Frost increases beech susceptibility to scolytine ambrosia beetles

Abstract

In the early 2000s, beech forests in Western Europe suffered from a so far unexplained burst of mortality. Necroses, ambrosia‐beetle and fungal attacks were observed on the trunks. The symptoms were similar to previous events reported throughout the 20th Century. One current hypothesis is that these phenomena were related to early frost events for which the trees were physiologically unprepared and which made them vulnerable to biotic attacks. In the present study, we aimed to test this hypothesis further, by retrospective meteorological analyses and also by an experimental approach. Our meteorological analyses highlighted the occurrence of cold waves a year before the beech declines were reported in 1929, 1942 and 1998. In our experimental approach, frost injuries were inflicted to mature trees in a beech stand using dry ice. The treated trees were more attractive to insects than untreated controls. Insect attacks were observed in the treated zones on the trees but colonization was not very successful. The galleries had aborted most of the time with only a few larval chambers. Very few insects were caught in emergence traps. The results of these two approaches support and strengthen the hypothesis that frost induced beech dieback. Frost injuries increased tree attraction to ambrosia beetles to the point of inducing attacks. However, the overall success of these attacks was much lower than that observed in the 2000s. These differences might reflect limitations in our experimental approach, where frost wounding was applied locally to the trees.

Vernal freeze damage and genetic variation alter tree growth, chemistry, and insect interactions

“…the limited studies that have examined the connection between freeze damage and insect susceptibility in trees, one (Thomson, Nicotra, & Steinbauer, 2001) revealed increased growth of two insect species on Eucalyptus, and another showed increased attraction of beetles to Fagus (LaSpina, De Cannière, Dekri, & Grégoire, 2013), suggesting that freeze damage may render trees more susceptible to insect attack. To date, studies examining the effects of freeze damage on trees have not addressed impacts on aboveground-belowground biomass allocation, or the connection between freeze-induced changes in particular plant traits (e.g., phytochemistry) and plant-insect interactions.…”

Are outbreaks of cambium‐feeding beetles generated by nutritionally enhanced phloem of drought‐stressed trees?

“…; La Spina et al. ). This causes the crowns to compensate for the lack of water by starting to die back, senescing at an accelerated rate and breaking down and exporting increased amounts of nutrients via the phloem either to storage in the roots or reallocation to new growth or reproductive tissues (Gates ; Bryant et al.…”

“…As a drought begins and intensifies, the shallow surface soils dry out, killing the trees' feeding roots (Thomas et al 2002;Anderegg et al 2013;La Spina et al 2013). This causes the crowns to compensate for the lack of water by starting to die back, senescing at an accelerated rate and breaking down and exporting increased amounts of nutrients via the phloem either to storage in the roots or reallocation to new growth or reproductive tissues (Gates 1964;Bryant et al 1983;Masclaux et al 2000;Soudry et al 2005;Millard and Grelet 2010;White 2011;Gonda-King et al 2014).…”

Increased Susceptibility to Aphids of Flowering Wheat Plants Exposed to Low Temperatures

“…The current study was conducted with experimental conditions which may not simulate those in the field. For example, La Spina et al (2013) found increased preference, but not performance, of insects on frosted beech trees by experimentally inflicting the frost damage. They concluded that the reduced performance was because the experimental conditions differed from that in natural conditions where the performance of the insects is greater.…”