Showing papers in "Phytoparasitica in 2003"

Biotype Q of Bemisia tabaci Identified in Israel

Abstract: The biotype status of samples of the whiteflyBemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) collected from several field and greenhouse sites in Israel during 1999–2000 was determined by polyacrylamide gel electrophoresis (PAGE) for general esterases, and by RAPD-PCR using primers of arbitrary sequence. Results of this survey provide the first published evidence for the occurrence of theB. tabaci Q biotype, alongside the more widely distributed B biotype. Based on the collected samples, it appears that both the B and Q biotypes are present in Israel, and that field populations consist of a mixture of the two biotypes. A possible link betweenB. tabaci biotypes and insecticide resistance is discussed.

Rootstock resistance to Fusarium wilt and effect on watermelon fruit yield and quality

Abstract: The potential of grafted watermelon for resistance toFusarium oxysporum f.sp.niveum on some Curcurbitaceae,Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) ofF. oxysporum f.sp.niveum except watermelon cv. ‘Crimson Tide’, which was susceptible to race 2. Fruit yield was positively (21–112%) affected byLagenaria rootstocks but negatively affected (200–267%) byCucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants onLagenaria rootstocks, the quality parameters for watermelon grafted ontoCucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility betweenCucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon.

Greenhouse and field screening of wild Lycopersicon germplasm for resistance to the whitefly Bemisia argentifolii

Abstract: Thirty-two accessions of wild tomato (Lycopersicon spp.) germplasm were evaluated for resistance to the whiteflyBemisia argentifolii Bellows ⇐p; Perring in a greenhouse choice bioassay. Density data were recorded for the adaxial and abaxial leaf surfaces for (i) all life stages ofB. argentifolii and (ii) types I, IV, V and VI trichomes. Individual plant selections (33 from 22 wild tomato accessions) with high resistance were subsequently tested in the field to verify the resistance found in the greenhouse screening. Resistance was defined by the density of all life stages of the whitefly observed on the eight leaflets sampled at nodes 5 and 7. Only type IV trichomes had a consistent (but low) and significant negative correlation between trichome density and whitefly density for various life stages. The highest whitefly resistance was observed inLycopersicon pennellii accessions LA 716, LA 1340 and LA 2560. The most resistantL. hirsutum f.typicum accessions were LA 1777 and LA 1353.

A new pathotype of Pseudoperonospora cubensis causing downy mildew in cucurbits in Israel

Abstract: Downy mildew, incited by the comycetePseudoperonospora cubensis (Berk.et Curt.) Rost., was recorded in Israel during the years 1979–2001 on cucumber (Cucumis sativus) and melon (Cucumis melo) and classified as pathotype 3. In July 2002 severe outbreaks of downy mildew occurred on pumpkin (Cucurbita moschata) and summer squash (Cucurbita pepo subsp.pepo). Host range pathogenicity studies revealed high compatibility of the new population with cucumber, melon, pumpkin and summer squash but low compatibility with watermelon. This new population was therefore designated as pathotype 6. The possible origin of this new pathotype in Israel is discussed.

Effect of a UV-deficient environment on the biology and flight activity of Myzus persicae and its hymenopterous parasite Aphidius matricariae

Abstract: Laboratory and field experiments were conducted to study the effect of UV filtration on the population growth, distribution and flight activity of the green peach aphidMyzus persicae (Sulzer) (Homoptera: Aphididae), and on the fecundity and host-finding behavior of the parasitic waspAphidius matricariae (Haliday) (Hymenoptera: Braconidae). The work was done in the Arava Valley of Israel, in walk-in tunnels covered with polyethylene film, to compare the effects of UV-absorbing filmversus those of regular film. Following artificial aphid infestation on pepper grown under the tested films, aphid population growth and spread under the UV-absorbing films were significantly less than under the regular films. The greatest impact of UV-absorbing film on aphid behavior was observed in winter and early spring, when temperature conditions favor aphid development. Elimination of UV by UV-absorbing film did not affect the parasitic activity ofA. matricariae. Previous results had indicated that covering the greenhouse with UV-absorbing films inhibited the invasion of aphids and other insect pests into it. That effect, in combination with those described in the present paper, makes the use of UV-absorbing films an effective component of IPM that aims to reduce the application of toxic insecticides.

