Influence of photoperiod,temperature and host plant on the production of diapause eggs inPetrobia (Tetranychina) harti (Acari: Tetranychidae)

Petrobia harti (Ewing) diapauses in the egg stage. Adult females lay either diapause or nondiapause eggs. On the University of Thessaloniki campus (41°N), the mite was found to develop on leaves ofOxalis corniculata L. throughout the year, while no mites were found on leaves ofOxalis articulata Savigny growing in the same area. In the laboratory the mite could be maintained equally well on detached leaves of both plant species, kept on wet cotton-wool.Forty to 90% females laying diapause eggs (dlf) were produced when the mites developed under LD 1212 and 19±1 °C, or LD 168 and 19±1 °C or 25±1 °C on leaves ofO. articulata detached from plants grown in the open in various seasons. Under the same conditions, a very low to zero percentage ofdlf was produced onO. corniculata. By rearing certain feeding stages on one of these twoOxalis hosts, and the other feeding stages on the other host, various percentages ofdlf were obtained. These percentages were the net effect of the antagonistic action of the twoOxalis species.By rearing the mites at LD 8.515.5, LD 1212 or LD 168 and a temperature of 19±1 °C onO. articulata leaves renewed every 3 days, or every 16–18 days, or not at all, it could be shown that diapause induction or aversion is caused by the direct effect of photoperiod on the mites, and not by an effect through the host leaves.When wholeO. articulata plants were grown under LD 168 and 19±1 °C in the laboratory, or developed in the open during April and May, flowers were produced, while under LD 1212 no flowering occurred. In the laboratory under diapause-inducing conditions, higher percentages ofdlf were produced on leaves detached from flowering plants than on leaves detached from plants not flowering.OnO. articulata leaves at 20 °C, photoperiods with photophases equal to or longer than 12 h induced from 70 to 80%dlf, while photoperiods with photophases equal to or shorter than 10.9 h induced very low to zero percentages. By transferring different chrysalis stages from a diapause-inducing (LD 1212) to a diapause-averting (LD 8.515.5) photoperiod, and vice versa, it was found that the nymphochrysalis through deutonymph stages were sensitive to photoperiod, the deutochrysalis and deutonymph being the most sensitive.Under an LD 1212 photoperiod, a temperature of 20 °C induced diapause, whereas 25 °C, 30 °C, or a daynight thermoperiod of 25 °C18 °C suppressed it.     

The natural history ofPetrobia (Tetranychina) harti (Ewing) andPetrobia (Mesotetranychus) tunisiae Manson (Acari: Tetranychidae) in the laboratory

Petrobia harti (Ewing) developed more rapidly, deposited more eggs and lived longer onOxalis corniculata than onO. articulata. No development took place on several other recorded host plants. In the field this mite was most abundant during early summer. Males made up less than 10% of the population, and no diapause eggs were seen in the field.Petrobia tunisiae Manson developed on various winter Gramineae, produced about 17 non-diapause eggs during its first generation and mostly diapause eggs in the second. A few diapause eggs kept in the laboratory and dipped in chloroform hatched even after 3 years. A summer diapause is postulated for this species.     

Effects of temperature and photoperiod on the termination of larval diapause in Lucilia sericata (Diptera: Calliphoridae)

Larvae of the blow fly, Lucilia sericata (Meigen), enter diapause in the third instar after cessation of feeding. The effects of temperature and photoperiod on the termination of diapause were examined. The diapause terminated spontaneously under the diapause-inducing condition of 20 degrees C and LD 12:12, although pupariation was not synchronous. Diapause development proceeded under a low temperature of 7.5 degrees C. Transfer to long-day conditions of LD 16:8 or to a high temperature of 25 degrees C induced prompt and synchronous pupariation. Low temperatures in winter probably play a predominant role in the termination of diapause under natural conditions.     

Effect of temperature,humidity and photoperiod on mortality of Mononychellus tanajoa (Acari: Tetranychidae) infected by Neozygites cf. floridana (Zygomycetes: Entomophthorales)

The effect of temperature, humidity and photoperiod on the development of Neozygites cf. floridana (Weiser and Muma) in the cassava green mite, Mononychellus tanajoa (Bondar) was studied in the laboratory. Dead infected mites began to appear 2.5 days after inoculation. At 33 and 28°C peak mortalities were higher and occurred earlier (after 2.5 days), than at 23 and 18°C. Mean LT₅₀ (time for half the infected mites to die) decreased with increasing temperature as follows: 3.9, 3.0, 2.9 and 2.5 days at 18, 23, 28 and 33°C, respectively. When placed under conditions of high relative humidity for a period of 24 h, the percentage of dead infected mites from which the fungus sporulated was highest at 28°C (51.4%) and lowest at 33°C (6.5%). The development of the fungus inside the mite was not significantly affected by ambient humidity or photoperiod. No significant interactions between tested factors were found.     

