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1.
The effect of different doses 5, 10, 15, 30, 40 and 50 KR of gamma irradiation on the infectivity ofSteinernema feltiae Filipjev nematode has been studied. It was found thatS. feltiae was inactivated by gamma irradiation. Motility of nematodes as well as the mortality and infestation intensity of the host decreased at the higher doses. Development of nematodes was inhibited at the highest dose. No reproduction of nematodes occurred with any of gamma irradiation doses.  相似文献   

2.
Ten Egyptian and imported entomopathogenic nematodes were evaluated for their pathogenicity to R. ferrugineus in both the laboratory and the field. In the laboratory, most nematodes were pathogenic to the pest larvae, pupae and adults. Larvae and adults were more susceptible to nematode infection (mostly 100?% mortality) than pupae enclosed in their cocoons. In the field however, the highest insect larval mortality was 66.67?% and most of nematodes failed in controlling the pest. Such failure could be due to hot weather, the tunnelling behaviour of the pest larvae and the too much sap in the infested sites in the trunks of palm trees.  相似文献   

3.
We report the results of experiments conducted with Ephestia kuehniella Zeller to determine the effects of gamma radiation on life stages. Eggs, larvae, pupae and adults were irradiated with increasing doses of gamma radiation (seven dose levels between 50 and 400 Gy for eggs and larvae, six dose levels between 50 and 350 Gy for pupae and four dose levels between 250 and 550 Gy for adults). All the experiments were conducted in a growth chamber maintained at 27 ± 1°C, 65 ± 5% r.h., and alternating 14 h light:10 h dark cycles. The number of adults that developed from irradiated eggs and larvae was lower than the untreated control. Doses of 200 Gy and above prevented adult emergence from irradiated eggs. Although a dose of 200 Gy was enough to prevent adult emergence from young larvae, 250 Gy should be used to prevent adult emergence completely from last instar larvae. Delayed developmental periods were observed for the treated eggs and larvae. Fecundity and egg hatchability were decreased depending on the doses applied. Decreased fecundity and egg hatchability were more prevalent when both the male and female pupae were treated compared to the treatment of female pupae only. There was no significant decrease in the fecundity of irradiated adults except 550 Gy, and no eggs hatched at doses of 300 Gy and above.  相似文献   

4.
E. Asai  K. Futai 《Forest Pathology》2005,35(2):135-144
Six‐month‐old Japanese black pine seedlings (Pinus thunbergii) were exposed to simulated acid rain (SAR) at pH 3 and 2 three times a week. After treatment for 2 months, the seedlings were inoculated with a virulent isolate (S10) of the pinewood nematode (Bursaphelenchusxylophilus), at three inoculum levels (Pi = 50, 160 or 500 nematodes per seedling). In seedlings inoculated with 500 nematodes, both population growth of nematodes and disease development were accelerated by pretreatment with SAR at pH 3 or 2. In seedlings inoculated with 50 nematodes, population growth of the nematodes was suppressed and more time was needed for seedlings to die when pretreated with pH 3 SAR. This suggests that exposure to pH 3 SAR increased not only the progress of mortality, but also simultaneously enhanced the tolerance limit of the seedlings to the pinewood nematode – the critical value of physiological burden (represented as a product of time and initial nematode population) necessary to kill a seedling. Exposure to pH 2 SAR accelerated nematode reproduction in seedlings and increased seedling mortality irrespective of the number of nematodes inoculated.  相似文献   

5.
The entomopathogenic nematodeHeterorhabditis bacteriophora Pionar (HP 88) and the bacteriumBacillus thuringiensis Berliner var.kurstaki were tested in the laboratory against the black cutworm, a widely distributed polyphagous insect pest of vegetables and field crops. The experiment was conducted under 15.7 °C (14 to 19 °C) to simulate the average winter temperature in Egypt. The two biocontrol agents influencedAgrotis ipsilon differently whereH. bacteriophora had a more promising control levels than that ofB. thuringiensis. Generally, nematode concentration of ca 500 infective juveniles/insect vial was highly effective (100% mortality) within nine days post nematode infection. The highest concentration of the bacteriumB. thuringiensis var.kurstaki (2,000 Intern. Units/mg) gave significant larval control after 12 days of bacterial infection. Combined effect of both the nematodes and the bacteria did not result in significantly greater control than that achieved by the nematodes used alone. The present results indicated that nematodes could be used successfully against the black cutworm,Agrotis ipsilon larvae during the winter which is the active season of this insect pest in Egypt.  相似文献   