Effects of organic and synthetic fertilizer sources on pest and predatory insects associated with tomatoes

Abstract: The effects of organic (composted cow manure) and synthetic (NPK) fertilizers on pests (aphids and flea beetles) and predatory arthropods (anthocorids, coccinellids and chrysopids) associated with tomatoes were evaluated in a 2-year randomized complete block field experiment. Our data suggested that the application of either organic or synthetic fertilizers could increase pest populations on tomatoes. However, there were lower populations of aphids on tomatoes grown with the organic fertilizer than on those grown with the synthetic fertilizers in the second year of the experiment, indicating that organic fertilizers may have the potential to reduce pest attacks in the long term. Anthocorid populations were larger on tomato plants with high aphid populations in the synthetic than in the organic fertilizers-treated plots.

Synergistic interaction between BABA and mancozeb in controlling Phytophthora infestans in potato and tomato and Pseudoperonospora cubensis in cucumber

Abstract: Spray mixtures consisting of the plant activator BABA (DL-3-aminobutyric acid) and the protectant fungicide mancozeb were significantly more effective than BABA or mancozeb alone in controlling late blight (Phytophthora infestans) in potato and tomato and downy mildew (Pseudoperonospora cubensis) in cucumber. A mixture composed of 5 parts BABA and 1 part mancozeb (w/w, a.i.) exhibited a higher synergy factor than the 1+1 or the 1+5 (BABA + mancozeb) mixtures. No synergistic interaction was detected between BABA plus mancozeb in controlling sporangial or cystospore germination, nor mycelial growth ofP. infestans in vitro. The results showed enhanced effect of mancozeb in BABA-induced plants, suggesting, therefore, that lower dosages of this fungicide may be sufficient to control late blight or downy mildew under field conditions.

Pymetrozine interferes with transmission of Tomato yellow leaf curl virus by the whitefly Bemisia tabaci

Abstract: Pymetrozine, a novel compound belonging to the class pyridine-azomethines, is a feeding inhibitor labeled for use against plant pests in the order Hemiptera. Pymetrozine was evaluated for its ability to interfere with whitefly transmission of the begomovirusTomato yellow leaf curl virus (TYLCV). Pymetrozine was applied as Fulfill TM 50 WG at two rates (0.291 and 0.582 g formulationl −1) to tomato seedlings with four to six true leaves. Viruliferous whiteflies (three to five per plant) were added 1, 4, 7 and 11 d after a single application of pymetrozine, and transmission rates were determined 4 wk after the addition of whiteflies. Pymetrozine provided protection against transmission of TYLCV by viruliferous whiteflies for up to 1 wk after a single apliation. No phytotoxicity was observed on tomato transplants. These results indicate that pymetrozine could be an effective tool for tomato transplant producers to protect susceptible transplants from infection by begomoviruses, such as TYLCV. Pymetrozine might also work well as part of an integrated approach to begomovirus management in greenhouse tomato fruit production.

Influence of environmental factors on field concentrations ofAlternaria solani conidia above a South African potato crop

Abstract: Trends in weather variables and concentrations of airborne conidia ofAlternaria solani were monitored in a potato field in South Africa during three potato-growing seasons in 2001 and 2002. Distinct seasonal variation was noted, with a drop in spore numbers during winter. Peaks in spore concentration coincided with periods favorable for spore formation and dispersal; most notable was the effect of interrupted wetting periods. Diurnal periodicity of spore dispersal was also observed, with the peak of spore concentrations between 9h00 and 18h00. Few spores were sampled at night, when wind velocity and temperature are lowest and relative humidity is highest. Increased numbers of spores were sampled during days of harvesting or when other ground-operated farm equipment was used. The results obtained in this study will be useful in establishing decision support systems to control early blight on potatoes in southern Africa.

Comparative effect of root-knot nematode on severity of verticillium and fusarium wilt in cotton

Abstract: The effect of root-knot nematode (RKN) (Meloidogyne incognita) onVerticillium dahliae andFusarium oxysporum f.sp.vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection byF. oxysporum is a well known effect but there are few reports of enhanced infection byVerticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated.

