Insecta, Homoptera, .
Description, Biology, Life Cycle, Damage, Common Names, Images
- Polyphagous species. Observed in Italy on Citrus, almond, vines, pear, plum jujube(Zizyphus), carob (Ceratonia) and rose (Rosa).
- Females secrete a pheromone. This attracts males, which emerge in the afternoon. Although they live for only one day, the males can move about 100 m upwind.
- Females are viviparous; eggs hatch just before being laid. Females produce 60 to 150 nymphs over a ten-day period.
- After a brief period of quiescence (2 to 4 hours), the nymphs leave the maternal scale and disperse on the host tree, preferably onto stems, but also onto foliage and fruits. The majority have settled one day later.
During the cold season, scale insects usually congregate on the sunnier parts of the foliage while, in the summer, they move to shadier zones. Reproduction is greatest during uniformly hot and dry conditions.
Summer heat, combined with even slight humidity, causes considerable mortality amongst newly emerged nymphs under the maternal scale.
- The imaginal moult usually occurs 6 to 6 weeks after egg hatch.
It is very difficult to distinguish between generations, which considerably overlap. Under favourable climatic conditions, there are four generations per year.
Overwintering takes place inall instars.
Viviparous females are active from the end of April to the first ten days of January; throughout this period, mobile nymphs are also found.
Settled N1 nymphs are also observed throughout the year except in April; N2 nymphs and young females are thus present at all times.
- The species is deleterious to Citrus. The presence of this scale insect weakens the infested organ and the plant itself by sucking the sap, causing therafter deformations by the action of toxic saliva.
Branches dry out and cortical lesions form, foliage yellows and falls, the fruits are encrusted with the scale insects which are very difficult to remove even by brushing in treatment systems (*) .
The following are important natural enemies: the fungus Cephalosporium lecanii, predatory ladybirds (Chilocorus sp.) and parasitoid chalcid (Hymenoptera).
Amongst the latter, Aphytis melinus has been employed with success as a biological control agent against California red scale in Morocco.
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