Effects and mode of action of some plant extracts on certain plant parasitic nematodes

Exposure to standard solution S extract ofPunica granatum, Thymus vulgaris andArtemisia absinthium for 72 h reduced the numbers of active nematodes by 100% forMeloidogyne incognita and by 95.7%, 71.4% and 42.9% forHelicotylenchus dihystera, respectively. Exposure to S/2 dilutions for 72 h reduced nematode motility by 100%, 77.3 and 72.7% forM. incognita, and by 92.9%, 37,1%, and 37,1% forH. dihystera, respectively. As exposure to S and S/2 extracts ofCitrullus colosynthis andRicinus communis reduced nematode motility by less than 32% forM. incognita and by less than 30% forH. dihystera. WhenM. incognita andH. dihystera were transfered to water for 72h, more than 85% of the individuals resumed normal movement at all extract dilutions except S ofA. absinthium andT. vulgaris and S and S/2 ofP. granatum. However, recovery ofM. incognita was more less than that ofH. dihystera. Exposure to S extracts ofP. granatum andT. vulgaris for 30 days reduced egg-hatching ofM. incognita by 100% and by 98.7% for S/2 dilutions. Also, 98.7% reduction in the egg-hatching was obtained by S ofA. absinthium. Extracts ofC. colosynthsis andR. communis gave less egg-hatching inhibition. Acetylcholinesterase (AChE) activity was suppressed by more than 75% inH. dihystera treated with S of each ofP. granatum, T. vulgaris andA. absinthium. However, the former extract gave the highest AChE inhibition (98.7%). When nematodes were treated with oxamyl (Vydate 24%), AChE activity was suppressed by 53.3%. The other extract dilutions suppressed AChE activity by less than 50%.     

Toxicity and antitermite activity of the essential oils from Cinnamomum camphora, Cymbopogon nardus, Melaleuca cajuputi and Dipterocarpus sp. against Coptotermes curvignathus

Efficacy of four different essential oils against the subterranean termite, Coptotermes curvignathus Holmgren, was assessed in various bioassays. Laboratory results indicate that the highest termite mortality was found in Dipterocarpus sp. essential oil after 24 h (LC₅₀ = 1.62 %) and the lowest in Melaleuca cajuputi (LC₅₀ = 4.60 %). The wood consumption in the filter paper treated with Dipterocarpus sp. oil is also smaller than for the other three essential oils tested. However, the other three essential oils also inhibited termite susceptibility of the specimens. Dipterocarpus sp. (keruing oil) was the most effective insect antifeedant and repellent against C. curvignathus. The results suggest that essential oils might have some beneficial activity of economic value and are considered good candidates for the development of new chemicals (repellents or antifeedants) for termite control.     

Chemical analysis of essential oils of Eupatorium adenophorum and their antimicrobial,antioxidant and phytotoxic properties

Essential oils from inflorescences and roots of Eupatorium adenophorum Spreng (Asteraceae) have been investigated for their antimicrobial, phytotoxic and antioxidant activities. Based on GC–MS, the oil from inflorescences is dominated by sesquiterpenes (55.9 %) with γ-cadinene (18.4 %), γ-muurolene (11.7 %), 3-acetoxyamorpha-4,7(11)-diene-8-one (7.4 %) and bornyl acetate (6.3 %) as the major constituents. The oil obtained from the roots contained both sesquiterpenes (34.3 %) and monoterpenes (32.5 %) in almost equal proportions with E,E-cosmene (19.9 %), γ-muurolene (10.1 %), isothymol (7.5 %), β-cadinene (7.0 %) and α-phellandren-8-ol (5.9 %) as the major constituents. Both oils exhibited significant antifungal activity against five phytopathogenic fungi. The inflorescence oil showed higher antibacterial activity against Klebsiella pneumoniae, while the root oil was more effective against Staphylococcus aureus. The oils strongly inhibited or delayed germination and seedling growth of the weed Phalaris minor in a dose-dependent manner. As evidenced by a DPPH assay, the essential oils also exhibited significant free radical scavenging activity.     

