Infection of plant-parasitic nematodes by Paecilomyces lilacinus and Monacrosporium lysipagum

Studying the mode of infection of a biocontrol agent is important in order to assess its efficiency. The mode and severity of infection of nematodes by a soil saprophyte Paecilomyces lilacinus (Thom) Samson and a knob-producing nematode trapping fungus Monacrosporium lysipagum (Drechsler) Subram were studied under laboratory conditions using microscopy. Infection of stationary stages of nematodes by P. lilacinus was studied with three plant-parasitic nematodes Meloidogyne javanica (Treub) Chitwood, Heterodera avenae Wollenweber and Radopholus similis (Cobb) Thorne. Paecilomyces lilacinus infected eggs, juveniles and females of M. javanica by direct hyphal penetration. The early developed eggs were more susceptible than the eggs containing fully developed juveniles. As observed by transmission electron microscopy, fungal hypha penetrated the M. javanica female cuticle directly. Paecilomyces lilacinus also infected immature cysts of H. avenae including eggs in the cysts and the eggs of R. similis. Trapping and subsequent killing of mobile stages of nematodes by M. lysipagum were studied with the above three nematodes. In addition, plant-parasitic nematodes Pratylenchus neglectus (Rensch) Chitwood and Oteifa and Ditylenchus dipsaci (Kuhn) Filipjev were tested with M. lysipagum. This fungus was shown to infect mobile stages of all the plant-parasitic nematodes. In general, juveniles except those of P. neglectus, were more susceptible to the attack than adults.     

ALLOPOLYPLOID SPECIATION IN TRAGOPOGON: INSIGHTS FROM CHLOROPLAST DNA

Tragopogon mirus and T. miscellus are classic examples of recent allopolyploid speciation. Previous studies documented that the diploid parents of T. mirus are T. dubius and T. porrifolius and those of T. miscellus are T. dubius and T. pratensis. Restriction fragment analysis of chloroplast DNA (cpDNA) provided additional evolutionary information regarding the origin of the allotetraploids. We analyzed 39 populations of the three diploid and two allotetraploid species with 18 restriction endonucleases. Six restriction site mutations and three length mutations were identified; these unambiguously differentiated the parental diploids. Previous morphological, cytological, and electrophoretic analyses indicated that T. mirus arose independently at least three times. Chloroplast DNA data suggest that T. porrifolius has consistently been the maternal parent of T. mirus. Chloroplast DNA data also document a minimum of two independent origins of T. miscellus: 1) populations from Pullman, Washington, have T. dubius as the maternal parent; 2) all other populations have T. pratensis as the maternal parent. Two restriction site mutations implicate certain populations of T. dubius in the formation of the Pullman populations of T. miscellus. The two rare diploid species, T. porrifolius and T. pratensis, typically appear as maternal parents of the allotetraploids; the widespread and common T. dubius is the maternal parent only for two populations of T. miscellus. These data suggest that pollen load may be an important factor in determining the male and female parents of allopolyploid angiosperms.     

Effects of Canavalia ensiformis and Mucuna pruriens intercrops on Pratylenchus zeae damage and yield of maize in subsistence agriculture