Effects of photoperiod and low temperature on diapause termination in the yellow-spotted longicorn beetle (Psacothea hilaris)

Abstract. .The effects of photoperiod and low temperature on diapause termination in the yellow-spotted longicorn beetle, Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae), were examined using a population from Ino, Japan. Diapausing insects obtained by rearing larvae under short daylength (12 or 13 h) at 25^oC were subjected to various treatments. When the photoperiod was changed at the same temperature, diapausing larvae showed a long-day response with a critical daylength between 13.5 and 14h. The diapause was terminated and consequently pupation occurred if the daylength was longer than 13.5 h. Chilling the diapausing larvae at 10^oC for 30 or more days also terminated diapause in most larvae irrespective of the photoperiods during and after chilling treatment. In contrast, the post-chilling photoperiod had a critical effect on development of diapausing larvae chilled for only 15 days.     

Some aspects of induction and termination of diapause in a Greek strain of the miteTetranychus cinnabarinus (Boisduval) Boudreaux, 1956 (Acari: Tetranychidae)

A Greek strain of the miteTetranychus cinnabarinus, collected from ivy (Hedera spec.) in Thessaloniki (41 °N), exhibits a facultative, imaginal diapause. Diapause is induced by photoperiod and the photoperiodic response is of the long-day type. The critical daylength is 12.5 h at 19 °C. A period of chilling is not necessary for the termination of diapause under long-day conditions. Diapausing females are sensitive to photoperiod at least during the first 11/2 month of diapause.     

Effect of temperature on toxicities of scopoletin and bisdemethoxycurcumin against Tetranychus cinnabarinus ( Acari:Tetranychidae )

为明确植物性杀螨活性物质东莨菪内酯与双脱甲氧基姜黄素对朱砂叶螨Tetranychus cinnabarinus雌成螨毒力的温度效应,采用玻片浸渍法测定了两者不同温度下的杀螨活性.结果表明:在8～26℃的温度范围内,东莨菪内酯和双脱甲氧基姜黄素对朱砂叶螨雌成螨的毒力呈正温度系数;在26～34°C的温度范围内两者对朱砂叶螨雌成螨的毒力呈负温度系数.其中26℃下东莨菪内酯和双脱甲氧基姜黄素表现出较好杀螨活性,处理后48 h的致死中浓度(LC50)分别为0.1884和0.3376 mg/mL;23℃下的毒力次之.致死中浓度(y)与温度(x)关系的拟合方程为:东莨菪内酯:y1=0.006x12-0.278x1+3.403;双脱甲氧基姜黄素:y2 =0.007x22 -0.354x2+4.826.对y求最小值得出,东莨菪内酯和双脱甲氧基姜黄素对朱砂叶螨雌成螨的最高毒力温度分别为23.2℃和25.3℃,LC50分别为0.1828和0.3504 mg/mL.据此认为,在一定的温度范围内,随着温度的升高,这两种植物性杀螨活性物质对朱砂叶螨的毒力与温度先呈正相关,到达最佳毒力温度后再呈负相关.     

Effect of temperature and sperm supply on the reproductive potential ofTetranychus evansi (Acari: Tetranychidae)

The biology ofTetranychus evansi Baker and Pritchard was studied at five different temperatures on excised leaves ofSolanum douglasii Dunal. The theoretical lower threshold temperature of development was ca. 13°C. The combined immature stages required ca. 148 day-degrees for completion. Progressively later initiation of mating resulted in higher peak proportions of females produced, up to an 8-day period between emergence and mating at 30°C. The proportion of male offspring always increased towards the end of the oviposition period, apparently because of sperm depletion. The calculated intrinsic rate of increase was highest (0.432) at 35°C, the highest temperature tested. At that same temperature, daily oviposition rate and net reproductive rate were maximum (9.5 and 111.77, respectively), and mean generation time and doubling time were minimum (10.92 and 1.6 days, respectively).     

