Fumigation of gypsophila flowers against Liriomyza trifolii1

Gypsophila cut flowers were fumigated with methyl bromide against Liriomyza trifolii. Complete control was obtained at a dose of 40 g/m³ methyl bromide, for 3 h at 15–18°C. To get satisfactory results without injuring the flowers they had to be conditioned at the above temperature for 6 h prior to fumigation.     

Fumigant doses for the control of Trogoderma granarium1

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.     

Depression of the minimum concentration of methyl bromide effective against diapausing warehouse moth larvae at 15°c by prior exposure at a moderate concentration

Warehouse moth (Ephestia elutella) larvae in diapause were exposed at 15°C to methyl bromide at 8 mg litre^?1 for 14.5 h and then immediately exposed at a lower concentration. The exposure at 8 mg litre^?1 killed 44–69% of the larvae treated. Subsequent concentrations down to 1.1 mg litre^?1 obeyed Haber's rule (concentration × time= k, a constant for mortality), but a higher concentration-time product (ct) was required for over 90% kill at 0.8 mg litre^?1. Only concentrations down to 1.9 mg litre^?1 obey Haber's rule if there is no prior exposure at a higher concentration. Although minimum effective concentrations are lower at 15°C than at 25°C, exposure at a higher concentration depresses the subsequent level to a similar extent at each temperature. The contribution to the efficacy of a treatment, of low concentrations persisting at the end of fumigation, is thus likely to be even greater at moderate to low temperatures than at 25°C. The implications for the development of resistance to methyl bromide are discussed.     

Effect of soil physical factors on methyl iodide and methyl bromide

Production and importation of methyl bromide is scheduled to be banned by 2001. Methyl iodide was evaluated as a possible replacement soil fumigant. The effects of soil moisture, temperature, soil texture and fumigation time on the efficacy of methyl iodide for the control of two common weeds, Abutilon theophrasti and Lolium multiflorum, were characterized and compared with those of methyl bromide. The optimal soil moisture for methyl iodide to kill both weed species in sandy soils was 14% water content (w/w). Greater efficacy was obtained when the temperature during fumigation was above 20°C. Compared to methyl bromide, the efficacy of methyl iodide was more consistent in different soils. Time to 100% mortality of weeds was 24 h for methyl iodide fumigation and 36 h for methyl bromide when 200 μM of fumigant was used. On a molar basis methyl iodide was consistently more effective than methyl bromide across the range of environmental factors tested. In terms of application technology and spectrum of activity, methyl bromide can be directly replaced by methyl iodide. © 1998 SCI     

Identification of economically important Liriomyza species by PCR‐RFLP analysis*

Only adult males of Liriomyza bryoniae, L. huidobrensis, L. sativae and L. trifolii can be identified with certainty on basis of their genitalia. Female adults, pupae and larvae can only be identified on the level of groups of species (L. bryoniae and L. huidobrensis vs. L. sativae and L. trifolii). Species identification in all developmental stages is possible using molecular biological techniques. Our method is a PCR amplification of a 790‐bp fragment of mitochondrial cytochrome oxidase II (COII) DNA followed by RFLP analysis. The method was tested on single larvae, pupae and adults and proved to be applicable to these three life stages. The specificity of the assay was assessed by comparing the results of the PCR‐RFLP analysis with those of morphological analysis using 60 Liriomyza specimens. Molecular and morphological identification agreed for all specimens analysed. PCR‐RFLP is a powerful diagnostic tool for rapid and reliable identification of all life stages of economically important Liriomyza species.     

