Investigation on survival of Aphidius nigripes Ashmead (Hym.: Aphidiidae) reared on infected potato aphid by Lecanicillium muscarium (Deut.: Moniliaceae).

Survival of larval stages of endoparasitoid Aphidius nigripes Ashmead was investigated on entomopathogen Lecanicillium muscarium (Zare and Gains) infected potato aphid Macrosiphum euphorbiae Thomas. Low and high concentrations of L. muscarium (10s and 10(7) blastospore/ml., respectively) were administered on parasitized aphid nymphs (by A. nigripes) on 0, 2, 4 and 6 day intervals base. Distilled water with surfactant agent was used as control and 3 replicates were applied. Ten days following inoculation by the pathogen, aphid mortality; aphid progeny and emerged parasitoids were sampled to estimate the aphid survival, treated aphid net reproductive rate (Ro) and survival of parasitoid, respectively. Results demonstrated that parasitoid and pathogen collectively enhanced aphid mortality and lowered its net reproductive rate compared to any single use of the agents (P<0.01). Mortality of immature parasitoid decreased when low concentration of fungus was applied and the same result obtained on any increase between fungus inoculation and parasitization interval. Parasitoid suffered a vast mortality rate in pupation period using high concentration of the fungal material. On the weight comparison base, there wasn't any significant differences (P>0.05) between emerged parasitoid adults, both from fungus infected mummified aphids and control treatments.

Preliminary evaluation of the effectiveness of a Verticillium lecanii isolate in the control of Thrips tabaci (Thysanoptera: Thripidae).

Thrips tabaci is a polyphagous pest that attacks many different crop and ornamental plant species. Recently, the need to reduce the use of insecticides in the control of thrips is more and more increasing. On that account, the possibility to make use of the entomopathogenic fungus Verticillium lecanii (DAOM198499) was evaluated in laboratory conditions. Suspension of 10(3) to 10(7) conidia/ml grown in liquid culture medium with a control (distilled water) treated on second larval stage of T. tabaci in controlled condition (16L: 8D photoperiod, 25 +/- 1 degrees C temperature, 98% RH in first 48h and 70% RH in next days). Preliminary results showed that mortality in lethal suspension (10(7) conidia/ml) of V. lecanii after 24 hours and 2-7 days in lower suspension appears. This suggests that strine DAOM 198499 of V. lecanii has the ability to control T. tabaci in greenhouse conditions.

Pathogenicity of the fungus, Verticillium lecanii, to the green peach aphid, Myzus persicae (Hom.: Aphididae).

Pathogenicity of the hyphomycete, Verticillium lecanii (DAOM 198499), was investigated to aphid, Myzus persicae under laboratory conditions. Analysis of lethal effect of six various concentrations 0, 10(4), 10(5), 10(6), 10(7) and 10(8) conidia/ml of V. lecanii against third nymphal stage of M. persicae, indicated significant mortality on aphids. Mean comparisons showed that there was significant difference between treatments. Three days after treatment, aphid mortality observed and after 12 days minimal mortality was 17.77 in control and maximum was 100 percent related to 10(7) and 10(8) conidia/ml. LC50 and LT50 values were estimated by probit analysis and life test. LC50 value for aphid mortality was 1.4 x 10(4) conidia/ml, LT50 values for concentrations 10(4), 10(6), 10(6), 10(7) and 10(8) conidla/ml was 10, 10, 9, 8 and 6 days, respectively. In this experiment, net reproduction rate of aphid's (R0) decreased significantly when concentration increased. These observations showed that V. lecanii (DAOM 198499) can be an active biological agent against aphids.

Phenolic compounds from Eucalyptus maculata.

From the chloroformic extract of the resinous exudate of the stems of Eucalyptus maculata, four phenolic constituents have been isolated. A new di-cinnamic acid glucose ester was isolated, in addition to cinnamic acid, 7-methyl aromadendrin and sakuranetin. The isolated compounds were elucidated using UV, IR, 1D and 2D NMR and MS.

Sesquiterpene lactone glucosides from Sonchus asper.

