Candole Byron L, Csinos Alexander S, Wang Dong
Department of Plant Pathology, Coastal Plain Experiment Station, University of Georgia, Tifton, GA, USA.
Pest Manag Sci. 2007 May;63(5):468-75. doi: 10.1002/ps.1363.
The effects of metam-sodium application rate on soil residence time, spatial and temporal distributions of methyl isothiocyanate and pest control efficacy were studied in a Georgia sandy soil. Metam-sodium 420 g L(-1) SL was drip applied at rates of 147 and 295 L ha(-1) in plastic-mulched raised beds. Methyl isothiocyanate concentrations in soil air space were monitored from four preselected sites: 10 and 20 cm below the emitter, and 20 and 30 cm laterally away from the emitter at 3, 12, 24, 48, 72, 120 and 240 h after chemigation. A higher rate of metam-sodium application resulted in higher methyl isothiocyanate concentrations in the soil. Highest methyl isothiocyanate concentrations were found at 20 cm below the emitter, and lowest at 30 cm laterally away from the emitter. Methyl isothiocyanate concentrations decreased with time and distance from the emitter. Lower methyl isothiocyanate concentration x time product values at 20 and 30 cm away from the emitter resulted in lower mortalities of Rhizoctonia solani Kühn and yellow nutsedge (Cyperus esculentus L.). The results demonstrated that methyl isothiocyanate can be delivered at lethal doses with drip-applied water downward within the beds. Lateral diffusion of methyl isothiocyanate from the point of application did not reach biologically active concentrations to affect the survival of R. solani or yellow nutsedge. Further studies on the lateral distribution of methyl isothiocyanate in sandy soils are needed to circumvent this limitation.
在佐治亚州的沙质土壤中，研究了威百亩施用量对异硫氰酸甲酯在土壤中的残留时间、空间和时间分布以及害虫防治效果的影响。在覆盖塑料薄膜的高畦中，以147和295 L·ha⁻¹的用量滴施420 g·L⁻¹的威百亩水剂。在化学灌溉后3、12、24、48、72、120和240 h，从四个预选位置监测土壤空气空间中的异硫氰酸甲酯浓度：滴头下方10 cm和20 cm处，以及滴头横向20 cm和30 cm处。较高的威百亩施用量导致土壤中异硫氰酸甲酯浓度更高。在滴头下方20 cm处发现异硫氰酸甲酯浓度最高，而在滴头横向30 cm处最低。异硫氰酸甲酯浓度随时间和与滴头距离的增加而降低。在距离滴头20 cm和30 cm处，较低的异硫氰酸甲酯浓度×时间乘积值导致立枯丝核菌和黄 nutsedge（Cyperus esculentus L.）的死亡率较低。结果表明，异硫氰酸甲酯可以通过滴灌水中的致死剂量向下输送到高畦内。异硫氰酸甲酯从施药点的横向扩散未达到影响立枯丝核菌或黄 nutsedge存活的生物活性浓度。需要对异硫氰酸甲酯在沙质土壤中的横向分布进行进一步研究，以克服这一限制。
