Development of a combined cold storage and methyl bromide fumigation treatment to control the American serpentine leaf miner Liriomyza trifolii (Diptera:Agromyzidae) in imported chrysanthemum cuttings

Individual chrysanthemum cuttings and leaves infested with eggs and larvae of the alien leaf miner Liriomyza trifolii, and batches of pupae, were treated in the laboratory to find an effective quarantine treatment to control the pest in imported cuttings. The laboratory tests were based on a statutory quarantine treatment of 2 days' cold storage at 1–2°C followed by methyl bromide fumigation at 15°C with a concentration time product (CTP) of 54 g h/m³, which is used to control Spodoptera littoralis on imported chrysanthemum cuttings. Treatments of 2 days' storage at 1–2°C followed by methyl bromide fumigation at 15°C with a range of CTPs were used to obtain accurate dose-response lines and estimate the LD99 and LD99 9 for each stage of L. trifolii. The largest estimates of the LD99 for eggs, larvae and pupae up to 3 days old were 40·04, 34·49 and 42·64g h/m³ respectively. These results indicate that the Spodoptera treatment should give high levels of kill of most stages of L. trifolii. However, the LD99 values for pupae more than 3 days old were greater than those for eggs, larvae and young pupae. Therefore if this treatment were adopted as a quarantine measure against L. trifolii, good prophylactic treatments and rigorous pre-packing inspections in exporting countries would need to be maintained, to minimise any risk of importing pupae. It would also be necessary to ensure that the temperature of the imported cuttings was raised uniformly to 15°C after cold storage and prior to fumigation. The practicality of the technique as a commercial treatment will depend on whether it is possible to achieve this without causing unacceptable phytotoxicity.     

Phytotoxicity of methyl bromide on chrysanthemum cuttings

The phytotoxicity of methyl bromide gas on chrysanthemum cuttings was investigated in relation to gas concentration, length of exposure, temperature, and variety and age of cuttings. Concentrations of 10.5 to 13.5 g/m³ for 4 to 5 h produced a concentration time product (CTP) of 54 g h/m³ which is suitable for safe fumigation of most varieties of chrysanthemum. Length of exposure was not critical up to 5 h. However, fumigations of cuttings which were more than 3 wk old generally caused excessive phytotoxicity and therefore cannot be recommended. There was less damage at temperatures of between 14 and 16°C than at higher temperatures. A table of predictions from a fitted regression equation is included to demonstrate the increased susceptibility of chrysanthemums at higher temperatures and ages of cuttings.     

Effects of acclimation and diapause on the cold tolerance of Trogoderma granarium

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.     

Ethyl formate fumigation and ethyl formate plus cold treatment combination as potential phytosanitary quarantine treatments of Drosophila suzukii in blueberries

Spotted wing drosophila, Drosophila suzukii (Diptera: Drosophilidae), is a serious invasive pest of berries and cherries in the U.S. and Europe and has become a major phytosanitary trade barrier. In this pilot study, we explored the potential of using stand-alone ethyl formate (EF) treatment and a combinatory treatment of EF and cold temperature as postharvest control options for D. suzukii in imported blueberries. Stand-alone EF fumigations were effective against D. suzukii with LCt_99% of 207.7 and 168.5 g·h·m^?3 for eggs, the most tolerant life stage, at 5 and 21 °C, respectively. In a scale-up (10 m³) trial conducted at 5 °C, complete control of D. suzukii eggs placed inside and outside of blueberry boxes was achieved using 70 g·m^?3 EF for 4 h with 5% blueberry loading ratio without deleterious impact on blueberry appearance such as soft spot or berry shrivel. In small scale pilot studies, 9-d stand-alone cold treatment at 5 °C was sufficient for complete control of D. suzukii eggs and larvae tested, but not pupae. The efficacy of this cold treatment appeared to be improved when D. suzukii eggs were first treated with low-dose EF (LCt_50% level) prior to the cold treatment. The combination treatment resulted in complete mortality of D. suzukii eggs, larvae, and pupae tested after 7, 5, and 9 d of cold treatment, respectively. Together, these results suggest that stand-alone EF treatment, or the combination treatment of low-dose EF and cold as a systems approach may have a potential as postharvest treatments for D. suzukii in blueberries.     