Host status of four leguminous cover crops [Canavalia ensiformis (L.) DC. (Jack bean), Crotalaria ochroleuca G. Don (Sunnhemp), Lablab purpureus L. (Hyacinth bean) and Mucuna pruriens (L.) DC. (velvet bean)] to Pratylenchus zeae Filipjev and effects of intercropping C. ensiformis and M. pruriens with Pan5195, H627 and Emap11 maize cultivars on P. zeae population and disease severity on maize were determined in greenhouse and field tests. Pratylenchus zeae significantly (P<0.05) reduced growth of C. ochroleuca by 36% but had no effect on C. ensiformis, M. pruriens and L. purpureus. While C. ensiformis, M. pruriens and L. purpureus reduced P. zeae population, C. ochroleuca increased it. In the greenhouse test, intercropping maize with C. ensiformis significantly (P<0.05) improved maize growth by up to 34%, Nematode populations in the roots of maize intercropped with either C. ensiformis or M. pruriens were significantly (P<0.05) reduced by up to 32% while nematode disease severity in these intercropping systems was reduced by up to 26%. In the field test, intercropping Emap11, Pan5195 and H627 with C. ensiformis significantly (P<0.05) increased maize grain yield by 190, 29 and 22%, respectively. Intercropping H627 with M. pruriens significantly (P<0.05) increased maize grain yield by 12%, but grain yields of Pan5195 and Emap11 declined by 79 and 40%, respectively. Root necrosis and soil nematode populations in the C. ensiformis–maize intercrop declined by up to 50 and 30%, respectively. Under pure maize stands, soil nematode populations increased by up to 35% in 90 days relative to the initial nematode population of three nematodes g⁻¹ of fresh soil. Section Editor: P. A. M. Bakker     

Additional origins of Ownbey's Tragopogon mirus

The allotetraploids (2n = 24) Tragopogon mirus and T. miscellus have become textbook examples of recently and recurrently formed allopolyploids. Both species formed following the introduction of three diploids, T. dubius, T. porrifolius and T. pratensis (each with 2n = 12), from Europe into the Palouse region of eastern Washington and adjacent Idaho, USA, in the early 1900s. The parentage of both allotetraploids is well documented (T. mirus = T. dubius × T. porrifolius; T. miscellus = T. dubius × T. pratensis), and both allotetraploids have formed repeatedly in the past approximately 80 years in the Palouse. On a larger geographical scale, T. mirus has also been reported from Flagstaff, Arizona (AZ), and more recently from Oregon (OR). However, the populations from OR and AZ have not been previously analysed with molecular markers to test the hypothesis of separate origin (vs. long‐distance dispersal). Here, we show that both the AZ and OR collections of T. mirus combine distinctive parental genotypes and are genetically differentiated from the T. mirus genotypes found in the Palouse. The OR sample of T. mirus has a genetically distinct T. dubius contribution that forms a clade in our analyses with a sample of what has been referred to as T. major (now considered a subspecies of T. dubius). Consistent with other naturally occurring T. mirus populations, plastid sequences indicate that T. porrifolius was the maternal parent for both the AZ and OR collections. Microsatellite data are also consistent with local formation of T. mirus from co‐occurring populations of T. dubius and T. porrifolius in OR and AZ. As with sequence data, T. dubius from OR is distinct from other samples of T. dubius at microsatellite loci, contributing a unique signature to T. mirus from this location. It will be useful to include these additional geographical origins of T. mirus, particularly the more genetically distant sample from OR, in ongoing investigations of the genetic and genomic consequences of recent allopolyploidy. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 297–311.     

Aggregated distribution of Ditylenchus dipsaci on broad bean seeds

The distribution of Ditylenchus dipsaci (Kühn) Filipjev between seeds in infested samples of broad bean seed was skewed so that the nematodes were concentrated on a few seeds. Such aggregation increases the likelihood of reproduction by the nematodes in infested plants and the consequent establishment of foci of infestation in the soil. These foci will be small and scattered giving the nematode the best chance of a finding a favourable environment in the field. The numbers of foci of infestation introduced by seed tend to be nearly constant, independent of the numbers of nematodes on the seed and therefore provide a stable unit of population.     

The distribution in time and space of parasitism in Epinotia tedella (CI.) (Lepidoptera: Tortricidae)

Abstract.

