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1.
Phosphine-induced delay in development of eggs was investigated as a mechanism of resistance to this fumigant in Liposcelis bostrychophila Badonnel. One-day-old eggs of a susceptible and a strongly resistant strain of L bostrychophila were exposed to a range of phosphine concentrations for 6days at 30 (+/- 1) degrees C and 70 (+/- 2)% RH. Delay in mean hatching period occurred in both susceptible and resistant eggs, although it was more pronounced in the latter. A maximum delay of 2.65 days was recorded for eggs of the susceptible strain at 0.01 mg litre(-1) (the highest concentration at which eggs survived) and 13.39 days for the resistant strain at 1 mg litre(-1) (the highest concentration tested). Delay in egg development time was positively correlated with increasing phosphine concentration. Our results reveal that the most successful strategy to control resistant L bostrychophila is to apply relatively low concentrations of phosphine for extended exposure times (eg 0.05 mg litre(-1) for 16 days) that allow all eggs to hatch to the much less tolerant nymph stage. 相似文献
2.
BACKGROUND: In spite of the extensive use of phosphine fumigation around the world to control insects in stored grain, and the knowledge that grain sorbs phosphine, the effect of concentration on sorption has not been quantified. A laboratory study was undertaken, therefore, to investigate the effect of phosphine dose on sorption in wheat. Wheat was added to glass flasks to achieve filling ratios of 0.25-0.95, and the flasks were sealed and injected with phosphine at 0.1-1.5 mg L(-1) based on flask volume. Phosphine concentration was monitored for 8 days at 25 degrees C and 55% RH. RESULTS: When sorption occurred, phosphine concentration declined with time and was approximately first order, i.e. the data fitted an exponential decay equation. Percentage sorption per day was directly proportional to filling ratio, and was negatively correlated with dose for any given filling ratio. Based on the results, a tenfold increase in dose would result in a halving of the sorption constant and the percentage daily loss. Wheat was less sorptive if it was fumigated for a second time. CONCLUSIONS: The results have implications for the use of phosphine for control of insects in stored wheat. This study shows that dose is a factor that must be considered when trying to understand the impact of sorption on phosphine concentration, and that there appears to be a limit to the capacity of wheat to sorb phosphine. 相似文献
3.
桃小食心虫在我国温带水果主产区广泛分布,严重威胁水果出口贸易。为明确纯磷化氢熏蒸处理桃小食心虫的可能性,本文系统研究了纯磷化氢在不同温度条件下对桃小食心虫的毒力。耐受性分析结果表明,桃小食心虫各虫态对磷化氢的耐受力有很大差别,1~2龄幼虫耐受性最弱,5龄老熟幼虫耐受性最强。室内毒力试验结果表明,25℃,0.14~0.70mg/L磷化氢熏蒸5龄老熟幼虫81~199h或15℃,0.28~0.84 mg/L磷化氢熏蒸136~166h,桃小食心虫死亡率可达99%;在25℃和15℃下,试虫达到一定死亡率的气体浓度、时间乘积(CT)关系式分别为k=C0.5 T和k=C0.2 T,说明在本试验所取浓度范围内,处理时间是影响磷化氢对桃小食心虫老熟幼虫毒力作用的主要因素,相同条件下高温比低温更有利于磷化氢熏蒸杀虫。本文首次对不同温度条件下纯磷化氢熏蒸桃小食心虫的毒力作用进行了系统研究,明确了纯磷化氢熏蒸技术在水果携带桃小食心虫的检疫处理中极具应用前景。 相似文献
4.
