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1.
Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a pest of stored grain in Africa, Asia, and Europe. It is a quarantine insect for much of the rest of the world. Control of T. granarium can be achieved with methyl bromide, but this fumigant is an ozone‐depleting substance and is being phased out worldwide. Thus, there is an urgent need to find new methods of control, including the use of low temperatures. Here, we assess the effects of diapause and cold acclimation on the cold tolerance of T. granarium. The percentage of larvae in diapause increased with larval density, reaching 57.3% when reared at a density of 73 larvae g?1 diet. The cold tolerance of T. granarium was assessed by the supercooling points (SCPs) of various life stages. The SCP of non‐acclimated insects ranged from ?26.2 ± 0.2 °C (mean ± SEM) for eggs to ?14.4 ± 0.4 °C for larvae. The lowest SCP for larvae, ?24.3 ± 0.3 °C, was obtained for diapausing‐acclimated larvae. Based on mean LT50 values, the most cold‐tolerant stage at ?10 °C was the diapausing‐acclimated larvae (87 days) followed by non‐diapausing‐acclimated larvae (51 days), diapausing non‐acclimated larvae (19 days), adults (4 days), non‐diapausing non‐acclimated larvae (2 days), pupae (0.4 days), and eggs (0.2 days). The estimated times to obtain 99.9968% mortality (Probit 9) for diapausing‐acclimated larvae are 999, 442, 347, 84, and 15 days at 0, ?5, ?10, ?15, and ?20 °C, respectively. Probit 9 is an estimated value used by quarantine experts to estimate conditions that are required to kill all insects. In light of the long exposure time needed to control T. granarium even at ?20 °C, cooling to below ?27 °C (i.e., below the SCP of eggs) will quickly kill all life stages and may be the best way to control this insect with low temperatures.  相似文献   

2.
To clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W1) and lateral width (W2) were larger in non‐diapausing than in diapausing pupae, and the W1/L and W1/W2 ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation.  相似文献   

3.
  1. The invasive sawfly Aproceros leucopoda causes severe defoliation of various elm species and thus can be a major pest in forest stands and urban environments.
  2. The overwintering biology of A. leucopoda has not been investigated so far; therefore, the aim of this study was to determine the cold tolerance strategy and cold hardiness of hibernating A. leucopoda eonymphs.
  3. The supercooling points (SCPs) of overwintering individuals varied geographically, monthly and interannually and ranged between ?12.14 °C and ?24.22 °C.
  4. As none of the eonymphs survived once the SCP had been reached, A. leucopoda is classified as a freeze‐avoidant species.
  5. Survival rates of overwintering eonymphs exposed to different sub‐zero temperatures above the SCP (?1.6 °C and ?4.0 °C for 10, 20 and 30 days and ?10.5 °C for 9 days) ranged between 89.2% and 100%, suggesting that A. leucopoda is not a chill‐susceptible species.
  6. Our results suggest that low winter temperatures may not be expected to be an important limiting factor for the overwintering success of A. leucopoda.
  相似文献   

4.
Supercooling points (SCP) of adult Diamesa mendotae Muttkowski, 1915 (Diptera: Chironomidae) were determined at 3, 5, 9, 12 and 17 days post-collection. Supercooling points were recorded using surface contact thermometry and a cooling rate of ca. 1°C min?1. Female SCPs averaged ?22.81, ?23.76, ?23.85, ?23.65, and ?20.87°C on each date post-collection and did not differ significantly. Male SCPs were statistically similar and averaged ?21.75, ?23.53, ?23.68, ?23.66, and ?22.92°C on each date post-collection. Paired comparisons of female/male SCPs on each date post-collection did not show significant differences over time. The overall mean SCP of D. mendotae (?23.05°C) is substantially lower than values of ?5.3°C and ?5.7°C published for adults and larvae of Belgica antarctica Jacobs 1900 collected at Palmer Station (Antarctica) and ?14.2°C for larvae of Paraclunio alaskensis Coquillett 1900 collected at Vancouver Island, British Columbia. In addition, the SCP of this species appears to be lower than that of other winter-active insect species reported in the literature. Although no adults survived after the SCP was recorded, further studies are necessary to determine if D. mendotae is a freeze-intolerant insect. Nevertheless, our results suggest that a low SCP could be used as a mechanism to facilitate emergence and adult activity of this species during winter conditions.  相似文献   

