Impact of frequency and intensity of defoliation on growth of Jarrah (Eucalyptus marginata): an experimental study with saplings

Effects of defoliation by Eucalyptus weevil, Gonipterus scutellatus, and chrysomelid beetles on growth of Eucalyptus globulus in southwestern Australia

“…This topic will be covered more fully elsewhere (Matsuki and Loch, unpublished data). The negative relationship between the level of damage to the growing tip and relative growth rate was expected as the negative relationship between damage levels and tree growth has been shown in other studies (e.g., Abbott et al, 1993;Raymond, 1995;Rapley et al, 2009). However, at least in this study, the interpretation of the negative relationship between growth and damage levels requires some caution.…”

“…Defoliation levels recorded during our study are likely to have a greater impact on growth of young saplings than established trees because saplings would have smaller amounts of stored carbohydrates to facilitate growth recovery after defoliation. This could explain why so many studies using saplings and young established trees have shown effects of damage on tree growth (Mazanec, 1966(Mazanec, , 1967(Mazanec, , 1968Cremer, 1973;Carne et al, 1974;Abbott et al, 1993;Stone, 1993a;Abbott and Wills, 1996;Stone et al, 1998;Collett and Neumann, 2002;Pinkard et al, 2006bPinkard et al, , 2007.…”

“…More frequent or regular removal of refoliating shoots, or disbudding, has a greater retardant effect on growth than single defoliation events (Mazanec, 1966(Mazanec, , 1967(Mazanec, , 1968Cremer, 1972;Candy et al, 1992;Abbott et al, 1993;Wills et al, 2004;Pinkard et al, 2006bPinkard et al, , 2007. Timing of defoliation may also influence eucalypt growth.…”

“…To date, approximately 10 studies have explored the relationship between insect defoliation and eucalypt tree growth either through insect exclusion or artificial defoliation, with further artificial defoliation studies investigating the impact of management practices such as pruning. A key theme emerging from these studies is that increased defoliation leads to greater reductions in growth, but at the same time, one-off defoliation of 50% or less of established trees typically has no impact on growth (Luckhoff, 1967;Abbott and Wills, 1996;Carne et al, 1974;Candy et al, 1992;Abbott et al, 1993;Pinkard, 2002Pinkard, , 2003Pinkard and Beadle, 1998a;Rapley et al, 2009). Also apparent from these studies is that the relationship between insect defoliation and eucalypt growth is a complex interaction that can be influenced by factors such as level and pattern of defoliation (Greaves, 1966;Bredenkamp et al, 1980;Elek, 1997;Collett and Neumann, 2002;Pinkard, 2002Pinkard, , 2003Pinkard and Beadle, 1998a,b;Pinkard et al, 2006bPinkard et al, , 2007, frequency and timing of defoliation (Cremer, 1972(Cremer, , 1973Wills et al, 2004;Pinkard et al, 2006bPinkard et al, , 2007, as well as environmental factors such as nutrient availability (Pinkard, 2002(Pinkard, , 2003Pinkard et al, 2006aPinkard et al, ,b, 2007.…”

Flooding effects on rapid responses of the invasive plant Alternanthera philoxeroides to defoliation

“…By contrast, defoliation treatments in our study were done only once during the experimental period. Frequent herbivory has been reported to reduce growth of the graminoids Bolboschoenus caldwellii, Phragmites australis and Schoenoplectus validus (Hayball and Pearce, 2004), and of Jarrah, Eucalyptus marginata (Abbott et al, 1993). Therefore, the effect of frequent defoliation of A. philoxeroides under flooded species may severely reduce the plant's vitality, but this still needs additional investigations.…”