Effects of temperature and photoperiod on termination of pseudopupal diapause in the bean blister beetle, Epicauta gorhami

Larvae of the bean blister beetle, Epicauta gorhami (Coleoptera: Meloidae), feed on grasshopper eggs in soil and undergo hypermetamorphosis. This beetle undergoes larval diapause in the fifth instar as a pseudopupa, a form characteristic of hypermetamorphosis in meloid beetles. This pseudopupal diapause is maintained for a long period if the larvae are kept under continuous diapause-inducing short-day conditions. In the present study, the effects of temperature and photoperiod on termination of pseudopupal diapause in E. gorhami were examined using pseudopupae obtained under 12L-12D at 25°C. Diapause was terminated by exposure to low or high temperature, but not by transfer to long-day conditions. The pseudopupal stage comprises diapause and post-diapause phases despite its unchanging appearance. The optimum low temperature for diapause termination was 10-15°C, and a higher or lower temperature was less effective. There was an individual variation in the low temperature requirement for diapause termination and post-diapause development may not occur until this requirement is satisfied. Although under natural conditions pseudopupae may encounter low temperatures that are effective for diapause termination at different ages, our results show that pseudopupae at various ages respond similarly to low temperature exposure. This response may ensure that resumption of development synchronizes in a population.     

Night-interrupting light inhibits diapause induction in the Kanzawa spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae)

The inhibitory effects of the timing, intensity (I_I) and period (I_T) of night-interrupting light on diapause induction of the Kanzawa spider mite (Tetranychus kanzawai) were investigated in a series of laboratory experiments. During a light and dark period of 8 and 16 h d⁻¹, respectively, a single 1-h night-interrupting light was applied at early (E), middle (M), and late (L) parts of the dark period: i.e., at 3, 7.5, and 12 h after the start of the dark period, respectively. No interrupting light was applied in the control treatment. The incidence of diapause was significantly lower in the M treatment (63%) compared to the control treatment (100%). In the E and L treatments, more than 90% of females entered diapause, which was comparable to the control treatment. Since the longest consecutive dark period during the E and L treatments was longer than the critical dark period (CDP) of 10.5-11 h d⁻¹, during which 50% of females entered diapause, the night-interrupting light probably failed to prevent diapause induction. However, in the M treatment, the longest consecutive dark period was shorter than the CDP; therefore, the night-interrupting light inhibited diapause induction. Moreover, the inhibitory effects of night-interrupting light in the M treatment increased as I_I and I_T increased. The dose of night-interrupting light (I_I × I_T) was significantly negatively related to the incidence of diapause. The median effective dose for 50% disturbance of diapause induction was 2.5 kJ m⁻² at wavelengths between 350 and 1050 nm. Our results suggest that the longest consecutive dark period and the dose of night-interrupting light should both be considered when a lighting-based physical control is applied to inhibit diapause induction and consequent overwintering of T. kanzawai in commercial agricultural fields.     

Effect of photoperiod on immature development and diapause induction in the Kanzawa spider mite, <Emphasis Type="Italic">Tetranychus kanzawai</Emphasis> (Acari: Tetranychidae)

The diapause response of the Kanzawa spider mite (KSM), Tetranychus kanzawai, was examined. KSMs were reared in aluminum bottles at 18°C with different combinations of light and dark periods created by the light-control unit. The developmental periods for all immature stages tended to decrease as the light period increased. The photoperiodic response curve for diapause induction showed that the critical (=50% diapause) light period was around 13 h days⁻¹. No diapause induction was observed when the light period was longer than 13.5 h days⁻¹ or under continuous light. At 13-h days⁻¹ light period, the developmental period for deutonymphal stage as well as for the total immature stages was longer in diapaused females than in non-diapaused females. These results indicate that immature development as well as diapause induction are affected by photoperiod and further suggest that diapause-inducing stimuli prolong the developmental period especially for the deutonymphal stage of KSMs.     

