Good management models for postemergence weed control require good estimates of which weed density produces an economic threshold yield. Because intraweed competition increases if weeds are aggregated, weed spatial pattern may be an important factor for inclusion in management models. Mathematical models of weed–crop competition have demonstrated that this may be the case, but the small number ...

weight to a finding published a decade ago by the group at St Jude Children’s Research Hospital. That finding stated that patients with low TPMT activity receiving 6-MP in combination with radiotherapy have increased risk of SMNs.6 The paper leaves many questions unanswered. Whether this association is caused by 6-MP therapy alone or whether high-dose MTX given along with 6-MP in maintenance co...