Effects of insecticide acetamiprid on photosystem II (PSII) activity of Synechocystis sp. (FACHB-898)

Effects of insecticide acetamiprid on photosystem II (PSII) activity of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence tests. Acetamiprid exposure increased the proportion of inactivated PSII reactive centers (PSII_X) and led to loss of active centers (PSII_A). High concentration (1.0 mM) acetamiprid decreased amplitude of the fast phase and increased the slow phase of fluorescence decay during reoxidation. The electron transport after Q_A was hindered by high concentration acetamiprid and more Q_A had to be reoxidized through S₂(Q_AQ_B)⁻ charge recombination. Acetamiprid decreased the density of the active reaction centers, electron transport flux per cross section and the performance of PSII activity but had little effect on dissipated energy flux per reaction center, antenna size and the maximum quantum yield for primary photochemistry (F_v/F_m). The target site of acetamiprid toxicity to the PSII of Synechocystis sp. was electron transfer on the acceptor side.     

Effects of fungicides JS399-19, azoxystrobin, tebuconazloe, and carbendazim on the physiological and biochemical indices and grain yield of winter wheat

The impact of four modern fungicides JS399-19 (2-cyano-3-amino-3-phenylancryic acetate) (novel fungicide), azoxystrobin (a strobilurin), tebuconazole (a triazole) and carbendazim (a benzimidazole), applied as foliar spray at the recommended field rate, on the physiology and biochemistry of the senescence process and grain yield was studied in winter wheat (Triticum aestivum L. cv. ‘Nannong No. 9918’) under natural environmental conditions. Fungicide treatments to wheat plants at growth stage [ZGS] 57 (3/4 of head emerged) significantly increased the chlorophyll (CHL) and soluble protein (SP) content and decreased the malondialdehyde (MDA) content and electrolyte leakage. Additionally, activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in flag leaves of the fungicide-treated plants were also higher than that in untreated plants. These coincided with elevated levels of H₂O₂ and reduced level of in the fungicide-treated plants. The results suggested that the fungicide-induced delay of senescence was due to an enhanced antioxidant enzyme activity protecting the plants from harmful active oxygen species (AOS). Because all fungicides can induce the delay of wheat senescence, fungicide-treated wheat shown higher grain yield than untreated wheat. Of all tested fungicides, JS399-19, azoxystrobin and tebuconazole showed similar effects on delaying senescence of wheat and enhancing the grain yield of wheat, but JS399-19 was more efficient in general.     

Growth, photosynthetic pigments and photosynthetic activity during seedling stage of cowpea (Vigna unguiculata) in response to UV-B and dimethoate

UV-B (0.4 W m⁻²) irradiation and dimethoate (100 and 200 ppm) treatments, singly and in combination, declined the growth, photosynthetic pigment contents and photosynthesis (O₂ evolution and CO₂-fixation) of cowpea (Vigna unguiculata). Contrary to this, low concentration of dimethoate (50 ppm) caused stimulation on these parameters, while together with UV-B it showed inhibitory effects. Carotenoids (Car) showed varied responses. It was found that carbon-fixation (¹⁴CO₂) was more sensitive to both the stresses than photosynthetic oxygen evolution. Photosynthetic electron transport activity was reduced by both the stresses, however, 50 ppm dimethoate besides inhibiting photosystem II (PSII) and whole chain activity, showed slight stimulation in photosystem I (PSI) activity. The individual effect of two stresses on PSII activity was probably due to interruption of electron flow at oxidation side of PSII which extended to its reaction center following simultaneous exposure. A similar trend was also noticed in case of CO₂ liberation (measured as ¹⁴CO₂ release) in light and dark. Results suggest that dimethoate (100 and 200 ppm) and UV-B alone caused heavy damage on pigments and photosynthetic activity of cowpea, leading to the significant inhibition in growth. Further, the interactive effects of both the stresses got intensified. However, low concentration (50 ppm) of dimethoate showed stimulation, but in combination, it slightly recovered from the damaging effect, caused by UV-B.     

