Physiological Characteristics of Citrus Plants Infested with Citrus Leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae)

Abstract

Plants and insects are members of diverse ecological communities. Feeding of herbivore insects may damage the host plants indirectly by altering the photosynthetic activity. The objective of this study was to evaluate the physiological changes in citrus plants due to citrus leafminer (CLM) Phyllocnistis citrella Stainton (Gracillariidae: Lepidoptera) larval feeding under field condition. Plants from four economically important citrus cultivars, Citrus reticulata (Kinnow and seedless Kinnow), Citrus tangerines (Fairchild), and Citrus paradisi Macfad (Grapefruit), were selected randomly and leaf damage was assessed through an image analysis technique. The results showed that percent leaf damage was higher at 44.2% on Fairchild compared to other cultivars at 19th day of post-feeding. The reduction in leaf photosynthesis (Pn), stomatal conductance (C), and transpiration rate (E) rates due to larval feeding through 19th day was found consistent in all cultivars except Grapefruit. After 13 days, Pn and gaseous exchange rates in damaged leaves of Grapefruit recovered to some extent but remained significantly lower than in control through 19th day. Reduction in all three physiological parameters in infested leaves was ranged as Fairchild > Kinnow > seedless Kinnow > Grapefruit compared to their level in control. Percent of leaf damage had a strong and negative relation with Pn, C, and E in all citrus cultivars except Grapefruit in which all variables showed a weak relation. Conclusively, P. citrella may cause a serious threat to citrus plants even at lower levels of infestation, and these physiological impairments could be more intense in regions with high P. citrella population.