Laboratory evaluation of the insect growth regulator lufenuron against Helicoverpa armigera on cotton

Abstract: An insect growth regulator (IGR), lufenuron (Match 5EC), was tested for its toxicity toHelicoverpa armigera on cotton. Potency of the IGR against the larval stage of the pest was demonstrated with respect to larval instars; the LC90 values of 1st, 2nd, 3rd, 4th and 5th instar larvae were 5.63, 7.89, 8.03, 11.39 and 14.76 mg a.i.l −1, respectively. However, different larval instars did not differ significantly with respect to LC50 and LC10. IGR-treated larvae had swollen heads and were significantly smaller (1.5–2.3 mm) than the untreated control (2.9 mm). Larval weight was significantly reduced from 190 mg in the control to 50–70 mg in the lufenuron treatment. IGR treatment in the larval stage significantly affected both pupal length and pupal weight. Pupal duration of the test insect was significantly extended by IGR treatment. Pupal deformities, including an inability to shed the last larval skin and formation of larval-pupal intermediates, occurred following treatment. A significant reduction in adult emergence was recorded. In addition, abnormalities in the form of development of cavities in the forewings of adult were evident. A significant decline in fecundity was noted in the studies.

NOTE: Utilization of Sounding Methodology to Detect Infestation by Rhynchophorus ferrugineus on Palm Offshoots

Abstract: The use of sounding equipment for the detection of boring larvae of the red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Col., Curculionidae), in palm trunks was evaluated and found to be useful. Employment of this method would improve the detection efficiency of weevils in palm offshoots, thereby avoiding the transfer of infested material and curtailing the spread of RPW infestations. Sound recordings of RPW larval activity are being studied for the development of a sound profile that will serve as a basis for future instrumental detection of RPW infestations within tree trunks.

Seed treatment prevents vertical transmission of Fusarium moniliforme , making a significant contribution to disease control

Abstract: Fusarium moniliforme is a widespread facultative endophyte, primarily associated with corn, where it causes extensive crop damage.F. moniliforme can be toxigenic, the carcinogenic fumonisins being accumulated predominantly when the fungus colonizes corn plants. The pathogen is transmitted both through contaminated seeds and through environmental inoculum. This study utilized markednit-mutantF. moniliforme inoculum in order to evaluate the quantitative significance of seedborne disease transmission. Greenhouse and field trials demonstrated that seedborne isolates were responsible for up to 50% ofF. moniliforme disease. Seed treatment with the fungicide prochloraz was found to control seedborne transmission and to protect againstF. moniliforme seedling blight. The elimination of seedborne inoculum resulted in reduced incidence of kernel rot and avoided the increment in soil inoculum accumulation associated with the introduction of infected seeds.

Dry mycelium ofPenicillium chrysogenum protects cucumber and tomato plants against the root-knot nematodeMeloidogyne javanica

Abstract: Incorporation into soil of dry mycelium ofPenicillium chrysogenum, a waste product of the pharmacological industry, enhanced plant growth and reduced root galling caused by the root-knot nematodeMeloidogyne javanica in cucumber and tomato plants. Incorporation into sandy loam soil in pots of dry mycelium at a concentration of 0.25% (w/w) resulted in complete protection of cucumber plants from the nematode. The number of juveniles recovered from soils containing dry mycelium was greatly reduced even at a concentration of 0.1% (w/w). In microplot studies conducted at two sites in two seasons, with three or four doses, dry mycelium caused a dose-dependent reduction in root galling index (GI) and promotion of plant growth of cucumber and tomato plants. Inin vitro studies, the water extract of dry mycelium immobilized nematode juveniles and reduced the egg hatching rate, but these effects were partly reversible after a rinse in water. Soil-drenching of cucumber and tomato seedlings with water extract of dry mycelium did not reduce GI or number of root-invading juveniles. The results show that dry mycelium promotes plant growth and protects plants against nematode infection. Protection, however, does not operatevia induced resistance.

A survey of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) in Diyarbakır, Turkey.

Abstract: A list is given of aphid parasitoids found in Diyarbakir Province, Turkey. In the survey, performed between 1998 and 2000, 16 species of aphid parasitoids were found on different hosts in Diyarbakir Province.Monoctonus mali is reported for the first time in the Turkish aphid parasitoids fauna.

Identification and pathogenicity of Fusarium spp. from stem bases of winter wheat in Erzurum, Turkey.