The toxicity of tributyltin oxide to the wood-boring beetles Lyctus brunneus Steph. and Anobium punctatum (Deg.)

When tributyltin oxide (TBTO) was tested by British Standard 3653 against Lyctus brunneus, 0·5 % solution, equivalent to 0·72 g/m₂ surface application, gave almost complete protection. Tests to BS 3651, using larvae of Anobium punctatum transferred into fully impregnated wood gave toxic limits of 1·39–2·93 kg/m³ TBTO when benzene was used as diluent. The use of white spirit as diluent gave lower toxic limits, probably due to combined toxic action of TBTO and white spirit residues. TBTO appears to have no contact action against the insects tested. Probit analysis of the test with A. punctatum gave an LD 50 of 0·254 kg/m³ and an LD99 of 3 kg/m³. The advantage of treating results by probit analysis rather than by deriving ‘toxic limits’ is discussed.     

TEMPERATURE,PHOTOPERIOD AND LIGHT INTERACTIONS ON GROWTH AND FERTILITY OF GLOSSOPHORA KUNTHII (PHAEOPHYTA,DICTYOTALES) FROM CENTRAL CHILE1

Excised ligulae of Glossophora kunthii from central Chile were cultured of temperatures of 5–25° C, photoperiods of 16:8 and 8:16 h LD cycles, with photon irradiances of 10 and 50 μmol · m^?2· s^?1. Growth of the ligulae, number of fertile ligulae and number of tetrasporangia forming on the ligulae were assessed. Ligulae tolerated temperatures between 10 and 23°C. Temperature interacted with daylength and photon dose, determining quantitative responses in the growth and fertility of ligulae. Growth was least at 8:16 h LD and was not affected significantly by temperature. It was greatest at 16:8 h LD, 50 μmol · m^?2· s^?1 and increased with temperature up to 20°C. Percentage of fertile ligulae and number of tetrasporangia increased with temperature at the 8:16 h LD cycle, reaching a maximum at 20°C. Fertility was low at 16:8 h LD, except at 20° C (and low photon dose) suggesting that reproduction at 20° C is independent of daylength in this species. Ligulae grew larger at the long-day photoperiods and the proportions of fertile ligulae were higher at the short-day photoperiods, irrespective of the total photon dose received. These results suggest that some aspects of growth and fertility are controlled by photoperiod.     

Hot water immersion of Allium hookeri roots for the control of the plant parasitic nematodes Meloidogyne javanica and Pratylenchus coffeae

Nematodes are important quarantine pests of bulbous plants such as hooker chives. Although control methods such as fumigation, chemical immersion, and heat are often applied, it has proved difficult to disinfect nematodes from plant roots in quarantine. As heat treatment has been successfully useful for the control of nematodes in other agricultural products in quarantine, we investigated the susceptibility and mortality rates of Meloidogyne javanica and Pratylenchus coffeae, which infest hooker chive roots, using a hot water immersion method. Heat damage to the hooker chive roots was noticeable at temperatures over 50°C. Temperatures for the effective time to kill 99% at 1 min (ET99) for M. javanica and P. coffeae juveniles were 49.3°C and 49.1°C, respectively. However, the time to kill 99% of M. javanica eggs at 48°C and 49°C were 27.0 min and 8.3 min, respectively. Using a thermal equilibrium formula, the optimum commercial scale condition, in a 1400‐L chamber, for nematode control without associated plant damage was water immersion at 48.2°C for 30 min or at 49.2°C for 13 min with a filling ratio less than 12%. This result can be applicable for the nematode disinfestation of hooker chive roots in plant quarantine.     