Activation of paraquat in the earthworm Allolobophora chlorotica is mediated by NAD(P)H-cytochrome c reductase activities

This study reports that earthworms, Allolobophora chlorotica, are capable of biotransforming paraquat, a toxic herbicide, resulting in the formation of reactive oxygen species (ROS). We found that in earthworms the reduction of paraquat is mediated by NADPH- and NADH-cytochrome c reductase activities. The formation of superoxide anion (O₂⁻) from the incubation of paraquat with the earthworm extracts was demonstrated by using both Cypridina luciferin analog (CLA) chemiluminescence and the SOD-inhibitable cytochrome c reduction reaction. In addition, in vivo exposure of earthworms to paraquat in solution (24 and 48 h) was performed to investigate whether or not the herbicide affects the levels of the NAD(P)H-cytochrome c reductase activities. Although in vitro NADPH-cytochrome c reductase reduces paraquat more easily than the NADH-dependent activity, after the in vivo exposure an increase of NADH-cytochrome c reductase activity(s) by 12% compared to control values was observed, whereas NADPH-cytochrome c reductase activity was not affected. Xanthine oxidase (XO) is an enzyme implicated in paraquat toxicity, however, no XO was detected in earthworm extracts nor hypoxanthine was a source of electrons for the herbicide reduction. For comparative reasons menadione, a redox cycling quinone, was also incubated with the earthworm extracts. It was found that the incubation of menadione with earthworm extracts formed about two times more (O₂⁻) than with paraquat. It is concluded that the exposure of paraquat to earthworms could elicit radical formation and consequently toxic effects via oxidative stress-mediated mechanisms. The reduction of paraquat by the reductases leads to the formation of paraquat radical, which reacts with molecular oxygen, accounting for the formation of superoxide anion. Further studies are required to conclude that the observed increase of NADH-cytochrome c reductase activity(s) should be used as a biomarker for paraquat exposure in earthworms.     

Identification of blackeye cowpea mosaic virus from germplasm of yard-long bean and from soybean,and the relationships between blackeye cowpea mosaic virus and cowpea aphid-borne mosaic virus

Two potyvirus isolates, one from germplasm of yard-long bean (Vigna unguiculata ssp.sesquipedalis) introduced into the Netherlands, and another one from soybean plants (Glycine max) in Indonesia, were compared with two virus isolates of blackeye cowpea mosaic virus (BICMV) from the USA and a Moroccan isolate of cowpea aphid-borne mosaic virus (CAMV). It is proposed that all five isolates be now considered BICMV on the basis of host ranges, symptoms and serology. From our results, and a reassessment of the literature it is suggested to drop the name CAMV in favour of BICMV.Samenvatting Twee potyvirussen, de een in Nederland ingevoerd met genenmateriaal vanVigna unguiculata ssp.sesquipedalis en de ander uit planten van sojaboon (Glycine max) in Indonesië, werden vergeleken met twee isolaten van blackeye cowpea mosiac virus (BICMV) en een Marokkaans isolaat van cowpea aphid-borne mosaic virus (CAMV). Op grond van waardplantenreeksen, symptomen en serologie stellen de auteurs voor om alle vijf isolaten te beschouwen als BICMV. Gebaseerd op de verkregen resultaten en een kritische beschouwing van de literatuur wordt de aanbeveling gedaan om de naam CAMV te laten vallen ten gunste van BICMV.     