Host status effect of cowpea and sunflower on the populations ofMeloidogyne javanica andRotylenchulus reniformis

A highly susceptible cowpea,Vigna sinensis cv. Baladi plants were tested as trap plants for eitherMeloidogyne javanica orRotylenchulus reniformis under greenhouse conditions. The plants were gathered by cutting them above the surface of the soil or by uprooting them, 1/2, 1, 3, 6, 12, 24, 36 and 48 days after nematode inoculation. Both of the mentioned nematodes began to mature and lay eggs after the 12th day from their inoculation. Hence, it is advised to pull up cowpea plants from 3–12 days after nematode inoculation. After planting sunflower,Helianthus annus cv. Miak replacing cowpea, the nematode populations were higher, in most cases, on sunflower plants replacing cutting cowpea than those on sunflower replacing uprooted cowpea. The highest percentages of nematode reduction were 98.55 and 99.57 forM. javanica and 95.09 and 92.90% forR. reniformis on sunflower plants replacing cutting and uprooted cowpea plants after 12 days from nematode inoculation, respectively.M. javanica andR. reniformis decreased the length and weight of sunflower plants as affected by planting time and method of cowpea harvest. This method of nematode control is cheaper, easy and pollution free.     

Abundance-dependent transmission of the pinewood nematode, <Emphasis Type="Italic">Bursaphelenchus xylophilus</Emphasis> (Nematoda: Aphelenchoididae), to the Japanese pine sawyer, <Emphasis Type="Italic">Monochamus alternatus</Emphasis> (Coleoptera: Cerambycidae), adult in its pupal chamber

The transmission ratio of the pinewood nematode (PWN), Bursaphelenchus xylophilus, to the emerging adult Japanese pine sawyer (JPS), Monochamus alternatus, in its pupal chamber is a determinant of the number of the nematodes carried by JPS beetles. To investigate the factors affecting the transmission ratio, we counted the number of the nematodes carried by 36 newly emerged JPS beetles and the number remaining in and around their pupal chambers, and then estimated the transmission ratio (the number of nematodes carried by a JPS adult as a percentage of the total number of nematodes aggregating in and around its pupal chamber). The total number of nematodes aggregating in and around a pupal chamber ranged from 0 to 19,041, and the number of nematodes carried by a beetle ranged from 0 to 18,920. The transmission ratio correlated with neither the water content of the wood around the pupal chamber nor the degree of wood discoloration caused by blue-stain fungus. The transmission ratio varied with the abundance of the nematodes aggregating in and around the pupal chamber. In pupal chambers with more than 1,000 nematodes, almost all the nematodes were transmitted to the beetle. However, in pupal chambers with fewer than 1,000 nematodes, the transmission ratio varied greatly, from 0 to 100%. These results suggest that aggregation of many PWNs in the pupal chamber might stimulate transmission of the PWNs to the JPS adult and that this abundance-related transmission might contribute to the large variation in the number of PWNs carried by the JPS beetle.     

Preliminary investigations on the effect of gamma irradiation on the infectivity of the entomoparasitic nematodeSteinernema feltiae (Filipjev) (Rhabditida,Steinernematidae)

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.     

Laboratory and field evaluation of the pathogenicity of entomopathogenic nematodes to the red palm weevil, Rhynchophorus ferrugineus (Oliv.) (Col.: Curculionidae)

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.     

Chemical composition and bioactivities of three Chrysanthemum essential oils against Tribolium confusum (du Val) (Coleoptera: Tenebrionidae)

