Submitted to: Pest Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2010
Publication Date: 9/6/2011
Citation: Caesar, A.J. 2011. The Importance of Intertrophic Interactions in Biological Weed Control. Pest Technology. 5(Special Issue 1): 28-33.
Interpretive Summary: Rationale for the dual implementation of insects and pathogens that interact directly for biological control of invasive weeds has a basis in the very earliest successes in which exotic, invasive perennial rangeland weeds were controlled. The control of such invasive weeds as prickly pear cactus species and St John’s wort are attributable to insect/pathogen interactions it is argued. The ecological effects of insect/pathogen interactions on plants in general show large effects on whole biomes across regions. Research on the dual effects of herbivory by nematodes interacting with soilborne fungi has shown that such interactions can alter plant succession. Thus, early research, the analogies between insect or nematode herbivory/plant pathogen interactions in different settings, and more recent findings indicate the power of such interactions. That this knowledge can be used to devise means of selecting biocontrol agents by assessing the propensity for interaction.
Technical Abstract: The earliest research leading to successful weed biocontrol included observations and some analysis that the strict “gate-keeping” by peer reviewers, editors and publishers does not often allow today. Within these pioneering studies was a valid picture of the biology of weed biocontrol that is applicable today. Two major studies pointed to successful weed biocontrol of perennials as an outcome of intertrophic interactions. Later work indicated that there was a consistent association of certain fungal species with insect damage. In recent years, ecological studies have provided evidence of the effect of the soil microbiota in combination with root herbivory on plant community structure and on invasiveness. This accretion of evidence and the authors own findings have led to the conclusion that in selecting agents for biocontrol of exotic perennial invasive plants, the capacity of the agent to synergistically interact with other agents should be included in the criteria. If the hypothesis that insect/pathogen interactions underlie successful biocontrol of herbaceous perennial invasive plant species, then efforts to restore native plants would be affected by the biotic legacy of the interactions. Evidence from a post-biocontrol native plant restoration has provided such evidence.