Movement of Invasives

Posted on Categories Uncategorized

This article was published in TNLAGreen September/October (2018) Issue. The below contains the contents of the article and additional resources pertaining to each pest.

Page index: Emerald Ash Borer | Asian Citrus Pysllid | Asian Gypsy Moth | Cactus Moth | Redbay Ambrosia Beetle | Asian Longhorn Beetle | Read-Headed Flea Beetle

The same old annual pests, such as aphids, thrips, twospotted spider mites, and whiteflies, can be rather annoying and a constant uphill battle to manage. For the most part, however, we have a good handle of these pests and can maintain them below economic threshold levels. We run into trouble when an irregular pest, such as a quarantine international invasive pest or a pest from a neighboring state, show up on the operation. We can fail to identify the species, and as a result, fail to act quickly to keep the pest under check. In this article, we try to provide a list of some of the rising pests and how to recognize them.

Emerald ash borer


First recognized as a pest in the US in the Detroit, Michigan area in 2002, this borer has resulted in mortality of over 99% of ash trees in many places it has established. They are a small beetle (1/2-inch long and 1/8-inch wide), a shiny emerald color on the outside, and a shiny purple on the top side of the abdomen (seen when wings are spread apart). The female adults lay their eggs on the outside of the tree and once the immatures emerge, they bore under the bark and feed on the living tissue in a serpentine pattern. Larvae spend their time in the tree during the winter and emerge as adults early April to May and June. Adult emergence holes appear like a “D” shape approximately 1/8-inch in diameter.

Emerald Ash Borer was first detected in the state of Texas in 2016, in traps deployed in the northeast. Currently, the only county under quarantine for Emerald Ash Borer (as of the writing of this article) is Harrison County. However, Marion and Cass counties have recently also seen Emerald Ash Borer infestations and will most likely be under quarantine by the time this article is published. Tarrant county also has an unconfirmed sighting, which raises a red flag for one of the first metropolitan areas in Texas that may get hit with Emerald Ash Borer. In short, the quarantine regulates movement of any “restricted articles” out of the quarantine zone and is very important for reducing the risk of further movement of Emerald Ash Borer. More details on the quarantine and pest can be found below:

Asian Citrus Psyllid


The Asian Citrus Psyllid, less than 1/8-in long, is an invasive plant bug (sucking insect pest) that was first detected in the continental USA in 1998 in Florida. Although only a moderate and manageable pest itself, it also vectors a virus known as citrus greening, Huanglongbing or yellow dragon disease, which makes the Asian Citrus Psyllid a pest of great concern. Symptoms of citrus greening include: yellowing of shoots, decreased foliage, tip dieback, chlorosis, and small, green, lopsided sour fruit. Infection can result in tree mortality in as little as five years.  Economic loss since the first introduction of citrus greening to Florida in 2005 is estimated at over $4.5 billion in lost citrus production and 8,200 jobs, with the vast majority of Florida producing-areas being affected.

Work done by Capoor et al. (1974) showed that after only 15 minutes of feeding on an infected tree, the Asian Citrus Psyllid has a chance to pass the disease to an uninfected tree. After 1 hour of feeding on an infected tree, the Asian Citrus Psyllid has a 100% chance of infecting a clean tree. Additionally, it is thought that adult psyllids can pass the disease directly to their offspring, resulting in even greater transmission of the disease.

Quarantine zones have included southern Texas counties of Hidalgo, Willacy, and Cameron. More recent quarantine counties include Fort Bend, Harris, and Montgomery. Additional resources below:

Asian Gypsy Moth


Although not (yet) known to occur in the USA, the USDA has determined this pest could wreak havoc if it establishes here – so recognizing, reporting, and eliminating any potential infestations very early will do everyone a great service. First identified in 1991 in West Coast Canada on shipping containers, the population was quickly eradicated before spreading. Ever since then until 2014, the Asian Gypsy Moth has been intercepted and eradicated on at least 20 occasions!

Not unlike other caterpillars, the larvae are defoliators, chewing leaves of a wide host range including larch, oak, poplar, alder, willow, and some evergreens. Additionally, each egg mass can contain anywhere from 100 to over 1,000 eggs. The European Gypsy Moth, another invasive caterpillar, already defoliate approximately 700,000 acres of forest and millions of dollars of damage each year. Establishment of the Asian Gypsy Moth is anticipated to result in faster spread, greater damage, and wider host range.

Cactus Moth


Ever since their introduction to Florida Keys in 1989, the moth larvae have been a major threat to the prickly pear cacti, Opuntia spp., of North America. According to a document from USDA APHIS, adult moths have a wingspan of approximately 0.86 – 1.4 inches and the females lay eggs in “stick” formation made up of 70 – 90 eggs. After approximately 30 days, larvae emerge from the eggs and feed primarily on the outside on the cactus, before entering into the cactus pad. Feeding from the cactus moth caterpillars can result in mortality of the entire plant.

