Pesticide poisoning has been an increasing problem in the Philippines, and vegetable farmers are exposed to pesticides to a far greater extent than rice or maize growers because of the nature of the chemicals and the largely manual techniques used. Of particular concern is the exposure of young children, who are often employed in vegetable growing from an early age. In one study in north-east Luzon Island in the Philippines, school children were found to start working in vegetable plots as young as 6-9 years of age. As well as watering and other tasks, their roles involved pesticide preparation and application. The children reported health symptoms such as headaches, skin irritation and abdominal pain after the use of chemicals1.
Eggplant is one of the most economically important crops in the Philippines, and is the leading vegetable crop both in terms of land area and production volume. However, high pest pressure from eggplant fruit and shoot borer (EFSB) leaves farmers dependent on frequent spraying of high levels of insecticides to protect the crop2. Surveys have shown that an overwhelming majority of eggplant farmers rely almost entirely on chemical insecticides to control EFSB, because other techniques such as manual removal of infected shoots, the use of biological control methods such as pheromone traps or enhancement of predator insects are too laborious and unreliable3.
However, the nature of the fruit and shoot borer pest makes insecticide control especially problematic. EFSB larvae feed internally: after eggs are laid at the surface, the caterpillars bore into the fruit or growing tips of the eggplants. Therefore, larvae are susceptible to insecticide spraying only a few hours after hatching, after which they become invulnerable by feeding inside the plant. Farmers therefore have to resort to very frequent sprays to control the pest, using some of the more toxic insecticides - many of which are banned in Western countries. Surveys show that eggplant growers in the Philippines spray their crop at least twice a week, with some spraying as often as every other day, adding up to 60-80 sprays during a normal production cycle of 4 months4.
Insecticides used are broad-spectrum, meaning they kill many more insects than the targeted fruit and shoot borer, resulting in impacts on ecosystems and a loss of insect biodiversity. Many of the insects killed may in fact be beneficial. The constant use of insecticides also leads to the buildup of resistance in the targeted pests, meaning farmers must resort to heavier doses and more toxic compounds. In the Philippines, organophosphate insecticides are the most common category used, with carbamates and synthetic pyrethroids following in popularity. Organophosphates can be absorbed by humans through skin or inhalation, resulting in nausea, diarrhea and effects on the nervous system. Many carbamates are known carcinogens, while pyrethroids may also cause users to experience dizziness, headache, nausea and diarrhea5. Very acute poisoning can be fatal.
Excessive use of pesticides also leads to residue in the soil and water, as well as on the crop itself. One study in Sta. Maria, Pangasinan, found that soil samples in 42% of eggplant farms tested positive for insecticide residues, some of which exceeded the maximum permitted limit. Soil residues included profenofos, triazophos, chlorpyrifos, cypermethrin, and malathion, while residues on the crop samples - a fifth of which tested positive - were cypermethrin and chlorpyrifos6. Because both eggplant harvesting and spraying happens every couple of days, withdrawal times before harvesting of the crop are often ignored, making residues on the vegetables more likely.
In contrast to broad-spectrum synthetic insecticide sprays, the Bt protein only affects the larvae of the eggplant fruit and shoot borer and related pest caterpillars. It is highly selective in its pesticidal action, while remaining non-toxic to humans. It has a soft environmental footprint. In fact, organic growers routinely use Bt as a foliar spray, although it is much less effective against EFSB when applied as a spray than when it is in Bt eggplant. In addition, because Bt is expressed within the plant and the fruit, it targets the EFSB very precisely. It is anticipated that the cultivation of Bt eggplant in Philippines will enable a dramatic reduction in broad-spectrum insecticide sprays by eggplant farmers in the country, with associated health, economic and environmental benefits.
- 1. Lu, J. et al, 2010: 'Trends of Pesticide Exposure and Related Cases in the Philippines', Journal of Rural Medicine, 5, 2, 153-164
- 2. Davalos, E. et al, 2011, 'Pests and Pesticide Use in Eggplant Production in Central Luzon', Technical Bulletin, vol 1., no.2, Department of Agriculture Philippine Center for Postharvest Development and Mechanization
- 3. Francisco SR. Socioeconomic Impacts of Bt Eggplant: Evidence from Multi-location Field Trials In: Gerpacio RV, Aquino AP, editors. Socioeconomic Impacts of Bt Eggplant: Ex-ante Case Studies in the Philippines. Ithaca, NY and Los Banos, Laguna: International Services for the Acquisition of Agri-Biotech Applications and the Southeast Asian Ministers of Education Organization-Southeast Asia Regional Center for Graduate Study and Research in Agriculture; 2014. pp 205–232.
- 4. Davalos, E. et al, 2011, 'Pests and Pesticide Use in Eggplant Production in Central Luzon', Technical Bulletin, vol 1., no.2, Department of Agriculture Philippine Center for Postharvest Development and Mechanization
- 5. Lu, J. et al, 2010: 'Trends of Pesticide Exposure and Related Cases in the Philippines', Journal of Rural Medicine, 5, 2, 153-164
- 6. Del Prado-Lu, J., 2015: 'Insecticide Residues in Soil, Water, and Eggplant Fruits and Farmers’ Health Effects Due to Exposure to Pesticides', Environmental Health and Preventive Medicine, 20, 1, 53-62