CHAPTER IV: ASIA

APPROACHES FOR THE REDUCTION OF THE USE OF METHYL BROMIDE AND ALTERNATIVES IN JAPAN

A. Tateya

Japan Fumigation Technology Association
1-26-6 Taito Taito-ku Tokyo 110-0016 Japan

Summary. In Japan, each prefecture has its own programme to develop and disseminate alternatives to methyl bromide, especially for vegetables, for the phase-out of this fumigant in 2005. These programmes, which vary depending on the crop, are based on pre-planting treatments. Due to the efforts of the stakeholders concerned, MeBr for soil fumigation is being gradually replaced by alternatives and the use of MeBr is decreasing. Physical, chemical and biological alternatives proved to be effective in controlling soilborne pests. In order to achieve a broad range control of the various pests, combinations of different methods are used.

Key Words: methyl bromide, physical alternatives, hot water, orugaloi film, rotations, resistance, biological control, fumigants, contact pesticides

I. INTRODUCTION

In Japan MeBr is mainly used for soil and quarantine treatments. Compared with other pesticides, the fumigation with MeBr is faster and leads to better results even under low temperatures.

The Japanese time frame for the period 1995 - 2000 to control the production of MeBr was as follows:

1. Freeze of production at the base level of 1991 in 1995
2. Five percent reduction in 1996
3. Ten percent reduction in 1997
4. Fifteen percent reduction in 1998
5. Twenty-five percent reduction in 1999
6. Thirty percent reduction in 2000

To date Japan has reduced MeBr production in advance of the control deadlines established by Montreal Protocol. Starting July 6, 1993, a campaign for the reduction of emission of MeBr was conducted by the government and the farmers were encouraged to use alternative methods to this fumigant. The Ministry of Agriculture, Forests and Fisheries (MAFF) issued a special notice to the farmers, providing guidance on the use and reduction of emission of MeBr. In case the use of MeBr was absolutely necessary, it was strongly recommended to cover the soil surface with polyethylene film or vinyl film sheet. This practice is suggested particularly for greenhouses.

In order to control the production and use of MeBr in Japan, manufacturers and / or importers are required to obtain permission from the Ozone Protection Office of the Ministry of International Trade and Industry (MITI) to synthesize and / or import MeBr. After review of the application, MITI gives a permission to synthesize and / or import under the production limit of Montreal Protocol. After that year has passed, they have to report the record of actual amount of synthesis, import, export and remaining quantity in stocks of MeBr for that year to MITI. Therefore, MITI obtains detailed information about the production and consumption of MeBr during each year. All this information is then provided to MAFF by MITI. Therefore, MAFF has full information on the amount of production, import, export, shipment for domestic use, and use for quarantine pests. According to the Article 7 of Montreal Protocol, every country is required to report to UNEP the volume of production, import and export of MeBr.

In Japan, each prefecture has its own programme for the development of the alternatives for MeBr phase-out. This programme is mainly based on the crops and soilborne pests present, and the need to control those pests by soil fumigation as pre-planting treatments, which vary from crop to crop.

II. CURRENT SITUATION OF METHYL BROMIDE USE IN JAPAN FOR SOIL TREATMENT

In 1999 the use of MeBr for soil treatment in Japan still amounted to 4,391 tons (Table 1), which means an extensive use by farmers. This fumigant is favourably used in pre-planting treatments in crops such as pepper, melon, watermelon, strawberry, cucumber and cut flower for the control of insects, nematodes, weeds and soil born pathogens

Table 1. Sales and volume of MeBr used in Japan (tons) *

^* Source: MAFF Plant Protection Division

such as viruses, bacteria, and fungi. In protected areas, such as greenhouses, it is absolutely necessary of the use of soil treatments. A remarkable advantage of MeBr is that it is effective against all sorts of soilborne pests, including plant viruses, with short treatments even under low temperatures during the winter. For disinfecting the soil in nursery beds and for transplanting, many farmers apply MeBr twice a year. For all these reasons it is still popular among the farmers. However, the supply of MeBr in Japan has been decreasing and prices increasing and it will be phased-out in 2005. The farmers realized this trend and they are trying to apply alternatives to control pests and diseases. MAFF and local authorities are making great efforts to control more pests and diseases with the existing substitutes and recommend farmers to use alternatives to this fumigant.