Under laboratory conditions, the acaricidal effect of wettable sulfur is influenced by climatic conditions and the stage of development of Tetranychus urticae. Its ovicidal effect results from the combined action of temperature and relative humidity (RH). Wettable sulfur becomes effective at 27.5 degrees C and 75% RH. Beyond this threshold, the acaricidal effect increases with rising temperature or humidity, to become complete at a temperature of 35 degrees C and 90% RH. Within the range of temperatures and humidities 20 degrees C/30% RH and 35 degrees C/90% RH the mortality of immatures (from protonymphs to teleiochrysalis) was total. Under similar experimental conditions, females usually died before the end of the experiment. Temperature and relative humidity increased the adulticidal potential of wettable sulfur. The fecundity of the sulfur-treated females and the viability of their progeny was found to depend on temperature and RH. According to the same climatic conditions, eggs were less susceptible than females, which were in turn less susceptible than juvenile stages. 相似文献
5.
实验室条件下系统研究了磷化氢(PH3)对储物害虫嗜卷书虱Liposcelis bostrychophila卵、各龄若虫和成虫的致死作用,并选用PH3间歇熏蒸以及PH3与气调交替处理等措施对嗜卷书虱进行处理,比较了不同处理措施对嗜卷书虱种群的控制效果。结果表明,PH3熏蒸处理对嗜卷书虱各虫态有不同的致死效果。对卵而言,24、72和120 h熏蒸处理的LC50分别为0.137、0.045和0.035 mg/L;而24 h熏蒸处理对若虫的LC50在4.285~7.364 μg/L之间,对成虫的LC50为20.404 μg/L;采用25 μg/L的PH3进行24 h熏蒸处理,间隔10 d后再分别进行第2次和第3次熏蒸处理,可以完全控制嗜卷书虱的发生。采用PH3 (12 μg/L)和气调(体积比例为35% CO2,1% O2,64% N2)交替处理能够延缓嗜卷书虱种群抗性的发展,交替处理3~5次可以完全控制嗜卷书虱的发生。 相似文献
6.
BACKGROUND: Wheat can be stored for many months before being fumigated with phosphine to kill insects, so a study was undertaken to investigate whether the sorptive capacity of wheat changes as it ages. Wheat was stored at 15 or 25 °C and 55% RH for up to 5.5 months, and samples were fumigated at intervals to determine sorption. Sealed glass flasks (95% full) were injected with 1.5 mg L?1 of phosphine based on flask volume. Concentrations were monitored for 11 days beginning 2 h after injection. Some wheat samples were refumigated after a period of ventilation. Several fumigations of wheat were conducted to determine the pattern of sorption during the first 24 h. RESULTS: Phosphine concentration declined exponentially with time from 2 h after injection. Rate of sorption decreased with time spent in storage at either 15 or 25 °C and 55% RH. Rate of sorption tended to be lower when wheat was refumigated, but this could be explained by time in storage rather than by refumigation per se. The data from the 24 h fumigations did not fit a simple exponential decay equation. Instead, there was a rapid decline in the first hour, with phosphine concentration falling much more slowly thereafter. CONCLUSIONS: The results have implications for phosphine fumigation of insects in stored wheat. Both the time wheat has spent in storage and the temperature at which it has been stored are factors that must be considered when trying to understand the impact of sorption on phosphine concentrations in commercial fumigations. Copyright © The state of Queensland (through the Department of Employment, Economic Development and Innovation) 2009. Published by John Wiley and Sons, Ltd. 相似文献
7.
小麦光腥黑粉菌热力杀菌的研究 总被引：1，自引：1，他引：0
本试验对小麦光腥黑粉菌冬孢子粉在９０℃,１００℃,１１０℃,１２０℃,１２５℃,１３０℃,１３５℃和１４０℃进行了干热杀菌试验,在７０℃,相对湿度７０％,７５％,８０％,８５％,９０％,７５℃,相对湿度６５％,７０％,７５％,８０％,８５％,８０℃,相对湿度５５％,６５％,７０％,７５％,８５％;８５℃,相对湿度６０％,６５％,７０％,８０％,９０％进行了湿热杀菌试验,并通过焓增量值同杀菌时间ＴＤ 相似文献
8.