Concurrent application of ethyl formate and 1‐methylcyclopropene to control Tetranychus urticae on exported sweet persimmons (Diospyros kaki Thunb. ‘Fuyu’)

Extending the shelf life of fruits during post‐harvest storage and eradicating pests associated with quarantine issues could together comprise the key steps toward expanding the exportation of sweet persimmon in South Korea. Here we firstly investigated the concurrent application of ethyl formate (EF), a methyl bromide alternative fumigant, which is currently considered a beneficial and safe fumigant in quarantine use, and 1‐methylcyclopropene (1‐MCP), an anti‐ethylene compound that is broadly used in post‐harvest systems, on sweet persimmon. We also suggest the proper fumigation methods to be follow when using these compounds. Tetranychus urticae, an important quarantine pest, was inoculated under the calyx of sweet persimmon, and the fruits were then fumigated using 35.0 mg L^?1 of EF for 6 h before and after treating with 1.0 μL L^?1 of 1‐methylcyclopropene for 24 h under storage conditions of 5°C. Our results showed that concurrent treatments with 1‐MCP and EF could be suitable for commercial purposes by extending shelf life, delaying color changes and softening, and offering complete control of the target pest, Tetranychus urticae.     

Comparison of cold hardiness and sugar content between diapausing and nondiapausing pupae of the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract. To understand overwintering of the cotton boll worm Helicoverpa armigera, cold hardiness and sugar content are compared between diapausing and nondiapausing pupae. Diapausing and nondiapausing pupae reared at 20 °C under short and long photoperiods are acclimatized with a reduction of 5 °C per 5 days to 0 °C. When the acclimation temperature reaches 0 °C, the survival of diapausing pupae is assessed. The survival gradually decreases as the period of treatment progresses and approximately half survive for 112 days. However, nondiapausing pupae survive only 14 days after exposure to 0 °C. The surpercooling points of nondiapausing, diapausing and acclimatized pupae are approximately −17 °C. The major sugars contained in pupae are trehalose and glucose. Even though trehalose contents in diapausing pupae (initial level: 0.6 mg 100 mg⁻¹ fresh weight) increase significantly during cold acclimation and continue increasing until 58 days after exposure to 0 °C (maximum level: 1.8 mg 100 mg⁻¹), glucose is maintained at low levels (0.02 mg 100 mg⁻¹) for 56 days at 0 °C. However, glucose contents increase (maximum level: 0.8 mg 100 mg⁻¹) with decreasing contents of trehalose 84 days after exposure to 0 °C. Glycogen content gradually decreases during cold acclimation. When nondiapausing pupae are acclimatized with a reduction of 5 °C per 5 days to 5 °C from the beginning of pupation until the eyespots move, trehalose content increases (maximum level: 1.0 mg 100 mg⁻¹). Glucose contents in nondiapausing pupae increase before eclosion (0.09 mg 100 mg⁻¹). From these results, diapausing pupae of H. armigera can overwinter in regions where average winter temperatures are higher than 0 °C, but nondiapausing pupae cannot.     

Evaluation of the efficacy of the methyl bromide fumigation schedule against Mexican fruit fly (Diptera: Tephritidae) in citrus fruit

Methyl bromide fumigation is widely used as a phytosanitary treatment. Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), is a quarantine pest of several fruit, including citrus (Citrus spp.), exported from Texas, Mexico, and Central America. Recently, live larvae have been found with supposedly correctly fumigated citrus fruit. This research investigates the efficacy of the previously approved U.S. Department of Agriculture-Animal and Plant Health Inspection Service treatment schedule: 40 g/m3 methyl bromide at 21-29.4 degrees C for 2 h. Tolerance ofA. ludens to methyl bromide in descending order when fumigated in grapefruit (Citrus X paradisi Macfad.) is third instar > second instar > first instar > egg. Two infestation techniques were compared: insertion into fruit of third instars reared in diet and oviposition by adult A. ludens into fruit and development to the third instar. Inserted larvae were statistically more likely to survive fumigation than oviposited larvae. When fruit were held at ambient temperature, 0.23 +/- 0.12% of larvae were still observed to be moving 4 d postfumigation. Temperatures between 21.9 and 27.2 degrees C were positively related to efficacy measured as larvae moving 24 h after fumigation, pupariation, and adult emergence. Coating grapefruit with Pearl Lustr 2-3 h before fumigation did not significantly affect the proportion of third instars moving 24 h after fumigation, pupariating, or emerging as adults. In conclusion, fumigation with 40 g/m3 methyl bromide for 2 h at fruit temperatures >26.7 degrees C is not found to be inefficacious for A. ludens. Although a few larvae may be found moving >24 h postfumigation, they do not pupariate.     

Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail,Papilio machaon (Lepidoptera: Papilionidae), from the Osaka population

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.     

Cold hardiness and sugar content in photo‐insensitive individuals of the cotton bollworm Helicoverpa armigera

Abstract A proportion of Helicoverpa armigera collected from fields in Okayama Prefecture (Western Japan; 34.6°N, 134.1°E) does not enter diapause when reared under a short days at 20 °C during the larval stages. However, diapause in such photo‐insensitive individuals can be induced when they are reared at moderately low temperatures, such as 15 °C, regardless of photoperiod. To determine whether such photo‐insensitive individuals can survive overwintering in fields, the present study compares the cold hardiness and sugar content between nondiapausing and diapausing pupae of photo‐insensitive individuals selected over several generations at 20 °C under a short day photoperiod (LD 10 : 14 h). Diapausing and nondiapausing pupae are obtained under the short days by rearing at 15 and 20 °C, respectively, during larval and pupal stages. These pupae are stepwise acclimated at a reduction of 5 °C every 5 days to 0 °C. Maximum survival periods of nondiapausing and diapausing pupae at 0 °C are approximately 30 and 90 days, respectively. Trehalose content in diapausing pupae increases, reaches a maximum level (1.95 mg 100 mg^?1 in males and 2.1 mg 100 mg^?1 in females) 28 days after exposure to 0 °C and then decreases. On the other hand, glucose content in diapausing pupae increases (maximum level: 0.32 mg 100 mg^?1 in males and 0.21 mg 100 mg^?1 in females) with decreasing trehalose content 42 days after exposure to 0°C. The decrease in trehalose content and the increase in glucose content may be linked to termination of diapause in H. armigera. These results suggest that, in Japan, the photo‐insensitive individuals can only survive in the mild winters of southern regions, and not in the severe winters of northern regions.     

Behavioral responses of Colorado potato beetle larvae to combinations of temperature and insolation, under field conditions

In short-term field trials at combinations of ambient temperature (°C) and insolation (W·m⁻²), larval Colorado potato beetles (Leptinotarsa decemlineata [Say] [Coleoptera: Chrysomelidae]) were observed after their release on the adaxial surface of leaflets on potato plants (Solanum tuberosum L. Solanaceae). The larvae either began feeding or moved under the leaflet; mean interval from release to expression of these behaviors (2.9±0.05 min [n =358]) was independent of air temperature and insolation. Proportion of larvae moving under the leaflet increased logistically with both air temperature and insolation. A 1 W·m⁻² change in insolation (P) evoked the same effect on this proportion as a 0.0838 °C change in air temperature (T _a ), so the two quantities were combined as T^*=T _a +P·0.0838 °C/(W·m⁻²), which has units of °C. The proportion of larvae moving under the leaflet increased logistically with T^*. In 1-day field trials we monitored air temperature, insolation and proportion of larvae under the leaflet, and compared the latter to predictions from the logistic regression derived from the short-term trials. Consistently more larvae occurred under leaflets than predicted from the logistic regression; this bias diminished as T^* increased until at T^*≥40 °C, observed and predicted proportions were equal. This pattern of deviation from the predictions of the logistic regression is consistent with a thermoregulatory strategy in which larvae move away from hostile conditions, rather than seek optimal conditions.     

