Where and how is Methyl Bromide used?
Methyl Bromide is used for three main purposes:
i. Soil fumigant: mechanised injection or manual surface treatment
Fumigating soil before planting high value crops such as tomatoes, peppers, melons, strawberries, flowers and tobacco. Soil fumigation is carried out prior to planting where crop productivity may be compromised by soilborne pests such as plant pathogenic fungi, nematodes, soil insects or weeds.
Depending on the type of application and the local soil, between 35%-60% of the Methyl Bromide is emitted to the atmosphere at the end of the fumigation when the sheets are removed, often 24 to 72 hours later, as is the case with strawberry production. In the case of row (bed) fumigation, as is the case with tomato production, the traps are left on for the entire growing season, some 60 to 120 days.
Injection technique.
Methyl Bromide gas, approximately 40-120 grammes per m², is injected into the soil at a depth of around 20-25 centimeter before a crop is planted. This will effectively sterilize the soil, killing the vast majority of soil pests. Immediately after the Methyl Bromide is injected, the soil is covered with plastic sheets glued together, which slow the movement of Methyl Bromide from the soil to the atmosphere. Another system of mechanised injection is ‘deep injection’ (depth around 80 cm, without plastic sheet covering).
For surface applications or the so-called ‘Hot gas method’
The area to be treated is covered with plastic sheeting and the liquid Methyl Bromide from cylinders is heated up in a heat exchanger, and as gas released into the space between the soil surface and the sheets. Worldwide, except for the USA, this is the principal method of application.
ii. In commodities:
Fumigating of commodities which may be infested with pests when harvested or later. The use of Methyl Bromide in this context is often necessary to meet quarantine and phytosanitary or other contractual requirements for import and export.
Methyl Bromide can be used to fumigate:
Durable commodities like grains, coffee and cacao beans, oil seeds, dried fruit, herbs, nuts, timber, cottonseed, wooden items.
Perishable commodities like fruit, vegetables, flowers. Food safety and health regulations are often requiring these fumigations.
Methyl Bromide gas is released as a vapourised gas or directly from its container into a fumigation chamber or under a tarp containing the commodities. Some commodities are treated multiple times during both storage and shipment.
Methyl Bromide is typically applied directly from the cylinder through a narrow bore application line culminating in an atomising jet to enhance the speed of vaporisation the fumigant.
Commodities may be treated with Methyl Bromide as part of a quarantine or phytosanitary requirement of an importing country.
The amount of Methyl Bromide introduced is calculated according to label, contractual and legislative requirements.
The degree of containment of Methyl Bromide achieved during fumigation can vary widely. Some commodities are fumigated in gastight, purpose build fumigation chambers while others are treated in very poorly sealed bagged stacks.
iii. In structures and transport:
Methyl Bromide is used to safeguard buildings, such as grain storage facilities, flour mills, food processing units, or vehicles, such as ships, freight containers, trucks or trains carrying agricultural commodities from all kinds of pests.
Also here the degree of containment of Methyl Bromide can vary widely. E.g. Some aircraft and modern buildings can be very gastight whereas older structures can at best be only partially sealed.
| Approximate dosage rates for various commodities |
The doses are sufficient for normal circumstances. If the temperature falls beneath 20 °C, increase the dose with 2% per degree centigrade. The output diminishes a lot for a temperature below 10 °C. As a result, it is not advised to use Methyl bromide in that case.
Because of the danger involved in handling methyl bromide this product is not free on sale in various countries but can be supplied to companies or persons approved by the Governamental Authorities concerned. Growers must be strictly comply with the instructions given by the fumigating contractors.
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| product to be treated | doses | duration of treatment | |
| fruit trees plants strawberries tobacco tomatoes greenhouses mushrooms hen-houses cereals fruits potatoes vegetables | 400 lbs/acre 850 lbs/acre 240 lbs/acre 850 lbs/acre 240 lbs/acre 3 lbs/1000Cu.ft. 2 lbs/1000Cu.ft. 3 lbs/1000Cu.ft. 3 lbs/1000Cu.ft. 3.5 lbs/1000Cu.ft. 3 lbs/1000Cu.ft. 3.25 lbs/1000Cu.ft. | 48 h 24 h 48 h 24 - 48 h 48 h 4 - 24 h 24 h 24 h 24 h 2 h 6 h 4 h | |
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Di mana dan bagaimana Methyl Beromid digunakan?
