Laboratory evaluation of steinernematid and heterorhabditid nematodes for control of the beetleMaladera matrida

The potential use of steinernematid and heterorhabditid nematodes against the beetleMaladera matrida Argaman (Coleoptera: Scarabaeidae) was determined under laboratory and greenhouse conditions. Infective juveniles (IJ’s) of the nematodeHeterorhabditis sp., Hp88 strain, mixed with soil at a concentration as low as 50 IJ’s/cm³ soil, resulted in 86% control. No increase in control was obtained with higher nematode concentrations. Soil surface application of the nematodes at concentrations of 160 and 640 IJ’s/cm² was sufficient to obtain 87% and 86% mortality, respectively, even at a depth of 40 cm below the soil surface. TheHeterorhabditis sp. Hp88 strain was found to be the most pathogenic to the beetle grubs at 25°C. Lower control levels of 30-47% were achieved byHeterorhabditis sp. HL81 strain,S. feltiae ‘All’ strain and 5.bibionis CR strain. The nematodeHeterorhabditis sp. BS strain did not have any effect on insect mortality. However, at a temperature of 16°C, the HL81 strain ofHeterorhabditis sp. was the most effective. Grubs 3-5 wk old were found to be the most susceptible developmental stage of infection ofHeterorhabditis sp. Hp88 strain. Pupae, which were exposed to the nematodes in the same experimental regime, were not affected. The results obtained in the present study suggest thatM. matrida is an attractive candidate for biological control by entomoparasitic nematodes.     

Entomopathogenic fungi and nematodes against larvae of the chestnut weevil,Curculio elephas (Coleoptera: Curculionidae): a laboratory evaluation

Pest control in chestnut orchards is mainly achieved by chemicals, but there is growing focus on the potential use of biological control agents. The larval susceptibility of the chestnut weevil Curculio elephas L. (Coleoptera: Curculionidae) to different strains/species of entomopathogenic fungi and nematodes was evaluated in laboratory by soil cup bioassays. In the experiments with fungi, a wild strain of Metarhizium anisopliae caused the highest larval mortality (about 90%) compared with a commercial and a wild strain of Beauveria bassiana (80% and 77% respectively). Regarding nematodes, the commercial strain of Heterorhabditis bacteriophora was more effective in the control of chestnut larvae (77% insect mortality) than Steinernema carpocapsae (43%).     

Evaluation of entomopathogenic nematodes for biocontrol of the european corn borer,Ostrinia nubilalis, on sweet corn in Israel

The potential of entomopathogenic nematodes for biological control of the European corn borer (ECB),Ostrinia nubilalis (Hübner), was evaluated under laboratory, screenhouse and field conditions. The ‘All’ and ‘Mexican’ strains ofSteinernema carpocapsae (Weiser) and the ‘HP88’ strain ofHeterorhabditis bacteriophora Poinar were compared in both dose response assays (5, 50 and 500 infective juveniles [IJ] per petri dish containing five 5th-instar ECB eggs; 72 h of incubation) and exposure time assays (3, 6 and 9 h of incubation). In the dose response assays the highest rates of ECB killing resulted from infestation with the Mexican strain ofS. carpocapsae. In the exposure time assays there were no significant differences between the killing rates of the three nematode strains. Sweet corn plants(Zea mays var.saccharata) grown in a screenhouse, were infested with ECB neonates and 4 days later sprayed with a suspension of the Mexican strain ofS. carpocapsae (50,000 IJ per plant). The number of ECB larvae found on treated corn plants after one week was significantly (P=0.05) lower (3- to 5-fold) than the number found on untreated plants. Similar treatment in the field significantly reduced the rate of economic ear damage from 20% to 5%. Contribution from the Agricultural Research Organization. No. 2260-E, 1997 series     

Biological control potential of Turkish entomopathogenic nematodes against the Mediterranean fruit fly <Emphasis Type="Italic">Ceratitis capitata</Emphasis>

The entomopathogenic nematodes Steinernema weiseri, S. feltiae, S. carpocapsae and two strains of Heterorhabditis bacteriophora, isolated from Turkish soils, were evaluated against larvae of the Mediterranean fruit fly (medfly) Ceratitis capitata in plastic cups under laboratory conditions with sandy loam soil and 10% moisture level. At a rate of 100 infective juveniles (IJs)/cm², the last instar larvae of C. capitata were susceptible to the entomopathogenic nematodes: the S. feltiae 09-31 strain recovered from Aydin provided 78% mortality, whereas S. weiseri and S. carpocapsae killed 50% and 56% of the larvae, respectively. Both strains of H. bacteriophora species caused less than 50% mortality. Except for S. feltiae, the majority of infected medflies died as prepupae or pupae within the puparia. More than 90% larval mortality was recorded at 200 and 400 IJs/cm² for S. feltiae. None of the nematode isolates infected the medfly pupae within the puparia. In pot experiments containing soil, S. feltiae caused 96% and 97% mortality at 100 and 200 IJs/cm², respectively. In pot experiments with grass present, more than 94% mortality was obtained in the presence of grass roots.     

