Colonization of vineyards by phytoseiid mites: their dispersal patterns inthe plot and their fate

The effect of wind and woody margins on the dispersal and population dynami cs of phytoseiid mites was studied in a vine plot for a period of two years . Mites were sampled in the plot and in the surrounding vegetation (crops a nd natural vegetation) in order to determine phytoseiid mite abundance. The surrounding vegetation was considered to be a reservoir of phytoseiids fro m where the vine plot could be invaded. Directional and non-directional soi l and aerial traps were placed in the plot to determine predatory mite exch ange between the two areas. Colonization of the plot occurred in two stages : first, mite migration into the plot, followed by their establishment. The two-year study partially clarified the first of these two stages. Kampimod romus aberrans was the main species caught in the aerial traps. Phytoseiid mite dispersal within the vine plot seemed to be affected by both wind (dir ection, intensity and regularity) and phytoseiid mite density in the woody margin. However, the woody margin had a large effect only over a short dist ance. Some observations pointed towards an effect of other reservoir areas but it was not possible to characterize these. The population density of th e phytoseiid mites in the plot increased from 1996 to 1998, but these incre ases are much smaller than one would expect on the basis of the number of m ites migrating by air in the plot. Moreover, blocks where most mites were t rapped were not the blocks where densities of phytoseiid mites on vine leav es were the largest. It therefore seems likely that not all migrants were a ble to develop. Their settlement pattern was not determined and this could constitute a potential research focus for the future.