The cactus moth has since moved westward into Louisiana. The USDA created an action plan to eradicate the cactus moth from 11 parishes in Louisiana to prevent movement of the cactus moth into Texas, Arizona, and the country of Mexico. The larvae are rather distinct, especially when seen on prickly pear cacti. If you see them, collect evidence (photo/contained specimen), let us know, and destroy the plant to prevent the larvae from developing into adults and infesting new plant materials.

Redbay Ambrosia Beetle


Anyone working a nursery is no stranger to ambrosia beetles. Typically, ambrosia beetles infest trees that are already dead or stressed and are merely secondary to a tree’s decline. Ambrosia beetles have a special relationship with a group of fungi known as ambrosia fungi. When the beetle infests a tree, it carries the fungi inside with it. The spread and growth of the ambrosia fungi provides the ambrosia beetle with the nutritional resources it needs to grow and develop.  The Redbay Ambrosia Beetle is a bit of an exception to typical ambrosia beetles, in that it can attack perfectly healthy trees. First detected in Georgia in 2002, the Redbay Ambrosia Beetle carries a unique fungus that can result in tree mortality in weeks to months.

Symptoms caused by infestation of Redbay Ambrosia Beetle and subsequent colonization of the fungus are collectively referred to as laurel wilt. The Redbay Ambrosia Beetle is currently known to infest redbay, sassafras, pondspice, pondberry, camphor, and potentially more.

Figure 11. Redbay ambrosia beetle adult. Photo: Michael C. Thomas, Florida Department of Agriculture and Consumer Services, Bugwood.org

Asian Longhorn Beetle


A wood borer that can result in mortality of many hardwoods, such as maple, boxelder, willow, and elm, was introduced through Brooklyn, NY in 1996. Adults are ¾-in to 1-½-in long, shiny black with white spots on the body and white stripes on the antennae. Antennae are about 1.5 – 2x longer than its body (hence the “longhorn”). According to USDA APHIS, symptoms of infestation include sawdust accumulating at the base of the tree, pencil-sized perfectly round exit holes, and yellowed/dropped leaves at the wrong time of the year.

Fortunately, no signs of Asian Longhorn Beetles have been seen in Texas yet, and the beetle has already been successfully eradicated from several states, including Illinois, New Jersey, and Manhattan, and eradication efforts are continuing in several areas of New York, Massachusetts, and Ohio. Signs or symptoms of infestation should be reported immediately online or via phone to USDA APHIS to prevent spread at 1-866-702-9938.

Figure 12. Adult Asian longhorn beetle. Photo: Donald Duerr, USDA Forest Service, Bugwood.org

Redheaded Flea Beetle


Flea beetles are not new to the US, and neither are the Red-headed Flea Beetles. In most recent years, however, increasing damage on ornamentals has become of concern to the industry. Danny Lauderdale from North Carolina Cooperative Extension describes the adults as being 1/10 to ¼-in long, shiny black with a red head. The flea beetle larvae are found in the soil feeding on the plant roots; although not a major source of damage at this stage, controlling them in the larval stage will prevent the adults from causing defoliation later on. Flea beetle adult damage resembles a small buckshot being fired at the leaves, with several small holes all over.

Seeing as how Texas is considered a part of its native range, you may already be dealing with infestations of the Red-headed Flea Beetle. Damage by the Red-headed Flea Beetles or other flea beetles should be prevented early in the season by controlling larvae in the pots. Adults migrating into the crop may also present a source of infestation, so periodic treatment for adults may also be necessary. Let us know if you think you have Red-headed Flea Beetle and whether they are a major source of damage at your operation – this would be useful information to help out our growers across the state. Go to https://sixleggedaggie.com/2018/07/24/movement-of-invasives

for related publications on control and management of this particular pest.

Conclusion

Being a grower can feel like a thankless job, especially with all of the challenges in finding reliable labor, praying for good weather, and fighting plant diseases and common insects. Taking time to become familiar with some of the new invasives can go a long way to prevent large crop loss, prevent spread, and help safeguard the green industry in Texas. The above list is a start but certainly not comprehensive. Some honorable mentions that I could not include in the article above include the Sirex Woodwasp, the Giant African Land Snail, and the New Guinea Flatworm. Whenever in doubt, don’t hesitate to contact us for help in identification.

To see the original article, go to September/October Issue of 2018: http://www.tnlaonline.org/tnla-green-magazine.html

Leave a Reply

Your email address will not be published.