Risk identification and mitigation for insecticide use in vegetables

Farmers resort to relying heavily on chemical control when insect pest pressure in vegetable production is very intense. Vegetable production offers a difficult situation for compliance to good agricultural practice, pre-harvest intervals in particular, when the financial situation is tight or when weather conditions require an early harvest. Some farmers spray every 2-3 days or even worse spray in the late afternoon and harvest early the next day. A nation-wide monitoring of vegetables in 2006 showed that about 30% of the samples contained detectable residues, which were generally below MRLs. There is therefore, a compelling need to identify risk and risk mitigation measures in this situation. Vegetables were sprayed at the recommended rate with insecticide late in the afternoon, harvested early in the morning of the next day and analyzed for residues. Home processing of vegetables, such as washing and boiling were done, while fresh fruits were also stored under ambient conditions to simulate wet market conditions to determine residues at this point in the supply chain. Dietary risk assessment for insecticides is made. Examples are discussed where insecticide residues at one day after spraying, were within and above ASEAN MRL's, another discusses a situation without ASEAN MRL. Home processing reduces pesticide residues which may be present in vegetables. Substantial reduction under ambient temperature and indoor sunlight was also noted. Malathion registered the greatest reduction of residues. In countries where harvesting of vegetables do not conform to registered good agricultural practice, a re-assessment can be made and use patterns re-registered after satisfying a dietary risk assessment. Supervised pesticide residue trials (SPRTs) on insecticide use in minor crops like okra, kangkong and pechay need to be done. ASEAN countries should continue to work together in collaborative research to produce SPRT data that can protect consumers as well as for CODEX MRLs to protect our exports.