So........ The problem with trying to cover a huge subject in a few hours often provides more questions than answers! The main points are 1) Any species that has 'found' it's ecological niche will thrive (this niche is often not available in their natural environment) such as Himalayan balsam, Japanese knotweed, grey squirrels, rabbits, blackgrass etc 2) Highly successful weeds in an agricultural situation are there because they produce a huge amount of seed and thrive in an environment that is provided for them. 3) The more seed, the more plants, the more mutations, the more diversity in the population, the more successful the plant is to change and adapt. Evolution is simply a numbers game. Minimum of 1 trillion blackgrass seeds produced every year in the UK 4) Crop competition is king - simple, grow an incredibly thick crop of high biomass crop with no gaps, weeds are often smothered and cannot compete, the greatest failings in the Uk to achieve that is often water logging but not exclusively. 5) Blackgrass is not a 'marsh' species, the fact it is able to produce secondary aerenchyma means that in wet and waterlogged situations it is able to last longer than any of the UK crops (rape has no ability to produce aerenchyma, wheat/cereals has had met of its natural ability bred out) simple selection, if you have wet areas, you have little or no crop competition and therefore where often you find the worse blackgrass areas - however this is not the only place! 6) There are many words to describe individual populations within a species, most seem, around the world to adapt the word 'ecotype' the chances are if you are doing something very different from your neighbour, your blackgrass will be a different ecotype. 7) The reason a spring crop is so successful the first time you grow it? simply the blackgrass is used to growing in a winter situation and has been outfoxed. Keep doing it and the population will soon adapt. 8) If you mix everything up all the time, cultivations, crop rotations etc, you will end up with a population that can has the ability to produce blackgrass in each scenario you present it - as a percentage game the numbers may be low to begin with, but will build and although a small percentage will become a worsening problem year on year. 9) Herbicides, synergy and antagonisms...... It was made clear to me, anywhere I travelled. A driver for resistance is applying a sub lethal dose of a herbicide, this can be caused by a huge amount of factors including spray water complexing, purposely cutting the rates and stress. It is well understood that applying many herbicides to stressed weeds will give poor control, e.g frost, water logging and drought etc yet on many labels around the world, stress is also labelled as "a previous application of a herbicide". It was suggested that Atlantis resistance was probably caused by pre ems causing a plant to become severely stressed and then when Atlantis was applied the plant under stress was unable to take in a lethal dose and therefore any survivors would quickly form resistance. 10) Herbicide stacking etc works very much on the principle that soil applied herbicides have a huge range of inefficacy due to the soil not being the 'perfect' carrier and more often than not sensitive plants will miss the application of the residual all together, these unaffected survivors can be removed by other residuals with different solubilities, KOc values, half life and volatilisations. It especially accounts for Avadex adding a bit extra because it is a totally different application method and formulation and often the reason why it seems to compliment sprayed on pre ems so well. However it also explains the huge variation in its control. 11) The generalised answer is fairly simple, improve the environment that doesn't favour blackgrass selection, trying to find the utopia is hard, if you can provide an environment that produces consistent crops that are competitive from field boundary to field boundary in any scenario, the blackgrass pressure will subside. Hope this explains what I have seen in a bit more detail, but probably as ever asks more questions than it answers!