Abstract: Four-hundred-sixty-eightFusarium andFusarium-like isolates were obtained from crowns and subcrown internodes of winter wheat grown in Erzurum, Turkey. Of these isolates, 34.8% wereFusarium acuminatum, 32.3% wereF. equiseti, 16.9% wereF. oxysporum, 15.0% wereMicrodochium nivale (formerlyFusarium nivale), 0.6% wereF. tabacinum and 0.4% wereF. solani. In pathogenicity tests on wheat, the highest disease severity was caused by isolates ofM. nivale, whereas isolates ofF. acuminatum, F. equiseti, F. oxysporum andF. solani were slightly virulent; isolates ofF. tabacinum were nonpathogenic. This is the first report ofM. nivale andF. tabacinum from wheat in Turkey.

Quantification of camalexin in several accessions of Arabidopsis thaliana following inductions with Peronospora parasitica and UV-B irradiation

Abstract: Five accessions ofArabidopsis thaliana, Ws-3, Nd-1, Ler, Col-5 and Oy-0, were inoculated withPeronospora parasitica isolate Emoy2 and the accumulation of camalexin within infected tissues was measured. The variations in camalexin accumulation in various accessions ofA. thaliana induced by a specific (P. parasitica isolate Emoy2) and a non-specific elicitor (UV-B irradiation) were investigated. Phenotypic examination of Emoy2/Oy-0 revealed that susceptibility was characterized by extensive asexual sporulation of the pathogen, whereas early restriction of the pathogen in infected plant tissues, accompanied by chlorosis and necrosis — which are associated with the hypersensitive response — was observed in Nd-1, Ws-3 and Ler. Partial resistance detected in Col-0 was characterized by low to medium sporulation of the pathogen. Camalexin was monitored by high pressure liquid chromatography (HPLC) and found to accumulate during both compatible and incompatible interactions and also following treatment with the abiotic inducer, UV-B. Among the accessions tested, Ws-3 yielded significantly more camalexin than the other accessions, regardless of which inducers (biotic or abiotic) were used. There was no significant correlation between resistance and camalexin accumulation in theA. thaliana/P. parasitica interaction. The results suggest that there is genetic variation in camalexin biosynthesis among accessions ofA. thaliana, rather than variation in types of induction.

Identification and pathogenicity of Rhizoctonia solani and binucleate Rhizoctonia anastomosis groups isolated from forage legumes in Erzurum, Turkey.

Abstract: Three-hundred-twenty-five isolates ofRhizoctonia (215R. solani and 110 binucleateRhizoctonia) were obtained from roots and crowns of alfalfa, sainfoin and common vetch grown in Erzurum, Turkey. The isolates were assigned to five anastomosis groups (AG) ofR. solani (AG-2-1, AG-3, AG-4, AG-5, and AG-10) and two anastomosis groups of binucleateRhizoctonia (AG-I and AG-K). In pathogenicity tests on alfalfa, sainfoin and common vetch, the highest disease severities were caused by isolates of AG-4 and AG-5. Isolates of AG-10 and AG-I were not pathogenic on the three tested forage legumes, whereas isolates of AG-K on alfalfa and sainfoin, and of AG-2-1 on sainfoin, were moderately virulent. Alfalfa isolate AG-3 was moderately virulent on sainfoin. This is the first report ofR. solani AG-3, AG-5, AG-10 and binucleateRhizoctonia AG-I on alfalfa. In addition, all theR. solani and binucleateRhizoctonia groups isolated from sainfoin and common vetch were recovered from these crops for the first time in Turkey.

Species of Oligonychus infesting date palm cultivars in the Southern Arava Valley of Israel

Abstract: In a study of date fruit damage caused byOligonychus spp., we investigated whether the cultivar affects phenology, and on what hosts the mites over-winter. Samples were taken from ‘Deglet Noor’, ‘Barhi’ and ‘Medjool’ trees from mid-April through mid-September during the years 1999–2002. In the ground-cover mites were monitored by collecting Bermuda grass (Cynodon dactylon) under each sampling tree. Over 99% of the mites collected on Deglet Noor and Barhi fruit were identified asO. afrasiaticus. Mean population levels ofO. afrasiaticus reached ten mites or more (initiation of infestation) on Medjool in the second half of May, whereas on Deglet Noor this did not occur before the first week of July. On Barhi the initiation of infestation varied between plots and years, ranging from the second half of May to the beginning of July, but always occurred earlier than Deglet Noor. Mite populations on the pinnae remained low from June through October, not exceeding seven mites per pinna, whereas on fruit strands they reached peak populations of approximately 4000 mites per strand. The sex ratio (proportion of females) ofO. afrasiaticus on fruit of all three cultivars was highly female-biased, usually above 0.85. During winter,O. afrasiaticus was found on Bermuda grass in the orchard ground-cover as well as on fronds of all three cultivars.