Oidium neolycopersici causes severe powdery mildew on all aerial parts of tomato, excluding the fruit. The objective of the present work was to examine factors that influence the development of O. neolycopersici on tomato and to identify potential methods for managing tomato powdery mildew. Under controlled conditions, the highest rates of conidial germination were observed at 25 degrees C, 99% relative humidity (RH) and minimal light, and the lowest on leaves adjacent to fruits. Optimal conditions for appressoria formation were 25 degrees C, RH ranging from 33 to 99%, and 1,750 lux light intensity. More conidia were formed at 20 degrees C, 70 to 85% RH, and 5,150 lux light intensity than at 16 and 26 degrees C, 99% RH, and 480 to 1,750 lux, respectively. Conidia survived and remained capable of germination for over four months when initially incubated at lower temperatures and higher RH, as compared with their fast decline under more extreme summer shade conditions. In growth chamber experiments, disease did not develop at 28 degrees C. Within the range of 70 to 99% RH, disease was less severe under the higher RH than the drier conditions. Disease was also less severe at lower light intensities. Data collected in three commercial-like greenhouse experiments involving various climate regimes were used to draw correlations regarding the effects of temperature and RH on the development of epidemics. Severity of powdery mildew was positively correlated with the duration of the range 15 to 25 degrees C, 1 to 4 weeks before disease evaluation (BDE), RH levels of 60 to 90% at 2 to 4 weeks BDE, and RH of 50 to 60% during the week BDE. Conversely, disease was negatively correlated with the duration of temperatures in the low and high ranges (5 to 15 degrees C and 35 to 40 degrees C) at 1 to 4 weeks BDE, with the duration of RH levels of 40% and below at 1 to 4 weeks BDE, and with 50 to 60% RH during the third week BDE. High (90 to 100%) RH was also negatively correlated with disease severity. These results suggest that the combination of high temperatures and low RH may help reduce O. neolycopersici powdery mildew severity in greenhouse tomatoes. 相似文献
9.
ABSTRACT Structural (space) solarization of a closed, empty greenhouse for sanitation involves dry heating to 60 degrees C and higher and low relative humidity (RH), under a fluctuating temperature and RH regime. Survival of inocula of Fusarium oxysporum f. sp. radicis-lycopersici and Sclerotium rolfsii during structural solarization was studied for 4 years (total of 12 experiments) in an attempt to develop a dynamic model for expressing the thermal inactivation of the pathogens. After 20 days of exposure, the populations of F. oxysporum f. sp. radicis-lycopersici and S. rolfsii were reduced by 69 to 95% and by 47.5 to 100%, respectively. The Weibull distribution model was applied to describe pathogen survival. The Weibull rate parameter, b, was found to follow an exponential (for F. oxysporum f. sp. radicis-lycopersici) and the Fermi (for S. rolfsii) functions at constant temperatures. To improve the applicability of the model, fluctuating conditions of both temperature and RH were utilized. The Weibull distribution derivative, expressed as a function of temperature and moisture, was numerically integrated to estimate survival of inocula exposed to structural solarization. Deviations between experimental and calculated values derived from the model were quite small and the coefficient of determination (R (2)) values ranged from 0.83 to 0.99 in 9 of 12 experiments, indicating that ambient RH data should be considered. Structural solarization for sanitation could be a viable component in integrated pest management programs. 相似文献
10.