6.
Laboratory experiments were carried out in Egypt to investigate the stimulatory effects of gamma radiation on theBombyx mori eggs (at late stage of development) with a view to possible improvement in silk production. Five doses of gamma radiation ranging from 0.01 to 1 Gy were applied. The greatest effect was achieved at a dose of 1 Gy as shown by significant increase of the larvae weight and their silk gland by 21.96 and 30.14%, the cocoon weight and their shell by 11.11 and 9.76%, the length of silk filament and its weight by 22.96 and 22.53% over the control. However, egg irradiation favourably influenced the fecundity of emerged adults.With one figure and one table  相似文献   

7.
[目的]日本学者Kosaka与Ogura发现松褐天牛成虫除携带松材线虫外,雌成虫卵巢内还携带有另一种线虫,他们将其命名为卵巢线虫,并认为这种线虫是松褐天牛成虫的寄生性线虫。我国对该种线虫的研究迄今未见报道。为了证明这种线虫在我国是否存在和分布,开展了本项研究。[方法]分期分批捕获刚羽化的松褐天牛雌雄成虫,采用解剖松褐天牛成虫松树木质部及感病的松褐天牛幼虫等方法,调查卵巢线虫的存在与分布。[结果]通过调查研究,发现我国的松褐天牛成虫体内有该卵巢线虫存在,分布于松褐天牛成虫、幼虫体内和松树木质部3个部位;在松褐天牛成虫体内的卵巢线虫通过松褐天牛雌成虫产卵而接种、进入寄主树木木质部中。同时,木质部的卵巢线虫也有一部分进入松褐天牛幼虫体内寄生,另一部分仍在木质部生活,当松褐天牛幼虫再次发育为成虫时,在木质部中的卵巢线虫和已被寄生的松褐天牛幼虫体内的卵巢线虫再次进入松褐天牛成虫体内,完成循环。卵巢线虫在松褐天牛雌、雄虫体内均有分布,携带率为44.4%,其中松褐天牛雌成虫携带率为43.8%,松褐天牛雄成虫携带率为45.0%,两者间无显著差异;每头松褐天牛成虫平均携带卵巢线虫574条,其中雌成虫平均携带816条,雄成虫平均携带308条,具显著差异。初步研究表明,卵巢线虫在松褐天牛成虫体内只能完成产卵到1~4龄的幼虫阶段,不能完成一个完整的世代;在松褐天牛幼虫体内寄生和在木质部生活的卵巢线虫能完成一个完整世代,但具体过程尚不清楚;调查中未观察到卵巢线虫对松褐天牛成虫有寄生致病或致死的现象,但对松褐天牛幼虫有寄生致死的能力;卵巢线虫常与松材线虫同时存在,而且侵入松树及离开松树的方式与松材线虫相同。[结论]我国松褐天牛体内也发现有卵巢线虫存在;目前尚不能证明该线虫对松褐天牛成虫具有寄生致死性,但对松褐天牛幼虫具有一定的寄生致死性;卵巢线虫的生活史与松材线虫相似,是否与松材线虫一样对松树具有危害性以及其病理作用还有待于进一步研究。  相似文献   

8.
The ability of the pine wood nematode,Bursaphelenchus xylophilus, a pathogen that causes pine wilt disease, to kill cortical cells of Japanese black pine,Pinus thunbergii, during early development of the disease was conjectured to be a function of nematode developmental stage. A tangential segment of bark was removed from a 2-cm-long current-year stem. The cortex-exposed segments with cut cortical resin canals were designated as + RC-segments and those without them as − RC-segments. When a nematode population containing many older juveniles and adults (NL) was inoculated onto the cut surface, the − RC-segments were still alive 4 d after inoculation, as were non-inoculated control segments. When cortex-exposed segments were inoculated with either a nematode population containing many younger nematodes (NS) or with nematodes isolated from inoculated pine cuttings that also contained many younger juveniles, most tissue cells in − RC-segments died 4 d after inoculation, suggesting that younger juveniles killed pine cells directly, in contrast with older juveniles and adults. When nematodes were inoculated onto + RC-segments in which they could easily enter resin canals, both NL and NS killed the segment tissues. This suggests that NL is pathogenic to pine cells while living in resin canals. Such differences in the pathogenicity of NL and NS to pine parenchymatous cells were also demonstrated in a pathogenicity assay system using bark peelings, which allowed an estimate of direct attack on the cambial cells by nematodes. Based on these results, we hypothesize that younger juveniles are pathogenic to pine parenchymatous cells, while adults and older juveniles are not pathogenic. This work was supported in part by Grants-in-Aid for Scientific Research (No.01440012 and 06454088) and for Young Scientists (to K.I.) from Ministry of Education, Science, Culture, and Sports of Japan, and by a grant from PROBRAIN.  相似文献   

