inefficient, as it has no effect, and the insecticide may kill predators of the Zimmerman pine moth.

© Ilex Farrell

3 thoughts on “Ilex VS Zimmerman Pine Moth

  1. There may be an alternate cure for the caterpillars. Ever hear of chitosan? I am still on the fence as to its proven efficacy on anything other than seed sprouting when it comes to vegetables. However, there is a company in Colorado Agrihouse (www.agrihouse.com) that makes a product called Beyond Plant Amendment. I know about them because of some consulting work I did with a company that was trying to private label or resell under a different name. They used to have several different formulations, from what I saw they were all the same thing, basically about 99% water and the rest was chitosan. I think they saw the light and just went with one overall plant tonic that they now list as a biocontrol (fancy wording because of all of the ridiculous EPA requirements when trying to register a product as organic.)

    Once you get past all of the crazy NASA marketing etc. you’ll see that the product has been used for the Pine Beetle Kill that is plaguing the West. According to the research done by Agrihouse and some professors at Colorado State University, the pine beetle carries a fungus or the fungus’s spores on it’s back. Once it chews into the tree, usually one weakened by drought or stress, it bores deep. From here the blue ring fungus as it’s called takes over the trees immune system and it dies a quick death.

    I’m not sure about the Zimmerman pine moth’s habits, but I always thought the immense amount of pitch that conifers put out was always a response to the pests, not the pests themselves? Anyhow, trees treated with very small amounts of soluble chitosan due just that, and secrete enormous amounts of pitch, sometimes forcing the beetles and their hitch hiking spores out of the tree entirely. There are many testimonials that praise this product, however I think it’s like anything in gardening etc. An ounce of prevention is worth a pound of cure. Just an idea, some people have actually rehabbed trees that were sick?

    Chitosan is not organically derived, that’s where the hold up with the EPA comes in. They basically can’t certify it as organic, because it is deacetylated crab shell. In this process, the glucosamine as it’s known in molecular terms, is treated with caustics, or acids that remove the acetyl groups from the molecule. It’s these caustics that make the product “tough” to certify, only because of the processing, not the end result. Look into it, I’m sure there’s more out there, lord knows I’ve done the research, just trying to forget now. LOL

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    • Whew! That’s a lot of 411!! Thanks for giving the extra info to my post. I’ll admit I’m a bit ‘green’ on pesticides, even organic pesticides as I don’t have a need to use them too often in my job or personal gardening. I will look into chitosan though, sounds like a ‘break-through’ product.

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  2. Pingback: Monday Memories | Midwestern Plants

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