5.
Diuraphis noxia is a newly established alien pest in the Czech Republic. There were two population explosions during the period 1993–2012. A successful overwintering of the anholocyclic populations of D. noxia was the cause of a population explosion in the oncoming growth season. Viviparous parthenogenetic females of the anholocyclic populations and diapausing eggs of holocyclic populations could overwinter at the same time. Analysis of the course of winter temperatures showed that a complete winter mortality of anholocyclic populations depended mainly on the duration of the freezing period, when temperature dropped below ?5°C, and on the intensity of the frost. We proposed the cumulative effective freeze (in minus degree days) as a key parameter for the aphid anholocyclic population's mortality during overwintering. This parameter equalled ?10.1 degree days for relatively warm winter period 2006–2007, whereas in the relatively cold winter period of 2009–2010, this parameter reached ?87.1 DD, which caused complete mortality of anholocyclic populations. A cumulative effective freeze could be used for short‐time prognosis of D. noxia population explosion.  相似文献   

6.
The winter-active Diamesa mendotae Muttkowski (Diptera: Chironomidae) is freeze intolerant in the adult stage with a low mean supercooling point (SCP) of ~−20 °C. However, cold-hardiness strategies for immatures of this species are unknown. In this study, we measured SCP values for D. mendotae larvae, pupae and adults using surface-contact thermometry. In addition, the lower lethal temperature (LLT) was determined for the larval stage. The mean SCPs for larvae (−7.4 °C) and pupae (−9.1 °C) were relatively high compared to adults (−19.7 °C). Our results indicate that the larvae of D. mendotae are freeze tolerant with a LLT99 (−25.4 °C), ~−10 °C lower than their minimum SCP (−15.6 °C). Freeze tolerance in these larvae may be a strategy to provide protection from short-term exposures to ice crystals or to permit diapause within frozen substrates. The change in cold-hardiness strategy from freeze tolerant to freeze intolerant between the larval and adult stages of this species is likely a result of the different habitats occupied by these two life stages.  相似文献   

7.
Supercooling point (SCP) and cold‐hardiness of the pollen beetle Meligethes aeneus (Fabricius) (Coleoptera: Nitidulidae) were investigated. Mature eggs from the oviduct were supercooled on average to ?28.0 °C and from oilseed rape buds to ?24.4 °C; first instars were supercooled to ?21.0 °C and second instars to ?16.8 °C. Despite their high supercooling ability, none of the eggs survived 24 h exposure to ?2.5 °C. The supercooling ability of adults varied significantly among feeding and non‐feeding beetles: high SCPs prevailed during the whole warm period, being about ?12 °C; low values of SCP of ?20 °C dominated in non‐feeding beetles. In spring and autumn, beetles displayed the same acclimation efficiency: after 1 week of exposure at 2.0 °C with no access to food their SCPs were depressed equally by about 3 °C. Meligethes aeneus beetles have a different response to low temperatures depending on the season. The lowest tolerance was found in reproductively active beetles after emergence from overwintering sites; the time needed to kill 50% of individuals (Ltime50) was 56.2 h at ?7 °C and the lower lethal temperature needed to kill 50% (Ltemp50) after 24 h exposure was ?8.6 °C. Cold hardiness increased from midsummer to midwinter; Ltime50 was 80 h in August, 182.8 h in September, and 418.1 h in January. Lethal temperature after 24 h exposure was ?9.1 °C in August and ?9.8 °C in September. In February, after diapause, the beetles started to loose their cold tolerance, and Ltemp50 was slightly increased to ?9.5 °C. Hibernating beetles tolerated long exposure at ?7 °C well, but mortality was high after short exposure if the temperature dropped below ?9 °C for 24 h. Despite the season, the beetles died at temperatures well above their mean SCP; consequently, SCP is not a suitable index for cold hardiness of M. aeneus.  相似文献   

8.
Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) is a key pest of grapes in Europe. It overwinters as a pupa in the bark crevices of the plant. Supercooling point (SCP) and low temperature survival was investigated in the laboratory and was determined using a cool bath and a 1 °C min?1 cooling rate. Freezing was fatal both to diapausing and non‐diapausing pupae. SCP was significantly lower in diapausing male (?24.8 °C) and female (?24.5 °C) pupae than in non‐diapausing ones (?22.7 and ?22.5 °C, respectively). Sex had no influence on SCP both for diapausing and non‐diapausing pupae. Supercooling was also not affected by acclimation. However, acclimation did improve survival of diapausing pupae at temperatures above the SCP. Survival increased as acclimation period increased and the influence was more profound at the lower temperatures examined. Diapausing pupae could withstand lower temperatures than non‐diapausing ones and lethal temperature was significantly lower than for non‐diapausing pupae. Freezing injury above the SCP has been well documented for both physiological stages of L. botrana pupae. Our findings suggest a diapause‐related cold hardiness for L. botrana and given its cold hardiness ability, winter mortality due to low temperatures is not expected to occur, especially in southern Europe.  相似文献   

