What are the special features of attack on the agricultural sector?
Agents are not hazardous to perpetrators
With the exception of a few agents of zoonotic disease, most of the diseases that are likely to be considered for an attack on the agricultural sector are completely harmless to humans. They are thus much less challenging to produce, stockpile, and disseminate than lethal human pathogens.
Few technical obstacles to weaponization
A military style attack by airplane on large acreage of crops would require crop dusters and large stockpiles of agent. Nevertheless, nothing would be difficult to obtain on the open market. However, such an attack would be difficult to do covertly, and the chance of capture would be very high. Less ambitious attacks would require much less in the way of equipment or agent stockpiles. If the goal is to cause only a few cases in order to disrupt trade, then no special equipment and only a few microliters of agent are needed. And, as discussed below, it is possible to introduce biological agents without even entering the target country.
Low security of vulnerable targets
Many potential sites for release of an animal agent, such as auction houses, have very low security. Access to large numbers of animals with destinations all over a country or region is simple and easy. Seeds, fertilizers, and pesticides provide routes for infection of crop plants, although of somewhat higher (but still not robust) security. And of course pastures and fields themselves have essentially no security at all.
Lower moral barrier to cross
It is often argued that there is an innate human revulsion to the use of disease as a weapon; if so, this could constitute an important disincentive to bioterrorism and biowarfare. However, it is unlikely that this sentiment extends to biological attack on plants or animals. Furthermore, the response after a biological attack on plants or animals would be less substantial than if the attack involved human victims, and the penalties of being identified as the perpetrator would be lighter.
Maximum effect may not require many cases
If the goal is to disrupt trade by introducing a highly contagious disease into territory from which it is absent, then the attack does not have to be constructed to cause a large number of cases÷a handful of cases may be sufficient. Obviously it is much easier to cause a small outbreak than a large one
Point source to mimic natural introduction can be effective
Because of the high background of naturally-occurring disease, it is possible that a deliberately instigated outbreak could be mistaken for a natural one. If avoiding detection is important, an attack would be constructed to take advantage of this confusion. Especially if the goal is disruption of international trade, where few cases are necessary, it is feasible to construct anattack to appear to be a natural point-source outbreak.
Multiple point source outbreaks can be initiated by contaminating imported feed or fertilizer, without even entering the country
Many countries import materials such as straw, animal feed, or fertilizer. This provides an opportunity for introducing serious pathogens, without having to even enter the target country. It also allows the possibility of initiating multiple outbreaks over a large geographic area, in a way that mimics a natural event (such as the recent outbreak of foot and mouth disease in Japanese cattle in two widely separated prefectures, thought to have been introduced on straw imported from China).