Microsatellite Primers Indicate the Presence of Asexual Populations of Venturia inaequalis in Coastal Israeli Apple Orchards

Abstract: This study was initiated to determine whether differences in genotypic diversity among populations of Venturia inaequalis (Cke.) Wint., as detected using neutral genetic markers, were related to the ecological conditions in which apples are grown in Israel. Since sexual reproduction in this fungal pathogen has an obligate requirement for sustained low winter temperatures, and since these requirements in Israel are met only on the Golan Heights, we were interested in whether lower elevation populations of this pathogen might be comprised of asexual clonal lineages. Unlike temperate apple growing regions, where the primary spring inoculum is ascosporic derived from overwintered pseudothecia, Israeli apple orchards at lower elevations in the Hula Valley and along the coastal plain rarely if ever experience low winter temperatures and pseudothecia have never been recovered. Two orchards were sampled from the Golan Heights (El Rom and Ortal, n = 38) and three orchards from the Hula Valley and coastal plain (Sede Eliezer, Ginaton and Be’er Tuvia, n = 40). Microsatellite primers were used to analyze population structure and the resulting binary data analyzed by both cluster and parsimony analysis. Populations from the coastal plain were genetically uniform within each of the orchards sampled, whereas populations from the Golan Heights showed levels of genotypic diversity ten times as high. The data support field observations that this pathogen does not reproduce sexually in regions characterized by the absence of low winter temperatures and is instead composed of clonal lineages. This may have bearing on control strategies for the disease in Israel.

The distribution of olive fruit fly captures with McPhail traps within an olive orchard

Abstract: The spatial distribution of olive fruit flyBactrocera (Dacus) oleae (Gmelin) (Diptera: Tephritidae) field captures with McPhail traps within an experimental orchard was evaluated. Contour maps were constructed to examine the patterns in the 3-year trapping data. Captures varied widely inside the olive orchard, with traps suspended on wild olive trees exhibiting the poorest performance. Favorable microclimate, created by a standing water pool, appeared to be responsible for increased trap captures during the hot summer months. The positive role of the olive tree fruit load is also discussed.

A new Praon species (Hymenoptera: Braconidae: Aphidiinae) of the Uroleucon parasitoid complex from the Mediterranean area.

Abstract: A new hymenopteran aphid parasitoid species (Praon uroleucon sp. n.) fromUroleucon sp. infestingCarduus acanthoides L. is described from Yugoslavia. It is diagnosed and illustrated with scanning electron microscope photographs and line drawings. The new species is placed in thePraon dorsale species group, and a key to species of that group is provided.

Impacts of atmospheric CO2 concentrations and soil water on the population dynamics, fecundity and development of the bird cherry-oat aphidRhopalosiphum padi

