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1.
The activity of diflubenzuron against eggs ofLobesia botrana Den. & Schiff. was assayed with a dipping procedure, at 22° and 27° C. The compound was much more active at 27°C (LC-50 = 0.0072%) than at 22°C (LC-50 = 0.195%).  相似文献   

2.
We investigated insecticidal effects of iminoctadine liquid formulation, a fungicide containing iminoctadine triacetate, on the silkworm Bombyx mori that is an important domesticated insect. Iminoctadine liquid formulation was incorporated in an artificial diet and fed to silkworms for 24 h on the first day of either the third or fourth instar, thereafter reared without the fungicide. Third instar larvae that ingested the diet containing 1% (wt/wt) iminoctadine liquid formulation died within 24 h (subacute toxicity), and those that ingested either 0.1% or 0.3% iminoctadine liquid formulation developed to the pharate fourth stage and then became deficient in molting (delayed toxicity). In fourth instar larvae, iminoctadine liquid formulation exhibited subacute toxicity and delayed toxicity at 0.3% and >1%, respectively. Furthermore, we fed the larvae a diet with iminoctadine liquid formulation for 24 h at different intervals in the inter-molting period of the third and fourth instar. Iminoctadine liquid formulation administered at an earlier stage in the inter-molting period exerted a more severe effect than a later administration. Iminoctadine triacetate, an anti-fungal ingredient in the iminoctadine liquid formulation, exhibited toxicity similar to that of the liquid formulation.  相似文献   

3.
Trichogramma platneri Nagarkatti (Hymenoptera: Trichogrammatidae) was recently introduced into Israel to improve the control of two lepidopterous pests,Boarmia selenaria (Schiffermiiller) andCryptoblabes gnidiella (Millière). Laboratory tests showed thatT. platneri attacks the eggs of both species. A method of freezing the eggs of the host,Ephestia cautella (Walker), at -20°C and gradual defrosting, used in the large laboratory breedings of the parasites, is described briefly. In laboratory tests 68.5% of the frozenE. cautella eggs, after 2 months of storage, were parasitized, compared with 70.3% of the fresh eggs.  相似文献   

4.
Field treatments in a vineyard with 0.015 or 0.01% a.i. of cypermethrin, fenvalerate, fenpropathrin or AC-222,705 were more efficient in controlling the grape-berry moth (Lobesia botrana Schiff.) and the honeydew moth (Cryptoblabes gnidiella Mill.) than four standard treatments consisting of two with 0.05% a.i. fenitrothion and two with 0.075% a.i. diazinon. In pyrethroid-treated plots, infestation at the end of the trials ranged between 2.5 and 12%, compared with 21% in the standard treatment plots and 34% in the untreated plots. Cypermethrin, fenpropathrin and AC-222,705 exhibited similar field activity, while that of fenvalerate was somewhat lower. Under laboratory conditions, cypermethrin at 0.005 and 0.01% a.i. was significantly more potent than fenvalerate, fenpropathrin and AC-222,705; at a higher concentration, 0.015% a.i., all pyrethroids were highly active, with mortality ranging between 75 and 95%. Under laboratory conditions the vinegar fly (Drosophila melanogaster Meig.) was in general more susceptible to pyrethroids than was the grape-berry moth. Cypermethrin and AC-222,705 at 0.005% a.i. and avermectin at 0.0035% a.i. were potent compounds against the vinegar fly and more active than fenvalerate and fenpropathrin.  相似文献   

5.
Using an iodometric method for the determination of malathion in emulsifiable concentrates, values of active ingredient in four commercial formulations and one primary reference standard were within ±0.7% weight/volume (w/v) of the stated concentrations. A standard deviation of 0.42% w/v and 95% confidence limits of ±0.9% w/v for a single determination were calculated for the method. Added moisture and elevated temperature were found to accelerate malathion breakdown in the commercial formulations. The greatest breakdown rate of 5.2% w/v per 100 days occurred with a formulation stored at 27 °C containing 0.5% v/v added moisture.  相似文献   