Use of heat for disinfestation and control of insects in dates: Laboratory and field trials

Heat treatment of dates at the time of harvest, was examined as an alternative to fumigation with methyl bromide, which has been phased out in Israel under the Montreal Protocol. In laboratory studies, the influence of 40°, 45°, 50° and 55°C on the levels of disinfestation and mortality ofCarpophilus hemipterus larvae was examined over a 2-h exposure period. The ratio of the number of insects found outside the feeding sites to the total number of insects, was greatest at 50°C (92.3%), significantly greater than at 40° and 55°C. At 50° and 55°C, 100% mortality was obtained. Since drying temperatures for most date varieties is between 45° and 50°C, and because percent disinfestation and control was most effective at 50°C, these findings were examined under field conditions. Field trials were carried out at a commercial drying station where the crated dates are placed on the ground inside a plastic-clad hothouse. The stacks were covered with plastic liners to form ‘drying ducts’ through which heated air was sucked using fans positioned at the opposite end of the ducts. It was shown that from 1 to 2 h were required for the dates to reach the set temperature of 50°C. During the following 2-h aeration, the dates were exposed to 50°C heated air, after which an examination of infested dates inserted into the drying ducts, and natural infestations showed that successful control and emigration were obtained. This method produced results comparable to those obtained with methyl bromide fumigation, and was suitable as a replacement technology for infestation control. http://www.phytoparasitica.org posting Nov. 7, 2005.     

Effects of low temperatures on pupal survival of the stone leek leafminer Liriomyza chinensis (Diptera: Agromyzidae)

Abstract

The cold-hardiness of Liriomyza chinensis pupae was measured in the laboratory by observing pupal mortality at low temperatures. Pupal mortality increased with decreasing temperature and with extended cold exposure time. No recently pupated pupae (6 h) were able to survive after 16 days of chilling at 0, 2.5 and 5°C, but 42.9% survival was observed at 10°C. Pupae at different developmental stages showed significant difference in mortality, with very low levels of mortality observed for older pupae (4 and 7 days) after exposure to 0°C for 16 days. The lethal time for 50% survival (LT₅₀) increased with increasing age of pupae. LT₅₀ for 4-day-old pupae exposed to 0°C was 52.1 days. Analysis of mean temperatures at several localities indicated that L. chinensis is able to overwinter outdoors in southern regions, but is unable to overwinter in open fields in northern regions of Japan, suggesting that overwintering in these regions would only occur in greenhouses.     

Residues in apples and sweet cherries after methyl bromide fumigation

Methyl bromide fumigations are used to treat apples, Malus domestica Borkh, and sweet cherries, Prunus avium (L), before export to Japan. In order to expand existing markets, additional cultivars are being prepared for export to Japan. As part of the approval process, residue analyses must be conducted and residues must be at acceptable levels. Five apple cultivars (‘Braeburn,’ ‘Fuji,’ ‘Gala,’ ‘Jonagold,’ and ‘Granny Smith’) were fumigated at 40 g m⁻³ for 2 h at 10 °C, and six sweet cherry cultivars (‘Brooks,’ ‘Garnet,’ ‘Lapin,’ ‘Rainier,’ ‘Sweetheart,’ and ‘Tulare’) were fumigated for 2 h with 64 g m⁻³ at 6 °C, 48 g m⁻³ at 12 °C, 40 g m⁻³ at 17 °C, and 32 g m⁻³ at 22 °C. Three replicates of fruit from each fumigation were analyzed for methyl bromide and bromide ion residues periodically with time. Methyl bromide residues for both apples and cherries were the highest immediately after fumigation, but rapidly declined so that only ‘Braeburn’ had residues >8 µg kg⁻¹ after 13 days and, except for ‘Lapin,’ all cherries were <1 µg kg⁻¹ after seven days. Average bromide ion residues were between 3.3 and 4.9 mg kg⁻¹ among apple cultivars, and between 3.7 and 8.0 µg kg⁻¹ among cherry cultivars. Published in 2000 for SCI by John Wiley & Sons, Ltd     

Effect of temperature on the toxicity of low concentrations of methyl bromide to diapausing larvae of the warehouse moth Ephestia elutella (Hübner)

The performance of low concentrations of methyl bromide against diapausing larvae of Ephestia elutella at 15 and 25°C was assessed in extended exposure periods. At concentrations of 1.9 mg litre^?1 and below, test batches required higher concentration-time (ct) products for 100% kill at 25°C than at 15°C. The minimum concentration at which the concentration: time relationship still applied was between 1.3 and 1.9 mg litre^?1 at 15°C, whereas at 25°C it was between 2.7 and 4.0 mg litre^?1. For many individuals within each population sample, however, lower concentrations at moderate dosage levels remained lethal. At 25°C, a ct product of about 90 mg litre^?1 h gave between 53 and 77% kill at 6.1, 4.0, 2.7 and 1.9 mg litre^?1. The trends observed suggest that the most tolerant members of the population have an enhanced ability to detoxify methyl bromide at the higher temperature. The implications of the results for the build-up of resistance and for practical control measures are discussed.     