III. ALTERNATIVE METHODS TO METHYL BROMIDE USED IN JAPAN FOR SOIL TREATMENT

Chemical control

A. Soil fumigants

The following fumigants are currently used in Japan:

1. Chloropicrin
2. 1,3 dichloropropene
3. Mixture of chloropicrin (40 %) and 1,3-D (52 %)
4. Mixture of chloropicrin (50 %) and 1,3-D (25 %)
5. Metam-sodium
6. Metam-ammonium
7. Methyl isothiocyanate
8. Methyl isothiocyanate + 1,3-D
9. Methyl isothiocyanate - DCIP

Fumigants are generally expensive and therefore farmers decide whether to carry out a soil treatment, or not, depending on the profitability of the crop and the severity of the damage by soil-born diseases and nematodes, due to the repeated cultivation of the same crop. Fumigants other than MeBr do not show better efficacy against nematodes, fungi, bacteria, viruses and weeds altogether. A mixture of chloropicrin (40 %) and 1,3-D (52 %) was recently registered in Japan. Choloropicrin is more effective against fungi and bacteria and 1,3-D against nematodes, therefore this formulation should effectively control pests and diseases altogether.

B. Contact type micro-granules

The most commonly used pesticides of this kind are:

1. Ethoprophos
2. Oxamyl
3. Carbosulfan
4. Pyraclofos
5. Benfuracarb
6. Fosthiazate
7. Dazomet

Fosthiazate and dazomet, contact pesticides used against nematodes, are currently the most widely used by farmers. Dazomet is very effective against nematodes, soil born diseases and weeds. However, unless it is applied properly, its application could cause phytotoxicity to the crop. On the other hand, it is extensively used as alternative in fields close to residential areas.

Systematic application of fostiazate after chloropicrin, or dazomet, seems to be very effective to control soil borne pathogens and nematodes. Nematodes, which survive from the first treatment, should be afterwards killed with the contact to the micro-granule of fosthiazate. Insufficient efficacy of chloropicrin and dazomet against nematodes is covered by fosthiazate

Physical control

1. Solar energy treatment (solarization)

In regions with high solar radiation, many farmers have gradually come to apply solar energy. This method of control seems to be one of the best ways for the control of soil pathogens. The efficacy in the control of pests and diseases depends upon the weather. In case of bad weather conditions, efficacy is usually lower. In order to exhibit the highest efficacy of this treatment against soil pests and soil-born diseases, it is necessary to use a sufficient volume of water. Some farmers are concerned with the trouble of the equipment to be used in greenhouses, since it is exposed to rust. Greenhouse facilities tend to degrade because of the high temperatures. Moreover, a water supply is indispensable and the treatment is lengthy. This treatment is not suitable for field where crops are planted during the summer.

2. Hot water treatment

This method was developed by Tsukuba National Research Centre. Water is boiled at 95°C and poured in the field. The treatment kills several organisms, including pests, pathogens, and weeds, and the effectiveness lasts up to three years in protected cultivation areas. It is necessary to improve the equipment producing hot water, reducing its size and decreasing its cost, in order to make it more affordable to farmers. This kind of treatment is not suitable for large areas.

3. Flooding

This is one of the most widely used methods in areas where eggplants, tomatoes, strawberries and cucumbers are cultivated. Soilborne diseases and nematodes are controlled. In the future, this method appears to be one of the most promising ways to control soil pathogens.

Pest control by cultivation type

1. Rotation with non-host plant

For the control of nematodes in taro (Colocasia antiquorum), yam (Dioscorea japonica) and other legumes, crop rotation is sometimes applied, but in the cultivation of the major root crops such as radish, carrot and chrysanthemum, cropping rotation is not applied. In cash crops, rotation is not usually applied for nematode control. The appropriate rotation must be identified in order to obtain the desired results. Rotation from sweet potato to taro, or burdock, which are all root crops, does not make sense for the control of nematodes. Instead, combination of root crops and paddy rice is efficient to control nematodes in the soil, because of the unfavorable conditions to their life obtained with soil inundation.

2. Rotation with nematode antagonistic plants

Oat grass, ginia grass, sorgo, marigold and crotalaria are antagonistic to nematodes and are used to control nematodes attacking the roots of several crops. However, this method is not popular among the farmers. It is labor intensive, these grasses need time to grow and their efficacy seems to be only partial in case of high population densities of the nematodes. Furthermore, the long time needed for the cultivation of these grasses (three months, and then an additional month in the greenhouse) does not allow an efficient use of the greenhouse facilities.

3. Use of resistant variety or rootstock

Varieties, or rootstocks, resistant to nematodes have been developed only for tomatoes and eggplants. This method is popular among farmers. It is effective, but some new nematode races appeared and in some places the resistance has been overcome.

Biological control of nematodes

Formulations of natural enemies are used in Japan to successfully control nematodes.

