The effect of previous defoliation of pole-stage lodgepole pine on plant chemistry, and on the growth and survival of pine beauty moth (Panolis flammea) larvae

Abstract

A study of the effects of defoliation by insects on the chemistry of lodgepole pine (Pinus contorta), and on the performance of Panolis flammea (Lepidoptera; Noctuidae) larvae, was carried out in a forest in northwest Scotland I year after a severe outbreak of P. flammea had caused extensive defoliation. Larval weight and survival were not significantly different on trees that had experienced different levels of defoliation in 1986. The nitrogen and tannin content of current and previous years' pine needles was not significantly affected by defoliation (although both were slightly greater in the foliage of defoliated trees). Phosphorus content of young pine foliage was lower (but not significantly lower except on one occasion) on heavily defoliated trees. On all sampling occasions, however, the nitrogen: phosphorus ratio was significantly higher on heavily defoliated trees. There were large differences in monoterpene composition of the previous year's shoots associated with defoliation intensity, but these differences had largely disappeared in the new growth. The results are discussed in relation to other studies on the effects of insect damage on plant chemistry and insect performance and in relation to the abundance of P. flammea in Scotland.

Asynchrony in larval development of the pine beauty moth, Panolis flammea, on an introduced host plant may affect parasitoid efficacy

“…Vanbergen et al (2003) showed that the original source of the larvae was of no importance (Scots pine or lodgepole pine) -all larvae grown on lodgepole pine had a longer lifespan than larvae grown on Scots pine. A similar situation was observed in the laboratory, where larvae removed from the field and reared on Scots pine foliage develop significantly faster than those reared on lodgepole pine (Watt 1989;Watt et al 1991;Leather et al 1998;Vanbergen et al 2003). The results of the study reported here confirm this finding in that larvae in lodgepole pine forests took approximately 10 days longer to develop than larvae on Scots pine, independent of the effects of temperature on the growth rates of the insects.…”

“…Their small jaws and undeveloped physiology restrict their diet to the young needles and flushing shoots and render them susceptible to attack from natural enemies (Hicks et al 2003) and disturbances from weather (Leather and Brotherton 1987;Hicks et al 2001b). In feeding experiments conducted in the field and laboratory, P. flammea larvae grown on Scots pine always developed significantly faster than those on lodgepole pine (Watt 1989;Watt et al 1991;Leather et al 1998;Vanbergen et al 2003;Hicks et al 2007). This is believed to result from Scots pine being the better host -in a nutritional sense -for the larvae, by providing more available nitrogen and significantly lower levels of secondary compounds (Watt 1989;Watt et al 1991).…”

“…In feeding experiments conducted in the field and laboratory, P. flammea larvae grown on Scots pine always developed significantly faster than those on lodgepole pine (Watt 1989;Watt et al 1991;Leather et al 1998;Vanbergen et al 2003;Hicks et al 2007). This is believed to result from Scots pine being the better host -in a nutritional sense -for the larvae, by providing more available nitrogen and significantly lower levels of secondary compounds (Watt 1989;Watt et al 1991). One would expect that increased larval developmental time would result in a longer exposure to natural enemies and, consequently, greater parasitism (Parry et al 1998).…”

Patterns of induced and constitutive monoterpene production in conifer needles in relation to insect herbivory

“…This lack of detection is based on past studies that have shown no dierence in needle monoterpene concentration for defoliated trees compared to undefoliated controls (Watt et al 1991;Barnola et al 1994). Gershenzon and Croteau (1991) suggest that, at least in mature needles, the lack of induction is due to the existence of developmental constraints on terpenoid synthesis.…”

Delayed induced resistance and increase in leaf fluctuating asymmetry as responses of Salix borealis to insect herbivory

“…Delayed induced resistance (DIR), when insects encounter the negative consequences of plant damage incurred during the previous growth season(s), has been demonstrated in birch (Neuvonen and Haukioja 1991), larch (Benz 1974), oak (Rossiter et al 1988) and mountain ash (Neuvonen et al 1987), whereas similarly designed experiments with other plants such as pines (Niemelä et al 1984(Niemelä et al , 1991Watt et al 1991); tea-leaved willow and bird cherry (Neuvonen et al 1987) revealed either mild or no response to damage. Furthermore, comparisons of responses between birch and mountain ash hinted that mechanisms underlying DIR -measured as reduced herbivore performance -may be species specific (Neuvonen et al 1987).…”