Hello Smokesteve, in my book there are three types of bananas
1) genetics. the plant just carries male, hermaphrodite and female genetics.
2) environmental stress related
3) last ditch effort by a female to pollinate.
this can cause some controversy and is only my opinion but here I go.
the first one will pollinate, it will give you male, hermaphrodite and/or female genetics in the seeds just like the plant they come from.
the second one is more likely to give you female seeds only as the process of making fem seeds is caused by stressing a female plant.
the third one is usually a sterile attempt.
you can spray them with water and remove the bananas to lessen the effect of pollination but there is also bananas you won't see inside your buds and by the time you see them usually the damage can been done, if their pollinators. So if you're absolutely in need of keeping the other strain seed free there's only one option but there is no guarantees that it hasn't already pollinate or isn't a pollinator at all. Before you go killing your plant let me ask you do you ever smoke weed that had seeds in it? Besides in my opinion I save those seeds then grow them without problems on the next generation, seeds are expensive.
hope this helps
Mr.furley