Article: Insect Invasions and Management

Brockerhoff, Eckehard G., Andrew M. Liebhold, and Herve Jactel. 2006. "The ecology of forest insect invasions and advances in their management." Canadian Journal of Forestry Research. Vol. 36. 2006. 263-268.


The authors wrote this paper to "enhance the sharing of information" between scientists studying invasive species management (Brockerhoff 2006, 263). It was originally presented at the International Union of Forest Research Organizations Conference on Forest Diversity and Resistance to Native and Exotic Pest Insects in New Zealand. 


I found this paper to be a good culmination of four specific areas of research. The theme of management relates to my research because management demonstrates the need for agencies to present consistent information internally and to the public. Management cannot progress on this issue without consistent information.


The authors, from New Zealand, Morgantown, WV, and France, respectively, share information about four subjects relevant to invasive species management

1. The role of global trade; 
2. biogeographical effects; 
3. biodiversity; 
4. and advances in "detection, monitoring, and management of invasive species and native pests" (264).

Although this report mentions several different insects, the authors describe the emerald ash borer along with the Asian long horned beetle, Anoplophora glabripennis, the great spruce bark beetle, Dendroctonus micans, and the red turpentine beetle, Dendroctonus valens, as cases receiving "much attention because they represent a significant threat to the health of forests and urban trees" (264). They cite an early study done by Haack et al. in 2002, which I will read soon. The rest of the report maintains a macro-view to all the problems of invasive species.


The research done on the role of global trade in invasive species movement shows a need for government action. Studies prove a relationship between "interception frequency and probability of establishment" (264). It also shows a need for more research from the agencies responsible for inspecting shipping containers (264).


Biogeography is the study of plant distribution, such as how forests move over time, and where nurseries develop new plant stocks. Phylogeny deals with the development and diversification of different animals or insects. These two areas of study interweave when researching pests in forests. Research has found that invasive bugs spread for these three reasons:

1. The plants lack a natural defense;
2. few or no natural enemies exist;
3. few or no natural competitors exist (265).

However, the factors leading to the phylogenic introduction of the invasive species can be complex and closely related to the movement of plant species by human benefactors. The authors note, "a reliance on exotic trees in forestry increases the need to exclude pest introductions" (265). 

I imagine this can be a revolving problem. Invasive species prey on native trees and kill them, so new species are introduced, but with them come other invasive species. I'll bet large nurseries have to tackle this problem every year.

Although I have always heard that diversified forests (and urban forests) are less susceptible to invasive species, the authors show that only some research finds this to be true. In other research (from Jactel et al. 2005), some "mixed forests have greater levels of attack than forests with less tree species richness" (265). However, they don't offer too many citations for this information. They agree that many cases exist showing the opposite. In the end, they call for more research (266).

DNA testing and pheromone traps provide two new methods for detecting invasive species. The DNA testing showed 100 percent accuracy in tests (Ball and Armstrong 2006)! Inspectors can sample any part of insect or larvae to find a match and identify a pest. However, a full database needs establishing first. This could be a "standardized tool for biosecurity managers around the world" (266). Pheromone traps prove successful, but studies have shown need for caution when interpreting the data because the number caught does not always relate to the population quantity in the area (Bentz 2006). Other control studies include the simple introduction of a native predator or fungus and confusing the pests by spraying sex pheromones (266).

The authors do note that an "eradication campaign" was "successful" in com patting two pests in New Zealand. The campaign incorporated trapping, spraying a fungus, and releasing sterilized males (267). I wonder what they mean by successful though. Is it a manageable amount of pests or did they eradicate them?

The authors conclude by noting these three things:

1. Invasions will only increase with increased trade;
2. Increased communication will be needed between agencies and scientists; 
3. While some programs to decrease established pests can work, the "primary goal" should be a reduction of the pests becoming established in non-native environments (267). In other words, stop them on the ships!

Other Works Cited

Ball and Armstrong. 2006. "A universal DNA-based identification system for insect pests: a test case with the Lymantriidae (Lepidoptera). Canadian Journal of Forestry Research.

Bentz. 2006. "Mountain Pine Beetle population sampling: inferences from Lindgren pheromone traps and tree emergence cages." Canadian Journal of Forestry Research.

Other Work to Explore

Hacket et al. "The emerald ash borer: a new exotic forest pest in North America. Newsletter. Michigan Entomology Society (47)