A time series analysis of monthly issuance of plant import permits in Nigeria

Abstract

An import permit is issued by the National Plant Protection Organization of each country, known in Nigeria as the Nigeria Agricultural  Quarantine Service (NAQS), to allow the importation of pest-free plants and prevent the introduction of quarantine pests or check the  entry of regulated non-quarantine pests of imported plant commodities. Issuance of import permits at the Post-Entry Quarantine,  Surveillance and Diagnostic Station (PEQDS), Ibadan is mostly for germplasm materials mainly used for cultivation, which poses a high  risk of pest introduction. Thus, this study investigated the statistical components of the issuance of import permits at the PEQDS using  the Time Series approach to determine the peak period of collection essential for planning phytosanitary activities to mitigate the  introduction of foreign pests. The dataset of the monthly issuance of import permits from January 2012 to July 2022 was analysed. From  the preliminary study, we observed that the series exhibit seasonal and stationary components with no definite trend pattern, hence we  modelled the series using a Seasonal Autoregressive Moving Average (SARIMA) model. Several models were estimated and the best model (SAR(12)) for forecasting the future import permit collectionwas selected based on the forecast accuracy measures. The forecasted  values indicated the highest issuance of import permits in May and September, each year and showed a fluctuating  movement over time in the future. To further prevent pest incursion and facilitate trade, NAQS needs to operate round-the-clock  surveillance, keep its staff on high alert and adequate facilities operational for more effective activities. Other factors responsible for low  and fluctuating issuance of import permits should also be investigated.