Analysis of the Spatio–temporal Distribution of Helicoverpa armigera Hb. in a Tomato Field using a Stochastic Approach

Abstract

Field surveys of Helicoverpa armigera Hb. (Lepidoptera: Noctuidae) were carried out in a 20 ha tomato field located in Extremadura, southwestern Spain. Geostatistical techniques were used to characterise the spatial and temporal variability of the insects. Interactions among meteorological factors and insect populations were also investigated. A global positioning system, geostatistics and a geographic information system (GIS) were used to locate sample points, characterise distribution patterns and map distributions of the insects. From the estimated values of insect densities on a regular 5 m by 5 m grid throughout the experimental area, using the block ordinary kriging technique, daily distributions of the pest were mapped. It was determined that the pest was concentrated at the borders of the tomato field, gradually colonising the inner area as cloudless days and northeastern winds (the same direction where another tomato field were 500 m apart) were pre-dominant. The results also showed the non-existence of correlations between other meteorological factors, temperature and relative humidity, with insect populations. These maps are fundamental to developing effective pest management and a powerful tool of a precision agriculture system.