Olive fly control – Part II: why use forecast models?
Forecast models play a very important role in the olive fly control: in the Part I of the article we have listed the benefits of their use, now let’s focus on the types of models.
The models are based on the knowledge of the relationships between past and future climatic conditions and the trend of fly infestation.
By consulting and analyze them it is possible to plan in advance, during the growing season, the control strategies to be undertaken both in conventional and organic systems and in field monitoring activities.
But what are the forecast models that support the olive fly control? Here are the ones available in OLIWES, which offers specific features for olive grove management within Agricolus platform.
Mortality model: the advantages
The model estimates daily the mortality, caused by high temperatures, of the pre-imaginal forms of the olive fly (eggs, first and second age larvae): the immature forms of fly are in fact very sensitive to the high temperatures that can occur in the summer months.
The model calculates the daily mortality with an exponential function of the temperature measured by the weather station in the field.
The daily mortality, expressed as a percentage, can be calculated from the date of observation of the first eggs in order to assess the possibilities of controlling the fly in the hottest summer period.
Or it can be cumulated over shorter periods, for example weekly, between one olive grove infestation survey and the next one.
In particularly hot years and in areas that are less affected by the mitigating effect of the sea, the knowledge of the degree of mortality can provide useful information on the percentage of population dead by “natural causes” and save control treatment if the levels of infestation are close to the threshold.
Development model: the advantages
The model simulates the generations of the olive fruit fly which is polyvoltine, that is performs a number of generations that varies depending on the year and the thermal availability of the place of interest.
The biofix of the model is the beginning of the ovidepositions of the first summer generation of olive fly, but can be conveniently moved by the user as detected in the field.
The model calculates the thermal sum necessary for the completion of a complete generation, and for each stage of development within each generation, based on the daily temperature values measured by a weather station in the field.
By consulting the model it is possible to have information on the stage of development prevailing at that time and to schedule the monitoring activities in the field for the necessary feedback of the output of the model and the most appropriate defense strategies, whether they are preventive adulticide (presence of adults of fly) and curative larvicide (presence of eggs and young larvae).
In Agricolus platform forecast models are integrated into a Decision Support System that helps olive growers in the main decisions to be taken for the management of the olive grove.
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