Essential oils from three species of Chrysanthemum growing in Tunisia (C. coronarium, C. fuscatum, and C. grandiflorum) were first analyzed by gas chromatography (GC) and GC/mass spectrometry (MS) and then evaluated for toxicity and antifeeding action against Tribolium confusum. The essential oils obtained from leaves and flowers shared a similar qualitative composition, but the relative proportions of the constituents were quite different. The essential oil of C. grandiflorum was rich in sesquiterpenoids, while those of C. fuscatum and C. coronarium were rich in monoterpenoids. The main common constituents of all the essential oils were ??-pinene, myrcene, ??-humulene, ??-caryophylene, spathulenol, and caryophyllene oxide. The most effective essential oil was obtained from the leaves of C. grandiflorum, that inhibited the relative growth rate (?0.03?mg/mg/d), efficiency of conversion of ingested food (?50.69%), relative consumption rate, caused an antifeeding effect (66.43%) and a high mortality (80%) of T. confusum larvae. Topical application C. grandiflorum essential oil caused a significant insect mortality that attends 27% after 7?days of treatment. While essential oil from C. coronarium flowers has contact and fumigant toxicity with a mortality of 9 and 13%, respectively. Results analysis highlights a relationship between essential oils composition and insecticidal activity against T. confusum. The study showed that each essential oil has specific chemical composition and act differently according to the nature of attributed test. The use of essential oils from different Chrysanthemum species with different methods helps poor farmers who store small amounts of grains to preserve it against pest infestation.     

Isolation of heterorhabditid nematodes from palm tree planted areas and their implications in the Red Palm Weevil control

Soil samples from 102 sites planted with intercropped palm trees in 8 Egyptian governorates were baited with greater wax moth larvae for the recovery of entomopathogenic nematodes. Only heterorhabditied nematodes were extracted from 5 sites in Alexandria, Behaira, Ismaelia, and Giza governorates. Evaluation of the novel isolates in the laboratory to identify the most efficient ones for biological control of the red palm weevil Rhynchophorus ferrugineus (Oliv.) showed that they are generally more virulent than other entomopathogenic nematode species. However, only two of the 5 strains, isolated from Behaira and Giza, survived a 24?h exposure period in palm weevil-infested tree tissue with a low viability of 19 and 14?%, respectively.     

Auswirkungen des Einsatzes entomopathogener Nematoden (Heterorhabditis sp.) im Freiland auf die Nichtzielfauna, 2. Teil: Diptera

The effects of entomopathogenic nematodes on nontarget Diptera of terrestrial ecosystems were investigated for the first time in the field. Experiments were conducted 1989 at four sites near Darmstadt (FRG) (mixed deciduous forest, forest border, orchard and summer wheat field). In field trials the nematode strainHeterorhabditis HL 81 was distributed at concentrations of 10⁶ ind./m² on plots of 100m² each. Diptera were sampled using emergence traps set on soil (photoeclectors) over a period of five to six weeks after nematode application. The obtained results demonstrate, that only in some cases an appreciable parasitation of Diptera by the employed nematode strain may have occurred. Only on one site (orchard) a significant reduction (α≦0,05) of several nontarget species of families was observed. On the contrary, in each of the four nematode plots some species or families emerged at higher rates compared with the untreated plots. Other causes for the unequal distribution of Diptera than the parasitation throughHeterorhabditis are discussed. The detrimental effects of a field application of entomopathogenic nematodes on the nontarget insect fauna must be considered negligible at the present state of knowledge.     

Activity of heterorhabditid nematodes at high temperature and in combination with cytoplasmic polyhedrosis virus

Percentage survival in aqueous suspensions and infectivity of six Egyptian entomopathogenic nematode isolates from the genus Heterorhabditis varied during the hot period of the year with daily temperature range from 18 to 24?°C. The isolate designated as AS1 had the highest mean of survival (87?%) and infectivity to Galleria mellonella larvae (90?%) after 10 days. When the nematodes coexisted with cytoplasmic polyhedrosis virus of 100 × 10⁶ polyhedra inclusion bodies/ml, which was reproduced within and killed Rhynchophorus ferrugineus larvae, the nematode survival was adversely and progressively affected by the increase in the viral suspension. Among tested concentrations, a viral suspension equal to one-fifth size of the nematode and virus suspension is the best for nematode activity in integrated control against the red palm weevil.     

Effect of the nematodeHeterorhabditis bacteriophora and the bacteriumBacillus thuringiensis as integrated biocontrol agents of the black cutworm

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.     

