As of 2005, methyl bromide will no longer be produced or imported for agricultural use in industrialized countries. The uncertain future of methyl bromide as a soil fumigant has stimulated research into the use of other soil fumigants for weed control. Laboratory experiments were conducted to determine the efficacy of methyl bromide (MB), methyl iodide (MI), propargyl bromide (PB), 1,3-dichloropropene (1,3-D), and metham sodium (MS) alone and in combination with chloropicrin (PIC) against Cyperus esculentus L (yellow nutsedge). The experimental design was a randomized complete block with three replications. All experiments were repeated. Tubers were imbibed for 24 h and mixed with soil adjusted to 14% moisture (w/w). Soil/tuber samples were fumigated for 48 h with MB, MI, 1,3-D, and PIC at 0.0, 3.1, 6.3, 12.5, 25, 50, 100, and 200 μm of active ingredient. Samples were fumigated with PB and MS at 0.0, 0.8, 1.6, 3.1, 6.3, 12.5, 25, and 50 μm of active ingredient. After fumigation and venting, each soil/tuber sample was wetted and placed in a Petri plate for 5 days. Shoot emergence was recorded. Additionally, to determine synergism response with PIC, 17% PIC was added to each fumigant/rate combination. Fumigation and data collection were performed as described above. Dose-response curves were constructed to determine the effective dose to control 50% of nutsedge emergence (ED50). PB and MS were the most efficacious fumigants with ED50's of 3.7 and 6.5 μm, respectively. EC50 values for all the fumigants were significantly lower than MB except for 1,3-D. All the fumigant-PIC combinations resulted in synergistic control of nutsedge.
Experiments conducted in vitro showed that coir [coconut (Cocos nucifera) mesocarp pith] suppressed growth of soilborne plant pathogens. Mycelial growth of Phytophthora capsici on potato dextrose agar (PDA) amended with an unsterilized coir suspension was strongly inhibited regardless of suspension concentration. Growth of P. capsici on PDA amended with a filter-sterilized coir suspension was uninhibited. Growth of Fusarium solani on water agar (WA) amended with unautoclaved coir was completely inhibited. Growth of F. solani on WA amended with autoclaved coir was uninhibited. Aspergillus terreus recovered from coir inhibited mycelial growth of various soilborne pathogens by up to 75%. The results from this study suggest that coir has the ability to suppress soilborne plant pathogens in vitro and this ability is largely due to microorganisms associated with the substrate.