A malathion-tolerant strain of the spiderChiracanthium mildei and its response to chlorpyrifos

Chiracanthium mildei L. Koch (Araneae: Clubionidae) spiders, from two populations, were collected and reared in the laboratory. One originated from a citrus grove at Kibbutz Afeq and the other from an experimental cotton field at the Newe Ya’ar Experiment Station. Laboratory evaluation indicated that the Afeq strain was more tolerant to malathion than the Newe Ya’ar strain (resistance factor of x3.3). When spiders of the Afeq strain were exposed to chlorypyrifos (Dursban) and malathion residues, chlorpyrifos was much more toxic.     

A survey of entomopathogenic nematodes (rhabditida) in the negev desert

The aim of the present survey was to isolate entomopathogenic rhabditids in an arid region. The survey was conducted in the Negev desert, located in the southern part of Israel. Soil samples were collected from 21 sites and the presence of entomopathogenic nematodes in the soil samples was determined by usingGalleria mellonella larvae as bait. Entomopathogenic nematodes, identified as heterorhabditids, were isolated only from soil samples obtained from under the canopy of irrigated fruit trees, planted in sandy soils. The nematodes from the new isolated populations were subjected to low relative humidity (75%) for 3 days after preconditioning for 72 h at 97% RH. Under these conditions, fewer than 10% survived for 48 h.     

Phoretic dispersal of the entomopathogenic nematode Heterorhabditis amazonensis by the beetle Calosoma granulatum

Entomopathogenic nematodes (EPN) have limited ability to travel and need to adopt alternative strategies to reach hosts that are far away. They can attach themselves to an organism that acts only as a dispersal agent to transport the EPN to places that they cannot reach by themselves. The larval and adult stages of Calosoma granulatum (Coleoptera: Carabidae) beetle are important predators of caterpillars that live in the soil of Brazilian agricultural systems. The nematode Heterorhabditis amazonensis (Rhabditida: Heterorhabditidae) is a native of Brazil and plays a major role in the control of Spodoptera frugiperda (Lepidoptera: Noctuidae) caterpillars. This study assessed the ability of C. granulatum to carry and disperse H. amazonensis. The experimental arenas consisted of two types of containers with substrate connected by a plastic tube through which the insects could move freely. Only one of the containers received infective juveniles (IJ) and the other was used as the test container. We first used C. granulatum larvae and adults to evaluate the influence of different concentrations of IJs on phoretic behavior. Then different distances traveled by the adult beetle were tested to measure their effect on IJ transport. The results showed that C. granulatum is a good phoretic dispersal agent and the transport of IJs by the larvae is less influenced than transport by the adult, by a change in the IJ concentration. The distance traveled by the adult influences the number of EPN carried and the detection of phoresy even at greater distances (40 cm) indicates that C. granulatum is capable of transporting the EPN for distances greater than those evaluated.     

Virulence and efficacy of different entomopathogenic nematode species against western flower thrips (Frankliniella occidentalis)

Virulence and efficacy of five species and strains of the entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae:Steinernema riobravis, Steinernema feltiae strains Ger. and UK, andHeterorhabditis bacteriophora strains HP88 and IS5, against the prepupal and pupal stages of the western flower thrips (WFT),Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), were investigated in the laboratory. Although all these nematodes controlled WFT to some extent, they differed in efficiency. The heterorhabditid nematodeH. bacteriophora strain HP88 was more specific to the soil-inhabiting WFT stages (36–49% thrips mortality). The steinernematid nematodesS. riobravis andS. feltiae strains Ger. and UK had only a slight effect (10% mortality) on prepupal and pupal populations of WFT, andH. bacteriophora strain IS5 had the least effect of all. A possible reason for such species variation is suggested and discussed.     