6.
Effects of ambient temperature on the acute oral toxicity of parathion were investigated in Japanese quail (Coturnix japonica) maintained at thermoneutral temperature (26°C) or exposed to elevated (37°C) or reduced (4°C) temperatures commonly encountered by free-ranging wild birds. Based upon estimates of the median lethal dosage, there was up to a twofold enhancement of parathion toxicity in birds chronically exposed to heat or cold. Twenty-four hours after administration of a low dosage (4 mg/kg body wt, po), there was markedly greater cholinesterase inhibition in surviving heat-exposed quail compared with those reared at 26°C (e.g., brain acetylcholinesterase depression of 42% versus 12%). There were no differences in hepatic activities of parathion oxidase, paraoxonase, or paraoxon deethylase which could account for greater toxicity to chronically heat-exposed birds. In contrast, 4 mg parathion/kg wt elicited less plasma cholinesterase inhibition in cold-exposed quail compared to thermoneutral controls (e.g., <10% versus 48% depression after 24 hr). Increased liver weight and a doubling of paraoxonase activity may have been associated with greater tolerance to sublethal doses of parathion in chronically cold-exposed quail. These findings, together with limited field observations, indicate that the hazard associated with anticholinesterase exposure of wild birds is substantially influenced by environmental temperature.  相似文献   

7.
The present study dealt with the functional responses of the parasitoid,Eretmocerus longipes Compere (Hym., Aphelinidae) to the densities of the whitefly,Aleurotuberculatus takahashi David et Subramaniam (Hom., Aleurodidae) at different temperatures under the laboratory conditions. The results showed that when the initial densities ofA. takahashi-3rd instar were raised from 10 to 320 ind./leaf, the numbers of parasitized nymphs increased as well, ranging from 7.0 to 23.1 at 20°C, 9.8 to 42.9 at 25°C, 6.7 to 39.9 at 30°C, and 1.8 to 8.3 ind./leaf at 35°C, respectively. The Holling Disk Equation was introduced to build up the models of functional responses. The response curves remained type II, although the numbers of parasitized nymphs were significantly different under different temperatures. The suitable initial densities of the host whitefly for parasitization were about 80 individuals per leaf. A negative relation was observed between the initial densities of the whitefly and the parasitization rates by the parasitoid. An increase in the initial densities ofA. takahashi-3rd instars ranging from 10 to 320 ind./leaf resulted in a decrease in the parasitization rate byE. longipes ranging from 70.0% to 7.2% at 20°C, 98.0% to 13.4% at 25°C, 67.0% to 12.5% at 30°C and 18.0% to 2.6% at 35°C with a value of 0.2877 was significantly smaller than that at 20°C with a vlaue of 1.3354, that at 25°C with a value of 1.6465 and that at 30°C with a value of 1.1199, respectively (p<0.01). The handling time (Th) forE. longipes was 0.1521 at 35°C, significantly longer than 0.0510 at 20°C, 0.0289 at 25°C and 0.0320 at 30°C, respectively (p<0.01). The maximum loading number (K) of the parasitized nymphs with a value of 34.5 ind./leaf at 25°C was similar to that with a value of 31.2 ind./leaf at 30°C, about 1.8 times as high as that with a value of 19.6 ind./leaf at 20°C and 4 times more than that with a value of 6.6 ind./leaf at 35°C. It was suggested that temperature affected the functional response by balancing searching rate and handling time. The optimal temperature range for the functional responses ofE. longipes to the densities ofA. takahashi-3rd instar was 25° to 30°C.  相似文献   

8.
Potato plants ‘Bintje’ were grown in growth chambers; one group of 27 plants at a daily regime of 15 h light and 9 h darkness with corresponding temperatures of 18 °C and 12°C, and a second group of 27 potato plants at a daily regime of 15 h light and 9 h darkness with corresponding temperatures of 22 °C and 17 °C. The plants of both groups were inoculated with potato virus X (PVX) 56 days after planting. Young leaves had a 3-fold higher ribosome and RNA content than ageing leaves. The decrease occurred earlier at 22 °C than at 18 °C. Although plants grown at 18 C produced smaller and fewer leaves than those grown at 22 C, the former produced a higher weight of tubers than those at the higher temperature. Although corresponding leaves of both groups showed considerable differences in ribosome and RNA contents, the rate of virus translocation to the tubers was equal in both groups. This can be explained by the different growth pattern.  相似文献   

9.
Field trials were conducted in 1971–1974 to control the honeydew moth,Cryptoblabes gnidiella Mill, withBacillus thuringiensis. Dipel, a commercial preparation containingBacillus thuringiensis var.kurstaki (HD-1 strain), was highly effective (at concentrations ranging from 0.25% to 1.5%) in killing caterpillars of all developmental stages. In both the field trials and additional laboratory trials, it had no adverse effect on the mealybugPseudococcus longispinus Targ.-Tozz., or on its parasites,Hungariella peregrina Compere andAnagyrus fusciventris Girault.  相似文献   