The potential of Chrysopa carnea as a biological control agent of Myzus persicae on glasshouse chrysanthemums

Larvae of C. carnea lived for 13-4 days at 21·1°C and consumed an average of 385 second-instar Myzus persicae or 425 Aphis gossypii. At 15·5°C the larval lifespan was 29·5 days though the consumption of M. persicae was hardly affected. M. persicae developing on glasshouse chrysanthemum plants were eliminated by the introduction of 1-day-old larvae at aphid: chrysopid ratios up to 50:1; third-instar larvae achieved control at a ratio of 200:1. At very low aphid densities control was less effective. Control by C. carnea of aphid populations developing on glasshouse chrysanthemums can be predicted mathematically.     

Methyl salicylate fumigation increases monoterpene emission rates

We aimed to assess the potential effects of fumigation by methyl salicylate (MeSA) on plant monoterpene production and emissions. We evaluated monoterpene production and emissions both by chromatographic and proton transfer reaction mass spectrometry at the whole plant-and leaf-scales, in MeSa-fumigated (ca. 60 mm³ m⁻³ in air) and control (without MeSa fumigation) holm oak (Quercus ilex L.) plants exposed to temperatures ranging from 25 to 50 °C. The MeSa-fumigated plants showed ca. 3–4-fold greater leaf monoterpene concentrations and emission rates than the control plants between the temperatures of 25 to 45 °C.     

Methyl benzoate fumigation for control of post-harvest pests and its effects on apple quality

Methyl benzoate is a newly discovered natural insecticide. In this study, we evaluated methyl benzoate as a potential fumigant for controlling four pests including western flower thrips (WFT), Frankliniella occidentalis, lettuce aphid, Nasonovia ribisnigri, rice weevil, Sitophilus oryzae, and bulb mites, Rhizoglyphus spp., at different temperatures and effects on post-harvest quality of apples. Methyl benzoate fumigations were effective against all four pests. Complete control of WFT and lettuce aphid was both achieved in 8, 16 and 24 hr at 25, 13 and 2°C, respectively. For rice weevil, complete control was achieved in 16 and 72 hr with and without rice at 25°C, respectively. Complete control of bulb mites was achieved in 64 hr at 25°C on peanut. In addition, a 24 hr methyl benzoate fumigation at 2°C had complete control of WFT but had no negative impact on visual quality of apples of three varieties 4 weeks after fumigation. These results suggest that methyl benzoate fumigation has potential to be an alternative treatment to methyl bromide fumigation, which has been phased out, for post-harvest pest control for stored products and may also have potential to control other pests on fresh products.     

New feasible quarantine disinfestation using ethyl formate for termites and ants on imported lumber

The interception of exotic ants and termites from stone and lumber imported into Korea is on the rise, including Solenopsis invicta. Currently, a relatively long exposure (24 h) of methyl bromide (MB) fumigation is the only practical disinfestation option for exotic ants and termites on imported stone and lumber. In this study, ethyl formate (EF) wase evaluated as a potential MB alternative to disinfest ants and termites in imported lumber, with a focus on S. invicta. As S. invicta is not established in Korea, we first determined whether Reticulitermes speratus, established in Korea, could be considered as an EF surrogate of S. invicta. From 1 h EF fumigation trials, workers of S. invicta were more sensitive to EF than those of R. speratus based on lethal concentration × time causing 99% mortality (LCt_99%), supporting that R. speratus can be used as an EF surrogate of S. invicta. When R. speratus workers were further fumigated with EF for 4 h at four different temperatures, LCt_99% values for R. speratus workers were 108.00, 63.31, 77.24, and 67.24 g h/m³ at 2, 5, 13, and 23 °C, respectively. From scale-up (0.65 m³) and commercial scale (76.4 m³) trials containing two infestation-prone lumber species, lauan (Shorea spp.) and acacia (Acacia spp.), 140 g/m³ EF at >5 °C for 4 h resulted in the complete control of R. speratus workers, suggesting that 140 g/m³ 4 h-EF-fumigation may be applicable as a potential MB-alternative treatment for disinfestation of invasive S. invicta on imported lumber.     

