One and two years impact of commercial thinning on spruce budworm feeding ecology and host tree foliage production and chemistry

Abstract

Field rearing experiments of spruce budworm, Choristoneura fumiferana (Clem.), were conducted in conjunction with foliar chemical analyses, one and two years after a commercial thinning (removal of 25% stand basal area) in a 50-year-old balsam fir, Abies balsamea (L.) Mill., stand. The first year after thinning, spruce budworm larvae reared on the residual trees developed five days faster and removed 43% more foliage than those reared on control trees, but in the second year they developed two days faster and removed 37% more foliage. The increase in larval development rate was related to an increase in foliar soluble sugars while a reduction in foliar monoterpenes caused by the thinning apparently accounted for the greater amount of foliage ingested by the larvae. The first year after thinning, trees were more vulnerable to spruce budworm because there was no increase in foliage production and the trees were more heavily defoliated. However, in the second year trees were less vulnerable to the insect because there was an increase in foliage production that exceeded the increase in defoliation, hence a net gain in foliage. Results from this study showed that commercial thinning could reduce the vulnerability of balsam fir trees to spruce budworm if thinning is conducted two years prior to budworm outbreak, but the same silvicultural procedure could increase the vulnerability to the insect if it is conducted during an outbreak. Key words: spruce budworm, balsam fir, chemistry, thinning, defoliation

Spruce budworm biological and nutritional performance responses to varying levels of monoterpenes

“…The principal monoterpenes that are produced by host tree foliage and their concentrations have been determined in several previous studies (Bauce et al 1994, Bauce 1996, Carisey & Bauce 1997a, 1997b, 1997c, Kumbasli et al 2011. Based on these data, six monoterpenes (α-pinene, bornyl acetate, camphene, δ-3-carene, terpinolene, tricyclene -Sigma-Aldrich, Milwaukee, WI, USA) were tested at different concentrations (Tab.…”

“…Concentrations of these compounds, like others present in the host plant foliage, are subject to spatial and temporal change. It is well known that terpenoid concentrations in foliar tissues generally increase with light intensity (Spring et al 1986, Bryant et al 1987, Gref & Tenow 1987, with nutrient availability (Björkman et al 1998), and following stand thinning, for example, in balsam fir (Bauce 1996, Lamontagne et al 2000, Fuentealba & Bauce 2012. Bauce et al (1994) showed that monoterpenes are positively correlated with the strong resistance offered by young balsam fir trees against budworm attack, compared to mature individuals.…”

Impact des éclaircies commerciales sur la croissance et la qualité du bois de l'épinette noire (Picea mariana (Mill.) BSP) en forêt boréale /

“…This low growth for both thinned and control stands before thinning may have been due to the spruce budworm outbreak, which occurred in the region in the late 1970s . Several studies have examined the interaction between spruce budworm outbreaks and CT (Bergeron et al, 1995;Bauce, 1996;Pothier, 1998) or pre-CT (Thibault et al, 1995;Tremblay, 2006). However, none of them deal with thinning conducted on a stand defoliated by spruce budworm a few years earlier.…”

Effet de l'éclaircie précommerciale et de l'éclaircie commerciale radiale et la qualité du bois de l'épinette noire de la sapinière à bouleau blanc du Saguenay-Lac-Saint-Jean /

“…En outre, les EC permettent de maintenir la vigueur des tiges résiduelles et la hausse potentielle de sa résistance à la tordeuse des bourgeons de Fépinette {Charistormaraftmîferama (Clem.)) (Bauce 1996;Bédard et al 2003;Tremblay 2006). …”