As failure to control Rhyzopertha dominica (F.) with phosphine is a common problem in the grain-growing regions of Brazil, a study was undertaken to investigate the frequency, distribution and strength of phosphine resistance in R. dominica in Brazil. Nineteen samples of R. dominica were collected between 1991 and 2003 from central storages where phosphine fumigation had failed to control this species. Insects were cultured without selection until testing in 2005. Each sample was tested for resistance to phosphine on the basis of the response of adults to discriminating concentrations of phosphine (20 and 48 h exposures) and full dose-response assays (48 h exposure). Responses of the Brazilian R. dominica samples were compared with reference susceptible, weak-resistance and strong-resistance strains from Australia in parallel assays. All Brazilian population samples showed resistance to phosphine: five were diagnosed with weak resistance and 14 with strong resistance. Five samples showed levels of resistance similar to the reference strong-resistance strain. A representative highly resistant sample was characterised by exposing mixed-age cultures to a range of constant concentrations of phosphine for various exposure periods. Time to population extinction (TPE) and time to 99.9% suppression of population (LT(99.9)) values of this sample were generally similar to those of the reference strong-resistance strain. For example, at 0.1, 0.5 and 1.0 mg L(-1), LT(99.9) values for BR33 and the reference strong-resistance strain were respectively 21, 6.4 and 3.7 days and 17, 6.2 and 3.8 days. With both strains, doubling phosphine concentrations to 2 mg L(-1) resulted in increased LT(99.9) and TPE. High level and frequency of resistance in all population samples, some of which had been cultured without selection for up to 12 years, suggest little or no fitness deficit associated with phosphine resistance. The present research indicates that widespread phosphine resistance may be developing in Brazil. Fumigation practices should be monitored and resistance management plans implemented to alleviate further resistance development. 相似文献
11.
ABSTRACT Potebniamyces pyri is the causal agent of Phacidiopycnis rot, a postharvest disease of pears. Infection of fruit occurs in the orchard, and symptoms develop during storage. Conidial germination of P. pyri in response to nutrient, temperature, wetness duration, relative humidity (RH), and pH was determined in vitro. Conidia germinated by either budding or developing germ tubes in various concentrations of pear juice solutions. The mode of conidial germination was nutrient-dependent. Low nutrient levels favored budding, whereas high nutrient levels favored germ tube development. Conidia germinated at 0 to 30 degrees C but not at 35 degrees C, with optimum temperature between 20 and 25 degrees C. Wetness durations of 4 to 5 h and 6 to 8 h at optimum temperature were required for budding and developing germ tubes, respectively, and 20 to 24 h of wetness was required to reach germination peaks. Regardless of temperature, conidia germinated primarily by budding in 10% pear juice. Secondary conidia, produced by budding of conidia, initially increased their dimensions and later germinated at 0 to 25 degrees C in the same manner as mother conidia. No germination of secondary conidia occurred at 30 degrees C. Germ tubes from conidia elongated at 0 to 25 degrees C but not at 30 degrees C. No germination occurred at 相似文献
12.
参照FAO推荐方法测定了磷化氢对嗜卷书虱(Liposcelis bostrychophila(Badonnel))2个品系、嗜虫书虱(L.entomophila(Enderlein))3个品系和小眼书虱(L.paeta(Pearman))3个品系等共8个不同来源书虱的毒力和抗性系数Rf,测定了磷化氢浓度为2mg/mL条件下供试各书虱品系的半数击倒时间KT50,分析了其LC50值与KT50值的相关性。结果为:3种书虱的8个品系对磷化氢的抗性差异明显,高抗性的嗜虫书虱的磷化氢抗性比敏感的嗜卷书虱高1000倍以上,各品系书虱的KT50值与Rf值呈正相关,相应LC50值之对数与KT50值的对数呈直线相关。结果表明,磷化氢对书虱成虫的半数击倒时间KT50值可以用来判断书虱抗性大小,并可用于快速判断抗性以指导现场熏蒸。 相似文献
13.
The present paper deals with developmental duration, emergence, longevity and fecundity ofAleurotuberculatus takabashi David & Subramaniam at different temperatures and humidity levels. The developmental time from egg to adult was 81.8, 56.9,
39.6, 29.9, 20.6 days at 15±1, 20±1, 25±1, 30±1, 35±1°C under constant relative humidity (RH) of 70±5%, respectively. At 25±1°C,
the total developmental time was slightly affected by humidity, ranging from 46.4 days at 40±5% RH to 39.2 days at 90±5% RH.