Effects of photoperiod and temperature on the termination of diapause in the univoltine seed wasp Eurytoma plotnikovi

Abstract Mummified pistachios containing fully grown diapause larvae of Eurytoma plotnikovi Nikol'skaya (Hym., Eurytomidae) were collected in early August and late September in coastal northern Greece and subjected to various photoperiod and temperature treatments, then maintained at 19 or 26°C and a long-day (LD 16:8 h), a changing, or a short-day (LD 10:14 h) photoperiod until pupation. In larvae of early August (beginning of diapause) subjected for 20 weeks to 19°C under a long, a changing, or a short photophase, followed by 19°C and a long photophase, 50% of the larvae pupated after 24, 18 and 13 weeks respectively. After exposure for 20 or even 12 weeks to a short photophase and low temperatures (10 or 4°C), pupation occurred after only 7–8 weeks and was more synchronous. The ranges of temperature for diapause development and post-diapause morphogenesis overlap. After exposure for 12 weeks to short days and low temperature, larvae of late September pupated much sooner under long days than under short days and sooner at 26° than at 19°C. E.plotnikovi depends on both temperature and photoperiod for diapause development, low temperature having a strong favourable effect on the earlier part and long day on the later part of diapause. In a few larvae of another pistachio seed wasp, Megastigmus pistaciae Walker, after a long enough period of low temperatures, diapause was terminated normally at 26°C and long days, or at 19°C and long or short days.     

The influence of physiological age of Argas reflexus larvae (Acari: Argasidae) and of temperature and photoperiod on induction and duration of diapause

The occurrence of diapause and quiescence was investigated in Argas reflexus engorged larvae, nymphs I and nymphs II. For diapause experiments, larvae were maintained at five different locations: at constant 20°C long day (LD; 17 h light:7 h dark) or short day (SD; 10 h light:14 h dark), at two locations with natural photoperiod and temperature and at one location with natural photoperiod but constant 15°C. At 20°C, diapause incidence was low in physiologically young larvae, increased with larval age, and then decreased to zero in specimens of increased physiological age. This pattern, observed both at constant LD and SD, suggests that the propensity to diapause changes with the physiological age of the unfed larva. The duration of diapause decreased with increasing larval physiological age at all locations, resulting in a seasonally synchronized moulting pattern. The results suggest that A. reflexus larvae are photoperiodically sensitive both before and after feeding and that decreasing daylengths may be particularly strong inductive stimuli. The developmental zero and thermal constant of the larvae were determined as 13.24°C and 220 degree-days, respectively. Degree-day measurements revealed that larval A. reflexus may enter a diapause of different length when fed between August and December and kept at natural daylength. Development of engorged nymphs I and nymphs II, but not of larvae, was ultimatively restricted at a temperature of 37.5°C, but immediately resumed at 25°C, demonstrating the occurrence of quiescence at high temperatures. Similarly, at a low temperature of 15°C, many nymphs I and II did not develop within 58 months, but did so successfully after transfer to 25°C, without additional food intake. Received: 20 May 1997 / Accepted: 4 August 1997     

Effect of anoxia on diapause termination in eggs of the false melon beetle, Atrachya menetriesi

The effect of anoxia on diapause development in the leaf beetle Atrachya menetriesi was investigated to elucidate the role of oxygen in regulation of egg diapause. While anoxia alone had no effect on diapause termination, it decreased diapause intensity before chilling. Such an effect reached a maximum level when anoxia lasted for about 10 days. Anoxia applied during the pre-diapause stage also reduced diapause intensity. On the other hand, anoxia terminated diapause when the diapause intensity had been lowered by sufficient duration of chilling (50 days at 7.5 degrees C). The effect of anoxia was temperature dependent; the larger effect was elicited when anoxia was combined with a higher temperature. A 50-day chilling caused more than 20% of eggs to terminate diapause upon transfer to warm conditions. However, when this chilling period was interrupted on the 20th day by a 5-day exposure to a high temperature of 20, 25 or 30 degrees C, the effect of the former chilling was cancelled partially or completely, suggesting that warming reversed diapause development. This reversing effect of a high temperature, however, was not manifested when the warming was combined with anoxia. The results suggest that anoxia inhibits diapause reversal and facilitates a certain process of diapause development. The sequence of exposure to anoxia and chilling is not important.     