Metil Beromid digunakan untuk tiga tujuan utama:
i. Tanah penyembur kimia: mekanikal suntikan atau rawatan permukaan manual
Fumigating tanah sebelum menanam tanaman bernilai tinggi seperti tomato, lada, tembikai, strawberi, bunga dan tembakau. Pengasapan tanah dijalankan sebelum menanam di mana produktiviti tanaman boleh dikompromi oleh perosak soilborne seperti kulat patogen tumbuhan, nematod, serangga tanah atau rumpai.
Bergantung kepada jenis permohonan dan tanah tempatan, antara 35% -60% Metil Beromid yang dilepaskan ke atmosfera pada akhir pengasapan apabila lembaran dikeluarkan, selalunya 24 hingga 72 jam kemudian, seperti kes dengan pengeluaran strawberi. Dalam kes berturut-turut (katil) pengasapan, seperti kes dengan pengeluaran tomato, perangkap ditinggalkan di seluruh musim yang semakin berkembang, kira-kira 60-120 hari.
Teknik suntikan.
Metil gas Beromid, kira-kira 40-120 gram per m², disuntik ke dalam tanah pada kedalaman sekitar 20-25 sentimeter sebelum tanaman ditanam. Ini secara berkesan akan mensteril tanah, membunuh majoriti makhluk perosak tanah. Serta-merta selepas Metil Beromid disuntik, tanah itu ditutup dengan kepingan plastik yang digam bersama, yang memperlahankan pergerakan bagi Metil Beromid dari tanah ke atmosfera. Satu lagi sistem suntikan mekanikal 'suntikan dalam' (kedalaman sekitar 80 cm, tanpa penutup lembaran plastik).
Bagi permohonan permukaan atau 'kaedah Hot gas' apa yang dipanggil
Kawasan yang dirawat ditutup dengan kepingan plastik dan Metil Beromid cecair dari silinder dipanaskan di dalam penukar haba, dan sebagai gas dilepaskan ke dalam ruang antara permukaan tanah tersebut dan kunci. Di seluruh dunia, kecuali Amerika Syarikat, ini adalah kaedah utama permohonan.
ii. Dalam komoditi:
Fumigating komoditi yang mungkin penuh dengan perosak apabila dituai atau kemudian. Penggunaan Metil Beromid dalam konteks ini adalah perlu untuk memenuhi keperluan kuarantin dan fitosanitari atau lain-lain kontrak untuk import dan eksport.
Metil Beromid boleh digunakan untuk mengasap:
Komoditi yang tahan lama seperti bijirin, kopi dan biji koko, biji minyak, buah-buahan kering, herba, kekacang, kayu, kapas, barangan kayu.
Komoditi yang mudah rosak seperti buah-buahan, sayur-sayuran, bunga. Keselamatan makanan dan peraturan kesihatan sering memerlukan fumigations ini.
Gas metil Beromid dibebaskan sebagai gas vapourised atau terus daripada bekas ke dalam ruang pengasapan atau di bawah TARP yang mengandungi komoditi. Beberapa komoditi yang dirawat beberapa kali kedua-dua semasa penyimpanan dan penghantaran.
Metil Beromid biasanya digunakan secara langsung dari silinder melalui garis permohonan sempit gerek yang memuncak dalam jet pengabus untuk meningkatkan kelajuan pengewapan penyembur kimia.
Komoditi boleh dirawat dengan Beromid Methyl sebagai sebahagian daripada keperluan kuarantin atau fitosanitari sebuah negara pengimport.
Jumlah Metil Beromid yang diperkenalkan dikira mengikut label, keperluan kontrak dan perundangan.
Tahap membendung Metil Beromid yang dicapai pada pengasapan boleh berbeza-beza secara meluas. Sesetengah komoditi diwasap dalam gastight, tujuan membina dewan pengasapan manakala yang lain dirawat di cerobong sangat buruk dimeteraikan tertangkap.
iii. Dalam struktur dan pengangkutan:
Metil Beromid adalah digunakan untuk melindungi bangunan, seperti kemudahan penyimpanan bijian, kilang tepung, unit pemprosesan makanan, atau kenderaan, seperti kapal, bekas muatan, lori atau kereta api membawa komoditi pertanian daripada semua jenis perosak.
Juga di sini darjah membendung Metil Beromid boleh berbeza-beza secara meluas. Cth. Beberapa bangunan pesawat dan moden boleh menjadi sangat gastight manakala struktur yang lebih tua pada tahap terbaik boleh hanya sebahagian dimeteraikan.
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