Pest-free plants: which Pieris cultivars avoid lace bugs

Summary

Over 60 Pieris taxa were evaluated for their susceptibility to Andromeda and azalea lace bugs. P. phillyreifolia and P. japonica 'Variegata' were consistently resistant to both species of lace bugs while P. japonica 'Cavatine' was consistently susceptible to both. P. japonica 'Temple Bells' and was notable in being highly susceptible to Andromeda lace bug, but resistant to azalea lace bug. Resistance in Pieris taxa to S. takeyai may be attributed to a combination of factors among which leaf toughness, moisture and stomatal characters may have a significant role. Finding cultivars that resist common pests reduces management requirements and unnecessary pesticide use.

Situation

The Ericaceous plant Pieris is a popular ornamental used in landscape or foundation plantings, shrub borders or for incorporating with other evergreens. Plants are prized for their glossy green leaves, clusters of red, pink or white urn-shaped flowers, and the striking colors displayed by new leaves. Lace bugs cause the most visible damage to Pieris. They not only weaken the plant but also reduce the attractiveness of the foliage, which affects the aesthetic value and marketability.

Response

Over 60 Pieris taxa were evaluated for their susceptibility to Andromeda and azalea lace bugs in multiple studies. Mechanisms conferring resistance were also investigated.

Impact

: P. phillyreifolia and P. japonica 'Variegata' were consistently resistant to both species of lace bugs while P. japonica 'Cavatine' was consistently susceptible to both. P. japonica 'Temple Bells' and was notable in being highly susceptible to Andromeda lace bug, but resistant to azalea lace bug. Experiments with extracts of leaf-surface lipids revealed that Pieris leaf wax does not have a role in resistance. Leaf wax extracts from the resistant species P. phillyreifolia applied on leaves of the susceptible cultivar P. japonica 'Temple Bells' did not affect feeding, oviposition or survival of S. takeyai, and neither did the reverse affect the resistance of P. phillyreifolia. Leaf penetrometer measurements indicated significantly higher force was required to puncture P. phillyreifolia leaves. This species also had higher fiber, lignin and cellulose content and lower leaf moisture content. Ultrastructural studies on leaves of selected Pieris taxa revealed significant differences in the number and size of stomata. P. phillyreifolia leaves had the highest number of stomata per unit area but they were the smallest in size, whereas P. japonica 'Temple Bells' leaves had a lower number but the largest stomata. Resistance in Pieris taxa to S. takeyai may be attributed to a combination of different factors among which leaf toughness, moisture and stomatal characters may have a significant role.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2011
• Geographic Scope: National
• County: Spalding
• Program Areas:
  • Agriculture & Natural Resources