Chlorosis, photosynthesis, and transpiration of azalea leaves after azalea lace bug (Heteroptera: Tingidae) feeding injury

Feeding injury caused by nymphs, males and females of the azalea lace bug, Stephanitis pyrioides (Scott), reduced rates of photosynthesis and transpiration in 'Delaware Valley White' azalea, Rhododendron mucronatum leaves. Females caused substantially more leaf feeding injury than males or nymphs. S. pyrioides was observed to insert stylets through stomata on the lower leaf surface and to feed almost entirely on upper palisade parenchyma tissue by piercing and removing cell contents. Lace bug feeding increased leaf stomatal resistance which indicated that gas exchange was restricted by stomatal closure. Feeding injury also reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll, but did not consistently affect chlorophyll a:b or specific leaf weight. Net leaf photosynthesis was negatively correlated with stomatal resistance and positively correlated with both chlorophyll content per unit leaf area and photosynthetic rate of remaining chlorophyll. These results indicated that S. pyrioides reduced leaf photosynthesis in azalea by damaging palisade parenchyma which restricted gas exchange through stomata and reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll.