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MONITORING STRAWBERRY PESTS AND DISEASES: A METHOD TO ESTIMATE YIELD LOSSES
As yield results alone are too imprecise, flower truss analysis was used to specify causes of injuries.
All flower trusses from 25–50 plants per field were collected along the monitoring route when the first berries were ripe.
The number of berries of different hierarchical order were counted and samples of normal ripe berries of the first, second and third order were weighed.
Flower trusses, buds, flowers and berries were classified as healthy or injured according to the cause of injury: strawberry blossom weevil, capsids, larvae, birds, grey mould, powdery mildew and any other recognizeable injury caused by a pest or disease.
Frost injury was also recorded.
The pest monitoring results were compared to injury levels and correlations were calculated for strawberry blossom weevil and capsids.
The monitoring results, the mean number of flower trusses per plant, the mean weight of berries and the price of berries/kg are needed to define economic losses due to a specified pest or disease.
This information can be used to set action thresholds at the farm level.
The flower truss analyses reveal only those losses caused by pests and diseases which attack the yield-bearing parts of the plant.
Monitoring of leaf- or root-damaging pests and diseases is also necessary, and generally accepted thresholds can be used.
Nematodes, strawberry mite, root weevils and root diseases should be controlled beforehand using healthy plants and crop rotation.