From the methanolic extract of the roots of Sonchus asper, two new sesquiterpene glucosides, together with two known sesquiterpene glucosides and a known aglycone were isolated. Structures were identified as 11beta,13-dihydrourospermal A, 15-O-beta-D-glucopyranosyl-11beta,13-dihydrourospermal A, 15-O-beta-D-glucopyranosylurospermal A, 15-O-[6'-(p-hydroxyphenylacetyl)]-beta-D-glucopyranosylurosperm al A and 14-O-methylacetal-15-O-[6'-(p-hydroxyphenylacetyl)]-beta-D-+ ++glucopyranosylurospermal A, by spectroscopic means.

Hirsutinolides from Vernonia cinerascens.

The aerial parts of Vernonia cinerascens, collected in Saudi Arabia, yielded a new hirsutinolide, together with three known lactones. The structure of the new compound was elucidated using, 1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HETCOR and HMBC.

Ultrastructural and cytochemical characterization of aphid invasion by the hyphomycete verticillium lecanii

Chronological events of the interaction between the hyphomycete Verticillium lecanii and the potato aphid Macrosiphum euphorbiae were investigated by light, scanning, and transmission electron microscopy. The parasitism of M. euphorbiae by V. lecanii appears to involve the following events: (i) adherence of conidia to the host cuticle through a thin mucilagenous matrix; (ii) germination of the conidia and production of mycelium that colonizes the surface of the cuticle; (iii) penetration of germ tubes into the aphid cuticle 24 h after application of the pathogen; (iv) extensive lateral development of hyphae accompanied by pronounced degradation of the cuticular layers by 72 h. Labeling with the WGA/ovomucoid-gold complex showed that penetration and colonization of the cuticle by the fungus resulted from localized enzymatic hydrolysis, likely through the synergistic action of chitinases and mechanical pressure; (v) production of blastospores and massive invasion of aphid internal tissues; (vi) assimilation of nutrients and accumulation of lipids by fungal cells; and (vii) production of conidiophores and release of the fungus from aphid cadavers. These observations bring further insights into the mechanisms by which V. lecanii parasitizes M. euphorbiae. They also provide a basis for comparing the modes of action of V. lecanii against hosts from fungal and animal origins. Copyright 1999 Academic Press.

Ultrastructural and Cytochemical Investigations of the Antagonistic Effect of Verticillium lecanii on Cucumber Powdery Mildew.

ABSTRACT Chronological events of the intercellular interaction between Verticillium lecanii and cucumber powdery mildew, caused by Sphaerotheca fuliginea, were investigated at different times after inoculation by transmission electron microscopy. V. lecanii hyphae colonized host structures by tight binding, apparently mediated by a thin mucilaginous matrix. As early as 24 h after application of the antagonist, increased vacuolation and disorganization of the cytoplasm of the pathogen hyphae were easily detected. By 36 h after treatment, plasmalemma retraction and local cytoplasm aggregation were typical features of damage. Labeling chitin with the wheat germ agglutinin (WGA)/ovomucoid-gold complex showed that intracellular invasion of S. fuliginea by V. lecanii did not cause extensive host cell wall alterations, except in the area of hyphal penetration. By 48 h after inoculation, further cytoplasm disorganization was observed, as evidenced by the loss of cell turgor and contortion of the cell wall. Such deformation suggests that penetration of the antagonist results from mechanical pressure or localized enzymatic hydrolysis through the action of chitinases, as confirmed by the pattern of labeling obtained with the WGA/ovomucoid-gold complex. By 72 h after contact between the fungi, S. fuliginea cells were markedly collapsed, depleted of their protoplasm due to extensive multiplication of the antagonist, and totally encircled by the antagonist. Based on the current observations, the antagonism of S. fuliginea by V. lecanii appears to involve the following events: (i) attachment of the antagonist to the powdery mildew fungus; (ii) mechanical pressure and production of cell-wall degrading enzymes such as chitinases; (iii) penetration and active growth of the antagonist inside the pathogen hyphae; and (iv) digestion of host tissues and release of the antagonist from dead cells of S. fuliginea. The interaction between V. lecanii and S. fuliginea also affected the morphological and structural features of the haustorial bodies, as shown by increased vacuolation, distortion, and necrotization of the haustorial lobes. These observations provide the first experimental evidence that V. lecanii, primarily known as an entomopathogenic fungus, also has the potential to colonize mycelial structures of S. fuliginea. V. lecanii, therefore, may become a valuable alternative to current management of cucumber powdery mildew in greenhouses.