The average annual rainfall in the UCRB varies from 1200 mm to 3000 mm, with an average of 2215 mm. Almost 70% of this rainfall occurs in the wet season. The wet season typically starts in November and ends in April, with an average monthly rainfall of approximately 250 mm (typical range: 100-500 mm). During the dry season from June to September, monthly rainfall is usually less than 50 mm (Deltares, 2010). Other months constitute a transitional period. The high annual rainfall and the mean daily temperature that varies between 18˚C and 30˚C provide favorable climatic conditions for growing vegetables in the UCRB.

2.2 Survey Design and Data Collection

A questionnaire was designed to obtain information about the amount and types of pesticides used by farmers living in the UCRB agricultural area. The questionnaire comprised 21 questions (see Supplementary Data 1 ) that focused on: 1) general information about the respondents (name, gender, age, address); 2) farmland information such as area, type of crops, harvest, planting period, and planting frequency per year; 3) pesticide application data such as brands purchased, type of pesticide, quantity, and frequency of application.