When to spray? Examples on incorporation of time-series of pheromone trap captures into plant protection technology


Abstract: In order to measure the lenght of the optimal time periods between the date of peak flight, as indicated by seasonal flight curves plotted by pheromone trap captures, and the date when pesticides can be applied most effectively, several pilot studies for selected pests were conducted in Hungary. In selecting pests, representatives of the extremes in the number of flights per season were chosen: those having three or four flights compared to that of having one flight only. Seasonal flight pattern of pests were monitored by pheromone traps. In all cases when large-capacity funnel type of traps were available on the market, this type was used. Captures obtained at recordings in course of the season provided time-series No. 1. The appearence of either newly hatched larvae of the subsequent generation, or new damage caused by these larvae was also regularly tracked in course of the season. These data sets provided time-series No. 2.In order to determine the length of time elapsed from peak flight to egglaying and hatching of larvae, synchrony between times-series No. 1 and No. 2 was statistically analysed by cross-correlation in the core-trial for Helicoverpa armigera. The date of egglaying was chosen as an indicator of optimal timing of pesticide application.Results showed that different strategies in timing of application of pesticides should be recommended for these groups of pests. Pests having three flights can effectively be controlled at peak flight (Helicoverpa armigera, Leucoptera malifoliella and Dasineura gleditchiae), or even earlier, at the sharply ascendent phase of the flight curve (Cameraria ohridella). In contrast to this, monitoring had little help in timing of control measures against Synanthedon vespiformis, which has one prolonged flight period.

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