The isolation of a further new race of Erysiphe graminis DC. f.sp. hordei Marchal and the genetical basis of the resistance of ‘Lyallpur 3645’

Besides the race Amsel-C₂, a new race of barley mildew (Erysiphe graminis DC. f.sp.hordei Marchal) has been isolated from a still resistant variety L 94. This race has provisionally been denoted Lyallpur 3645-C₁₇. It is able to overcome the resistance of Lyallpur 3645.It appears most likely that the barley variety Lyallpur 3645 has two closely linked genes for resistance, one for hypersensitivity and the other for an intermediate type of reaction. The first is present in the variety Amsel and both in Heine 4808.The reactions indicate that race Lyallpur 3645-C₁₇ has only one gene for virulence in addition to the ones present in race Amsel-C₂.A survey is given of the seedling reaction of some 60 previously very or moderately resistant varieties, after infection with the two new races.Samenvatting Twee fysio's van gerstemeeldauw,Erysiphe graminis DC. f.sp.hordei Marchal zijn gevonden, waarvan één niet eerder is beschreven. Dit laatste fysio wordt voorlopig aangeduid als Lyallpur 3645-C₁₇, het andere is het zgn. Amsel-C₂-fysio.Met behulp van beide fysio's is duidelijk geworden dat de lijn Lyallpur-3645 twee nauw gekoppelde resistentiegenen bezit; een gen voor een overgevoeligheidsreactie en een ander gen voor een intermediaire reactie.In het ras Amsel is alleen het overgevoeligheidsgen aanwezig, in Heine 4808, evenals Amsel afkomstig van kruisingen met Lyallpur 3645, zijn beide genen aanwezig.Het fysio Lyallpur-3645-C₁₇ lijkt daarom één gen voor virulentie meer te hebben dan Amsel-C₂.Tenslotte is een overzicht gegeven van de kiemplantreactie na infectie met beide fysio's van ongeveer 60 gerstrassen die eerder zeer goed of matig resistent waren.     

Inhibitory influence of inorganic salts on banana postharvest pathogens and preliminary application to control crown rot

Lasiodiplodia theobromae, Thielaviopsis paradoxa, Colletotrichum musae, C. gloeosporioides, Fusarium verticillioides, and F. oxysporum were screened in vitro for sensitivity to Na₂CO₃, NaHCO₃, CaCl₂, NaCl, and NaClO. The spore germination of all pathogens was completely inhibited by Na₂CO₃ 4g/l, NaClO 5g/l, and NaHCO₃, CaCl₂, and NaCl 6g/l each. Dipping the bananas for 10–15min in these concentrations reduced the incidence of crown rot (compared with the untreated fruits) 17 days after harvest in fruits treated with NaClO by 67%, with NaHCO₃ by 62%, with NaCl by 38%, and with CaCl₂ by 33%. Na₂CO₃-treated fruits had the same incidence of crown rot as untreated fruits.     

Efficiency of the mixed biocide GCSC-BtA against vegetable pests of different arthropod orders in the south-eastern China

The present paper deals with the efficiency of the mixed biocide GCSC-BtA against vegetable pests of five orders of arthropod insects in the south-eastern China, i.e., diamondback moth, Plutella xylostella (L.); green peach aphid, Myzus persicae (Sulzer); yellow-fanded flea beetle, Phyllotreta vittata Fabricius; vegetable leaf miner, Phytomyza nigricornis Macquart; and vegetable spider mite, Tetranychus neocaledonicus Andre. The results show that the mixed biocide GCSC-BtA has a higher efficacy of control against all of the five pests than the commercial biocide B.t. and insecticide Diazinon. GCSC-BtA gave a higher mortality value of 92.18% against P. xylostella as compared to the biocide B.t. with a value of 64.70% and Diazinon with a value of 50.00%. Similar mortalities were obtained with the other four pests regarding the efficacy of the three products tested against them.The concentration-mortality regression equations were calculated by the probit analysis, from which the average mortalities were calculated. The values calculated for GCSC-BtA were 81.13% for P. xylostella, 75% for M. persicae and T. neocaledonicus, 69.23% for P. vittata, and 61.03% for P. nigricornis as compared to those caused by Diazinon: 33.33%, 27.42%, 66.31%, 44.54%, 19.65% for P. xylostella, M. persicae, P. vittata, P. nigricornis, and T. neocaledonicus, respectively. Based on LC₅₀, P. xylostella was most susceptible to GCSC-BtA with a LC₅₀ value of 0.3445, followed by B.t. with a value of 0.8404 and Diazinon with a value of 1.3160. The LC₅₀ value of GCSC-BtA for M. persicae was 0.4660 which was about three times less than that of Diazinon. LC₅₀ value of GCSC-BtA for P. vittata was 0.3954 which was about the same as that of Diazinon. P. nigricornis and T. neocaledonicus were also much more susceptible to GCSC-BtA than to B.t. and Diazinon. It is concluded that GCSC-BtA kills more target pests than B.t. and is more effective than Diazinon in controlling the vegetable pests.     

