Hollies and their Pests

Mark Wilhelm

Authors:  Mark Wilhelm, Matthew Borden, Dr. Adam Dale

Faculty Mentor:  Dr. Adam Dale

College:  College of Agricultural and Life Sciences

Abstract

Hollies, such as the native Ilex vomitoria (yaupon holly) and I. opaca (American holly), and the non-native I. cornuta “Dwarf Burford”, are common ornamental plants in the southeastern U.S. Several groups of insect pests affect these plants, including the psyllid Gyropsylla ilecis, the aphid Toxoptera aurantii, leafminer flies (Agromyzidae), and multiple scale species (Diaspididae and Coccidae). A literature review was conducted on several common holly pests, particularly the poorly known yaupon psyllid, Gyropsylla ilecis. Additionally, an experiment examined the relative susceptibility of the three previously mentioned holly species to the tea scale, Fiorinia theae. Both previous literature and the new study suggest that I. vomitoria incurs negligible damage from most common holly pests. This, combined with the plant’s native status, drought tolerance, and marketability as a beverage, make it an excellent candidate for replacing the common I. cornuta “Dwarf Burford” in landscapes.

Poster Pitch

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Poster

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12 Responses
  1. Tarolyn Plumley

    Hi Mark! Awesome poster. I think it’s very important to plant native ornamentals especially in a place like Florida where there are so many different pests and a variety of pathways for invasive species. Like Dr. Dale says in class “right plant right place” !!

    1. Mark

      Hey Tarolyn. Yes, I agree with this, particularly since non-native plants have the potential to sustain invasive pests. I didn’t talk much about it in this poster, but yaupon holly has the additional advantage of producing a delicious tea.

  2. Keara Clancy

    Hi Mark!

    Great poster- it’s nice to see a solid rationale for planting natives. Are leafmining flies host-specific, hence the lack of pests on Burford Holly? What kind of damage do they induce on the plants?

    Best,
    Keara

    1. Mark

      Keara, I’m glad you asked. Leafminer flies vary in how specialized they are on a particular host. Phytomyza species are generally pretty specific to at most a few species of Ilex, or often only one. Although Phytomyza is not limited to North America, I don’t know of any records of it on Ilex cornuta (native to China). They cause mines to form, as in the picture. Usually this damage, especially on hollies, is quite minor. Sometimes they can be present in high numbers, and can do more damage. They are mainly and aesthetic issue, and are not likely to be a major problem on an holly species to my knowledge.

  3. Nice work, Mark. Do you have any speculation about why Burford (Chinese) holly seems to be more susceptible to tea scale than the two species native to North America?

    1. Mark

      Well, tea scale is native to Asia, where Ilex cornuta also occurs naturally. It is possible that tea scale have become adapted to this host over a long period and do not perform well on other non-native holly species. Another possibility is the caffeine content (as you know, an insecticidal alkaloid): Ilex vomitoria has substantially more caffeine than other Ilex species. I will link a study that discusses this; unfortunately, I don’t know of any study that examines caffeine content in Ilex cornuta.

  4. Matt Borden

    Well done Mark, hope it went well! Playing devil’s advocate here of course, but in what situations (if any) do you think Burford hollies might have advantages?

    1. Mark

      Hey Matt,
      As you know, Burford holly is more resistant to two-lined spittlebug than is American holly. Yaupon holly can have a thin canopy and often requires frequent pruning to keep new sprouts from coming up from the roots. If you ask me though, it’s hard to beat the yaupon holly.

  5. Kelly Laplante

    Hello Mark!
    Great presentation. I was wondering how much of an aesthetic effect leaf curling may have for the Yaupon holly? Since it is such a diverse plant that can be used ornamentally, I was wondering if curling leaves may degrade the aesthetic appearance, while perhaps not physically harming the plant enough to cause any real damage.

    1. Mark

      Kelly,
      I don’t know of any instances where aphid damage such as leaf curling has been a serious issue on yaupon holly. Even as an aesthetic concern, I think it would generally be pretty minor. Yaupon psyllid is a much bigger aesthetic problem.