• 1 The temporal and spatial distribution of parasitism in Epinotia tedella was investigated within two spruce stands.
• 2 Most eggs were laid by the host female early in the season. The parasitoid, Pimplopterus dubius, was subjected to a temporal stress, and it also exhibited a greater oviposition rate early in its life. The temporal distribution of attack frequencies by P.dubius and Apanteles tedellae showed a good adaptation to the phenology of the host.
• 3 The spatial distribution of flight activity indicated a preference to exposed sub-habitats by P.dubius and to dark and sheltered sub-habitats by A.tedellae. The distribution of host larvae showed an aggregation in the lower and central parts of the canopy, and so did the attacks by A.tedellae— even more pronounced. The attacks by P.dubius showed a slightly inverse aggregation pattern. Apparently, the distribution of attacks was caused by preference to physical conditions, rather than local host densities.
• 4 The decreasing log. area of discovery on increasing log. parasitoid density is obviously a ‘pseudo-interference’ phenomenon caused by the aggregation of A.tedellae, and temporal asynchrony in P.dubius.
• 5 P.dubius dominated in young stands and its importance decreased with increasing age of the stands. The importance of A.tedellae was greatest in stands between 20 and 40 years old, and it dominated in those stands that were especially dense and dark, due to absent thinnings.

     

Spatial and temporal distribution of endemic entomopathogenic nematodes in a heterogeneous vegetable production landscape

Entomopathogenic nematodes within the families Steinernematidae and Heterorhabditidae (Order: Rhabditida) are potential biological control agents for many soil-dwelling vegetable pests. However, their low persistence and efficacy after field releases have resulted in limited use in pest management programs. Understanding the factors regulating natural populations of entomopathogenic nematodes may provide insight into practices to conserve populations within production systems. A series of investigations were conducted within a vegetable production area in Willard, Ohio during 2000–2003 to gain insight into the population ecology of endemic populations of entomopathogenic nematodes. A total of 440 sites across four habitats associated with the production landscape were sampled to ascertain the natural occurrence of these beneficial nematodes. Habitats included cultivated areas, grassy banks adjacent to cultivated areas, undisturbed shrub lands and forests. Twelve sites along grassy banks were monitored over a growing season to estimate associations between abiotic and biotic factors and endemic populations. Entomopathogenic nematodes were only detected along grassy banks adjacent to the cultivated areas; nematodes were recovered from 15 to 30% of sites sampled in 2001 and 2002, respectively. Two species of nematodes were isolated, Heterorhabditis bacteriophora Poinar and Steinernema feltiae Filipjev. H. bacteriophora was the most prevalent nematode species and was recovered from 60% of positive samples. Nematode populations varied temporally and spatially along grassy banks; mean population density over the growing period was 1313 infective juveniles/m². Neither macro- nor microarthropod communities nor soil temperature differed between sites at which nematodes were detected and those at which nematodes were not detected. Soil moisture, however, was associated with the occurrence and persistence of nematodes along grassy banks; mean soil moisture at sites at which nematodes were detected and those sites at which nematodes were not detected was 37.3 and 26.8%, respectively. Water management is an important component of vegetable production and our results suggest that soil moisture manipulation would be important in the establishment and sustained presence of entomopathogenic nematode populations within cultivated areas over the growing season.     

Effect of Insect Growth Inhibitors Upon Hatching of the Nematodes Nippostrongylus brasiliensis and Nematospiroides dubius

Summary

The effect of certain insect growth inhibitors upon hatching of eggs of the nematodes Nippostrongylus brasiliensis and Nematospiroides dubius is described. Two azasteroids did not affect hatching while a nonsteroidal amine and amide inhibited hatching, apparently by blocking embryogenesis. Possible modes of action by the hatching inhibitors and their potential use as novel nematicides are discussed.     

Costs of secondary parasitism in the facultative hyperparasitoid Pachycrepoideus dubius: does host size matter?