Effect of posttreatment temperature on the toxicity of five synthetic pyrethroids toTetranychus urticae Koch (Acari: Tetranychidae)

The synthetic pyrethroids bioallethrin,d-phenothrin, and fenvalerate, when tested by the slidedip technique, were more toxic to female two-spotted spider mites,Tetranychus urticae Koch, at 30°C than at 20°C. LC₅₀ values differed by 1.7-, 3.8-, and 5.3-fold, respectively. Two other synthetic pyrethroids, flucythrinate and cyfluthrin, gave similar toxicity values at these two temperatures. The greater sensitivity ofT. urticae at a warmer temperature to the first three pyrethroids differs from insect toxicity studies, which often show negative temperature relationships.University of Minnesota Scientific Journal Series No. 14954     

Plant water stress, leaf temperature, and spider mite (Acari: Tetranychidae) outbreaks in California vineyards

We evaluated the relationships between plant water status and leaf temperature, and between leaf temperature and spider mite (Acari: Tetranychidae) and predatory mite (Acari: Phytoseiidae) populations in eight vineyards in California in 2006 and 2007. Temperature of south-facing leaves increased significantly by 0.8°C for every 1.0°C increase in ambient air temperature, and by 5.3°C for every one MPa drop in leaf water potential. Peak population densities of Pacific spider mite, Tetranychus pacificus McGregor, increased significantly with increasing frequency of leaf temperatures above 31°C. In contrast, peak population densities of Willamette spider mite, Eotetranychus willamettei (McGregor), showed no relationship with the frequency of leaf temperatures above 31°C. This differential relationship between the two mite species and high leaf temperatures is consistent with their upper thresholds for development, which are 40°C for T. pacificus and 31°C for E. willamettei, as identified in a previous study. Predatory mite population densities showed no relationship with peak population densities of either spider mite species during the analysis period, but decreased with the frequency of leaf temperatures above 31°C. In addition, predatory mite population densities were significantly higher on south-facing than interior leaves after adjusting for the effect of leaf temperature. These results help to explain why outbreaks of T. pacificus occur in warmer or water-stressed vineyards, whereas E. willamettei develops higher populations in cooler or well-irrigated vineyards. In addition, these results suggest that regulated deficit irrigation should be implemented with caution, especially in those vineyards with a high risk of T. pacificus outbreaks.     

Predation and life table of Feltiella acarisuga (Diptera: Cecidomyiidae) preying on eggs of Tetranychus urticae (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7 degrees C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower ( approximately 1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. The intrinsic rate of natural population increase (r), net reproductive rates (R(o)), gross reproductive rate (Sigmam(x)), generation time (T), doubling time (DT), and the finite rate of increase (lambda) of F. acarisuga were estimated by life table analysis at 0.1155/d, 15.25 eggs per female, 21.69 eggs per female, 23.6 d, 6.0 d, and 1.1225/d, respectively. Because the r value of F. acarisuga is relatively lower than that of T. urticae, frequent release of F. acarisuga may be necessary to suppress populations of T. urticae.     

The effect of temperature on life history parameters of Tetranychus evansi (Acari: Tetranychidae)

The effect of four constant temperatures (21, 26, 31 and 36°C) on biological (survival and duration of developmental stages, fecundity and longevity of females and sex ratio) and demographic parameters (R0, G, rm and ) of Tetranychus evansi was studied in the laboratory under controlled conditions: 75 ± 10% RH and 12L : 12D. The lower thermal threshold was 10.3°C. The shortest developmental time (6.3 days) was obtained at 36°C. Maximum fecundity was recorded at 31°C with 123.3 eggs per female. The highest intrinsic rate of increase (rm) (0.355) was obtained at 31°C. The optimal temperature for population growth seems to be 34°C. © Rapid Science Ltd. 1998     

Effect of temperature and photoperiod on diapause development in a Douglas fir seed chalcid, Megastigmus spermotrophus

Douglas fir seeds infested by diapausing larvae of a chalcid, Megastigmus spermotrophus, were transferred under different temperature and photoperiod regimes at various dates during autumn and winter. Both winter diapause and prolonged diapause were compared to the diapause patterns observed in control lots kept under natural conditions. The results showed that exposure to low temperatures in autumn and winter is required for the completion of diapause development. Median adult emergence dates and the date of transfer of larvae to 20°C were negatively correlated. The frequency of prolonged diapause of larvae transferred to 20°C decreased significantly after November. When larvae were submitted to different constant temperatures, the longer the daylength, the higher and faster the reactivation. These results suggest that chalcid larvae can perceive daylength through the seed coat. This phenomenon is probably related to the fact that most of the infested seeds falling in autumn are usually covered by a layer of leaf litter during the winter. Received: 14 June 1996 / Accepted: 24 February 1997