9.
The effects of transgenic Bt cotton on the overwintering generation of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), are unknown. We hypothesized that a Bt cotton diet may adversely affect fitness of this generation and examined fresh weight, lipids, glycogens, low-molecular-weight sugars and SCPs (supercooling points) of pupae, as well as survival of larvae, diapausing pupae and adult emergence in comparison with controls. Field and laboratory experiments showed that larvae fed on Bt cotton had a decreased pupation rate, and fewer entered diapause and emerged as adults compared with larvae fed non-Bt cotton. Furthermore, larvae fed Bt cotton had reduced pupal weight, glycogen content and trehalose levels both in diapausing and in non-diapausing pupae, and only diapausing pupae had an increased SCP compared to controls. The SCPs of diapausing pupae reared on Bt cotton were significantly higher than those reared on non-Bt cotton. The trehalose levels of diapausing pupae reared on Bt cotton were significantly lower than those of larvae reared on non-Bt cotton. Thus, these results suggest that a Bt cotton diet weakens the preparedness of cotton bollworm for overwintering and reduces survival of the overwintering generation, which will in turn reduce the density of the first generation in the following year. Effects of transgenic Bt cotton on the overwintering generation of cotton bollworm appear to have significantly contributed to the suppression of cotton bollworm observed throughout northern China in the past decade.  相似文献   

10.
11.
The bruchid beetle, Bruchidius dorsalis Fahraeus (Coleoptera: Bruchidae), has a multivoltine life cycle and shows geographical variation of overwintering stages in Japan. Our previous study found that B. dorsalis enters larval diapause in the final instar under short photoperiods. In cooler areas, we observed that most individuals overwinter in the final larval stage in diapause, whereas beetles at different developmental stages (non‐diapausing young instars, diapausing instars, and adults) were overwintering in warmer areas. In this study, we investigated geographical variation in the photoperiodic response for induction of larval diapause at 20 °C (three populations) and 24 °C (two populations) to clarify the overwintering strategy of B. dorsalis. We observed that (1) diapause incidence at 20 °C changed sharply from ca. 100% to 0% with a change in photoperiod in all the populations, (2) critical photoperiod was longer at 20 °C in populations from cooler areas, and (3) critical photoperiod at 24 °C was shorter than at 20 °C and a fraction of the larvae did not enter diapause, even under short photoperiods. Overwintering stages estimated from these results were consistent with those actually observed in the field. This study indicates that the geographical variation of overwintering stages is likely to reflect adaptive diapause induction in each local environment.  相似文献   

12.
13.
Abstract This study reports on the low temperature tolerance and cold hardiness of larvae of false codling moth, Thaumatotibia leucotreta. We found that larvae have mean critical thermal minima (lower limits of activity) of 6.7°C which was influenced by feeding status. The effects of low temperature exposure and duration of exposure on larval survival were assessed and showed that the temperature at which 50% of the population survives is ?11.5 ± 0.3°C after 2 h exposure. The supercooling point (SCP, i.e., freezing temperature) was investigated using a range of cooling rates and under different conditions (feeding and hydration status) and using inoculative freezing treatments (in contact with water or orange juice). The SCP decreased significantly from ?15.6°C to ?17.4°C after larvae were fasted for 24 h. Twenty‐four hour treatments at either high or low relative humidity (95.9% or 2.4%) also significantly decreased SCP to ?17.2°C and ?18.2°C respectively. Inoculative freezing (by water contact) raised SCP from ?15.6°C to ?6.8°C which could have important implications for post‐harvest sterilization. Cooling rates did not affect SCP which suggests that there is limited phenotypic plasticity of SCP during the larval life‐stage, at least over the short time‐scales investigated here. In conclusion, larvae of T. leucotreta are chill‐susceptible and die upon freezing. These results are important in understanding this pest's response to temperature variation, understanding pest risk status and improving post‐harvest sterilization efficacy.  相似文献   

14.
Abstract The sugarbeet root maggot Tetanops myopaeformis (Röder) overwinters as a freeze‐tolerant third‐instar larva. Although most larvae are considered to overwinter for only 1 year, some may exhibit prolonged diapause in the field. In the laboratory, they can live for over 5 years using a combination of diapause and post‐diapause quiescence. In the present study, the cold survival strategies of these larvae during storage is investigated by measuring their supercooling points in combination with survival data. Supercooling points (SCPs) change significantly during storage, highlighted by a marked increase in the range of SCPs recorded, although the ability to tolerate freezing is not affected. Additionally, a freezing event ‘re‐focuses’ the SCPs of aged larvae to levels similar to those seen at diapause initiation. This change in SCPs is dependant not only on the initial freezing event, but also on the parameters of the incubation period between freezing events. Finally, the temperatures of larval overwintering microhabitats are monitored during the 2007–2008 boreal winter. The results indicate that, although overwintering larva are physiologically freeze‐tolerant, they may essentially be freeze avoidant during overwintering via microhabitat selection.  相似文献   

