Dr Sunita Facknath of the Faculty of Agriculture - Interview on Alternatives to Pesticides
Are there really alternatives for pesticides in a tropical country like Mauritius?
Yes, indeed there are several alternatives for Mauritius, amongst them the use of natural enemies which eat or parasitise the pests and eventually kill them. This is known as Biological Control. In the developed countries, one can buy live natural enemies (most of them are themselves insects), just as we buy chemical pesticides. These living insects, which come in small bottles/envelopes, are released into the garden/field and they go around eating/killing the pests within a short time. However, there is no company in Mauritius that “manufactures” these natural enemies for sale. Yet it could represent a simple, highly lucrative business, perhaps as an SME. There are also commercially available pesticides which are not chemicals, but rather contain microscopic organisms, such as bacteria, virus, and fungus or nematode worms. Such pesticides are called Microbial Pesticides; they are sprayed just like conventional chemical pesticides but act differently on the pest. They are not harmful to humans, pets or other animals. However, they take a few days (sometimes up to 12 days) to kill the pest, and farmers are not happy to wait that long for the product to take effect. However, it must be understood that during this time, the pest does not feed and therefore does not cause any further damage to the crop. It is necessary to educate farmers about such products and to encourage them to use it.
Other alternatives include the use of colour-sticky traps. Certain insects are attracted to specific colours, yellow-coloured plasticised boards coated with a non-drying adhesive attract and kill leaf-miners that damage potato, brinjal, chilli and onion plants. Other simple methods are the spraying of dilute soapy water, or oil-water mixture (a few drops of soap/detergent is added to allow oil and water to make an emulsion). Ash or other abrasive materials can be sprinkled around seedlings to kill snails and slugs.
Also, most people are not aware that many of our common, well-known local plants have good pesticidal properties, and can be made into effective pesticides. People know about medicinal plants, but very few people are aware that there are pesticidal plants as well. Some examples include neem, citronella, eucalyptus, vetiver, ayapana, l’herbe bouc... While pesticidal preparations of neem are available commercially, one can make simple extracts using a grinder/blender and strainer and spray them by using a conventional knapsack/handheld sprayer. They are known as Botanical Pesticides and can control several pests. One drawback is that their effect is not very persistent, and fresh extracts have to be prepared and applied weekly. However, this same property can be considered an advantage, since the extracts do not remain long in the environment and therefore do not contaminate soil, water or food. Also, if used correctly they are not toxic to humans, pets, and other animals.
Some plants growning together with the main crop can help to repel and reduce pests in the field, like carrots grown together with cabbages can reduce numbers of the diamond back moth (little green larvae common in cabbage, cauliflowers, petsai).
Since quite a long time, we have been taught of using biological means in the elimination of pests in agriculture, particularly in the production of vegetables, but to no avail. Why this failure?
Biological control of pests has worked excellently in sugarcane. There is practically no insecticide application in sugarcane fields. Over the years, there have been many introduced biological control agents (natural enemies of pests) by the MSIRI and sufficient numbers of these have been successful to the point that there is no need to spray insecticides. The natural enemies continue to keep the insect pests in check. You will be interested to know that the first biological control in Mauritius dates back to 1762, when mynah birds were deliberately introduced into Mauritius to eat the red locusts that were causing huge damage to sugarcane plants at the time! However, biological control is a bit more complicated in the vegetable sector. Vegetables are short cycle crops and there is less time for the natural enemies to act. Also, the pesticides that the farmers continue to use kill large numbers of the natural enemies. In Mauritius, there must be a completely new approach to pest control in vegetables, with the use of Integrated Pest Management (IPM), wherein the farmer uses a number of different methods such as biological control, botanical and microbial pesticides, coloured traps, repellent plants... However, for IPM to work efficiently, it is important that all the farmers in the region adopt IPM. If chemical pesticides are sprayed in the neighbourhood, this will kill the natural enemies and also make biological and microbial control ineffective.
How far can the use of alternatives to pesticides in the production of vegetables be less costly to farmers?
The economics of the use of alternatives depends on several factors, for example greater the number of farmers using microbial pesticides, commercial botanical pesticides, greater will be the production of these products and their price will fall. The high labour cost in Mauritius is another important factor in overall production costs. The transition from a chemical-intensive pest control approach to an IPM approach will need a shift in the attitudes and mentality of producers as well as consumers, and a change in agronomic practices. Only if the transition is wide-spread over all the vegetable growing regions, will it work well and efficiently. When that happens, it can be even cheaper than the current cost of spraying insecticides. Moreover, it would help to make the environment healthier, and to give us cleaner and safer foods. Pesticide use has been linked to cancer and other serious diseases, and mere economics should not be allowed to take precedence over health and environmental issues.
How far can alternatives to pesticides help to meet the objectives of 'Food Security' as set by the authorities?
Most people understand the term Food Security to mean having enough food to eat. That is not the whole picture. Food security also means having access to sufficient, safe, nutritious food at all times in order to maintain a healthy and active life. It is being increasingly believed that pesticide residues in food contribute to the development of different cancers, and also cause foetal deformities. Therefore, any approach that reduces the use of synthetic chemical pesticides can help in meeting the food security objective, and also to environmental sustainability which is the main aim of the Prime Minister’s Maurice Ile Durable programme, and one of the Millennium Development Goals set by the worldwide community for the protection of our planet and our health.
Source: News on Sunday, Nov. 2011