Quantification of pesticide dosage and determinants of excessive pesticide use in smallholder vegetable production systems in Tanzania

The use of pesticides for diseases and insect pest control has become a key component in smallholder vegetable production. This study therefore quantified the concentration of pesticide active ingredient per unit production land (kg a.i/ha), and drivers of increased pesticide use in smallholder vegetable production systems in Tanzania. Through field surveys and observations, data were collected from 385 farmers from Iringa, Arusha, and Kilimanjaro regions. A binary probit model was used to derive factors fostering increased pesticide use. High dose rates with increased frequency of application were evident. The concentrations of active ingredients (kg a.i/ha) were far above the world averages for fungicides (17.18 kg a.i/ha in tomato and 13.05 kg a.i/ha in onion), insecticides (5.86 kg a.i/ha in tomato and 6.37 kg a.i/ha in onions) and herbicides (3.78 kg a.i/ha in onions). Furthermore, 47.9 % of all pesticides were wrongly used. Most farmers (88.6 %) lacked knowledge of pest control and 88.9 % of farmers were unaware of pesticide safety practices. There was an increasing trend in pesticide use (58.4 %). WHO Class II hazard-classified pesticides (68.9 %) dominated smallholder vegetable production. Extremely hazardous (Class Ia) and highly hazardous (Class Ib) pesticides were also used. The binary probit model showed that the number of crops grown, pesticide mixing, and region contributed positively to the likelihood of increased pesticide use. In contrast, farmers' perception of the effectiveness of pesticides, lack of access to safe use information, poor use of safety gear, and inability to read pesticide labels had a negative impact. Excessive pesticide use jeopardizes the sustainability of smallholder vegetable production. Pesticide control and monitoring at the farm level, restricted use of highly hazardous pesticides, application of greener pesticides, and the use of specialized pesticide spray men in smallholder vegetable production would lessen and protect farmers and the environment from pesticide exposure.