Climatic and edaphic characteristics constrain the distribution of the quarantine pest Anastrepha grandis

The South American cucurbit fruit fly, Anastrepha grandis (Macquart) (Diptera: Tephritidae), is an economically important pest of cucurbits and is classified as a quarantine species in many countries. In Brazil, A. grandis has a limited distribution; it is absent from northern and northeastern Brazil and distributed discontinuously in other parts of the country. To indirectly evaluate the influence of climatic and edaphic variables on the occurrence of A. grandis, we used data based on 4 years of cucurbit fruit collections from all mesoregions of the state of São Paulo. Our results show evidence that A. grandis is constrained by a minimum air temperature above 12 °C, low (29 °C) maximum air temperature, and by low rainfall and relative humidity, occurring at altitudes from 520 to 780 m. More importantly, A. grandis was not collected in central to western São Paulo, where sandy soil and low soil water availability predominate and the climate is hot and dry. Our findings suggest that soil texture and moisture may be limiting factors for pupal survivorship of A. grandis, and consequently edaphic characteristics should be taken into account in studies on its geographical distribution. Based on our results, central to western São Paulo state can potentially be classified as an area of low pest prevalence. Moreover, in countries where cucurbit species are cultivated in such conditions, it is not likely that A. grandis could become established. The South American cucurbit fruit fly (Diptera: Tephritidae) is a pest of cucurbits and classified as a quarantine species in many countries. To evaluate the influence of climatic and edaphic variables on its occurrence, we used 4 years data of cucurbit fruit collections throughout São Paulo state, Brazil. The distribution of Anastrepha grandis was constrained by altitude, high temperature, low relative humidity, and soil texture. No fly was collected from sandy soils and at an elevation below 600 m.