Distribution of infestation by lentil gall midge Contarinia lentis (Dipt.,Cecidomyiidae) in lentil fields: statistical model

The horizontal distribution of infestation by Contarinia lentis in lentil f ields, not subjected to chemical control, was recorded and analysed in the Slovak Republic during outbreaks of this pest in 1986-89. Infestation level was defined as the percentage of galls from the total number of galls, pod s, and flowers. The highest levels of infestation were found along the edge s and the lowest levels in the centres of fields. The distribution of the i nfestation between the edge and the centre has been described for Is fields using a nonlinear function containing two parameters. The first parameter represents the infestation level at the edge. The second parameter represen ts the rate of decrease of infestation from the edge towards the centre of the field. The relationship between the first parameter and the distance to the adult midge emergence site and the relationship between the second par ameter and the mean velocity of winds carrying females from the emergence s ite is described using exponential functions. The results indicate that (I) the longer the distance to the midge emergence site, the lower the infesta tion at the edge; and (2) the greater the wind velocity, the weaker the dec rease in infestation from the edge towards the centre of a field.