Phagostimulants enhancing the efficacy ofBacillus Thuringiensis formulations against the Giant Looper,Boarmia (Ascotis) Selenaria,in avocado

In both laboratory and field trials, as well as in semicommercial scale applications, the minimum concentration ofBacillus thuringiensis (B.t.) required to secure satisfactory larval mortality ofBoarmia selenaria could be halved, from 0.5% to 0.25%, by addition of 1% of the commercial phagostimulant Coax. Another phagostimulant product, Gustol, was inactive. Coax did not attract caterpillars from a distance. However, individual, Coax-treated spots on the avocado leaf surface were consumed by the larvae to a significantly greater extent than control. The same difference in palatability was recorded when the spots were treated with a mixture of Coax and aB.t. formulation. This explains, at least partially, the aforementioned advantageous effect of Coax in practical control of the looper byB.t.     

Modeling the survival of two soilborne pathogens under dry structural solarization

ABSTRACT Structural (space) solarization of a closed, empty greenhouse for sanitation involves dry heating to 60 degrees C and higher and low relative humidity (RH), under a fluctuating temperature and RH regime. Survival of inocula of Fusarium oxysporum f. sp. radicis-lycopersici and Sclerotium rolfsii during structural solarization was studied for 4 years (total of 12 experiments) in an attempt to develop a dynamic model for expressing the thermal inactivation of the pathogens. After 20 days of exposure, the populations of F. oxysporum f. sp. radicis-lycopersici and S. rolfsii were reduced by 69 to 95% and by 47.5 to 100%, respectively. The Weibull distribution model was applied to describe pathogen survival. The Weibull rate parameter, b, was found to follow an exponential (for F. oxysporum f. sp. radicis-lycopersici) and the Fermi (for S. rolfsii) functions at constant temperatures. To improve the applicability of the model, fluctuating conditions of both temperature and RH were utilized. The Weibull distribution derivative, expressed as a function of temperature and moisture, was numerically integrated to estimate survival of inocula exposed to structural solarization. Deviations between experimental and calculated values derived from the model were quite small and the coefficient of determination (R (2)) values ranged from 0.83 to 0.99 in 9 of 12 experiments, indicating that ambient RH data should be considered. Structural solarization for sanitation could be a viable component in integrated pest management programs.     

Parasitism of <Emphasis Type="Italic">Trichoderma</Emphasis> on <Emphasis Type="Italic">Meloidogyne javanica</Emphasis> and role of the gelatinous matrix

Trichoderma (T. asperellum-203, 44 and GH11; T. atroviride-IMI 206040 and T. harzianum-248) parasitism on Meloidogyne javanica life stages was examined in vitro. Conidium attachment and parasitism differed beween the fungi. Egg masses, their derived eggs and second-stage juveniles (J2) were parasitized by Trichoderma asperellum-203, 44, and T. atroviride following conidium attachment. Trichoderma asperellum-GH11 attached to the nematodes but exhibited reduced penetration, whereas growth of T. harzianum-248 attached to egg masses was inhibited. Only a few conidia of the different fungi were attached to eggs and J2s without gelatinous matrix; the eggs were penetrated and parasitized by few hyphae, while J2s were rarely parasitized by the fungi. The gelatinous matrix specifically induced J2 immobilization by T. asperellum-203, 44 and T. atroviride metabolites that immobilized the J2s. A constitutive-GFP-expressing T. asperellum-203 construct was used to visualize fungal penetration of the nematodes. Scanning electron microscopy revealed the formation of coiling and appressorium-like structures upon attachment and parasitism by T. asperellum-203 and T. atroviride. Gelatinous matrix agglutinated T. asperellum-203 and T. atroviride conidia, a process that was Ca²⁺-dependent. Conidium agglutination was inhibited by carbohydrates, including fucose, as was conidium attachment to the nematodes. All but T. harzianum could grow on the gelatinous matrix, which enhanced conidium germination. A biomimetic system based on gelatinous-matrix-coated nylon fibers demonstrated the role of the matrix in parasitism: T. asperellum-203 and T. atroviride conidia attached specifically to the gelatinous-matrix-coated fibers and parasitic growth patterns, such as coiling, branching and appressoria-like structures, were induced in both fungi, similarly to those observed during nematode parasitism. All Trichoderma isolates exhibited nematode biocontrol activity in pot experiments with tomato plants. Parasitic interactions were demonstrated in planta: females and egg masses dissected from tomato roots grown in T. asperellum-203-treated soil were examined and found to be parasitized by the fungus. This study demonstrates biocontrol activities of Trichoderma isolates and their parasitic capabilities on M. javanica, elucidating the importance of the gelatinous matrix in the fungal parasitism.     

