There is a lot to be learned about invasive arthropods

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Oops, my mistake!

During the earlier part of this week, I attended an Invasive Arthropod Workshop at Clemson University in South Carolina. The workshop was sponsored by the Southern Plant Diagnostic Network. Seventy bug geeks from all over the country were in attendance. These included state university diagnosticians, USDA/APHIS/PPQ identifiers, state department of agriculture entomologists, survey entomologists with the Cooperative Agricultural Pest Survey (CAPS) program and taxonomic experts in various groups of arthropods. The purpose of the workshop was to provide training in screening and identifying exotic and invasive arthropods that are either currently established in the United States and expanding their range, or other exotic species that are knocking on our door. It was a most excellent workshop.

It was at this workshop, that I learned that I had misidentified a very common home invading insect almost 20 years ago, when I first became the insect diagnostician in the MSU Department of Entomology. The bug that I incorrectly identified then, and for which I have provided the wrong information for nearly 20 years to the citizens of Michigan is the
Western conifer-seed bug, Leptoglossus occidentalis (Hemiptera: Coreidae). I had erroneously called it the Leaf-footed pine seed bug, Leptoglossus corrculus (Hemiptera: Coreidae). Dang!

The Western conifer-seed bug was a topic of the invasive species workshop, because it is a native species that has been rapidly expanding over the past several decades and now threatens southern United States pine seed plantations. Like boxelder bugs and Asian lady beetles, the Western conifer-seed bug invades homes and other structures in the fall of the year seeking protected sites, in which to overwinter. The leaf-footed pine seed bug does not share this annoying habit. Double dang!

Good stuff for you to know about invasive arthropods

If you are willing to forgive me and read further, I would like to share with you some other interesting things that I learned about invasive arthropods from the workshop. When my kids were in elementary school, many of the projects they were assigned included coming up with one or two fun facts about the topic they had been assigned to research and write up. Given there is nothing “fun” about invasive arthropods, I will call the following some “Not so fun facts” about exotic and invasive arthropods. These were presented by Joe Cavey, National Identification Services, Plant Safeguarding & Pest Identification, USDA/APHIS/PPQ.

  • Two percent of accidentally introduced species of arthropods become established in the United States.
  • 65 percent of 212 insect major pests accidentally introduced into the United States, were not known as pest insects in their native areas.
  • Seven percent of the animal and plant accidental introductions become pest species.
  • The likelihood that an introduced arthropod will become established is extremely unpredictable, and we cannot predict what effect an insect species will have on the ecosystems it invades, although we tend to think it will generally be bad.

The following not-so-fun facts are based on information gleaned from the 1.4 million data records in the USDA/APHIS/PPQ Pest Interception Database since 1984 (McCullough et al. 2006).

  • Of all pest groups tracked in this database, (i.e., insects, mites, snails and slugs, plant pathogens, nematodes and weeds,) 78 percent of all exotic organisms that are intercepted by PPQ are insects.

The major means or pathways by which these pests gain entry into the United States

  • Plants for propagation as cargo, e.g. imported nursery stock.
  • Plant products not for propagation as cargo, e.g. fruit and vegetables.
  • Miscellaneous cargo, e.g. machinery, ceramic tiles.
  • Plant material carried by international travelers.
  • Conveyances, e.g. ships, aircraft or railroad cars.
  • Mail.
  • Organism imports, e.g. live insects for butterfly houses.
  • 61 percent of intercepted pest were found in personal baggage and 31 percent were discovered in cargo.

But cargo is considered riskier because…

  • Pests in cargo are tougher to detect.
  • Cargo is shipped to multiple sites.
  • Large volumes involved in cargo mean large infestations.
  • Only 2 percent of the cargo entering the United States is inspected.

Where do most of the interceptions take place?

  • 73 percent of pest interceptions occur at airports.
  • 13 percent of pest interceptions occur at land borders.
  • 9 percent of pest interceptions occur on ships.

The most frequent origins of intercepted pests are:

  • Central and South America; 21 percent.
  • Caribbean: 19 percent.
  • North America (Mexico and Canada): 17 percent.
  • Asia: 14 percent.
  • Europe: 10 percent.
  • Pacific Islands: 9 percent.

The major means or pathways that are of highest concern:

  • Nursery stock.
  • Wood packing materials.
  • Cut flowers.
  • Oddly, ceramic tiles and quarry products.

The following not-so-fun facts about exotic insects pertain only to forest insect pests. These were presented by Bob Rabaglia, Forest Health Protection, USDA Forest Service.

  • 400 exotic species affecting forests and forest products are established in the United States.

Ecologically, these exotic species…

  • Impact the structure and composition of our forests.
  • Aid other destructive forces that act upon our forests.
  • Impact wildlife and fisheries.
  • Impact water quality.

Economically, these exotic species…

  • Reduce yield; the cause mortality and growth loss.
  • Affect quality of our forest products.
  • Impact recreation.
  • Increase management costs of our forests.

The most common orders of intercepted exotic insects affecting trees and forests

  • Homoptera (leafhoppers, aphids and scales)
  • Lepidoptera (moths and butterflies)
  • Hymenoptera (sawflies, bees, wasps and ants)
  • Coleoptera (beetles)
  • Cerambycidae (longhorned beetles)
  • Buprestidae (metallic wood boring beetles)
  • Scolytidae (bark beetles)

Bark beetles are the most commonly intercepted beetle.

Exotic bark and wood-boring beetles that have become established since 1989 by family..

  • Scolytidae (25+)
  • Cerambycidae (4)
  • Buprestidae (2)

The most common pathway for these exotic bark beetles is solid wood packing material (SWPM) for tile, machinery, granite, ironware; seeds.

The origins of these exotic bark beetles

  • 117 different countries of origin.
  • The top 10 are Italy, Germany, Spain, Mexico, Jamaica, Belgium, France, China, Russia and India.

Some examples of the number of exotic bark beetle interceptions in solid wood packing material by state between1985 and 2000:

  • Michigan:115 interceptions.
  • New York: 451 interceptions.
  • Ohio: 327 interceptions.
  • Florida: 1102 interceptions.
  • Texas: 1203 interceptions

The number of first reports or detections of established species of exotic bark beetle in North America by year:

  • <1980: 29
  • 1980’s: 8
  • 1990’s: 10
  • 2000’s: 8

The continent of origin of established exotic bark beetles in North America:

  • Europe: 4
  • Eurasia: 12
  • Asia: 27
  • Africa: 11
  • South America: 1

In summary, one would have a hard time not thinking these not-so-fun facts about exotic insects paint a pretty grim picture for our forests and landscapes.

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