Abstract: The impacts of elevated CO2 and soil water on the population dynamics, adult fecundity and nymphal period of the bird cherry-oat aphidRhopalsiphum padi (Linnaeus) were evaluated in three experiments: (i)Combined effects of CO 2 and soil water on aphid populations. Spring wheat was grown in pots at three CO2 concentrations (350, 550 and 700 ppm) and three soil water levels (40%, 60% and 80% of field water capacity, FWC) in field open-top chambers (OTC) and infested with the bird cherry-oat aphid. Aphid population dynamics were recorded throughout the growing season; at the same time, adult fecundity and duration of the nymphal period were recorded. Chemical composition of spring wheat leaves was also analyzed. (ii)Indirect effects of CO 2 concentrations and soil water on aphid adult fecundity and nymphal period. The experiment was conducted with the leaf discs method in the laboratory. Aphids were reared on leaf discs excised from the treated wheat in OTC with different CO2 and soil water levels. (iii)Direct effects of CO 2 concentrations on aphid adult fecundity and nymphal period. Aphids were reared on leaf discs excised from the wheat grown under natural conditions. The experiment was conducted with the leaf disc method in OTC with the three CO2 concentrations. It was found that the direct effect of CO2 concentration on aphid population parameters was minor. CO2 and soil water affected aphid population indirectly through their effects on wheat characteristics. The aphid population under 550 ppm CO2 was far larger than the one under 350 ppm CO2, whereas the population under 700 ppm CO2 was slightly higher than that under 550 ppm CO2. The largest aphid population was obtained with the 60% soil water treatment, regardless of CO2 treatment. The effects of CO2 concentration on aphid population were, however, not significantly correlated with soil water level. Adult fecundity increased with CO2 concentration, the highest fecundity being achieved under 60% FWC treatments. The nymphal period was not affected by CO2 concentration. The shortest period occurred under 60% FWC. Atmospheric CO2 and soil water had significant effects on the chemical composition of the wheat leaves. Aphid population size was positively correlated with leaf water content, concentrations of soluble proteins, soluble carbohydrates and starch, and negatively correlated with DIMBOA and tannins concentrations.

Further suppression ofBotrytis cinerea disease in cucumber seedlings by chitosan-copper complex as compared with chitosan alone

Abstract: Chitosan-copper complex compared with chitosan alone enhanced suppression ofBotrytis cinerea rot development on four-true-leaf cucumber seedlings in controlled growth chambers. This paper constitutes the first report of such enhancement. The optimal concentrations for the most effective suppression ofBotrytis development were 0.2 gl −1 chitosan and 1.6 mmole copper. After 12 days’ incubation, marked and significantly better disease suppression was obtained with chitosan-copper complex (75% suppression) than with chitosan alone. The chitosan-copper complex could be a very promising decay control agent for use in both conventional and organic agriculture.

Checklist of agromyzidae (Diptera) of Turkey, with a new record

Abstract: The first checklist of Turkish leafminers of the family Agromyzidae (Diptera), comprising 78 species, is presented.Melanagromyza cunctans (Meigen, 1830) is recorded as new for the Turkish leafminer fauna.

Seasonal abundance and spatial distribution of the predatorMacrolophus costalis and its preyMyzus persicae on tobacco

Abstract: Field studies were conducted to assess the population and the spatial dynamics of the predatory bugMacrolophus costalis Fieber (Hemiptera: Miridae) and of its prey, the aphidMyzus persicae (Sulzer) (Hemiptera: Aphidoidea), on tobacco. From an untreated tobacco field in Tithorea (central Greece), tobacco leaves were collected from the upper and the lower half of the plants from June until September, in 1999 and 2000. The numbers ofM. costalis andM. persicae individuals per leaf were counted. Most aphids were observed during July and August (early and mid season), with densities dropping markedly in September. In contrast,M. costalis population densities increased late in the season (September). Significantly higher numbers of aphids were found on the upper half of the plants than on the lower half. In contrast, significantly moreM. costalis individuals were observed on the lower half. Iwao’s Regression Analysis was used in order to characterize the spatial pattern of the two species. According to this model, in both sampling seasons, aphids andM. costalis nymphs displayed an aggregated spatial pattern, whileM. costalis adults were found to be randomly distributed among sampling units. Although moreM. costalis individuals were recorded on leaves with relatively high aphid densities, this species did not react numerically to changes in prey density. In addition, a significant number of bugs were found on leaves with low aphid densities or no aphids at all.

Epidemiology and effects of verticillium wilt on yield of olive trees (cvs. Barnea and Souri) irrigated with saline water in Israel