The developmental threshold and the thermal constant for the stage from egg to adult were 10.1°C and 542.8 day-degrees. It
was estimated that the whitefly has about 10 generations a year in Fuzhou region in southeastern China. Lowest mortality rates
of 12.4% for the egg, 6.8% for the nymph and 3.1% for the puparium were obtained at 15±1°C, while they were highest with 92.1%
for the egg, 48.2% for the nymph and 36.3% for the puparium at 35±1°C. The mortality rates were slightly affected by humidity,
ranging from 17.6% at 40±5% RH to 27.9% at 90±5% RH for the egg, 11.2% at 40±5% RH to 19.6% at 90±5% RH for the nymph, and
6.4% at 40±5% RH to 11.6% at 90±5% RH for the puparium. The emergence rate of adults decreased as temperature increased, ranging
from 89.1% at 15±1°C to 21.5% at 35±1°C, so did the longevity of adults, ranging from 9.6 days at 15±1°C to 2.9 days at 35±1°C.
The number of eggs per female was significantly affected by temperature (P.01), valuing 29.4 eggs per female at 15±1°C, 36.7
at 20±1°C, 52.4 at 25±1°C, 42.9 at 30±1°C, and 6.1 at 35±1°C. The optimal temperature for reproduction was about 25°C. 相似文献
14.
The diapausing larvae of Trogoderma granarium are among the most tolerant of all storage pests to fumigation and effective dosage schedules are required. For this purpose, the toxicity of methyl bromide (MeBr), phosphine, methyl chloroform (MC), ethylene dichloride (EDC) and chlorobromomethane, and of mixtures of MeBr and MC, EDC and MC, and phosphine and MeBr, to diapausing larvae of the pest was examined at 15, 20 or 25°C. At 15 and 20°C the tolerance of larvae was high and very high dosages of MeBr or liquid fumigants, or long exposures to phosphine, were required for total kill. At 25°C larvae were more susceptible to phosphine but retained a high tolerance of other fumigants. A mixture of 2% MeBr in MC showed evidence of potentiation at 25°C and achieved control of larvae at moderate dosages. 相似文献
15.
Experiments were conducted to determine the effects of temperature, relative humidity (RH) and duration of wetness period on in vitro germination of conidia and infection of detached pear leaves by Venturia nashicola , the causal agent of pear scab. Conidia germinated only in near-saturation humidity (RH > 97%). The final percentage germination (24 h after inoculation) at 100% RH without free water was less than half that in free water. Conidia germinated over the range of temperatures tested (5–30°C); the optimum temperature for germination was ≈21°C. Changes in percentage germination of conidia over time were fitted by logistic models at each individual temperature. Polynomial models satisfactorily described the relationships between two (rate and time to 50% of maximum germination) of the three logistic model parameters and temperature. The minimum length of the wetness period for successful infection of detached pear leaves by conidia was observed at several temperatures. The shortest length of wetness period required for infection was 7 h at 22°C. Two polynomial models fitted well the relationship between the minimum wetness duration required for infection, and temperature. 相似文献
16.
17.
Owing to increased tolerance and the development of resistance in stored product insects to the fumigant phosphine, in recent years there has been a shift in the target terminal concentration from 100 ppm (100 mL m(-3)) to a higher level of 1000 ppm to achieve 100% insect mortality in 7 day commodity treatments. Therefore, there is a need to investigate whether the revised target concentration could be achieved for food commodities fumigated with phosphine at the standard dose of 2 g m(-3) for 7 days under airtight conditions at > or = 25 degrees C. When different types of food commodity (total 74) were fumigated (300 g per replicate) with phosphine at 2 g m(-3) for 7 days, the terminal gas concentrations in the free space of the commodities varied from 0 to > 2000 ppm. In chambers containing no substrate, a 1417 ppm concentration was recorded. Paddy rice, most of the oilseeds, shelled tree nuts, butter beans, cardamom, green gram splits, coriander powder, rice bran and cocoa powder were more sorptive (> or =60%), such that the target concentration of 1000 ppm was not achieved at the end of 7 days. For these commodities, increased doses of 3-6 g m(-3) were required to attain 1000 ppm. In-shell almonds, green cardamom, in-shell peanuts, leaf tea, tamarind pulp and sunflower seeds were exceptionally sorptive (>90%), so that 0, 41, 112, 168, 203 and 217 ppm respectively were noted at the end of 7 days; the dose must exceed 6 g m(-3) for effective fumigation of these commodities. 相似文献
18.