A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Phytoplasma suspected symptoms of little leaf, flat stem, witches’ broom and leaf yellowing were recorded on the four legume species, cowpea (Vigna unguiculata (L.) Walp.), pigeon pea (Cajanus cajan (L.) Millsp.), lentil (Lens culinaris Medikus) and mung bean (Vigna radiata (L.) Wilczek) in the states of Delhi, Uttar Pradesh (UP) and Kerala from 2014 to 2016. DNA specific fragments of approximately 1.3 kb were amplified from symptomatic samples of cowpea, pigeon pea, lentil and mung bean in nested PCR assays by using two sets of universal phytoplasma nested specific primers P1/P7 followed by 3Far/3Rev. No DNA amplifications were observed in any of the non-symptomatic legume samples with same primer pairs. Pair wise sequence comparison, phylogeny and virtual RFLP analysis of 16S rDNA sequences of the four legume species confirmed the association of four different groups and subgroups of phytoplasmas in the present study. The mung bean witches’ broom at Delhi was identified to be associated with strain related to ‘Ca. P. aurantifolia’ (16SrII-D), pigeon pea little leaf at Faizabad, UP with strain related to ‘Ca. P. phoenicium’ (16SrIX-C), lentil witches’ broom at Faizabad, UP with ‘Ca. P. trifolii’ (16SrVI-D) and cow pea flat stem disease at Kerala with ‘Ca. P. cynodontis’ (16SrXIV-A). Association of ‘Ca. P. cynodontis' (16SrXIV-A) infecting cowpea, ‘Ca. P. trifolii’ (16SrVI-D) in lentil and phytoplasmas strain related to ‘Ca. P. phoenicium’ (16SrIX-C) infecting pigeon pea are the new reports to the world.     

Feeding deterrents forphilosamia ricini (samia cynthia subsp.Ricini) fromtithonia diversifolia

Tagitinin A and C and hispidulin isolated fromTithonia diversifolia (Hemsl.) Gray, were potent feeding deterrents, when evaluated against 4th instar caterpillars of the Eri-silkworm(Philosamia ricini Hutt.) (Lepidoptera: Saturniidae); tagitinin F was not.     

Native entomopathogenic nematodes isolated from Turkey and their effectiveness on pine processionary moth,Thaumetopoea wilkinsoni Tams

Two native entomopathogenic nematodes were isolated from soil samples in Eastern Mediterranean region of Turkey and characterized based on 28S rDNA region. BLASTN homology and phylogenetic analysis of SK17 and SK-71 isolates indicated 98% and 99% identity to Steinernema affine and Steinernema feltiae, respectively. The results were constructed by neighbour-joining and bootstrap tree methods. Efficacy of S. affine (SK-17 strain) and S. feltiae (SK-71 strain) was tested against the larvae of pine processionary moth, Thaumetopoea wilkinsoni Tams, and remarkable mortality rates were obtained. Both strains caused complete mortality upon application of 500 IJs in foliar tests. However, the same strains caused 30% and 33% mortality at 80 IJs/cm² in soil applications. It was concluded that these native strains could be considered as potential biocontrol agents for reducing the damage caused by T. wilkinsoni larvae.     

Morphological and molecular characterisation of Trichodorus golestanensis (Nematoda: Trichodoridae), a new species from Iran

Several species of trichodorid nematodes cause economically important disease on plants. Trichodorus comprises most of the trichodorid species. Trichodorus golestanensis n. sp. is described from a forest park in northern Iran. The new species belongs to the T. lusitanicus morpho-species group and is characterized in male by three ventromedian cervical papillae of which two at level of onchiostyle region, three ventromedian precloacal supplements, the posterior one just anterior to retracted spicules and ventrally curved spicules with mid-blade indentation provided with a few bristles. Females are distinguished by well developed triangular vaginal sclerotized pieces in lateral optical view, a rhomboid-shaped vagina and a transverse slit-like vulva in ventral view. Molecular analysis using the sequence of D2-D3 expansion segment of 28S rDNA differentiated the new species and confirmed the relationships of T. golestanensis n. sp. with T. andalusicus and T. asturanus. The sequences of D2-D3 regions were also provided for previous trichodorid records from Iran T. gilanensis, P. teres and N. minor together with discussion of their relationship.     