15.
The frequency of extreme events, such as cold spells, is expected to increase under global warming. Therefore, the ability of insects to survive rapid changes in temperature is an important aspect to investigate in current population ecology. The hemlock looper (HL), Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), a defoliator of boreal balsam fir forests in eastern Canada, overwinters at the egg stage on tree trunks and branches where eggs can be exposed to very low subzero air temperatures. Using eggs from the island of Newfoundland (NL) and Quebec mainland (QC), we undertook field and laboratory experiments to determine: (1) their supercooling point (SCP) in mid‐January and mid‐February; (2) overwintering mortality; (3) cold tolerance to various combinations of subzero temperatures (?25, ?30, ?33, ?35, or ?37 °C) and exposure durations (2, 4, 8, 12, or 16 h); and (4) potential causes of death at subzero temperatures above the SCP. Regardless of population or sampling date, eggs supercooled on average at ?40.1 °C. In the field, 59% of eggs from either population that overwintered in Sainte‐Foy (QC) and Corner Brook (NL) hatched successfully, whereas none did in Armagh (QC) or Epaule (QC). In the laboratory, 50% of eggs survived after 4 h at ?34.4 °C or after 14 h at ?32.9 °C. In contrast, regardless of exposure duration, >50% of eggs hatched at temperatures ≥?33 °C, but <50% did so at ≤?35 °C, suggesting high pre‐freeze mortality. However, when eggs were attached to thermocouples and exposed to temperatures ranging from ?25 to ?37 °C for 16 h, 69% froze at temperatures of ?35 to ?37 °C, but only 2% did at ?25 or ?30 °C. Time to freeze decreased as subzero temperatures declined, and this was more evident in island eggs than in mainland eggs. Overall, eggs can freeze after a brief exposure to subzero temperatures higher than the standard SCP, and are thus highly vulnerable to cold spells.  相似文献   

16.
Potato tuber moth (PTM), Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae) is an invasive insect pest damaging solanaceous crops. We measured the supercooling point (SCP) and survival at low temperature of different development stages to determine which would be capable of overwintering in the Korean climate and adapting to low temperatures. The SCP ranges from ?23.8°C of the egg to ?16.8 of fourth instar larvae (L4). After short periods of low temperature acclimation in L3 (third instar larva), L4 and prepupae, only the prepupal stage showed a significant lowered SCP from ?20.78 to ?22.37°C. When exposed to different subzero temperature for two hours the egg turned out to be the most cold tolerant stage showing LT50 of ?21.7°C followed by the pupal stage with ?15.89°C. One hundred percent mortality was observed when the larvae or adults were exposed to temperatures below ?15.1°C even for a period as short as 2 h. The results suggest that PTM pupae and egg would be the main overwintering stage in Korea where winter temperature does not drop below ?15°C.  相似文献   

17.
The cold-hardening capacity of larvae of the pink maize stalk borer,Sesamia nonagrioides Lef., was examined. Supercooling points (SCPs) of field collected diapausing larvae from south-east and south-west France and non-diapausing and diapausing laboratory-reared larvae did not differ and ranged between –5 and –8°C. Thus, this insect possesses sufficient supercooling ability to avoid freezing over its normal environmental temperature ranges. Despite this, we found thatSesamia presents paradoxical cold reactions. Mortality of cold acclimated diapausing larvae after short-term exposure to temperatures above the SCP is high, supporting the view thatSesamia is cold-sensitive. On the other hand,Sesamia could survive freezing for at least 24 h to temperatures close to the SCP. This ability does not seem to be related to haemolymph trehalose, the sole cold-accumulated compound detected by gas chromatography and mass spectrometry. Despite the mildness of the winter 1990–1991, only 5% of the field population survive and pupate in April. The main part of the population died from November to January, the period during which larvae were mainly located in the part of the corn stem above the ground and experienced air temperatures. After January, all surviving larvae were excuusively located in the root, 10 cm below the soil, where they experienced milder temperatures than air. They exhibited a constant low rate of mortality, possibly independent of the cold. In their current distribution area, survival of overwintering larvae ofS. nonagrioides is only related to the microclimate of the overwintering site and freezing tolerance capacity seems to be irrelevant. This study allows us to propose a non-pollutant pest control method based on the behavioral strategy of this insect.  相似文献   

