Just to be clear, when I said "
From a plant health POV the only hop material that should be crossing international boundaries" I was talking from the ideal perspective of what we'd like to happen, rather than what actually happens. That's close to how some countries like New Zealand work as they have a big advantage from not having hop diseases in the country.
I guess you can put pests and diseases into three categories - the ones that are known and you know you want to keep out, in human terms for the UK you would think of Ebola and rabies. So in hop terms NZ is in this position for eg downy mildew. Then there's new variants of existing diseases - like flu - where you don't know when a bad one is going to show up, but at least you know roughly how they work and how to control them. And then there's the whole new diseases like Covid where you don't know they're coming and you don't have controls, so all you can do is rely on quarantine to keep them out, and the plant equivalent of lockdown once they're in.
So that's why in theory the default is to rely on quarantine, to keep out the ones that you don't know about, but they're rare so in the real world that the rules get flexed and hence you get plant passporting. But between say the UK and Continent there's been so much exchange that all the common diseases are already shared - and stuff like new varieties of mildew will arrive in time on the wind, but my instinct is still to quarantine etc.
are the diseases you mention only carried in the soil associated with the rhizomes or can they be carried by the plant itself? if the latter, are imported cones and pellets treated some way to prevent contamination of local plants?
So again there's three main categories. There's things that rely on live plant material and die pretty quickly when they can't access it - typically viruses and aphids etc. There's things that can be carried on dead plant material like cones - typically the leaf diseases like mildew - which at least can be treated fairly easily. And then there's the soilborne stuff like
Verticillium which is far more difficult as it forms spores and can be protected in the middle of lumps of dry soil. Then it can escape once the soil is wet again.
I never had any professional involvement with plant health in hops so I don't know the details of killtimes etc, but I'd imagine that just processing cones will kill most things - they're typically getting around 65°C for 6-8 hours and then vacuum packed, which should take care of any insects and I'd imagine most of the aerial nasties, presumably what's left isn't considered a significant hazard at least in the UK, but they may be more cautious when eg importing into NZ.