10.
Meteorus pulchricornis is a parasitic wasp, which plays an important role in the biological control of lepidopteran pests. Through assessment of the effect of host instar and temperature on fitness-related traits of M. pulchricornis, this study ascertained the establishment potential of M. pulchricornis in the fields. Results showed that M. pulchricornis accepted Spodoptera exigua for oviposition and the progenies developed successfully in hosts of all ages at three constant temperatures, 20°C, 25°C and 30°C. Parasitoid survivorship from oviposition to adult eclosion was highest at 25°C, followed by 20°C and 30°C. Cocoon weight and hind tibia length differed significantly when the parasitoid was exposed to 20°C, 25°C and 30°C. The fitness-related traits of M. pulchricornis did not increase linearly with the host age at different temperatures. The host quality was found to be optimal at intermediate host instars, which the female parasitoid preferred to parasitize. The larval development rate increased with temperature in a linear fashion up to 30°C. The threshold for larval and pupal development of M. pulchricornis was 4.2°C and 1.6°C, respectively. These results have implications for predicting the population dynamics of M. pulchricornis in situ and optimizing mass rearing of the parasitic wasp under laboratory conditions.  相似文献   

11.
PH 60-40 is of very high toxicity toSpodoptera littoralis eggs in laboratory experiments; 100% kill was obtained by dipping young eggs in a 0.000 025% a.i. dilution in water of a 5% liquid formulation of the compound.  相似文献   

12.
Susceptibility of almond fruit(Prunus dulcis (Mill.) Webb.) to anthracnose caused byColletotrichum gloeosporioides Penz.(=Gloeosporium amygdalinum Brizi) was investigated. Fruits were punctured, and a drop of spore suspension of the desired size and density was placed on the wound. Fruits were placed in a humid chamber for one week at 22°C. The diameter of the lesion of the infected fruits was used as an indicator of susceptibility. Disease development was found to be negatively correlated with the age of the fruit. The inoculation concentrations used in this research have no effect on the disease development, although the volume of the drop affected the size of the lesion to some extent. With constant, high relative humidity (saturation), the diameter of the anthracnose lesion increased by 1 mm per day, while under dry room conditions the increase was less than 0.5 mm per day. At 22°C lesions developed faster than at either 15° or 27°C. A detailed procedure for assessing sensitivity of fruit to anthracnose is described. This should enable improved comparison of susceptibility between genotypes and in different environments.  相似文献   

13.
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   

14.
The toxicity and LD50 of O,S,S-trimethyl phosphorodithioate were reexamined in the rat. Animals treated orally (single dose) with this compound exhibited early cholinergic signs followed at approximately 5 hr by delayed toxic signs, with an LD50 of 43 mg/kg. Contamination of O,S,S-trimethyl phosphorodithioate by as much as 5% (w/w) O,O,O-trimethyl phosphorothioate provided only limited antagonism to the dithioate's toxicity. In contrast, the addition of 5% O,O,S-trimethyl phosphorodithioate to O,O,S-trimethyl phosphorothioate gave protection against the toxic effects of the latter compound up to 80 mg/kg of toxicant. Pretreatment of rats with as little as 5% O,O,O-trimethyl phosphorothioate, 24 hr prior to treatment with 200 mg/kg O,O,S-trimethyl phosphorothioate, gave complete protection against the toxic effects of this compound. Conversely, administration of 10% (w/w) O,O,O-trimethyl phosphorothioate 4 or 24 hr after treatment with 60 or 80 mg/kg of O,O,S-trimethyl phosphorothioate provided only partial protection at 4 hr and no protection from the effects of the toxicant at 24 hr. The ability of O,O,O-trimethyl phosphorothioate to antagonize the toxicity of this compound depended markedly on the route of administration (oral, intravenous, or intraperitoneal). At 4 hr past treatment with toxicant, only oral administration of the antagonist provided full protection. Intraperitoneal and intravenous administration of antagonist 4 hr after treatment with toxicant were partially effective and completely ineffective, respectively, in halting the toxic effects of this compound.  相似文献   

