Stephanitis lace bugs affecting ericaceous plants
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The Andromeda lace bug Stephanitis takeyai Drake and Maa (Hemiptera: Tingidae) is an important pest of pieris, a popular ericaceous ornamental shrub. In the first project, over sixty Pieris taxa (species, cultivars and hybrids) were evaluated for their reaction to S. takeyai and S. pyrioides (Scott), the more economically important species, using no-choice, multi-choice and whole plant assays. P. phillyreifolia and P. japonica ‘Variegata’ were identified as resistant to both species of lace bugs while P. japonica ‘Cavatine’ was susceptible to both. P. japonica ‘Temple Bells’ was highly susceptible to S. takeyai, but resistant to S. pyrioides. Oviposition by S. takeyai was noted in various Pieris taxa, whereas S. pyrioides did not oviposit in any of the Pieris taxa. In the second project, some of the potential mechanisms of resistance in selected Pieris taxa to S. takeyai were examined. Assays with extracts of Pieris leaf-surface wax revealed that they did not have a role in resistance. Resistance in Pieris taxa to S. takeyai appeared to be a combination of different factors like leaf toughness, moisture and stomatal characters. The resistant P. phillyreifolia leaves were tougher, lower in moisture and had smaller stomata than susceptible taxa. The acceptability of ten ericaceous hosts to S. takeyai was assessed in the third study. In no-choice tests maximum leaf damage was recorded on P. japonica and Rhododendron calendulaceum, while slight but non-significant damage was noted on Vaccinium arboreum and Rhododendron ‘Hampton Beauty’. Nymph emergence was recorded on P. japonica, R. calendulaceum and Rhododendron ‘Hampton Beauty’. In multi-choice tests maximum leaf damage was recorded on P. japonica whereas R. calendulaceum suffered only slight damage. This showed that several plants, which may not be favorable hosts, could still act as reservoirs for the pest. In the fourth project effectiveness of insecticides available to the homeowner, supplemented with a natural enemy Chrysoperla carnea (green lacewing) in suppressing the azalea lace bug was compared. Treatments using traditional insecticides (acephate and imidacloprid) were significantly more effective in controlling the lace bugs than alternative methods like oil and soap. C. carnea did not contribute significantly to the lace bug suppression.