Although hyperparasitism frequently occur in parasitic insects, many aspects of this strategy remain unknown. We investigated possible fitness costs of hyperparasitism as influenced by host size. Our study was conducted with the facultative hyperparasitoid Pachycrepoideus dubius Ashmead (Hymenoptera: Pteromalidae), which parasitizes host species differing greatly in size. We compared some fitness traits (level of successful parasitism, development time, sex ratio and offspring size) of P. dubius developing on large secondary/primary (Delia radicum L. (Diptera: Anthomyiidae)/Trybliographa rapae Westwood (Hymenoptera: Figitidae)) or small secondary/primary host species (Drosophila melanogaster L./Asobara tabida Nees (Hymenoptera: Braconidae)). In no-choice and choice experiments, P. dubius was able to develop on different stages of T. rapae (L2 (endophagous), L4 (ectophagous), and pupae) but that it preferred to parasitize unparasitized D. radicum pupae over pupae parasitized by T. rapae. Furthermore, in P. dubius, hyperparasitism was associated with fitness costs (lower level of successful parasitism, smaller adult size) and these costs were greater on the smallest host complex. We hypothesize that the size of D. melanogaster pupae parasitized by A. tabida may be close to the suboptimal host size for P. dubius beneath which the costs of hyperparasitism make this strategy nonadaptive. Hyperparasitism in terms of trade-offs between host quality and abundance of competitors is discussed.     

A new species of freshwater threadfin, <Emphasis Type="Italic">Polynemus aquilonaris</Emphasis>, from Indochina,and redescription of <Emphasis Type="Italic">Polynemus dubius</Emphasis> Bleeker, 1853 (Perciformes: Polynemidae)

 The taxonomic status of two nominal species of Polynemus, viz. P. dubius Bleeker, 1853 and P. longipectoralis Weber and de Beaufort, 1922, is revised. Although regarded as separate taxa up to the present time, examination of the holotype of P. longipectoralis revealed its close similarity to the type series of P. dubius, in the synonymy of which the former is now included. Polynemus dubius is redescribed as a valid species and a lectotype of the species is designated. In addition, a new species, P. aquilonaris, previously identified as P. dubius or P. longipectoralis, is described from Indochina on the basis of 28 specimens. Polynemus aquilonaris differs from P. dubius in having higher counts of pored lateral-line scales [80–86 (mode 81) vs. 69–79 (78) in the latter] and scale rows below the lateral line [14–17 (mode 14, rarely 13 or 17) vs. 13 (rarely 12)], and lower counts of gill rakers [25–29 (mode 27) vs. 29–33 (30), respectively]. The former is known from Indochina (Chao Phraya and Mekong River systems including Lake Tonle Sap), whereas the latter is currently known from the Malay Peninsula, Sumatra, and Kalimantan. Received: March 29, 2002 / Revised: February 2, 2003 / Accepted: February 10, 2003     

Entomopathogenic nematodes control Plum Sawflies (Hoplocampa minuta and H. flava)

Plum sawflies are among the most damaging pests of European plum. Current control strategy implies insecticide application. Three species of entomopathogenic nematodes (EPN), Steinernema feltiae Filipjev, S. carpocapsae Weiser and Heterorhabditis bacteriophora Poinar were tested under laboratory and field conditions to assess effectiveness against larval and adult stages. Laboratory tests resulted in up to 100% mortality of last instar larvae before construction of a cocoon. However, the nematodes were not able to penetrate the cocoon. Foliar application did not result in plum sawflies larvae infestation by EPNs. Under field conditions, the nematodes reduced the number of emerging adults by application against sawfly larvae in the previous year before migration into the soil for overwintering by 62%–92%. Application of the nematodes against adults just before their anticipated emergence resulted in reduction of fruit infestation up to 100%. Mean results of 5 trials using caged trees were 47.8% with S. feltiae, 56.3% with S. carpocapsae and 62.9% with H. bacteriophora. In open field trails, control of adults obtained with S. feltiae at 0.5 million nematodes/m² was 98.2 and 67.8% and at 0.25 million m⁻² 41.7 and 41.2%. Forecasting adult emergence and optimal soil moisture conditions are essential for success of the nematode application.     

