Purple Nutsedge Control with Allyl Isothiocyanate under Virtually Impermeable Film Mulch

Nutsedge control is challenging in commercial vegetable production in the absence of methyl bromide, and therefore, an effective alternative is needed. This study investigated allyl isothiocyanate (ITC) as a methyl bromide alternative for purple nutsedge control under polyethylene-mulch. Greenhouse experiments were conducted to compare the retention of allyl ITC in treated soil (3,000 nmol g(-1)) under low-density polyethylene (LDPE) and virtually impermeable film (VIF) mulches. Field experiments were conducted to evaluate the effectiveness of allyl ITC (6 rates: 0, 15, 75, 150, 750, 1500 kg ai ha(-1)) under VIF mulch against purple nutsedge. Additionally, a standard treatment of methyl bromide+chloropicrin (67 : 33%) at 390 kg ai ha(-1) under LDPE mulch was included for comparison. In the greenhouse experiment, the predicted half-life of allyl ITC under LDPE and VIF mulch was 0.15 and 0.59 d, respectively. In the field experiment, it was predicted that allyl ITC at 1,240 and 1,097 kg ha(-1) under VIF mulch is required to control purple nutsedge shoot and tubers equivalent to methyl bromide + chloropicrin at 4 wk after treatment (WAT). It is concluded that allyl ITC under VIF mulch would need to be applied at 2.8 to 3.2 times the standard treatment of methyl bromide + chloropicrin under LDPE mulch for commercially acceptable purple nutsedge control.