9.
The pinewood nematode (PWN) Bursaphelenchus xylophilus is an invasive pathogen that was introduced from North America to Asian countries and Portugal and is devastating native pine forests. Some native European and Asian Bursaphelenchus nematodes also have weak to moderate pathogenicity to native pine species. To evaluate the potential risk of native Bursaphelenchus species, we inoculated ten Japanese Bursaphelenchus species into native pine species (the dominant forest species) in Japan, and evaluated their pathogenicity using mortality and tracheal tissue damage as indices. Inoculation was conducted on August 3, 2007, and the symptoms were observed every 2 weeks until February 1, 2008. None of the inoculated trees, excluding the pathogenic PWN inoculated control, showed external disease symptoms; however, four species [a less pathogenic PWN isolate, B. luxuriosae, Bursaphelenchus sp. NK215 (undescribed), and NK224 (undescribed)] caused tracheal tissue damage in inoculated seedlings and showed weak pathogenicity. Therefore, we conclude that there are some potentially pathogenic native species of nematodes distributed in Japan. Interestingly, two of these weakly pathogenic species, B. luxuriosae and NK215, are not associated with Pinaceae trees, suggesting that nematode pathogenicity may be a pre-adaptive character. More experimental studies under different conditions are necessary to accurately evaluate the potential risk of these pathogens.  相似文献   

10.
Toxicity of ivermectin (Ivecop-12), a derivative of avermectin B, produced by a soil actinomycete, Streptomyces avermitilis, was evaluated in laboratory against the larvae of Spirama retorta Cramer (Lepidoptera: Noctuidae), a major stenophagous insect defoliator of Albizia spp. (family Leguminosae) in nurseries and young plantations. The study was conducted with eight treatment concentrations of lethal and sub-lethal doses. Results revealed that ivermectin is highly toxic and induce larval mortality when applied separately on host plant leaves and larvae, and on leaves and larvae of the insect pest together. The nature of treatment affects the larval mortality. Treatment of host plant leaves alone as well as leaves together with larvae showed 100% mortality by the treatment of 0.075% concentration whereas only 95% larval mortality was recorded due to larval treatment by the concentration of 1.2%. The LC50 value of the tested product was worked out to be 0.014, 0.170 and 0.012% for leaf and larval treatments separately and leaf and larval treatments together, respectively, against the insect pest. This clearly shows that ivermectin is more effective in larval killing when ingested through food. Further, the adults developed from treatments of sub-lethal concentrations and subsequently, when mated laid significantly (P < 0.05–0.01) less number of eggs and also showed significant (P < 0.05–0.01) reduction in hatching percentage compared to control. These observations suggest that the tested bioproduct, ivermectin, interfere physiological programming of larvae thereby causing alteration in fecundity and fertility of the target insect pest.  相似文献   

11.
The efficacies of four strains of entomopathogenic nematodes on infecting and killingSpodoptera littoralis were tested in the laboratory concerning soil temperature, nematode dose and emergence from the insect cadavers. All the tested nematodes attained almost 100% insect mortality at 4, 10 and 25 °C but at 35 °C,Heterorhabditis bacteriophora (HP88) achieved the least (64%). As soil temperature rise to 35 °C, the most adversely affected nematode in terms of recycling efficiency wasH. bacteriophora (EASD98) followed bySteinernema riobravis, H. bacteriophora (HP88) and finallyH. indicus (EAS59). Although all nematodes could infect and kill the host insects at 35 °C, those ofH. bacteriophora (EASD98) could not emerge from the cadavers. Differences in the numbers of emerging infective juveniles as related to nematode concentration and different degrees of soil temperatures were obvious and may be considered in developing a biocontrol strategy for the management of the cotton leaf-worm.With 4 tablesThis research was supported by the NARP project No. H-035 and is a part of a M. Sc. thesis by Mr. Atwa Ahmed Atwa.  相似文献   