Effects of aldicarb and benomyl on nematodes, vesicular arbuscular mycorrhizas and the growth and yield of forage maize

The effects of aldicarb and benomyl on plant-parasitic nematodes, vesicular arbuscular mycorrhiza and the growth of forage maize were measured in 1980—1982 in two field experiments at Woburn, Bedfordshire and in a pot experiment using loamy sand soil from the field site. The most numerous migratory nematode, Tylenchorhynchus dubius increased three to four-fold during each season in untreated soil and was effectively controlled by aldicarb. Pratylenchus species were fewer but equally well controlled. The cereal cyst-nematode (Heterodera avenae), a serious maize pathogen in Northern France, was relatively scarce in untreated roots and was further decreased by aldicarb treatment; post-harvest H. avenae egg numbers were not affected by treatments; they declined equally because maize is such a poor host. Significant yield benefits (up to 37%) followed aldicarb treatment and were ascribed to nematode control in the absence of attribution to insect or other pests. Benomyl did not increase yields nor did it significantly affect the incidence of mycorrhiza. The results confirm that considerable losses of forage maize can be caused by nematodes in light soil and that aldicarb is an effective nematicide even at the rate of 1·7 kg a.i./ha.     

Density-dependent effects of multiple predators sharing a common prey in an endophytic habitat

Multiple predator species feeding on a common prey can lead to higher or lower predation than would be expected by simply combining their individual effects. Such emergent multiple predator effects may be especially prevalent if predators share feeding habitat. Despite the prevalence of endophagous insects, no studies have examined how multiple predators sharing an endophytic habitat affect prey or predator reproduction. We investigated density-dependent predation of Thanasimus dubius (Coleoptera: Cleridae) and Platysoma cylindrica (Coleoptera: Histeridae) on a bark beetle prey, Ips pini (Coleoptera: Scolytidae), in a laboratory assay. I. pini utilize aggregation pheromones to group-colonize and reproduce within the stems of conifers. T. dubius and P. cylindrica exploit these aggregation pheromones to arrive simultaneously with the herbivore. Adult T. dubius prey exophytically, while P. cylindrica adults enter and prey within the bark beetle galleries. Larvae of both predators prey endophytically. We used a multiple regression analysis, which avoids confounding predator composition with density, to examine the effects of varying predator densities alone and in combination on herbivore establishment, herbivore reproduction, and predator reproduction. Predators reduced colonization success by both sexes, and decreased I. pini reproduction on a per male and per female basis. The combined effects of these predators did not enhance or reduce prey establishment or reproduction in unexpected manners, and these predators were entirely substitutable. The herbivores net replacement rate was never reduced significantly below one at prey and predator densities emulating field conditions. Similar numbers of each predator species emerged from the logs, but predator reproduction suffered from high intraspecific interference. The net replacement rate of P. cylindrica was not affected by conspecifics or T. dubius. In contrast, the net replacement rate of T. dubius decreased with the presence of conspecifics or P. cylindrica. Combinations of both predators led to an emergent effect, a slightly increased net replacement rate of T. dubius. This may have been due to predation by larval T. dubius on pupal P. cylindrica, as P. cylindrica develops more rapidly than T. dubius within this shared habitat.     

Studies on Anhydrobiosis of Pratylenchus thornei

Large populations of Pratylenchus thornei, a winter pest of cereals, legumes, and potatoes in the northern Negev region of Israel, survive 7-8 months of summer drought and return to full activity at the beginning of the rainy season. To demonstrate that it survives the summer in an anhydrobiotic state, all developmental stages of P. thornei were exposed to gradually reduced relative humidity (RH) using glycerin water solutions. At 97.7% RH the nematodes were coiled and able to survive exposure to 0% RH. About 40% of artificially desiccated nematodes could be reactivated by gradually increasing the humidity to the final water environment. Desiccated nematodes could withstand temperatures up to 40 C. Reactivated individuals showed intestines apparently devoid of reserve materials. Only 3% survived three cycles of desiccation and reactivation. P. thornei reactivated after anhydrobiosis multiplied twice as much within Vicia sativa roots as did fresh nematodes.     

