Very few topics can raise as many strident voices as “pesticides”. Chemists, farmers, environmentalists, entomologists, biologists, agricultural specialists, health officials, governments, consumers, and concerned citizens of all varieties have valid interests in the development, use, and environmental and health effects of pesticides.
Methyl bromide (MeBr) was introduced as a pesticide in 1932. It is effective against nematodes, fungi, and weeds. For growers of strawberries, tomatoes, peppers, melons, cucumbers and squash, it has been the pesticide of choice for decades. But it is also a major ozone–depleter. The 1987 Montreal Protocol on Ozone Depleting Substances called for the ban of MeBr by 2005. The United States was allowed “critical use exemptions”, which are still being used extensively in American agriculture while researchers are working to find alternatives to MeBr. Plant pathologists, horticulturists, agricultural economists, chemists, entomologists, and other scientists are looking for effective integrated pest management.
The Agricultural Research Service (ARS) of the US Department of Agriculture is just one of many organizations working worldwide to replace MeBr. ARS scientists at the US Horticultural Laboratory in Fort Pierce, FL, developed a unique mixture of waste materials and combined it with soil solarization to combat nematodes and weed seeds in Florida. They mixed poultry litter with molasses derived from sugar cane waste products. The researchers covered the soil in the test fields with black plastic for solar heating and then tested various combinations of water and the litter–molasses mixtures.
Fall crops of pepper and spring crops of eggplant were treated and evaluated. The litter–molasses mixture reduced the number of nematodes and “controlled grass weeds just as well as methyl bromide.” The soil temperatures were hot enough to destroy many plant pathogens (see Alternatives Eyed for Methyl Bromide and Investigating Two Pathways to Replacing Methyl Bromide).
MeBr is such an effective umbrella pesticide that there is no single substitute. We will be reporting on other solutions in the weeks to come.