12.
Susceptibility of various stages of Calloso-bruchus maculatus F. to Gamma radiationLarvae and pupae of the southern cowpea weevilC. maculatus were exposed to gamma radiation from a co 60 source.All the fully grown larvae ofC. maculatus when exposed to gamma radiation (3000 rad) died before adult emergence. Larval irradiation decreased fecundity and longevity of the resulting adults.The results indicated thatC. maculatus was more resistant to irradiation injury when irradiated in the pupal stage than when irradiated at earlier stages. Adults exposed to 3000 rad in the pupal stage were completely sterile.  相似文献   

13.
A study was made on the susceptibility of the cotton leafworm, Spodoptera littoralis (Biosd.), to the nematode, Steinernema carpocapsae (All) and Heterorhabditis bacteriophora. Three concentrations of each nematode species were used (75, 150, and 300 infective juveniles) for each treatment. The nematode, H. bacteriophora, gave 100% mortality 96, 90, and 48 h, respectively, post-treatment of S. littoralis larvae with 75, 150, and 300 infective juveniles. On the other hand, S. carpocapsae (All) gave 100% mortality 120, 90, and 56 h post-treatment, respectively. Therefore, H. bacteriophora was more potent against cotton leafworm than S. carpocapsae. Studies on the infestation intensity of the nematode species against the cotton leafworm showed the predominance of H. bacteriophora over S. carpocapsae, while in studies of the reproductive rate those of S. carpocapsae predominate. The bacterial symbionts of each nematode species were isolated and tested alone against cotton leafworm at concentrations ranging between 1×102 and 5×103 bacterial cells/larva. The results showed a higher activity of Photorhabdus luminescens than that of Xenorhabdu nematophilus.  相似文献   

14.
A foliar nematode, Litylenchus crenatae ssp. mccannii, is associated with beech leaf disease (BLD) symptoms. Information about the types of tissues parasitized and how nematode populations fluctuate in these tissues over time is needed to improve surveys as well as understand the nematodes role in BLD. During this study, the nematode was detected throughout the known range of BLD by researchers at both Canadian and US institutions using a modified pan method to extract nematodes. Monthly collections of symptomatic and asymptomatic leaves during the growing season (May–October), and leaves and buds between growing seasons (November–March), revealed that nematodes were present in all tissue types. Progressively larger numbers of nematodes were detected in symptomatic leaves from Ohio and Ontario, with the greatest detections at the end of the growing season. Smaller numbers of nematodes were detected in asymptomatic leaves from BLD‐infected trees, typically at the end of the growing season. The nematode was detected overwintering in buds and detached leaves. The discovery of small numbers of nematodes in detached leaves at one location before BLD was detected indicates that nematodes may have been present before disease symptoms were expressed. Other nematodes, Plectus and Aphelenchoides spp., were infrequently detected in small numbers. Our findings support the involvement of the nematode in BLD and indicate that symptoms develop only when certain requirements, such as infection of buds, are met. We also found that the nematode can be reliably detected in buds and leaves using the modified pan extraction method.  相似文献   

15.
The major bioecological characteristics of Bracon intercessor Nees (Hymenoptera: Braconidae), a parasitoid of the poplar clearwing moth, Paranthrene tabaniformis (Rott.) (Lepidoptera: Sesiidae), were studied from 1987 to 2003. Poplar shoots infested with P. tabaniformis larvae were collected in 11 localities in Bulgaria and examined in the laboratory, and infestations were also studied in the field. B. intercessor was recorded in seven localities and was found to be a gregarious external larval parasitoid of P. tabaniformis. Two generations of the parasitoid developed on the host. The first (summer) generation was associated with early and mid-stage (up to third instar) host larvae, and the second (overwintering) generation with third- to fifth-instar larvae. The average number of parasitoid individuals feeding on a host was 4.5 and 12.4 in summer and overwintering generations, respectively. The maximum number recorded was 25 individuals per host in the overwintering generation. B. intercessor overwintered as a mature larva on the host and completed its development in early spring. The adults from the overwintering generation appeared in April, about 1 month prior to emergence of P. tabaniformis. The life cycle of B. intercessor was not in close synchrony with the development of P. tabaniformis in the spring, but the parasitoid adults which fed on honey-sugar solution lived for up to 31 days (males) and 86 days (females), respectively. This suggests that, in the field, B. intercessor females eclosing in the spring could survive until the host larvae appear if nectar is available. Adults of the summer generation emerge from July to September when sufficient suitable host larvae are available. B. intercessor was responsible for 1.5% of the average mortality of the P. tabaniformis overwintering larvae. The host mortality caused by the summer generation of the parasitoid ranged from 3.2% to 5.8%.  相似文献   

