By its nature, a terminator gene does not spread very well. Even if the gene manages to cross pollinate to other plants (which it probably will), it still won't

By its nature, a terminator gene does not spread very well. Even if the gene manages to cross pollinate to other plants (which it probably will), it still won't go viral because the infected plants would be (relatively) sterile. What is more scary is some of the mosquito killing genes that are being developed. Those are actually being designed to spread throughout entire species of Mosquitos, despite making them infertile. This is a far more difficult problem that a simple terminator gene.