As long as our food supply looks like huge fields of a single species with all other living things in the area blasted away with poisons, we will continue to have pests develop to overcome the poisons, because there's an endless sea of food for whichever ones do develop the right traits. If our food came from localized varieties with their own "immune system" in the form of a local ecosystem of beneficial bugs, bacteria, fungi, and other plants, it would be far harder for a pest to travel from place to place with such resounding success. Unfortunately we haven't figured out how to scale that up to the levels we need yet (or we could, but it would involve far more people taking up farming then we have right now).
This threat has been around for ages. That’s why you grow tomatoes in an enclosure, and why your citrus plant might die in Florida.
"This threat": you mean the one described in TFA, or the one that one might presume from the headline? Because what is described in TFA threat seems new. But your comment dismisses it as "it's always been this way", when in fact, it hasn't.
yes, but the point they make is that it is getting worse due to the warming climate. Tropical fungi in England for instance.