A phylogenetic framework for root lesion nematodes of the genus Pratylenchus (Nematoda): Evidence from 18S and D2-D3 expansion segments of 28S ribosomal RNA genes and morphological characters

The root lesion nematodes of the genus Pratylenchus Filipjev, 1936 are migratory endoparasites of plant roots, considered among the most widespread and important nematode parasites in a variety of crops. We obtained gene sequences from the D2 and D3 expansion segments of 28S rRNA partial and 18S rRNA from 31 populations belonging to 11 valid and two unidentified species of root lesion nematodes and five outgroup taxa. These datasets were analyzed using maximum parsimony and Bayesian inference. The alignments were generated using the secondary structure models for these molecules and analyzed with Bayesian inference under the standard models and the complex model, considering helices under the doublet model and loops and bulges under the general time reversible model. The phylogenetic informativeness of morphological characters is tested by reconstruction of their histories on rRNA based trees using parallel parsimony and Bayesian approaches. Phylogenetic and sequence analyses of the 28S D2–D3 dataset with 145 accessions for 28 species and 18S dataset with 68 accessions for 15 species confirmed among large numbers of geographical diverse isolates that most classical morphospecies are monophyletic. Phylogenetic analyses revealed at least six distinct major clades of examined Pratylenchus species and these clades are generally congruent with those defined by characters derived from lip patterns, numbers of lip annules, and spermatheca shape. Morphological results suggest the need for sophisticated character discovery and analysis for morphology based phylogenetics in nematodes.     

Effects of Hydroclytic Enzymes on Plant-parasitic Nematodes

Proteases, lipase, and chitinase killed Tylenchorhynchus dubius in vitro and in soil. Tylenchorhynchus dubius was more susceptible to the enzymes than Pratylenchus penetrans. Papain was the most effective protease, and other enzymes were less effective. Heating enzymes to 80 C for 10 min greatly reduced nematicidal effectiveness. Scanning electron micrographs showed that papain and chitinase produced structural changes in the cuticle of T. dubius. Lipase removed a thin outer layer. Papain removed material filling the striata, or furrow, between the horizontal bands. When added to soil, chitinase, lipase, collagenase, and proteases (papain and bromelain) decreased motility of T. dubius populations up to 75%. Bromelain was the most active in soil against T. dubius, and collagenase was the most active in soil against P. penetrans.     

Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice

Dobson C., Sitepu P. and Brindley P. J. 1985. Influence of primary infection on the population dynamics of Nematospiroides dubius after challenge infections in mice. International Journal for Parasitology15: 353–359. Similar proportions of the inoculum of Nematospiroides dubius larvae reached sexual maturity by 14 days after administration of 50–400 larvae but more adult worms had been expelled by day 63 after infection from those mice infected with 50 vs 400 larvae. There was a significant correlation between time and worm expulsion for all inoculum size groups except for mice given 400 larvae.In mice reinfected with 100 larvae, after termination of primary infections derived from 10 through 400 larvae, more worms from the challenging dose were recovered from mice given greater compared with those given smaller numbers of larvae at primary infection. The N. dubius population size after challenge infection was correlated positively both with number of larvae administered as the primary infection and with the resultant population size during that infection. The serum anti-N. dubius antibody titres after reinfection were higher in mice given 400 compared with those given fewer larvae at primary infection, and the fecundity and female to male sex ratio of the N. dubius populations decreased in proportion to these antibody titres.Protective immunity against challenge N. dubius infection, in mice which had been drenched free of adult worms established from 400 larvae for 5 down to 1 weeks before reinfection, increased from 45% (1 week) to 80% (5 weeks). There was a negative correlation between the population size of N. dubius during challenge infection and the duration between anthelmintic treatment and challenge infection.     

