Zimbabwe's agriculture slowly phasing out methyl bromide

The phasing out of methyl bromide and other ozone-depleting chemicals under the Montreal Protocol poses major challenges for Zimbabwe's agricultural sector, two of the country's major pesticide users have said.

Zimbabwe uses carbonfluorocarbons, halons and methyl bromide in for grain preservation, refrigeration, fire fighting and in various other industrial uses. Under the Montreal Protocol, developing countries were expected to have completely phased out the use of methyl bromide, halons and chloroflourocarbons by 2010.

Grain Marketing Board (GMB) quality assurance manager Ms. Patience Mutukwa said the grain parastatal was faced with daunting challenges following the introduction of a new preservative chemical, phosphine. "We stopped using methyl bromide in January this year in compliance with
the Montreal Protocol, which makes mandatory the phasing out of ozone-depleting substances by all countries that are signatories of this protocol," she said.

Mr. Meanwell Gudu of the Tobacco Research Board (TRB) said tobacco farmers were reluctant to discard methyl bromide. He said it was, however, important for farmers to wean themselves from using methyl bromide in favour of the float trays. "The new method entails cutting down on costs during planting and tending their seedlings. The use of methyl bromide is not necessary under this new method of growing seedlings," he said.

However, some farmers said they were finding it hard to access the float trays and were still using the old way of planting their seeds and using methyl bromide as a herbicide.

Although the GMB had made strides in replacing methyl bromide, "we finding using phosphine a bit time consuming since we deal in bulk storage. This fumigant has a few disadvantages over methyl bromide," Mutukwa said. She said phosphine required the grain to be exposed for a longer time at lower temperatures when compared to methyl bromide. She added that close monitoring was required while fumigating, as phosphine was flammable in high concentrations.

It was against this background that GMB was expected to draw up a budget for the purchase of other equipment suitable for the new method of fumigation. The grain organisation was also working closely with international researchers on other effective fumigation options.

Research conducted by countries such as Italy, which uses carbon dioxide as a fumigant, has shown that some insects had developed resistance to phosphine.

allafrica.com