Temperature-dependent development of the great European spruce bark beetle Dendroctonus micans (Kug.) (Coleoptera: Curculionidae: Scolytinae) and its predator Rhizophagus grandis Gyll. (Coleoptera: Monotomidae: Rhizophaginae)

Abstract

1 Dendroctonus micans is an invasive species that has spread throughout Britain, which prompts the question: how is the voltinism of this pest and its biocontrol agent Rhizophagus grandis affected by climate? 2 Dendroctonus micans and R. grandis were reared at a range of constant temperatures.Lower developmental threshold temperature (LDT) and day degree (DD) requirements for the egg, larval and pupal stage of D. micans were estimated to be 7.4 ∘ C 153 DD, 6.6 ∘ C 527 DD and 7.2 ∘ C 126 DD, respectively. At 12.5, 15 and 17.5 ∘ C, prior to prepupal cell formation, fifth-instar larvae underwent a diapause, which has not been observed previously in this species. Prepupal development rate also did not increase linearly with temperature. 3 For R. grandis, the LDT and DD requirements for the egg, larval, prepupal and pupal stages were 5.7 ∘ C 84 DD, 6.2 ∘ C 263 DD, 8.1 ∘ C 90 DD and 6.8 ∘ C 178 DD, respectively. At 12.5 and 15 ∘ C, most prepupae failed to pupate, which is indicative of a facultative diapause. 4 The key developmental parameters reported in the present study may be used to model the phenology of the beetles throughout their range, providing better-timed control strategies or to predict outbreak risk under climate change as a result of reduced biocontrol effectiveness.

The lifecycle of Agrilus biguttatus: the role of temperature in its development and distribution, and implications for Acute Oak Decline

“…Although a relatively low number of replicates was used to generate the lower threshold temperatures and thermal requirements of A. biguttatus , the threshold temperatures reported in the present study for the egg stage, and the threshold temperatures and degree‐day sums for egg and pupal development, were similar to those reported for another temperate Agrilus species, A. planipennis (Lyons & Jones, ; Duan et al ., ). The degree‐day values for the egg and larval stages of A. biguttatus were also in line with those of two damaging European bark boring pests, Hylobius abietis Linnaeus (Coleoptera: Curculionidae) and Dendroctonus micans Kugelmann (Colepotera: Scolytidae), as found in comparable studies (Inward et al ., ; Gent et al ., ). The egg and larval threshold temperatures of A. biguttatus , however, were considerably higher than those of H. abietis , which has egg and larval thresholds of 8 and 4.5 °C respectively, or D. micans , which has egg and larval thresholds of 7.4 and 6.6 °C, respectively.…”

“…The egg and larval threshold temperatures of A. biguttatus , however, were considerably higher than those of H. abietis , which has egg and larval thresholds of 8 and 4.5 °C respectively, or D. micans , which has egg and larval thresholds of 7.4 and 6.6 °C, respectively. Their development at lower temperatures allows the two insects to colonize much cooler parts of the U.K. than A. biguttatus : H. abietis is found throughout the U.K. (CAB International, ), and the range of D. micans includes parts of southern Scotland (Gent et al ., ).…”

Diapause and overwintering of two spruce bark beetle species

“…In addition to dormancy, many bark beetle life history events are temperature‐driven, including developmental rates and thresholds, survival, thresholds for the onset of swarming or feeding, and thermal sums to complete ontogenetic phases (Bakke, ; Bentz et al ., ; Lobinger, ; Coeln et al ., ; Wermelinger & Seifert, , ; Doležal & Sehnal, ; Gent et al ., ; Schebeck & Schopf, ). Because winter temperatures in temperate regions frequently drop below the melting point of water, temperature also plays a major role in overwintering survival, and cold adaptations are often related to the expression of dormancy (Zachariassen, ; Hodek & Hodková, ; Denlinger, ; Bale, ; Sømme, ; Sinclair et al ., 2003a,b; Danks, ; Lee, ).…”

“…The life histories of I. typographus and D. rufipennis are strongly influenced by seasonal events and they respond with similar physiological strategies. For example, both species enter diapause to buffer against harsh winter conditions and to synchronize life cycles, a widespread strategy in insects that is described for multiple bark beetle species (Ryan, ; Scott & Berryman, ; Birch, ; Führer & Chen, ; Gehrken, ; Schopf, ; Sieber & Benz, ; Langor & Raske, , b; Schopf, ; Hansen et al ., ; Doležal & Sehnal, ; Lester & Irwin, ; McKee & Aukema, ; Gent et al ., ). In addition, voltinism of both species is influenced by differing diapause strategies.…”

Diurnal temperature fluctuations improve predictions of developmental rates in the spruce bark beetle Ips typographus

“…DT L and DT U vary amongst insect species, but typically differ by about 20 °C from each other (Dixon et al 2009). This relationship has been described with different functions primarily based on laboratory experiments conducted under constant temperatures (Rebaudo and Rabhi 2018), including numerous bark beetle species affecting Northern hemisphere forests (Bentz et al 1991;Wermelinger and Seifert 1998;Peter 2014;Gent et al 2017;Schebeck and Schopf 2017;Davídková and Doležal 2019).…”