15.
Three defoliating (D) pathotype isolates and five nondefoliating (ND) pathotype isolates of Verticillium dahliae from cotton in central China were tested for adaptation to various temperatures in conidial germination on water agar (10?C33°C), mycelial growth on potato dextrose agar (10?C33°C) and infection of cotton seedlings (Gossypium hirsutum cvs. ??E Mian 24?? and ??Yin Rui 361??) (25?C33°C). Results showed that the D-pathotype isolates adapted better than the ND-pathotype isolates to 30°C for conidial germination and mycelial growth, although the isolates of the two pathotypes had the same optimum temperature of 25°C. Under day/night temperatures of 25/25, 27/27 and 30/25°C for 20 and 25?days, the D-pathotype isolates induced the defoliation syndrome on seedlings of the two upland cotton cultivars, whereas the ND-pathotype isolates did not induce defoliation syndrome. The values for the areas under the disease progress curve (AUDPC) and the vascular discoloration index (VDI) were higher for the D-pathotype isolates than those for the ND-pathotype isolates in each temperature treatment. Under 30/30 or 33/27°C, at least two of the three D-pathotype isolates still had higher AUDPC values and/or VDI values than all the ND-pathotype isolates on E Mian 24. Therefore, the D-pathotype isolates appear more aggressive than the ND-pathotype isolates in infection of cotton. Results also showed that the cotton cultivar Yin Rui 361 was more tolerant than the cotton cultivar E Mian 24 to infection by both pathotypes of V. dahliae. This study suggests that the D-pathotype isolates can well adapt to high temperature and heavily infect cotton under 25?C30°C, and these features might be responsible for the rapid spread of this pathotype in central China.  相似文献   

16.
Y. Levy 《Phytoparasitica》1984,12(3-4):177-182
Exserohilum turcicum (Pass.) Leonard and Suggs, the causal agent of northern leaf blight of corn, overwinters onSorghum halepense L. plants and on corn debris (dead leaves). Spqrulating lesions ofE. turcicum were observed on sorghum plants in the winter (February). Spores from these lesions were pathogenic to susceptible sweet corn plants cv. ‘Jubilee’. Infected sporulating leaves of corn were stored for 1 year at 20°C (40-60% relative humidity), at 5°C (60% relative humidity), or buried 5 cm underground. During the storage period, 32% and 22% of the spores formed chlamydospores, at 20° and 5°C, respectively. Leaves buried 5 cm underground were totally decomposed after 6 months. After 4 months, 25% of the spores in the buried leaves had formed chlamydospores. Spores with chlamydospores were pathogenic to corn plants. The viability of spores without chlamydospores stored at 20°, 5°C or buried underground was 0, 60 and 0%, respectively. In a parallel experiment infected leaves were stored under similar conditions and allowed to sporulate. No sporulation occurred on infected leaves buried in soil. Spores produced on infected leaves stored at 20° and 5°C were highly pathogenic to corn plants. In leaves treated with 0.1N glucose, chlamy dospore formation was significantly inhibited.  相似文献   

17.
The oriental fruit fly, Bactrocera dorsalis (Hendel), is a major polyphagous insect pest with a worldwide distribution. The effects of temperature on stage-specific development in B. dorsalis were investigated at eight constant temperatures (13.0 °C, 14.4 °C, 16.2 °C, 19.5 °C, 23.8 °C, 27.7 °C, 31.8 °C and 34.8 °C). B. dorsalis developed successfully from the egg stage to the adult stage at all the tested temperatures, except at the lowest temperatures (13.0 °C and 14.4 °C). Stage-specific lower developmental thresholds and thermal constants were determined using linear regression. The lower and higher temperature threshold (TL and TH, respectively) were estimated using the Sharpe-Schoolfield-Ikemoto model. The lower developmental threshold and thermal constant from egg to adult emergence were 9.8 °C and 325.5 degree-days, respectively. The intrinsic optimum temperatures of the egg, larval, pupal and egg to pupal stage were 20.7 °C, 21.8 °C, 21.1 °C, and 22.4 °C, respectively. The temperature range of the B. dorsalis total immature stage from TL to TH was 20.4 °C (13.8 °C - 34.2 °C). The stage-specific developmental completion of B. dorsalis was determined using a two-parameter Weibull function. The daily adult emergence frequency of B. dorsalis was estimated in relation to adult age and temperature using non-linear developmental rate functions and the Weibull function. The date of cumulative 50% adult emergence estimated using non-linear functions was approximately one day earlier than the experimentally observed date. Thermal performance was compared among B. dorsalis populations from different locations.  相似文献   

