Phenology of two scale insects, Coccus hesperidum and Icerya purchasi (Hemiptera: Coccomorpha) on Citrus in Mostaganem, Algeria

Abstract

In Mazagran, Mostaganem Province, Algeria, the seasonal variation in abundance of the scale insects (Hemiptera: Coccomorpha) Coccus hesperidum LINNAEUS, 1758 (Coccidae) and Icerya purchasi MASKELL, 1879 (Monophlebidae) was studied in an orchard on two host plant species, orange ( Citrus sinensis) and lemon ( C. limon) between December 2018 and November 2019. Every ten days, samples of leaves were collected for monitoring insect numbers. In C. hesperidum on orange and lemon trees respectively, there were three or four population peaks annually (P<0.0001). In I. purchasi, there were three generations annually (P<0.0001). In both scale insect species their abundance was correlated with temperature (P<0.0001 for C. hesperidum, and P=0.010 for I. purchasi) but not with relative humidity levels. Lemon trees had the higher scale insect abundance on 50% of days sampled, for both C. hesperidum and I. purchasi (P<0.005), whereas orange had lower numbers of both scale species. C. hesperidum and I. purchasi occurred on all three sample plots; numbers of both species (particularly C. hesperidum) showed a positive relationship with wind speed (P<0.0001 and P=0.002, respectively), as strong winds probably picked up and carried crawlers into the sample plots situated downwind.