Ethyl formate fumigation for the disinfestation of red imported fire ants Solenopsis invicta Buren

The red imported fire ant, Solenopsis invicta Buren, is a serious invasive pest of quarantine significance. Potential establishment of this ant is of great concern in S. invicta free countries such as South Korea, where there have been multiple recent interceptions. The majority of those detections have been concentrated around main port areas of imported common trade containers, suggesting that disinfestation of the containers, in addition to inspection and disinfestation of containers with agricultural commodities, is necessary for the prevention of S. invicta introduction. So far, however, no regulations and protocols are in place for inspection, detection, and disinfestation of S. invicta in such containers. As a first step toward supporting such regulation, we investigated whether S. invicta could be effectively controlled using ethyl formate, a methyl bromide alternative. Ethyl formate fumigation treatment was effective in controlling 99.9% of S. invicta workers and female alates at 46.1 and 37.7 g h m⁻³ at 13 °C and 23 °C respectively. Our results provide evidence to support its use to disinfest S. invicta in containers. We discuss additional factors that need to be considered to develop disinfestation protocols for S. invicta in commerce shipping containers.     

PHYSIOLOGICAL RESPONSES OF ANABAENA VARIABILIS (CYANOPHYCEAE) TO INSTANTANEOUS EXPOSURE TO VARIOUS COMBINATIONS OF LIGHT INTENSITY AND TEMPERATURE1

Light intensity and temperature interactions have a complex effect on the physiological process rates of the filamentous bluegreen alga Anabaena variabilis Kütz. The optimum temperature for photosynthesis increased with increasing light intensity from 10°C at 42 μE·m^?2·s^?1 to 35°C at 562 μE·m^?2·s^?1. The light saturation parameter, I_K, increased with increasing temperatures. The maximum photosynthetic rate (2.0 g C·g dry wt.^?1·d^?1) occurred at 35°C and 564 μE·m^?2·s^?1. At 15°C, the maximum rate was 1.25 g C·g dry wt.^?1·d^?1 at 332 μE·m^?2·s^?1. The dark respiration rate increased exponentially with temperature. Under favorable conditions of light intensity and temperature the percent of extracellular release of dissolved organic carbon was less than 5% of the total C fixed. This release increased to nearly 40% under combinations of low light intensity and high temperature. A mathematical model was developed to simulate the interaction of light intensity and temperature on photosynthetic rate. The interactive effects were represented by making the light-saturation parameters a function of temperature.     

Effects of photoperiod and temperature on diapause induction and termination in the swallowtail,Sericinus montelus

Abstract Sericinus montelus overwinters as diapausing pupae. In the present study, the effects of photoperiod and temperature on diapause induction and termination of diapause are investigated. The results obtained demonstrate that high temperature can reverse the effect of short day‐lengths on diapause induction. Under an LD 12 : 12 h photoperiod, all pupae enter diapause at 15, 20 and 25 °C, whereas all pupae develop without diapause at 35 °C. No pupae enter diapause under an LD 14 : 10 h photoperiod when the temperature is above 20 °C. Photoperiodic response curves obtained at 25 and 30 °C indicate that S. montelus is a long‐day species and the critical day‐length is approximately 13 h at 25 °C. At 25 °C, the duration of diapause is shortest when the diapausing pupae are maintained under an LD 16 : 8 h photoperiod and increases under LD 14 : 10 h and LD 12 : 12 h photoperiods. Under an LD 16 : 8 h photoperiod, the duration of diapause is shortest when the diapausing pupae are maintained at 25 °C, followed by 20 and 30 °C, and then at 15 °C. These results suggest that a moderate temperature favours diapause development under a diapause‐averting photoperiod in this species. The duration of diapause induced by an LD 12 : 12 h photoperiod is significantly longer at 25 °C than those at 15, 20 and 30 °C, and is shortest at 15 °C. At 25 °C, the duration of diapause induced by LD 6 : 18, LD 12 : 12 and LD 13 : 11 h photoperiods is similar and longer than 90 days. Thus, the diapause‐inducing conditions may affect diapause intensity and a photoperiod close to the critical day‐length has significant influence on diapause intensity in S. montelus.