It looks like a rather over-confident claim to me.
There's this "for example" ... and then we're given one example. Whether the claims made for the one example or not are valid it's not much to hang one's hat on.
Surely, the point is that they can do specific things they wish to do - such as make crops "[resist] insect infestation". (However, can we know in advance that that will be permanent and that insects won't adapt?) But what they can't do is not cause problems they haven't thought about. This is one of the biggest problems with every kind of social experiment - that there are always unforeseen circumstances. Theoretically, as an Chemistry academic told me, if you pump a little low-grade nuclear waste into the sea it's OK, because it's not enough to matter - except that in practice you don't get perfect mixing, so in practice it's most certainly not OK ... as has been found. If you want a non-scientifc example take various forms of social security payments, which have been devised to fulfil important social needs but which have had the wholly unforeseen and unfortunate consequence of undermining the social structure of the family.
I mean what the heck haven't these people foreseen?
Insect infestation is, of course, a problem in the first place because agribusiness has so many acres of maize packed in so tight together. Virtually all "pest" problems are a result of over-intensive farming practices, monoculture being a prime example. That's something that's not even supposed to be raised, let alone questioned, in a discussion such as that article is meant to give rise to.