Vayias BJ Athanassiou CG Kavallieratos NG Tsesmeli CD Th Buchelos C 《Pest management science》2006,62(5):456-464
Laboratory tests were conducted to assess the insecticidal and residual effects of three diatomaceous earth (DE) formulations, Insecto, PyriSec and SilicoSec, against Tribolium confusum Jacquelin du Val on wheat and maize. Quantities of wheat and maize were treated with the above formulations at 500, 1000 and 1500 mg kg(-1) and stored at 25 degrees C and 55% relative humidity (RH). Samples were taken on the day of storage and every 30 days until completion of a 360 day period of storage. Adults of T. confusum were exposed to these samples at 25 degrees C and 55% RH and the mortality was measured after 24 and 48 h and 7 and 14 days of exposure. Adult mortality was higher on wheat than on maize. At the beginning of the storage period, mortalities after 14 day exposure on maize treated with the highest rate were 60, 63 and 81% for Insecto, PyriSec and SilicoSec respectively, while on wheat the mortality was 100% for all DEs. On the same commodities 360 days after treatment the respective mortality figures for wheat were 99, 98 and 100%, while in the case of maize they did not exceed 7%. Generally, mortality at exposures < or =48 h decreased with increasing storage time. Furthermore, although mortality on wheat increased with dose, the increase in DE dose from 1000 to 1500 mg kg(-1) resulted in only a small increase in mortality. Thus a DE treatment of 1000 mg kg(-1) was shown to provide long-term protection of wheat against T. confusum, although higher DE application rates and exposure intervals are needed for a satisfactory level of protection of maize against this pest. 相似文献
19.
ABSTRACT Sweet pepper-Leveillula taurica microclimate relations were studied under controlled conditions and in commercial greenhouses. Conidial germination occurred at 10 to 37 degrees C and was optimal at 20 degrees C. Conidial viability declined as temperatures increased to 40 degrees C for 6 h. Leaf colonization was optimal at 15 to 25 degrees C. Severe leaf infections occurred at 15 to 20 degrees C and conidiation was suppressed at 20 to 25 degrees C. Highest germination rates were observed at 75 to 85% relative humidity (RH). Severity of leaf coverage by symptoms was high for plants which were subjected to longer periods of temperatures between 10 to 15 degrees C and daytime RH between 85 to 95%, and positively correlated with nighttime RH. Disease severity was negatively correlated with lengthy periods of temperatures >25 degrees C, day and night average temperatures, and average daytime RH. Conversely, leaf shedding was relatively high under conditions characterized by long periods of temperatures >20 degrees C and <13 degrees C, and positively correlated with average daytime temperatures and periods of RH <75%. Increasing nighttime temperatures by heating and daytime temperatures by closing the greenhouse side walls reduced disease in two commercial greenhouse experiments. A midseason shift from a cooler greenhouse climate to warm daytime climate halted epidemic development. Flower number and yield were reduced in infected crops. 相似文献
20.
玉米象各发育期对磷化氢的敏感性 总被引：1，自引：0，他引：1
结果表明,磷化氢对玉米象(Sitophilus zeamais Motschlscky)成虫有较强的毒力。玉米象各发育期对磷化氢的敏感性为:成虫>幼虫>卵>蛹,幼虫的耐药力与成虫接近,卵与蛹的耐药力几乎相同,卵、蛹的耐药力比成虫、幼虫约大2倍。因此,磷化氢熏蒸效果检查,不仅应对所有虫态检查,而且应保持储粮中较长时间没有活虫发生;在保持磷化氢有效浓度条件下,增加暴露时间能增效;CT值能全面检查磷化氢实仓熏蒸效果。未来用CT值代替剂量值,对进一步改善磷化氢熏蒸技术和提高药效,具有重要的现实意义。 相似文献