Effect of gamma radiation on sterility ofliriomyza trifolii flies

The effect of low doses of gamma radiation applied toLiriomyza trifolii Burgess eggs or 1st-instar larvae, on the ensuing flies was studied. Doses of 50 or 40 Gy resulted in very few individuals reaching the adult stage; the life span of these flies was very short and they did not breed. A 25-Gy dose applied at the 1st instar allowed the development of many individuals into adults which emerged successfully, fed, and oviposited viable eggs which completed their development to adults. Contribution from the Agricultural Research Organization. No. 3024-E, 1990 series.     

Efficacy of methyl iodide and synergy with chloropicrin for control of fungi

Efficacy of soil fumigation with methyl bromide and methyl iodide against Botrytis cinerea, Colletotrichum gloeosporioides, Fusarium oxysporum, Gliocladium virens, Phytophthora citricola, Phytophthora citrophthora, Pythium ultimum, Rhizoctonia solani and Verticillium dahliae was determined in laboratory experiments in closed fumigation chambers. Pythium ultimum was the most sensitive fungal species with EC₅₀ values for methyl bromide and methyl iodide of 15.5 and 8.6 µM , respectively. R solani was the least sensitive with EC₅₀ values of 253.4 and 161.4 µM for methyl bromide and methyl iodide, respectively. Relative potency ([methyl bromide]/[methyl iodide]) values ranged from 5.2 for P citricola to 1.5 for F oxysporum. Methyl iodide was 2.7 more efficacious than methyl bromide averaged over all fungal species. Methyl bromide/chloropicrin and methyl iodide/chloropicrin applied jointly were 2.2 and 2.8 times more efficacious, respectively, against F oxysporum than when the compounds were applied singly. Combining methyl bromide and methyl iodide with chloropicrin resulted in a significant synergistic increase in activity against F oxysporum. © 2000 Society of Chemical Industry     

Development of a fumigation treatment of oak logs against Ceratocystis fagacearum1

European veneer manufacturers depend greatly on oak imports from the USA. To prevent the accidental introduction of the American oak wilt disease (Ceratocystis fagacearum) into the member states of the European Community, a disinfection treatment was developed for oak logs with respect to the special demands of the veneer industry. Laboratory experiments and field trials in Europe and the USA showed that the fungus can be eradicated from large oak logs with bark attached, by a fumigation with 240 g methyl bromide/m³ applied for 3 days at temperatures of 3°C or above.     

The newest leafminer pest in Israel,Liriomyza huidobrensis

The pea leafminer,Liriomyza huidobrensis (Blanchard), recently introduced into Israel, has proven to be extremely proliferous and difficult to control. It is a much more serious pest of vegetable and flower crops than the previously introducedLiriomyza trifolii (Burgess). Photosynthesis is reduced and cosmetic damage is incurred when adult flies stipple plant leaves with feeding punctures and larvae mine the leaves. This paper will review briefly the history, biology and potential control measures of the pea leafminer.     

Effect of short exposures to a high concentration on the subsequent toxicity of low concentrations of methyl bromide to diapausing larvae of the warehouse moth,Ephestia elutella (Hübner)

Ephestia elutella larvae in diapause were exposed at 25°C to methyl bromide at 12 mg litre^?1 for 3.5 or 7.5 h and then immediately exposed to a lower concentration. The minimum effective concentration (that at which Haber's rule, concentration × time = k, a constant for mortality, still applied) was about 3 mg litre^?1 in tests with no previous exposure toa high concentration, but it was about 2.5 mg litre^?1 for individuals surviving a 3.5 h exposure to 12 mg litre^?1, and was about 1.6 mg litre^?1 for those surviving a 7.5 h exposure to 12 mg litre^?1. These exposures to 12 mg litre^?1, respectively, killed 2–20% and 50–75% of larvae exposed, and hence the smaller the proportion of survivors of exposure to a high concentration, the lower the minimum effective concentration needed against them. Thus the low concentration persisting at the end of a practical fumigation should contribute significantly to the success of the treatment and be much more effective than any similar low concentration present soon after the introduction of gas.     

