Photosynthetic responses of field-grown Pinus radiata trees to artificial and aphid-induced defoliation

Abstract

The phloem-feeding aphid Essigella californica represents a potential threat to the productivity of Pinus radiata plantations in south-eastern Australia. Five- and nine-year-old field trials were used to characterize the effects of artificial and natural aphid-induced (E. californica) defoliation, respectively, on shoot photosynthesis and growth. Photosynthetic capacity (A max) was significantly greater following a 25% (D25) (13.8 μmol m -2 s -1) and a 50% (D50) (15.9 μmol m -2 s -1) single-event upper-crown artificial defoliation, 3 weeks after defoliation than in undefoliated control trees (12.9 μmol m -2 s -1). This response was consistently observed for up to 11 weeks after the defoliati..