Non-Chemical Alternatives to Methyl Bromide for Soil-Borne Pest Control Ricardo Labrada

Soil-borne pest complex, a constraint to agricultural production  Soil-borne pests are a major constraint to the production of several economically important crops, especially in horticulture.  Disinfection of soil is therefore an essential activity to control soil-borne plant pathogens, weeds and arthropod pests.  There are several effective chemical and non chemical methods for combating soil-borne pests, but none of them has the same broad spectrum of action as Methyl Bromide.

- with the use of MB as a soil fumigant, no ecological information was necessary. The effectiveness of the fumigant was a guarantee of highly effective control of most pathogens and other pests in soil. - There are several non-chemical alternatives able to suppress the growth and development of various pests in soil, which may be technically effective and economically feasible. However, most of them may have a very selective activity, i.e. controlling a group of pathogens or other pests, but not affecting others. - In this context, success for the application of non- chemical alternatives requires an integrated approach involving combinations of multiple control strategies according to the pest presence/abundance in soil. Some years ago this author asserted:

Drawbacks of some non-chemical alternatives - Non-chemical alternatives offer various advantages, the main one being their environmental viability. Each of these alternatives has its own limitations, either technically or economically. - They cannot be implemented everywhere, this will depend on socio-economical status of farmers, soil and climatic conditions, and species of organisms to be controlled in soil, for example: - 1. Grafting is a selective measure to be integrated in the control system to be adopted. It allows to prevent damage from specific pests, but not the whole complex

Drawbacks of some non-chemical alternatives (II) 2. Heating - it is not easy to obtain uniform temperature at the required soil depth. Further, there is a need for adequate water and fuel. 3. Steam heat - Equipment and fuel are expensive, and treatment between crops is labor and time-consuming. 4. Soil solarization fails in several temperate countries, and in hot climate areas, where the required period of solarization is not followed. In some countries, farmers cannot afford to wait 6-8 weeks for planting the crops. Control of root-knot nematodes has proven difficult with the use of soil solarization.

Drawbacks of some non-chemical alternatives (III) 5. Biofumigation has also been somewhat erratic for the control of certain soil-borne diseases. 6. Soilless technology require good control of nutrient and salinity, and are not affordable by all farmers, since there are several costs related to the disinfections, recycling and disposal of solution and substrates. 7. Most of the biological control agents should be used in preventative treatments since they won´t be able to cut the development of any established disease. They are usually applied in combination with other control measures as part of an IPM system.

IPM is part of the solution  Since none of the non-chemical options taken separately can replace MB, IPM could be a viable strategy.  Place by place farmers need to know what soil-borne pests are in soil and based on this they should be able to implement combinations of chemical and/or non-chemical alternatives to effectively control soil-borne pests.  A prescription which does not take into account the problem of the existing soil-borne organisms will be probably a failure in short term. Problems of resistance and other unimportant organisms in the past may arise from such “blind” solutions.

What can we do now? 1. An aggressive awareness campaign of the problem MB using all media available in affected countries. 2. Use of existing funds for additional training among farmers, cooperatives and other stakeholders of the need to implement IPM based on rational combinations of effective and environmentally safe control methods for soil-borne organisms. 3. Not using any banned chemical as an alternative to MB phase out. Any new alternative should comply with the existing national and international phytosanitary and pesticide regulations, most of them based on other international protocols and conventions. 4. Difficulties of registration cannot be seen as a constraint. Any alternative should be affordable by any stakeholder and should follow the existing environmental regulations in the countries.

5. More cooperation with national and international Plant Protection organs and ongoing projects related to pesticides and soil pest control may help to find new solutions to the existing problems.

ROTTERDAM CONVENTION on the Prior Informed Consent Procedure for Certain Hazardous Chemicals and Pesticides in International Trade TEXT AND ANNEXES (Revised in 2011) 6. Inclusion of methyl bromide in the annex III of the Rotterdam convention as a banned chemical to have surveillance of any use or purchase of the chemical in some countries.

7. Disposal of MB cylinders is a need and could be part of the extensive worldwide initiative on disposal of unwanted chemical pesticides

Thanks for your kind attention