MITE PARASITIZATION ON ARMORED SCALE INSECTS - HOST SUITABILITY

Suitability of three armored scale insects (Homoptera: Diaspididae), t heir stages, the host plants and their parts, for the parasitic mite H emisarcoptes coccophagus Meyer was investigated. The studied scales we re chaff scales, Parlatoria pergandii Comstock and P. cinerea Hadden, infesting grapefruit and orange orchards, latania scale, Hemiberlesia lataniae (Signoret), and oleander scale, Aspidiotus nerii Bouche occur ring on acacia (Acacia cyanophylla) branches and leaves. Host suitabil ity was evaluated by mite survival, mean intensity (active mites/attac ked scales) and fecundity. It was highest on latania scale, lowest on oleander scale and intermediate on chaff scales. Results of laboratory experiments were consistent with these field findings: while developi ng on oleander scale, mites suffered 3x higher mortality, and their ge neration time was twice as long as on latania scale; the full egg clut ch on the latter was high whereas on oleander scale it was negligible. Our data suggest that ovipositing females of latania and oleander sca les, but not of chaff scales, are more suitable hosts than young scale females and the latter more suitable than immature stages. No direct effects of acacia plant parts on host suitability were detected. Citru s species affected chaff scale suitability for the mite through their effect on host diaspidid size. The ability of H. coccophagus to contro l pestiferous diaspidids may depend on the specific host scale, its ag e structure and the specific host plant. The implications of these fin dings for the biological control of armored scale insects are discusse d.