Evaluation of Trichoderma spp. as a Biocontrol Agent Against Soilborne Fungi and Plant-parasitic Nematodes in Israel

The optimal conditions required to market Trichoderma as a biocontrol agent against soilborne fungi and nematodes are discussed. These include a proper formulation, an efficient delivery system, and alternative methods for Trichoderma's application.The implementation of Trichoderma in integrated pest management (IPM) can be achieved using a soil treatment which combines reduced amounts of biocides/fungicides and the Trichoderma preparation. Biocontrol activity can be increased by combining two (or more) types of biocontrol agents. Moreover, the construction of a genetically modified Trichoderma can lead to the improvement of certain traits which are absent or not highly expressed in the native microorganism isolated from its natural habitat.Different Trichoderma harzianum and T. lignorum isolates were tested for their nematicidal activity against the root-knot nematode Meloidogyne javanica. In short-term experiments, improved growth of nematode-infected plants and decreases in the root-galling index and the number of eggs per gram of root were achieved when nematode-infested soils were pre- exposed to the T. harzianum preparations. A long-term experiment resulted in improved growth and higher yield of nematode-infected plants, but no significant change in the galling index, either by pre-exposure of the fungus to the soil or by enrichment in the root-ball.As biocontrol is an integral part of the IPM philosophy, judicious use of Trichoderma against soilborne pathogens, when demonstrated to be consistently effective, practical and economic, can serve as a model for the introduction and implementation of other biocontrol means into IPM.     

Use of a self-expanding metallic stent for the treatment of a urethral stricture in a young cat

A 4-month-old intact male domestic shorthair cat was evaluated for urinary outflow obstruction after several weeks of medical management for traumatic urethral rupture. Positive-contrast retrograde urethrography and anterograde cystoscopy performed 4 weeks after the initial urethral injury confirmed a stricture approximately 1cm distal to the bladder trigone at the site of the initial urethral tear. A self-expanding metallic urethral stent (SEMS) was placed under fluoroscopic guidance to relieve the urethral stricture and re-establish luminal patency. After stent placement, the cat was able to void urine normally with minimal urinary incontinence noted. This resolved several months post-stent placement. No known clinical complications persisted other than mild intermittent hematuria.     

Methods for Determining Pythium Suppression In Container Media

Pythium damping-off and root-rot are among the most important soilborne diseases of greenhouse plants and seedlings grown in container media. It has been shown previously that composts may be conducive, suppressive or partially suppressive to Pythium diseases. The major goal of this work was to investigate rapid, practical and reliable methods for determining of the degree of suppressiveness of container media to Pythium damping-off. Several inoculation methods were tested in greenhouse bioassays, survival of propagules in suppressive versus conducive media was studied under laboratory conditions. Although both greenhouse and laboratory tests could indicate disease suppression, a bioassay with cucumber seedlings is suggested to be the most simple, effective and comprehensive method for testing suppression of Pythium diseases in compost amended container media.     

Nematicidal Activity of Chrysanthemum coronarium

Organic amendments and green manure are potential alternatives to the harmful chemical control means currently used against plant-parasitic nematodes. In this work, Chrysanthemum coronarium was applied to the soil as a green manure to control the root-knot nematodes Meloidogyne incognita and M. javanica. Chrysanthemum coronarium significantly reduced nematode infection of tomato roots and improved plant-top fresh weight, both in the greenhouse and in microplots. Other green manures, derived from Anthemis pseudocotula, wild chickpea (Cicer pinnatifidum), Geranium spp. and wheat, were not as effective as C. coronarium. Chrysanthemum coronarium, retained its nematicidal activity even when applied as a dried material. Only mature C. coronarium plants, in their flowering stage, exhibited nematode control activity, but the green plant parts were more effective than the flowers. An aqueous extract of C. coronarium exhibited in vitro, nematostatic activity towards M. incognita and M. javanica second-stage juveniles and inhibited their hatching from eggs and egg-masses; its nematostatic activity was expressed also against other phytonematode species such as Heterodera avenae and Pratylenchus mediterraneus, but did not affect the beneficial entomopathogenic nematode Steinernema feltiae.