Temperature-dependent development of Agrotis ipsilon (Lepidoptera: Noctuidae) and its stage transition models

The black cut worm Agrotis ipsilon (Hufnagel) is a destructive crop pest worldwide and a typical cut worm damaging plant parts below the soil surface, which requires a thorough phenological prediction of the target stage for proper management. Temperature is an essential factor affecting the phenology and dynamics of insect populations. So, this study was conducted to evaluate the temperature-dependent development of A. ipsilon fed on Kimchi cabbage (Brassica campestris) in a wide range of temperatures (10 to 40 ℃) in the laboratory. The linear and nonlinear relationship between temperature and development rate (1/development time) was analyzed. The lower threshold temperatures (LT) for eggs, larvae, and pupae were estimated to be 12.1 °C, 9.6 °C, and 11.2 °C, respectively, with thermal constants (degree days for development completion) of 31.3, 342.2, and 181.3 DD at each stage, respectively. Additionally, the thermal constant for tracking the phenology of each stage was determined using a common LT of 10.4 ℃: 40.3 DD for eggs, 315.6 DD for larvae, and 199.6 DD for pupae. Consequently, we provided newly the stage transition models for all stages of A. ipsilon using two basic components of the nonlinear development rate and distribution models to simulate the proportion of individuals shifted from one stage to the next stage. These models in their current form will be useful for constructing a population model for A. ipsilon in the future. Furthermore, the variation in the development time of A. ipsilon reported in previous studies was discussed using 95% confidence limits of the estimated line of our nonlinear models.

     

Responses of phosphine-resistant strains of two stored-product insect pests to changing concentrations of phosphine

Abstract: The susceptibility of eggs, pupae and adults of Tribolium castaneum (Herbst) and adults of Rhyzopertha dominica (F.), (both phosphine-resistant strains) to phosphine at fixed concentration-time (ct) products, with either constant or increasing or decreasing concentrations was studied at 25 (± 1)°C. At lower ct products, falling concentrations of phosphine generally caused reduced insect mortality in all the three exposure periods in the range 12 to 72 h. However, in R. dominica, both increasing and decreasing concentrations were less effective than constant concentrations. At higher ct products, no significant change in the mortality response was observed in either species after exposure to constant or changing concentrations. The findings indicate the need to maintain sufficiently high concentrations of phosphine until the end of the fumigation period.     

溴甲烷、环氧乙烷真空熏蒸杀虫灭菌技术研究

真空情况下,利用溴甲烷、环氧乙烷杀虫、灭菌是一种安全、快速、有效的技术措施。为了使此技术广泛应用到农林种子、苗木、卫生防疫以及文史资料诸方面杀虫灭菌,试制成功一台容积工立方米的PCV-1000程序控制真空熏蒸机,并进一步进行溴甲烷、环氧乙烷杀虫灭菌效果及其熏蒸后残余毒气处理方法的研究。溴甲烷75—90克/立方米处理2小时,环氧乙烷90—120克/立方米处理3小时,可杀死各种形式的包装内的谷斑皮蠹和花斑皮蠹幼虫,赤拟谷盗和锈扁谷盗成虫以及玉米象和绿豆象各虫态等害虫。环氧乙烷灭菌能力较强,对动物炭疽菌、4001芽孢杆菌500克/立方米处理5小时或300克/立方米处理12小时,灭菌效果100%。溴甲烷和环氧乙烷混合使用对棉花枯萎病菌效果良好,对棉籽发芽率影响不大。熏蒸后残余毒气处理,用5%氢氧化钠酒精液吸收溴甲烷,破坏率可达96%以上。环氧乙烷用自来水淋洗法,水合分解率可达98%以上。     

