Atmospheric emissions of methyl isothiocyanate and chloropicrin following soil fumigation and surface containment treatment in bare-root forest nurseries

Methylisothiocyanate (MITC) and chloropicrin (CP) are alternatives to methyl bromide for soil fumigation. However, surface transport of MITC emission has been cited as the cause for seedling damage in adjacent fields at several bare-root forest-tree nurseries. Field experiments were conducted at nurseries in Wisconsin and Georgia to measure air emissions of MITC and CP after fumigation. Four treatments were tested as combinations of two fumigants (dazomet or coapplication of CP and metam sodium) and two surface containment treatments (tarp or water seal). A very small percentage (<5%) of the applied equivalent of MITC was lost through either surface treatment over a 2-week period, and lower emissions occurred with the water seal. Cumulative emissions of CP accounted for 10%-22% of the applied CP. With all surface containment treatments, more than 70% of total cumulative emissions of either MITC or CP occurred within 1 week of application. Either surface containment treatment can be used by nursery managers to reduce risk of MITC emissions that could cause damage to nearby seedling crops or harm to humans.