I haven't read much of the background material either because it's all too much, but
this wikipedia articles says that, "Independent studies show that while the photodegradation half-life time of most neonicotinoids is around 34 days when exposed to sunlight, it might take up to 1386 days for these compounds to degrade in the absence of sunlight and microorganism activity."
I don't know how true this is, I don't know it it's alarmist rubbish and I don't know of any counter-statements. I don't know the effect of seed coatings on micro-organisms and I don't know how deep OSR roots travel nor how far cemicals in seed dressings will migrate in the soil, if at all. I have seen oil seed rape feilds with plenty of weeds around the margins and plenty of rooks and crows looking for worms and grubs, so perhaps the long half life quoted is in sterile, laboratory controlled, conditions and not in the real outdoor world where the remains of crops are ploughed in and what was the root area is exposed to daylight in preparation for the next xcrop.
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