18.
Silk infection by Fusarium verticillioides is caused by conidia produced on maize crop residues and results in kernel infection and consequent accumulation of fumonisins. Studies were carried out in both controlled and field conditions to understand the dynamics of sporulation on maize residues. The effect of temperature (5°C to 45°C) and incubation time (3 to 41 days) on spore production on maize meal agar was described by a logistic model that accounted for 85% of variability. The rate parameter depended on the length of incubation and the asymptote on temperature. Maximum sporulation occurred at 27°C, with a progressive increase between 5°C and 27°C and then a rapid decline, with no sporulation at 45°C. Fusarium verticillioides strains from different geographic origins showed different sporulation capabilities, with similar optimum temperatures. Pieces of stalk residues inoculated with F. verticillioides and placed above the soil between rows of maize crops, in 2003 to 2005, produced conidia continuously and abundantly for some weeks, particularly during the period after silk emergence, with an average of 1.59 × 107 conidia g−1 of stalk, over a wide range of environmental conditions. Sixty-seven percent of variability of the spore numbers found on stalks was accounted for by a multiple regression model. Precipitation (rain or overhead irrigation) in the 14 days before stalk sampling decreased the number of spores, whilst the number of days with conducive conditions of moisture (i.e. days with rainfall, average relative humidity >85% or vapour pressure deficit <4 hPa) and greater degree-days (base 0°C) in the 14 and 3 days before sampling, respectively, increased sporulation.  相似文献   

19.
The oral toxicity of 5-benzyl-3-furylmethyl-(1R, cis)-chrysanthemate (cismethrin) to female rats decreased as their environmental temperature was raised. Acute oral LD50 values increased from 157 mg/kg at 4°C to 197 mg/kg at 20°C and to > 1000 mg/kg at 30°C. Cismethrin was much more toxic given intravenously when the LD50 was 4.5 mg/kg. This value did not change at different environmental temperatures. Irrespective of the environmental temperature, or route of adminstration, following the respective LD50's cismethrin caused tremors in rats when brain levels of 0.5–1.0 μg/g were reached and, at death, brain concentrations were 3.9–5.1 μg/g. These results suggested that the accumulation of cismethrin by the brain could be used as a model for the nervous system as a whole. The isomeric 5-benzyl-3-furylmethyl-(1R, trans)-chrysanthemate (bioresmethrin) was about 50 times less toxic to rats than cismethrin. After an intravenous LD50, tremors started when brain concentrations were 4–5 μg/g. At death, brain levels were 25–35 μg/g. Plasma esterases were about equally active in hydrolysing cismethrin and bioresmethrin, whereas liver microsomal esterases hydrolyzed bioresmethrin over 10 times more rapidly than cismethrin. It is suggested that the lower toxicity of bioresmethrin is not only due to its faster metabolism but to an intrinsically lower toxicity at the critical site of action in the nervous system.  相似文献   

20.
Microcosm studies were carried out to test the survival of Ralstonia solanacearum biovar 2 (race 3) in soil at the permanent wilting point (wp) water content and at field capacity (fc) water content and on various material. Soils were placed at permanent ?5°C, 4°C, 15°C and 20°C and weekly fluctuating ?10/0/+10°C and the material at 5, 15 °C, 20°C with relative humidity (rh) uncontrolled or at constant 10% or 90%. In soil, survival was clearly dependent on temperature independent of water content. At 20°C Ralstonia solanacearum could be reisolated up to 364 days, at 15°C up to 290 days, at 4°C up to 209 days and at fluctuating temperatures (?10/0/+10°C) only up to 18 days. The lower the temperature, the more the population declined. At 15°C and 20°C appr. 107 cfu/g soil were detected after 100 days, whereas at ?5°C only 102 cfu/g soil were detected after only 18 days. The pathogen was longer detectable in sandy-clay loam than in lighter sandy soil. It could be longer reisolated at wilting point and the populations did not decline as rapidly as at field capacity. Ralstonia solanacearum could best survive on material surfaces like rubber, plastic and varnished metal with maximum survival of 40 days at 5°C and 10% rh. In general there is a low risk of Ralstonia solanacearum overwintering under European climatic conditions when the fields are cleared of plant debris and the soil is frozen. Contamined material surfaces pose the risk of pathogen transmission to healthy tubers.  相似文献   

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