Abstract: Epidemiology ofVerticillium dahliae on olive trees (cvs. ‘Barnea’ and ‘Souri’) irrigated with saline water was studied over a period of 3 years. Disease incidence in cv. Barnea increased from 18.9% to 40.5% in the first year, while disease severity decreased from 4.2 to 2.4 (on a scale of 2–10). In the first month after pruning of diseased branches (June 1999), disease incidence was 26.9% and it increased to 60.6% by May 2000. No changes in disease severity were observed from this time until the end of the study. In cv. Souri, disease incidence doubled during the 3 years of the study (from 22.1% to 44.8%), and disease severity increased from 2.4 to 2.9. The disease caused significant reduction of yield in cv. Barnea in 1999 and 2000 (48.3% and 12.0%, respectively). In cv. Souri yield was measured only in 2001, where a reduction of 66.8% was observed.V. dahliae was isolated from both diseased and symptomless trees. A significant decrease in the isolation rate ofV. dahliae from diseased cv. Barnea trees occurred between the first year (47.9%) and the third year (5.3%); positive isolations were obtained in all seasons, without differences between seasons. In cv. Souri, the fungus was isolated in significantly higher rates during the winter and spring (55% and 50%, respectively). Our findings strongly support the assumption that natural recovery occurs in cv. Barnea 4–5 years after planting, but not in cv. Souri.

Herbicide safeners: Effective inducers of plant defense gene-enzyme systems

Abstract: Kriton Kleanthis Hatzios, born 1949, Director, Virginia Agricultural Experiment Station (VAES) and Assoc. Dean for Research, College of Agriculture and Life Sciences, Virginia Polytechnic Inst. and State U. (Virginia Tech). B.Sc. in Agricultural Sci./Chem. (1972), Aristotelian U. of Thessaloniki, Greece; M.Sc. (1977) and Ph.D. (1979), both at Michigan State U.; 1979, Asst. Prof.; 1984, Assoc. Prof.; 1988, Prof., all at Virginia Tech. 1997-2000, Head of the Dept. of Plant Pathology, Physiology and Weed Science at Virginia Tech. 1999-, Director, VAES and Assoc. Dean for Research, College of Agric. and Life Sciences, Virginia Tech. Dr. Hatzios served as tutor (major advisor, coadvisor or lab res. supervisor) to 22 doctoral and three master's candidates. Main research interests: Action, fate and selectivity of herbicides and herbicide safeners; herbicide resistance in crops and weeds. Publications: Four books authored or edited: Metabolism of Herbicides in Higher Plants [co-author with D. Penner, 1982,

Characterization of a Phytotoxic Glycoprotein Produced by Phoma eupyrena - A Pathogen on Water Lettuce

Abstract: Phoma eupyrena, the causal agent of leaf blight disease of water lettuce, when purified by affinity and ion exchange chromatography produced an extracellular glycoprotein (Pe 65) in concentrations of ∼ 8 µg ml−1 in the stationary culture. Coomassie-blue stained SDS-PAGE analysis of culture filtrates and purified Pe 65 showed its molecular mass to be 65 kDa. The blighting and necrosis of leaf tissues were observed within 4–6 days when 1–5 µg of Pe 65 was injected into the mesophyll of water lettuce. These symptoms closely resembled those caused by foliar inoculation with the pathogen. Recognition of Pe 65 by N-glycosidase F treatment and by polyclonal antibodies raised in rabbit against the whole glycoprotein, indicated that the protein is a highly glycosylated protein (50% carbohydrate) and that it is strongly enclosed by the antigenic glycosidic moiety.

Nitrogen effect on competition between winter cereals and littleseed canarygrass

Abstract: Field experiments were conducted in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between littleseed canaryglass (Phalaris minor Retz.) and wheat (Triticum aestivum L.), barley (Hordeum vulgare =distichum L.) or triticale (Triticosecale). The presence of 400P. minor plants per square meter until early March did not have an adverse effect on dry weight of any crop. However, their further presence significantly reduced dry weight of wheat and triticale, but not that of barley. Grain yield of wheat and triticale was reduced 48% and 47%, respectively, by season-long competition ofP. minor, whereas the corresponding reduction for barley was only 8%. Crop yield reduction due toP. minor competition resulted mainly from reduction in ear number and less from reduction in 1000-grain weight. Nitrogen fertilization (150 kg N ha−1), compared with control (0 kg N), slightly increased yield of all crops grown without weed competition. The same treatment also increased dry weight and competitive ability ofP. minor against wheat and triticale, compared with that of control (0 kg N); the split application of nitrogen (50 kg N ha−1 before crop sowing and 100 kg N ha−1 in early March) caused a slightly greater increase inP. minor dry weight than did 150 kg N ha−1 applied once before crop sowing. Dry weight ofP. minor grown with barley was not affected by nitrogen fertilization, but it was severely reduced compared with that ofP. minor grown with wheat or triticale.