The toxicity of phosphine,methyl bromide, 1,1,1-trichloroethane and carbon dioxide alone and as mixtures to the pupae of red flour beetle,Tribolium castaneum herbst

The toxicity of phosphine, methyl bromide, 1,1,1-trichloroethane (methyl chloroform) and carbon dioxide and mixtures of phosphine + methyl bromide, methyl bromide + methyl chloroform, phosphine + carbon dioxide, and methyl bromide + carbon dioxide to one- to two-day-old pupae of Tribolium castaneum Herbst was studied. Joint action ratios estimated at LD₅₀ and LD₉₀ for a 24-h exposure indicated no enhancement of toxicity for mixtures of phosphine and methyl bromide, or methyl chloroform and methyl bromide on the pupae. Carbon dioxide up to 40% in air enhanced the toxic action of phosphine as well as of methyl bromide. Higher levels of carbon dioxide, however, failed to improve the toxicity of phosphine or methyl bromide proportionately. Carbon dioxide used alone produced a maximum of 11% mortality of the pupae exposed to 10–70% levels for 24 h. The order of toxicity of the fumigants both at LD₅₀ and LD₉₀ was phosphine > methyl bromide > methyl chloroform.     

Zur Kenntnis der Blattminen-MotteCameraria ohridella Desch. & Dim. (Lep., Lithocolletidae) anAesculus hippocastanum L. in der Tschenchischen Republik

Cameraria ohridella was recorded first in 1985 in Macedonia. It gradually expanded to north and west and at present it is a serious pest of Horse ChestnutAesculus hippocastanum in the Czech Republic, having been established at about 80 localities. There are 4–5 overlapping generations with sizes of the larvae of 0.4–4.0 mm. The larva develops inside the leaf tissue in the upper parenchym layer of the leaflet and causes a mine, the size of which is broadened with growing larva. First adults start to fly at the end of April. After mating the females lay single eggs on the leaves. Larval development lasts 25–30 days followed by the prepupa I and II. The latter spins a cocoon in which the pupa of the last generation hibernates. The development from L4 to the prepupa lasts for 3–6 days at 22°C. During the summer it is possible to find all larval and prepupal stages in attacked leaves. FourAesculus species:A. parviflora Walk,A. carnea Haey.,A. glabra Walk andA. indica J. Hobb. were found to be resistent toC. obridella. A. lutea H. J. was liftle andA. pavia L. was heavily attacked. The parasitization ofC. o. larvae was very low. Only 2 parasites were found in 1500 mines in the first and second generation ofC. o., and 40 parasites in 1000 mines of the fourth and fifth generation. The highest mortality takes place in moths, eggs and young larvae. It was found in all 4 generation that there were i. m. 50 eggs/leaflet from which i. m. 3 hibernating pupae resulted. Supposing 2 moths (1♀, 1♂)/leaflet emerged in spring which produced 50 eggs (75 eggs/♀—33% moth mortality), the density of eggs in the first generation after hibernating being the same as in the last (fourth) generation before hibernating. As to the whole populations density in this case we can calculate as following: 3 pupae/leaflet on the tree=3000 pupae/leaflets pro m² on the soil=2000 emerging moths pro m²=50,000 moths (25,000 ♀♀) pro tree (namely 25 m² projecting area of the tree crown×2000 moths).      

Toxicity of methyl bromide to soil-borne fungi

Nineteen fungal isolates, mostly plant pathogens cultured on agar, were subjected to fumigation with methyl bromide at known concentration x time product (CTP, concentration in mg/1 x time in h) in a fumigation chamber at controlled temperature. Survival of the fungi was determined by sub-culturing on fresh agar. An order of methyl bromide tolerance of the fungi was cetermined and it was shown that at low concentrations of the fumigant, prolonged exposure, to give a normally toxic CTP, did not kill important soil-borne pathogens. The implication of this in relation to field fumigations is discussed.