18.
The threats posed by climate change make it important to expand knowledge concerning cold and heat tolerance in stenothermal species from habitats potentially threatened by temperature changes. Thermal limits and basal metabolism variations were investigated in Pseudodiamesa branickii (Diptera: Chironomidae) under thermal stress between ‐20 and 37 °C. Supercooling point (SCP), lower (LLTs) and upper lethal temperatures (ULTs), and oxygen consumption rate were measured in overwintering young (1st and 2nd instar) and mature (3rd and 4th instar) larvae from an Alpine glacier‐fed stream. Both young and mature larvae were freezing tolerant (SCPs = ‐7.1 °C and ‐6.4 °C, respectively; LLT100 <SCP and > ‐20 °C) and thermotolerant (ULT50 = 31.7 ± 0.4, 32.5 ± 0.3, respectively). However, ontogenetic differences in acute tolerance were observed. The LLT50 calculated for the young larvae (= ‐7.4 °C) was almost equal to their SCP (= ‐7.1 °C) and the overlapping of the proportion of mortality curve with the CPIF curve highlighted that the young larvae are borderline between freezing tolerance and freezing avoidance. Furthermore, a lower ULT100 in the young larvae (of ca. 1 °C), suggests that they are less thermotolerant than mature larvae. Finally, young larvae exhibit a higher oxygen consumption rate (mgO2/gAFDM/h) at any temperature tested and are overall less resistant to oxygen depletion compared to mature larvae at ≥10 °C. These findings suggest that mature larvae enter into a dormant state by lowering their basal metabolism until environmental conditions improve in order to save energy for life cycle completion during stressful conditions.  相似文献   

19.
Overwintering larvae of multivoltine and univoltine populations of Leptalina unicolor were reared under various constant and fluctuating temperatures superimposed on a photoperiod of either 12 h of light and 12 h of darkness (LD 12:12) or LD 15:9. Diapause of the larvae terminated in midwinter (by early February). All the larvae of both populations pupated after two molts without feeding and the head capsule width of the final instar larvae was smaller than that of the penultimate instar ones. The photoperiod did not significantly affect larval development, but long‐day conditions (LD 15:9) hastened pupal development. The thermoperiod had a significant effect on the development of the multivoltine population. When multivoltine population larvae were kept under a low fluctuating temperature regime (cryophase/thermophase = 14/20°C), the period until adult eclosion was shorter than that under a constant temperature of 17°C. On the contrary, when larvae were kept under a high fluctuating temperature regime (24/30°C), the period until adult eclosion was longer than that under a constant temperature of 27°C. However, the univoltine population did not show such a reaction to the fluctuating temperature. The durations of final instar larva and pupa of the multivoltine population were shorter than those of the univoltine population. The developmental zeros of penultimate and final instar larvae and pupae of the univoltine population were lower than those of the multivoltine population. The head capsule width of penultimate instar larvae and the forewing length of adults of the univoltine population were larger than those of the multivoltine population for both sexes.  相似文献   

20.
During the late 1960s, larvae of the flightless midge Eretmoptera murphyi Schaeffer were accidentally transferred from the sub‐Antarctic island of South Georgia to Signy Island in the maritime Antarctic. Higher insects are rare in the Antarctic and the introduction and establishment of a new species is an unusual event. The fly has overcome the two major barriers to colonization of the Antarctic by new species: the geographical isolation of the region and its severe climate. Larvae of the flightless midge overwinter in the surface layers of soil on Signy Island where the temperature may fall to below ?10 °C, compared with as little as ?1.5 °C on South Georgia. This suggests the possession of a level of pre‐adaption to colder conditions. Summer‐collected larvae have a supercooling point (SCP or whole body freezing point) of approximately ?5.0 °C but survive experimental exposure to ?13 °C, giving them a level of freeze tolerance. After acclimation at ?4 °C for 4 days, the SCP changes little but the temperature at which 50% of the population would die decreases to lower than ?19 °C. Larvae are also resistant to dehydration. Under experimental conditions of 88% relative humidity at 5 °C, larvae lose water linearly (0.42% h?1) over the first 30 h but resist further water loss once their water content decreases to approximately 1.4 g g?1 dry weight. All larvae survive these conditions for the duration of the experiment (55 h). Eretmoptera murphyi is well adapted to survive on Signy Island, and these studies suggest that it has the ability to survive at more extreme locations at higher latitudes if it were to be inadvertently transferred to a suitable habitat.  相似文献   

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