Prediction of annual generations of the tomato leaf miner Tuta absoluta on tomato cultivations in Egypt

Abstract

BackgroundTomato crop is the first vegetable crop in Egypt; it covers about 3% of Egypt’s total planted area. The tomato leaf miner Tuta absoluta is a polyphagous insect pest which feeds on several solanaceous plant species and preferentially on tomato causing high losses in productivity. This study aims to predict the annual generations and expected times for moth emergence in order to select the best time for the pest management.MethodsSpecimens of T. absoluta were collected from infested tomato field and reared under controlled temperatures to calculate the thermal requirements for development and completing the whole generation. The duration of different developmental stages of this insect and the life table parameters were estimated. The data were used to calculate the thermal constant and developmental zero for different developmental stages using the formula of Jasic (Bihemoslov 72:383-390, 1975) mathit{mathsf{y}}=mathit{mathsf{n}} left(mathit{mathsf{t}}-mathit{mathsf{x}}right) .ResultsEcological studies were performed to evaluate the adverse effects of climatic changes on insect populations based on accumulation of the thermal requirements for development. The developmental zero was 5.79 °C and the thermal constant was 171 DDs to complete the pupal stage development. Based on these values, the pupae development can be repeated 36 times during 2012 when the mean annual temperature was 22.8 °C. In Giza governorate, the average life cycle duration during 2012 was 52.44 days when the mean annual temperature was 22.8 °C, the number of annual generations was 8.05, and the timing of the first generation was 11.66 days in April 2012 while the 8th generation cycle was obtained after 28.2 days of January 2013. In Qena governorate, the mean annual temperature was increased to be 26.04 °C, so the annual generations increased to 9.52. The first generation was recorded by the end of April 2012 while the 9th generation was completed on 24.4 days of December 2012. In Merssa-Matrouh governorate, the mean annual temperature was 20.53 °C and the number of the annual generations was found to be 7 during 2012. The first generation occurred on the day 19.86 of April 2012 while the 7th generation cycle was detected after 30.98 days of January 2013. This means that there must be successive emergence of the adults but with variations during the different months and locations in correlation with variation of temperatures.ConclusionThe accumulated thermal requirements appeared to be a very critical factor affecting insect development to complete the annual generations of T. absoluta in Egypt. This helps in designing the effective program and the best time for the pest management.