Ugandan Farmers Cautioned Against Overusing Pesticides and Contaminated Irrigation Water

Vegetable farmers in Uganda are increasingly relying on polluted water from rivers, wetlands, and runoff laden with pesticides and fertilizers to irrigate crops like tomatoes, lettuce, cabbages, and carrots. This practice, driven by water scarcity, results in residues building up on leaves, causing stunted growth and significant yield reductions.

Dr. Gabriel Ddamulira, programme leader for Horticulture and Oil crops at the National Crops Resources Research Institute in Namulonge, highlights the dangers of overapplying these inputs. He notes that such overuse harms both crops and human health, as residues linger in air, water, and on plant surfaces. Farmers are urged to follow package instructions precisely and avoid contaminated sources, especially in swampy areas.

The issue is particularly acute for tomatoes and traditional greens like nakati, buga, and cowpeas. Sensitisation efforts have shown progress among chilli exporters, who adhere to strict international standards after a 2018 EU ban. Recommendations include a 14-day no-application period before harvest and embracing best practices from planting to picking.

A Johns Hopkins University study, published in Environmental Science and Technology, reinforces these concerns through experiments on tomatoes, carrots, and lettuce irrigated with treated wastewater containing psychoactive drugs. Researchers found these compounds accumulate heavily in leaves—over 200 times more in tomato leaves than fruits, and seven times in carrot leaves versus roots—though edible parts show lower levels.

Lead author Daniella Sanchez stresses the need for advanced understanding of how plants process such contaminants amid growing water shortages. In Uganda, challenges persist in rice schemes like Agoro, where foul water spreads diseases, but solar-powered clean water systems offer hope despite underuse.

Source: Daily Monitor (Uganda)