Thermal time clock for estimating phenological development of schistocerca piceifrons piceifrons Walker (Orthoptera: Acrididae) in northeastern Mexico

Abstract

The Central American locust, Schistocerca piceifrons piceifrons Walker, is an economically important agricultural pest in Mexico and Central America. This species is characterized by its ability to gregarize and migrate long distances. High infestations of S. p. piceifrons have occurred in northeastern Mexico since 1998, particularly in the Huasteca region (South Tamaulipas, East San Luis Potosi, North Veracruz and the State of Hidalgo). The aim of this study was to develop a model that relates the life cycle of the Central American locust with the climatic conditions of northeastern Mexico. The model is expressed in terms of a Thermal Time Clock calculated from mean monthly temperatures and photoperiod. Historic temperature data of 20 y, from 20 meteorological stations, were used to calculate average monthly (ψmonth) and yearly (ψyear) values for thermal time (units are °C-days). For these calculations we used the Allen sine method, a lower temperature threshold (k1 =15.3 °C) and an upper thermal threshold (k2 = 38.5 °C). An average Thermal Time Locust Development Clock (TTLDC) was calculated using the relationship (ψmonth/ψyear) *360, which quantifies the monthly angular contribution on the clock (ψ = 10.6 α). Essentially, the clock is a translator between thermal time and calendar time (or vice versa) and may be used to forecast locust-stage development dates, starting from a given "Bio-fix" point. This clock can be used to program management activities of this pest. Field observations from 2001 to 2008, on population density and development stages of the Central American locust, were consistent with the development times recorded in the TTLDC.