16.
H. Zhao  C. Chen  S. Liu  P. Liu  Q. Liu  H. Jian 《Forest Pathology》2013,43(6):444-454
To assess the role of bacteria in pine wilt disease (PWD), aseptic M form (with a mucronated tail) and R form (with a round tail) of Bursaphelenchus xylophilus and B. mucronatus were obtained and compared, in terms of reproduction and pathogenicity, with non‐aseptic nematode. In addition, bacteria isolated from non‐aseptic nematodes and pine trees inoculated with non‐aseptic nematodes were identified. The results indicated that the bacteria associated with nematodes significantly lowered the reproduction of R form of B. xylophilus and B. mucronatus. Both the non‐aseptic and aseptic R forms of B. xylophilus induced death in all infected 7‐ to 8‐year‐old pine trees, while the non‐aseptic and aseptic M forms of B. xylophilus and B. mucronatus caused almost no plant mortality. High numbers of the non‐aseptic and aseptic R forms of B. xylophilus were distributed throughout the inoculated trees, while B. mucronatus and M form of B. xylophilus nematodes were lower in number and their distribution in stems limited within the inoculation site. Bacteria isolated from non‐aseptic nematodes were not recovered from the pine trees inoculated with these same kinds of nematodes. Two species of bacteria were both isolated from non‐aseptic B. mucronatus and from R form of B. xylophilus. Microbacterium trichotecenolyticum was common to both the control and inoculated pine trees. These results suggest that R form of B. xylophilus is the causal agent of PWD and that bacteria cannot increase the virulence of B. xylophilus and B. mucronatus.  相似文献   

17.
病虫害影响竹子生长,制约着竹林产业发展。由于植物线虫病害症状比较隐蔽,植物线虫对竹林的影响通常难以评估且容易被忽视。本文对国内外竹子线虫的种类、分布和寄主等方面进行了综述。全世界已报道竹子寄生线虫82种,隶属于4目、12科、29属,其中,国内报道了竹子线虫36种;美国和印度的竹子寄生线虫比较丰富,分别报道了38种和20种。植物线虫对竹子的致病性研究较少,印度报道了植物线虫对竹子造成的损失,美国报道了2种寄生线虫侵染竹子的组织病理学研究。本文对我国竹子寄生线虫研究的方向进行了探讨,为今后竹子寄生线虫研究和防治工作提供重要参考。  相似文献   

18.
Any means helpful for the promotion of termite feeding activity has potential for use in a matrix in termite bait application. Therefore, energy transfer by gamma irradiation is worthy of consideration for converting wood into termite-accessible material. Wood specimens gamma-irradiated at 100 kGy and at lower levels were tested for their degrees of polymerization (DP) of cellulose and biological resistance. The DP of cellulose adversely decreased with increased doses of gamma irradiation. Termite wood consumption rates, which were determined by laboratory tests using undifferentiated larvae (workers) of Coptotermes formosanus Shiraki, were significantly higher at 100 kGy than at other doses. On the other hand, the decay resistance of gamma-irradiated wood against the fungi Fomitopsis palustris (Berkeley et Curtis) Murrill and Trametes versicolor (L. ex Fr.) Quel did not vary by irradiation dose.  相似文献   

19.
The effect of gramma radiation on the rice weevil,Sitophilus oryzae (L.) was studied. Adults were subjected to 12 doses ranging from 0 to 180 Gy of gamma radiation from a60Co source. The time to onset of death and the duration of the period of mortality were investigated. Survival of the adults was decreased with increase of the doses. LD50 and LD99,9 values were calculated.With one figure and one table  相似文献   

20.
本文报道应用昆虫病原线虫Steinernema spp.室内对木麻黄毒蛾的侵染能力。通过斯氏属九个线虫品系对木毒蛾的侵染力测定筛选出S.feltiae Agriotos为最佳品系;能寄生低、中、高龄幼虫及蛹;可在3天内把害虫致死。供试的其它八个线虫品系也能不同程度地致死害虫,并在死虫体内繁殖。S.f.Agriotos线虫的剂量对木毒蛾的致死速度及效果有影响,以1000条线虫/害虫侵染期线虫为最适宜剂量,林间对木毒蛾幼虫的致死率平均为89.6%。  相似文献   

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