Sensitivity of caterpillars of the pine tree lappet moth Dendrolimus pini to native isolates of entomopathogenic nematodes

Abstract

The pine tree lappet moth Dendrolimus pini (Lasiocampidae) is one of the most dangerous pests of pine Pinus sylvestris stands in Central Europe. To develop biological control method of this pest, the bioassay was made to assess the sensitivity of D. pini caterpillars to native EPMs strains representing two species: Steinernema feltiae and Heterorhabditis megidis in laboratory conditions. The results showed higher activity of S. feltiae strains which parasitized 86.7 - 100% of D. pini caterpillars, compared to the 20-100% of insects parasitized by H. megidis strain. Most nematodes were found in caterpillars treated with S. feltiae (in average 40 IJs/caterpillar), the least – in individuals parasitized by H. megidis (in average IJs/caterpillar). No effect of dose and temperature on parasitizm was found with S. feltiae strains while in H. megidis increased doses resulted in higher extensity of parasitism. The results indicate higher biological activity of S. feltiae strains and advisability of their further studies in field experiments.     

Potential biopesticides for crucifer flea beetle, <Emphasis Type="Italic">Phyllotreta cruciferae</Emphasis> (Coleoptera: Chrysomelidae) management under dryland canola production in Montana

The crucifer flea beetle, Phyllotreta cruciferae (Goeze), is an economically important and dominant pest of canola (Brassica napus L) in the Northern Great Plains of the USA. The current flea beetle management strategy is based on using synthetic chemical treated seeds and if necessary, foliar spray of chemicals at canola seedlings in early spring for targeting adult population. However, there is an increasing demand for development of alternative management strategies for P. cruciferae pertaining to concerns over the development of resistance to synthetic insecticides and non-target effects on pollinators and other beneficial insects. Replicated field trials were conducted to test the efficacy of several commercially available biopesticides including Entrust® (spinosad), entomopathogenic nematode Steinernema feltiae?+?Barricade® (polymer gel 1%), Aza-Direct® (azadirachtin), Pyganic 1.4® EC (pyrethrin), Grandevo® SC (Chromobacterium subtsugae), Venerate® XC (Heat killed Burkholderia sp. strain A396 as seed treatment and foliar application) and Gaucho® (imidacloprid) (chemical check) for the P. cruciferae management at two locations (Conrad and Sweetgrass) of Montana in 2016. Biopesticide products were evaluated based on canola leaf area injury ratings and seed yield levels. Although, there was no clear trend of canola yield increase, selected biopesticide treatments were effective in maintaining low leaf area injury ratings as compared to untreated control. Entrust was able to maintain low leaf area injury ratings (8.5–14.5%) when compared to untreated control (16.0–21.4%) at both the locations. Entomopathogenic nematodes, Steinernema feltiae?+?Barricade® and Venerate® applied as foliar treatments maintained significantly lower feeding injury pressure at Sweetgrass (11.8%) and Conrad (13.4%) locations respectively, when compared to the untreated control. Our study results suggest that these biopesticide treatment results were comparable in efficacy to the chemical seed treatment Gaucho®. Other two biopesticide products- Aza-Direct® and Pyganic 1.4® EC treatments did not provide effective control of P. cruciferae at both the locations.     

一种对桃小食心虫高毒力的斯氏线虫Steinernema sp.(CB-2Y)

本研究在室内用“沙埋法”比较了两种斯氏属昆虫病原线虫Steinernema sp.(CB-2Y)和S.feltiae Agriotos对桃小食心虫的侵染力,结果表明CB-2Y线虫对桃小食心虫幼虫和冬茧的侵染力都高于Agriotos线虫。接线虫笫7天桃小食心虫LD50,CB-2Y组为49条线虫,而Agriotos组为158条;冬茧的LD50分别为1330条和24046条。在桃小冬茧开始活动期(6月15日)分别施用两种线虫,一个月后检查桃小食心虫成虫羽化率,CB-2Y线虫的控制效果明显优于Agriotos,在1024条线虫/桃小食心虫冬茧时(75条/cm~2),越冬代桃小食心虫的羽化率分别为8.2％和29.2％。     

Resistance to root-knot nematodes on passion fruit genotypes in Brazil

With the expansion of passion fruit cultivation in Brazil, phytosanitary problems have increased, among them, the occurrence of root-knot nematodes. This research aimed to study the response of passion fruit genotypes to Meloidogyne incognita, M. javanica and M. enterolobii in addition to evaluating the life cycle of M. enterolobii in the passion fruit genotype ‘FB 200’. The genotype response was carried out in a greenhouse. Each pot’s soil was inoculated with 5000 eggs. Gall index, egg mass index and nematode reproduction factors were evaluated at 120 days after inoculation. All genotypes studied were resistant to M. incognita, M. javanica and M. enterolobii, except ‘Roxinho do Kênia’, which was susceptible to the three nematode species. The life cycle of M. enterolobii in “FB 200” passion fruit was studied in a growth chamber at 26 °C with a photoperiod of 12 h. Seven days after transplantation, each plant was inoculated with approximately 400 second-stage juveniles. Evaluations were done at 7, 14, 21, 28, 35, 42 and 49 days post inoculation. The nematode did not complete its life cycle.     