• The fungus Monacrosporium phymatopagaum (Drecheler) Subramanian
• was registered to control the nematode Meloidogyne incognita.
• Pasteuria penetrans (Pasteuria wettable powder) is a bacterium which invades the body of the host, inhibiting nematode activity and reproduction. The spores of this bacterium are very resistant under a wide range of temperatures and dry conditions, being able to survive several years in the soil. It can build up large populations and is able to control nematodes for many seasons. In case of serious nematode attack, it is recommended to use it together with chemical nematocides, except chloropicrin and MeBr. For the control of soilborne diseases and nematodes, chemical fungicides and nematocides must not be used together with this bacterium. With the continuous cultivation of the same crop in the same field, the populations of this bacterium in the soil increase and are able to control nematodes. Once the population of the nematodes are reduced, the efficacy of P. penetrans lasts very long. Pot test data showed that it was still effective after nine years. Currently its cost is still too high to allow a generalized use by farmers.

Combination of existing methods

The improvement of the quality of products, the use of labor saving practices and lowering costs are major agricultural goals. Farmers tend to grow repeatedly the same kind of plant in the same field, resulting in the development of large nematode populations and heavy reduction of the yield. The continuous cropping pattern, which is prevailing among farmers growing cash crops such as tomato, pepper and melon, are likely to result in large nematode populations. Existing alternatives do not exhibit quick and excellent efficacy and durability as MeBr does. For existing alternatives, it is difficult to control both soil-born pathogens and nematodes with a single substitute. Therefore it is necessary to combine the existing pest control methods to reduce the nematode populations down to an acceptable level of damage. We have to use this approach for the development of alternatives to MeBr.

IV. CURRENT USE OF THE MAIN AGRICULTURAL CHEMICALS FOR SOIL TREATMENT

Chloropicrin, 1,3-dichloropropene (1,3-D) and MeBr are the mosty widely used agrochemicals (Table 2) with the share of 84 % in 1991. However, this figure comes down to 73 % in 1997. Even though chloropicrin and 1,3-D and their mixture have occupied rather big share, the use of metam sodium, dazomet and fosthiazate increased and farmers have been accustomed to use them effectively.

Table 2. Volume of sales of agricultural chemicals for soil treatment (tons)

^* Source: MAFF Plant Protection Division

V. RECENT TRENDS FOR THE DEVELOPMENT OF ALTERNATIVES

In order to encourage the use of alternative methods to the use of MeBr, the range of application of the existing pesticides is being expanded and they are being registered for all suitable target pests. Considering the fact that at present new chemicals are not easily developed, this approach is rather useful for the development of alternatives, along with the combination of existing pesticides. Those combinations might be as effective as MeBr. Generally speaking, the cost is the key factor for the choice of alternatives by the farmers.

In 1999 the mixture of 40 % chloropicrin and 52 % of 1,3 dichloropropene was registered. It has excellent efficacy for the control of arthropod pests, diseases and weeds. In addition, the special formulation makes it far less irritant than regular chloropicrin.

Dazomet is one of the promising substitutes which many researchers consider effective to the pests, soil born diseases and weeds altogether. It is formulated as micro-granules, so it does not need irritating additives for its safe use.

Although metam sodium has been already registered, it is now under review for registration of a new formulation for better application. This pesticide needs a lot of water to be effective. Abundant watering before and after the application allows metam sodium to diffuse uniformly in the soil.

There are the three kinds of pesticides which can be used as pre-planting treatments: MeBr, which is a gas, and Chloropicrin, 1,3 D and metam sodium which are liquid. Dazomet is in micro-granules. Despite different formulations, the active ingredient works invariably as gas in the soil. This gas itself might be phytotoxic, so it is necessary to remove it from the soil before planting.

In some prefectures the so-called Orugaloi film replaces polyethylene transparent films. This film is composed of several layers of polyamide and polyethylene, which have the property of being impermeable to MeBr gas and it is used to reduce the emission of MeBr into the atmosphere. Using such a plastic material it is possible to significantly reduce the rates of any chemical used as fumigants. The problem is that this material is much more expensive than conventional polyethylene transparent sheets and this prevents its extensive use by farmers.

• Solarization is popular among the growers of melons, strawberries, tomatoes, etc. It is quite effective in the region with high solar radiation during the summer. This treatment is very easy and cheap, so the farmers use it whenever possible.
• Flooding is also applied as the pre-planting treatment for strawberries, to kill pests and diseases in the soil.
• Grafting on resistant stocks is also feasible for the cultivation of tomatoes, melons and watermelons. It is also effective against pests and soil born diseases.
• Currently seedling dealers generally sterilize the soil of nurseries to grow pest free seedlings for sale.