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Xenorhabdus nematophila is a symbiotic bacterium of the entomopathogenic nematode Steinernema carpocapsae (Weiser). It produces several toxic proteins which interfere with the immune system of insects. The current study shows that purified pilin protein could be a virulence trait of X. nematophila . The fifth instar larvae of Spodoptera exigua (Hübner) was injected with purified pilin. Changes in the cellular defenses in terms of total haemocyte counts and granulocyte percentage and humoral factors including total protease, phospholipase A 2 , and phenoloxidase activities (humoral defense) as well as the expression of the three main antimicrobial peptides attacin, cecropin, and spodoptericin were measured at specific times. The level of THC and granulocytes in larvae with different concentrations of pilin protein were less than the negative control. Also agglutination of haemocytes was observed 8–16 h post-injection. The pilin protein activated phenoloxidase in the initial hour post-injection, by 2 hpi, activity was stable. The activities of phospholipase A2 and protease activities reached maximum levels at 12 and 4 hpi, respectively, and then decreased. The expressions of attacin, cecropin, and spodoptericin in larvae treated with pilin protein were up-regulated above that of the normal sample. The overexpression of cecropin was greater than the other antimicrobial protein mRNA transcripts. The spodoptericin expression had an irregular trend while expressions of attacin and cecropin reached maximum levels at 4 hpi and then decreased. Generally, after the injection of pilin protein, the cellular and humoral immune system of S. exigua is activated but this toxin was able to inhibit them. This is the first report of the role of pilin protein when the bacterial symbiont of S. carpocapsae encounters the humoral defense of an insect. [ABSTRACT FROM AUTHOR]

In Brazil, the sugarcane borer, Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae), is controlled with massive releases of the hymenopteran parasitoid Cotesia flavipes Cam. (Hymenoptera: Braconidae); over 3 million hectares of sugarcane are treated annually with 18 billion parasitoids. In order to meet this demand, parasitoids are produced in D. saccharalis under laboratory conditions where a Nosema sp. is reported to be an important problem in mass rearing of the host. The goals for this work were to study the pathogenicity of the Nosema sp. and the progression of the disease in the host under laboratory conditions. The average median lethal time (LT 50 ) of Nosema sp. in first instar D. saccharalis varied from 9 ± 0.3 to 42 ± 2.3 days at concentration of 5 × 10 5 –0.5 spores/mm 3 artificial diet (10 7 –10 spores/μl). For third instar, the average of LT 50 ranged from 32 ± 0.7 to 37 ± 0.7 days at concentration of 5 × 10 5 –5 × 10 2 spores/mm 3 artificial diet (10 7 –10 4 spores/μl in saline). The concentration necessary to cause 50% mortality (LC 50 ) of first instar larvae was 5.6 (0.9–17.6) spores/μl and the estimated LC 50 for third instar larvae was 1,200 (200–4700) spores/μl. The impacts of Nosema sp. on D. saccharalis were analyzed for first instar larvae fed 0.5 spores/mm 3 artificial diet. Duration and viability of the larval and pupal stages, adult longevity, pupal weight and fertility life table were measured for offspring of mating pairs composed of infected females and uninfected males or infected males and uninfected females and compared to offspring of uninfected pairs. Nosema sp. infection resulted in adverse effects on all biological parameters measured except for the duration of the larval and pupal stages and the weight of the male pupae, which did not differ statistically between infected and uninfected groups. The intrinsic rates of growth ( r m ) were greater for uninfected pairs compared to pairs with either male or female infected. The growth rate of individual larvae produced by uninfected adults was 48.2% faster than of larval offspring of infected females and it was negative (−0.003) when males were infected. Our study confirms the negative impact of the Nosema sp. in mass rearing of D. saccharalis for parasitoid production but shows potential for use as a microbial control agent of the sugarcane borer. [ABSTRACT FROM AUTHOR]

Rose sawfly,Arge ochropus(Gmelin), is one of the most important pests of ornamental plants such as roses and wild rose bushes in Northern Iran. We investigated the interactions between the insecticides imidacloprid and the entomopathogenic nematodesHeterorhabditis bacteriophoraandSteinernema carpocapsaeas control agents of fifth-instar larvae in the laboratory. The larvae were very susceptible toS. carpocapsae(LC50: 21 infective juvenile per larva) andH. bacteriophora(LC50: 32). Combinations of two imidacloprid rates (LC30and LC50) and four rates of each nematode species (LC25–LC75) were tested. Combinations with the lower imidacloprid rate except for that with the highestH. bacteriophorarate caused higher mortality than both respective single-agent treatments. In combination with the higher imidacloprid rate, only one combination withH. bacteriophoraand two combinations withS. carpocapsaecaused higher mortality than both respective single-agent treatments. Interactions were generally stronger at the lower imidacloprid rate and were stronger forS. carpocapsae(synergistic in seven combinations, additive in one) than forH. bacteriophora(synergistic in two, additive in six). Synergistic imidacloprid-S. carpocapsaecombinations could be a useful tool for the control ofA. ochropuslarvae that would simultaneously control other common pests susceptible to imidacloprid. [ABSTRACT FROM PUBLISHER]

The haemocyte reactions of the white grub larvae Polyphylla adspersa to entomopathogenic nematodes (EPN), together with the host haemocyte types, have been studied. Six types of identified haemocytes included the prohaemocytes, granulocytes, plasmatocytes, oenocytoids, coagulocytes and spherulocytes. The granulocytes were :he dominant (65.2%) haemocyte type followed by the plasmatocytes (22.1 %). Both haemocyte types encapsulate EPN. White grub larvae and last larval stage of Galleria mellonella were individually infected with monoxenic Heterorhabditis bacteriophora or Steinernema glaseri. The maximum total haemocyte counts (THC) level of the white grub larvae against the nematode S. glaseri occurred at 12 h post-injection. In addition, by 8 h post-injection, the granulocyte and plasmatocyte levels decreased. The cell reactions of the grubs against H. bacteriophora in terms of THC and differential haemocyte counts and the encapsulation rate started earlier and were more pronounced than those against S. glaseri. The maximum percentage of the encapsulation observed in the white grub larvae against S. glaseri (27.3 ± 0.7%) and H. bacteriophora (36.5 ± 3.5%) occurred at 12 and 8 h post-injection, respectively. EPN-triggered encapsulation in P. adspersa larvae was more extensive than in G. mellonella larvae. [ABSTRACT FROM AUTHOR]