Eucalyptus essential oil as a natural pesticide

Eucalyptus (family Myrtaceae), an Australian native, represented by around 700 species is a genus of tall, evergreen and magnificent trees cultivated world over for its oil, gum, pulp, timber, medicine and aesthetic value. Among the various wood and non-wood products, essential oil found in its foliage is the most important one and finds extensive use in food, perfumery and pharmaceutical industry. In addition, the oil possesses a wide spectrum of biological activity including anti-microbial, fungicidal, insecticidal/insect repellent, herbicidal, acaricidal and nematicidal. The present paper discusses this environmentally benign pest control using eucalyptus oils against bacteria, fungi, insects, nematodes, weeds and mites. The use of eucalyptus oil as a natural pesticide is of immense significance in view of the environmental and toxicological implications of the indiscriminate use of synthetic pesticides and overcoming/reducing the problem of increasing pest resistance.     

Interaction of root-knot nematode and mycorrhizal fungi on common beanPhaseolus vulgaris L.

The interactions of root-knot nematode and VAM fungus on common bean plants (Phaseolus vulgaris L.), and the sequence of nematode infection were studied in the greenhouse. The inoculation with VAM fungus caused a significant increase in plant height and fresh weight compared with non treated plants.Meloidogyne infection unsignificantly decreased plant height and dry weight. When fungus was inoculated at 15 and 30 days prior toM. incognita infection, a significant increase in fresh weight was observed. There were no significant differences in total nitrogen (mg/plant) between plants inoculated withM. incognita alone or those inoculated with bothM. incognita and VAM fungus at the same time or 15 days after the fungus inoculation. Plants preinoculated with VAM fungus 30 days prior to nematode infection had a significant increase in total nitrogen. The inoculation with VAM fungus caused a significant increase in phosphorus content. However, it was significantly decreased in plants inoculated with nematode alone and in plants inoculated with VAM fungus andM. incognita at the same time. Gall index and final nematode population were significantly increased when nematodes were treated at the same time with fungus, although there were significant decrease in nematode final population and gall index when the plants were treated with nematodes at 15 and 30 days after mycorrhizal infection. A decrease in percentage of fungal colonization was observed when nematodes were inoculated with fungus at the same time.     

Canadian conifers as hosts of the pinewood nematode (Bursaphelenchus xylophilus): Results of seedling inoculations

Seedlings of 22 species of conifers from across Canada were inoculated with m and r form isolates of the pinewood nematode (Bursaphelenchus xylophilus). In an experiment made under ambient (summer‐fall) temperatures in a shadehouse at Victoria, British Columbia, Canada, 8 of the 22 conifer species were killed by the nematodes, but mortality was low, i.e. 4–30%. Pines (eastern white, Jack and red) were more susceptible than other conifers. Yellow cypress, eastern white cedar, western red cedar and western hemlock were not killed by the nematodes. In a second experiment made at elevated temperatures (30°C‐16h long days, 25°C‐8 h long nights) in a greenhouse, 18 of the 22 conifer species died following nematode inoculation. Again, pines (lodgepole, eastern white, western white and red) were among the most susceptible tree species and the four conifers that were unaffected in the first experiment were not killed. Tamarack and western larch, both immune at ambient temperatures, were the two most susceptible conifers at elevated temperatures. Compared to ambient temperatures, seedlings at elevated temperatures died quicker and contained more nematodes. M and r form nematodes were equally pathogenic in both experiments.     

The use of entomopathogenic nematodes in the control of stored-product insects

This review highlights the latest findings regarding the use of entomopathogenic nematodes against post-harvest insects. Due to their requirements for moisture, entomopathogenic nematodes had received, until lately, limited attention for application to the dry storage environment. Recent improvements of their formulation and application approaches, as well as the discovery of new, more virulent strains have enhanced the efficacy of entomopathogenic nematodes and renewed interest in using entomopathogenic nematodes in the stored-product environment. The nematode species tested against storage insects belong exclusively to the genera Steinernema and Heterhorhabditis. The virulence of entomopathogenic nematodes against post-harvest insects varies depending on the nematode species and strain. Usually, only a single-nematode species or strain is not equally effective against all major stored-product insect pests; therefore, one nematode strain or species cannot be suitable for controlling all species present in the storage environment, where several insect species coexist. The successful application of entomopathogenic nematodes in storage environments for controlling post-harvest insects is highly dependent on several biotic and abiotic factors, such as the host life stage, temperature, and relative humidity. Entomopathogenic nematodes have still to overcome substantial hurdles to become a reliable alternative for commercial applications in warehouses and storage facilities. However, the use of innovative, enhanced methods of formulation and application, such as encapsulation or bait traps, could boost the exploitation of entomopathogenic nematodes in storage facilities against post-harvest insects.     