Field evaluation of entomopathogenic nematodes for the biological control of the annual bluegrass weevil,Listronotus maculicollis (Coleoptera: Curculionidae), in golf course turfgrass

The ability of entomopathogenic nematodes to suppress larval populations of the annual bluegrass weevil, Listronotus maculicollis, was investigated under field conditions over a 3-year period (2006–2008). Combination of nematode species, application rate and timing produced strong numerical yet few statistically significant reductions. Steinernema carpocapsae Weiser, S. feltiae Filipjev, and Heterorhabditis bacteriophora Poinar applied at 2.5×10⁹ IJs/ha reduced first generation late instars between 69 and 94% in at least one field trial. Steinernema feltiae provided a high level of control (94%) to low densities (~20 larvae per 0.09 m²), but gave inadequate control for higher densities (24 and 50% suppression). No significant differences were found among treatment timings. However, applications timed to coincide with the peak of larvae entering the soil (fourth instars) generally performed better than applications made prior to (preemptive) or after the majority of the population advanced from the fourth instar. Nematode populations declined sharply between 0 and 14 days after treatment (DAT). Although nematode populations later increased (at 28 DAT), indicating an ability to recycle within hosts in the environment, they were nearly undetectable 56 DAT when the second generation host larvae were present in the soil. Applying commercially available nematode species at standard field rates cannot reliably reduce L. maculicollis immature densities on golf courses, nor will single applications suppress multiple generations. Future research will need to identify application strategies to improve biocontrol consistency.     

Liquid Culture of the Entomogenous Nematode Steinernema feltiae with Its Bacterial Symbiont

The insect-parasitic nematode, Steinernema feltiae Filipjev strain 42, was reared in liquid culture along with its bacterial symbiont, Xenorhabdus nematophilus Thomas &Poinar. First-stage juveniles developed into reproducing adults in a maintenance salts medium containing resuspended Xenorhabdus cells and the yeast Kluyveromyces marxianus (Hansen) van der Walt or cholesterol. Cultures with media depths greater than 4 mm required aeration. Nematode populations increased as bacterial density increased. An optimal culture system was obtained when the bacteria and nematodes developed in a semidefined medium containing tryptic soy, yeast extract, and cholesterol and were incubated on a rotary shaker at 25 ± 1 C. Under these conditions, up to 86% of the final population were infective juveniles.     

Biocontrol of the apple sawfly,Hoplocampa testudinea,with entomogenous nematodes

Four types of experiments were conducted to assess the pathogenicity of entomogenous nematodes against the apple sawfly,Hoplocampa testudinea Klug (Hymenoptera: Tenthredinidae). In Petri dish,Steinernema carpocapsae (Weiser) DD 136 strain,S. carpocapsae All strain,S. feltiae (Filipjev) andHeterorhabditis bacteriophora Poinar caused 100% larval mortality 72 h after the treatments. In semi-field conditions under dwarf apple trees, a single treatment with either 40 or 80S. carpocapsae All strain/cm² caused significant (>80%) larval mortality. No significant increase in mortality was obtained with a second application. In 1990, late treatment with 80S. carpocapsae All strain/cm² caused significant (39.1%) pupal mortality. In 50×50 cm quadrats under dwarf apple trees, treatment with 40 and 80S. carpocapsae All strain/cm² were done in spring 1989. In spring 1990, respectively 22 and 25 apple sawfly adults emerged from quadrats treated with 40 and 80S. carpocapsae All strain/cm², whereas 78 adults emerged from untreated quadrats. In a foliar application experiment, a single treatment withS. carpocapsae All strain significantly reduced the percent of fruit showing secondary damage. The possibility of using entomogenous nematodes as part of an integrated pest management in apple orchards is discussed, with particular reference to the integration of programs aimed at managing plum curculio,Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) populations.