Assessment and forecast of damages caused by Cydia pomonella in apple orchards of Northern Africa (Algeria)

The codling moth, Cydia pomonella (L.), is a major pest in apple orchards worldwide. We carried out a two-year study in Northern Africa (Algeria), where the environmental conditions could affect codling moth phenology and host selection. Infestation rates in Golden Smoothie apple orchards (18% on average) were twice as high compared to Gala Brookfield and Granny Smith due to differences in the nutrient content and maturation phenology. A significantly higher proportion of fruits were attacked in the eastern and southern sides of the canopies, doubling those recorded at the centre, northern or western orientations. Infestation rates at the eastern sides of Golden Smoothie apple trees (average 32%) were especially remarkable. Adult flight phenology did not differ between years, and infestation rates were related to the number of adults caught in the middle of the first flight period (beginning of May). Hence, farmers could predict infestation rates in advance and start treatments against eggs and larvae to avoid further damages when necessary. In the two study years, adult moth numbers were already very high then, with peaks of more than 40 adults collected per trap weekly (four times the threshold recommended to start treatment). The application of insecticides in our study area does not start until the last days of April, but our results show that this is too late. Treatments targeting eggs and larvae should start no later than April 12th, when adult numbers are not so high yet and there are already eggs. Only doing this it will be possible to keep apple infestation rates below the acceptable threshold for commercialization in this region of Algeria (Sidi Bel Abbes).