Foliar nematode,Litylenchus crenatae ssp. mccannii,population dynamics in leaves and buds of beech leaf disease‐affected trees in Canada and the US

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.     

Behavioral responses of Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) to four essential oils in Thailand

The behavioral effects of four essential oils extracted from orange peel (Citrus aurantium L.), cinnamon leaf (Cinnamomum verum J. Presl), citronella grass (Cymbopogon winterianus Jowitt), and clove flower [Syzygium aromaticum (L.) Merrill & Perry] were evaluated against two medically important species of mosquitoes, Aedes aegypti (L.) and Culex quinquefasciatus Say, using an excito-repellency test system. Ae. aegypti was collected from a small village in Kanchanaburi Province and Culex quinquefasciatus was captured from an urban area of Bangkok. Mosquitoes from the F1–F3 generations were tested in the excito-repellency test chamber for contact excitation and non-contact spatial repellency. Results showed that both species demonstrated varying levels of behavioral escape responses to different essential oils, showing a clear dose response depending on percent w/v concentration used. Orange oil produced the least response in both mosquito species, while citronella and clove the greatest. In general, Cx. quinquefasciatus exhibited much stronger behavioral responses to all four essential oils than Ae. aegypti. From this study, we conclude that the essential oils from various botanical sources should continue to be screened for protective properties against mosquitoes and other biting arthropods.     

Survival and infectivity of entomopathogenic nematodes under environmental stress

At two experiments, infective stage juveniles of three heterorhabditid nematode isolates andSteinernema riobravis were placed in sterilized sandy soil in sealed containers buried in corn field during summer. Containers were removed daily for 10 consequent days and surviving juveniles were recovered from the soil by Baermann funnel method, then the remainder of soil was subjected toSpodoptera littoralis-baiting technique. Apparently, the low level of soil moisture (3%) and ceiling temperature levels (up to 42°C) as well as faint electric conductivity (0.48 mmhos/cm) of the soil containing the nematodes resulted in a rapid decline in the number of nematodes recoverable from the soil over time by Baermann method. The percentage of recovery for the nematode isolates EAM8, EIS7 and EAS59 by the Baermann funnel was 35.6%, 43.9% and 20.5% for the total nematodes recovered in the first trial, respectively. The nematode numbers increased when the recovery time extended from 24 to 48 h at 23°C. Insignificant differences were found between nematode numbers recovered daily in both trials. The average number of the recoveredS. riobravis was more (P0.05) than that of any other nematode isolate. Nematodes which were not recoverable by Baermann technique were infective when bioassayed over the period of the two experiments. The infective juveniles which survivied the stressed conditions are recommended to be subcultured through selection regime in order to obtain an improved nematode strain.With 2 tablesThis research was supported by NARP-H035/Nematode Project.     

内寄生真菌Esteya vermicola对松材线虫侵染活力的测定

从不同培养基、不同测定方法、不同菌株、不同孢子浓度4个方面测定内寄生真菌Esteya vermicola孢子对松材线虫的侵染活力,结果表明:该真菌离体分生孢子对松材线虫有侵染活力;PDA固体培养比PDB液体培养所得孢子能更有效的粘附和杀死松材线虫;在WA平板上,采用浸渍法测定孢子对线虫的侵染活力比其他处理效果好;在供试的3个菌株(CUN 120806、CBS 10082和CBS 115803)中,CBS 115803菌株对松材线虫具有较高侵染活性;4个不同浓度(1×109、1×108、1×107、1×106个·mL-1)孢子对线虫的作用中,随着孢子浓度降低,孢子对线虫侵染能力也随之降低。