It turns out this has been uncovered along with a huge list of other horrifying practices on Okinawa by the USA in Sheldon Harris' book Factories of Death (http://www.scribd.com/doc/91284707/Factories-of-Death).

It was part of the more wide-ranging chemical and biological weapons program, Project 112 (https://en.wikipedia.org/wiki/Project_112).

There's a huge community of veterans who have served at Okinawa who research this stuff online and on the island in order to help process compensation claims and lawsuits against the US government (e.g. http://vets.yuku.com/forums/74/Agent-Orange-Heart-Disease-Pr...).

So this isn't new, but it is absolutely disgusting.

Here's a non-paywalled article:

http://www.globalpost.com/dispatch/news/afp/140111/us-biolog...

    The US army conducted field experiments of biological weapons,
    which could harm rice cropping, in the Japanese island of
    Okinawa in the early 1960s, a press report said Sunday.
    
    The same experiments were also conducted on the US mainland
    and in Taiwan, Kyodo news agency reported, citing US military
    documents it said it had obtained.
    
    [...]
    
    The obtained documents mention test sites including Nago
    and Shuri, both in Okinawa, but it is not known whether the
    experiments were conducted within the premises of US bases
    there, Kyodo said.
    
    In the field tests, the army "used a midget duster to
    release inoculum alongside fields in Okinawa and Taiwan,"
    measuring dosages at different distances and the effect on
    crop production, the documents said.

Note from a FUD standpoint how well the reports avoid discussing the topic of simulant substances being used. Follow the money (lawsuits).