Phylogenetic analysis of the citrus Huanglongbing (HLB) bacterium based on the sequences of 16S rDNA and 16S/23S rDNA intergenic regions among isolates in China

Phylogenetic analysis of Chinese isolates of the citrus Huanglongbing (HLB) bacterium based on the 16S rDNA and 16S/23S rDNA intergenic regions sequences was carried out. Nine HLB samples collected from different hosts with different symptoms in seven Chinese provinces, were subjected to PCR for amplifying and sequencing the 16S rDNA. The identity level among Chinese isolates was 98.5% to 100% and was the same with the Indian HLB isolate ‘Poona’ (GenBank accession number: L22532). By contrast, identity values were 97.5% to 97.8% with Candidatus Liberibacter africanus strain ‘Nelspruit’ (L22533), 96.3% to 97.3% with Ca. L. africanus subsp. ‘Capensis’ (AF137368), 95.3% to 96.5% with the Ca. Liberibacter sp. ‘LSg2’ (AY919312), and 94.9% to 96.0% with a strain of Ca. L. americanus from Brazil (São Paulo State; AY742824). A phylogenetic tree constructed with 16S rDNA sequences showed that all Chinese isolates belong to Ca. L. asiaticum. Analysis of the 16S/23S rDNA intergenic region was conducted on 18 HLB-diseased citrus samples with different symptoms, collected in seven provinces. These isolates showed no obvious variation and had an identity level >99.0% with one another. Sequence analysis of 16S/23S rDNA intergenic region and the relative phylogenetic tree showed that the Chinese isolates are very close to Ca. L. asiaticus, and distinct from Ca. L. africanus and Ca. L. americanus. These results suggest that the Chinese HLB isolates belong to the species Candidatus Liberibacter asiaticus. This is the first report on the classification of HLB isolates from China based on molecular investigations.     

Control of phytophthora leaf blight of taro (Colocasia esculenta) by fungicides and roguing

Six fungicides were evaluated under laboratory and field conditions for control of Phytophthora leaf blight of taro,Coloeasia esculenta, incited byPhytophthora colocasiae. Inin vitro tests Deraosan 65W was the most effective in inhibiting the mycelial growth of the test pathogen followed by Difolatan 80W, Fytolan (copper oxychloride), Apron 35F, Topsin-M 50W and Dithane Z-78 75W. Excellent control was obtained with Demosan 65W and Difolatan 80W, good control with Apron 35F, fair control with Fytolan, and poor control with Topsin-M 50W and Dithane Z-78 75W. Results ofin vivo tests were correlated with those of thein vitro tests. Roguing of infected leaves did not eradicate the pathogen but can only delay epiphytotics.     

Enhanced ambient storage stability of an entomopathogenic nematode through anhydrobiosis

Limited shelf‐life is a major obstacle to large‐scale use of entomopathogenic nematodes in biological control. Recently, the development of a water‐dispersible granular formulation (WG) containing entomopathogenic nematodes was described. This paper reports that storage stability of Steinernema carpocapsae Weiser infective juveniles at 25 °C is enhanced from three to six months in this WG. It is also demonstrated that the enhanced stability is achieved through the induction of partial anhydrobiosis that reduces oxygen and lipid reserve utilization by infective juveniles. Nematode infectivity is unaffected during storage under partial anhydrobiosis in the WG formulation. © 2000 Society of Chemical Industry     

Screening insecticides against the tobacco whitefly (Bemisia tabaci) on cotton,using a leaf cage laboratory method

Over 20 insecticides were screened against the tobacco whitefly,Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), on cotton. AsB. tabaci feeds only on live plants, a suitable laboratory test method incorporating young cotton plants was developed. Both cover sprays and systemic insecticides applied to the soil were tested. Triazophos, pyridaphenthion, azinphos-methyl, bendiocarb and flucythrinate were found to be effective and persistent. The best of the systemic insecticides was aldicarb, followed by butocarboxim.