Prepared by N. W. Schaad1, J. J. Shaw2, A. Vidaver3,J. Leach4, and B.J. Erlick5 1USDA ARS-Foreign Disease-Weed Science Unit, Ft. Detrick, MD 21702;2Inst. Molecular Biology and Medicine, University of Scranton, Scranton, PA;3University of Nebraska, Lincoln, NE 68583;4Kansas State University, Manhattan, KS 66506;5USDA ARS-Special Interagency Programs, Beltsville, MD 20705
Schaad, N.W., Shaw, J.J., Vidaver, A., Leach, J. and Erlick, B.J. 1999. Crop Biosecurity. APSnet Features. Online. doi: 10.1094/APSnetFeature-1999-1099
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Because of the great importance and interest in the topic, this feature article has been prepared to provide a platform for interested members and others to further discuss and develop ideas for dealing with crop biosecurity issues. Numerous representatives of the administration and congress have publicly registered great concern regarding the threat of biological warfare (BW) to this country, especially manifested as bioterrorism. In comments that were widely circulated in the press, Secretary of Defense William Cohen warned Americans of the likelihood of biological weapons attacks in the coming months and years. One of the most important points made by the Secretary is that being prepared for an attack which may employ bioweapons of mass destruction is, by itself, a strong deterrent.
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While not generally addressing plant diseases in the context of BW, the world wide web provides numerous resources of accurate and not-so-accurate information concerning general biological warfare and terrorism. As such, one should very carefully validate the sources and factual content of all data acquired through these resources. One resource is ZKEA. ZKEA offers online information about emerging diseases and has a large section on biological warfare issues that provides good background information, as well as many links.
This issue is discussed by R. L. Forster (see abstract) in his symposium presentation on "Ground Surveillance." To address this problem in rapidly and accurately reporting diseases, APS has discussed the possibility of supporting development of a global electronic reporting system to track new and emerging pathogens. There are some excellent resources for reporting plant diseases and emerging plant diseases on the World Wide Web. However, these are not designed to address or help identify anti-crop activity and quality control is an issue.
A list of plant pathogens that have been generally considered as potential anti-crop weapons can be compiled from several sources. One key source is the Australia Group. This informal group, comprising more than thirty nations including the U.S., was established in the 1980s to try to control the export of dual-use items and technology for chemical weapons by applying export licensing measures. In the 1990s controls for human, animal and plant pathogens and dual-use biological equipment were added. More than a dozen plant pathogens included for export control by the Australia Group are listed because of their harmful potential if transferred to nations with biological weapons programs or terrorists. An additional list of pathogens was provided by Weller et al. (1999) who discussed agents in the context of biological weapons and the problems that are posed for universities who wish to conduct research with organisms generally considered to be potential animal or plant weapons (Weller et al., 1999). Collectively, several plant pathogens believed to be suitable for weaponization are presented in Table 1. We assess that most of these pathogens have numerous deficiencies as bioterrorist or BW agents and, as such, may be inappropriate or too difficult to be used.
In his symposium presentation on epidemiology and risk prediction, Dr. L. V. Madden unveiled a probabilistic model for assessing the risk of crop bioterrorism (Dr. L. V. Madden, "Epidemiology and risk prediction," see abstract). The model includes the probability of introduction, initial establishment, disease spread, and control. If asked to list the top 10 candidate plant pathogens with high risk potential for deliberate introduction, most plant pathologists would probably list those pathogens with which they are most familiar and have historically caused severe crop losses in the past. Because a deliberate introduction may involve non-traditional agents or modified agents and might not follow historical trends, such a decision based on personal experience and history may very well be misleading. A better approach is to develop criteria and a numerical rating system or "Effective Pathogen Index" (EPI) to assess risk and probability of harm (N. W. Schaad, "What is an effective pathogen?" (see abstract). A criteria and a numerical score such as the following could be developed:
A perfect organism would have a EPI of 10 (for example, add the total points and divide by 10). Similar criteria for a BW agent as part of a state supported BW program could be developed. These criteria could include many of the above plus points for ease of genetic manipulation. To prepare our agricultural system to withstand a deliberate release of a plant pathogen, a serious evaluation of the appropriate threat agents must be performed. As stated by Dr. R. Hickson ("Subtle forms of strategic indirect warfare: infecting "soft" biological targets; some psychological, economic, and cultural consequences," see abstract) the psychological, economic, and cultural consequences of crop bioterrorism, especially attacks on such soft targets as crop seeds, could have a disproportionally adverse effect on our agriculture and society.
Additionally, training in these areas is much needed for those with responsibilities and interest in all sectors of crop agriculture including pathology extension specialists, students, crop consultants, federal and state regulators, and farm advisors at various levels.
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