Gamma radiation sensitivity of larvae and adults of the red flour beetle, Tribolium castaneum Herbst

In this study, the susceptibility of larvae and adults of Tribolium castaneum (Herbst) to gamma radiation was investigated in the laboratory in Turkey. Gamma radiation was applied at 6 dose levels between 20 and 200Gy to 13–15day-old adults and at 5 dose levels between 20 and 180Gy to 18–20day-old larvae of T. castaneum. All experiments were performed in growth chambers maintained at 27±1°C and 70±5% r.h. The larvae proved to be the more susceptible stage, survival to the adult stage being prevented by exposure of the eggs to 100Gy; the adult stage was less susceptible. LD₅₀ and LD₉₉ values were determined as 19,75 and 42,97Gy for larvae and 33,21 and 64,50Gy for adult stage, respectively. It was concluded that 100Gy is the effective dose for both larval and adult stages.     

Relative susceptibilities of eleven potato cultivars and breeders' clones toGlobodera pallida pathotype Pa 3, with a discussion of the interpretation of data from pot experiments

Curves according to the equationPf=M (1-e ^–aPi/M ) fitted well to the relations according to Seinhorst's (1993) modelPf=y _e y _h M(1-e ^–aPi/M ) between initial egg densities of potato cyst nematodes (Globodera rostochiensis, G. pallida)Pi up to 5T _h (T _h =the tolerance limit of haulm weight) andPf at the end of the growing season (a=maximum rate of reproduction,M, M=different theoretical maximum egg densities). Variation of estimates ofM, due to variation of the parameters of the submodelsy _e andy _h for the effect of weight reduction of haulms (and, therefore, of roots) on cyst production and damage to root tissue on egg production, respectively, was small enough to be ignored relative to experimental error. Therefore, ratios of values ofM, determined in simultaneous pot experiments with different potato cultivars, are reliable measures of the relative host status of these cultivars at initial egg densitiesPi of these nematodes up to about 5T _h . Variation between potato cultivars of growth reduction and damage to root tissue by the nematodes reduces the reliability of ratios of rates of relative susceptibility of these cultivars.The ratios between the maximum rates of reproduction ofG. pallida, pathotype Pa 3, on 8 out of 9 cultivars and one breeder's clone of potatoes and this rate on the susceptible cvs Bintje and Irene (relative susceptibilitiesrs _a ) could be considered to be equal to the ratios of maximum population densitiesM on these cultivars (relative susceptibilitiesrs _M ) (relative susceptibilities independent of initial egg density). The latter ratios were 0.59 times the first (relative susceptibilities negatively correlated with initial egg density) in one cultivar and one breeder's clone. Relative susceptibilitiesrs _a andrs _M of the tested cultivars and breeders clones suggest the existence of continuous ranges of both relative susceptibilities between 0.50 and 0.15 with, in a great majority of cases,rs _a =rs _M .     

Influence of mixed biocide GCSC-BtA on the pupae and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host. Plutella xylostella (L.) (Lep., Plutellidae)

This paper deals with the influence of the mixed biocide GCSC-BtA on the pupal and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host, Plutella xylostella (L.) (Lep., Plutellidae). The results show that mortalities of the pupae of P. xylostella in the direct-dip bioassay were 84.67%, that of the adults in the residue bioassay at 1.2500mg/ml concentration of GCSC-BtA were 78.00% which were significantly higher than the mortality values for the pupae with 54.62% and adults with 48.13% of A. plutellae. In contrast, cypermethrin showed extremely high toxicity to the pupae with 94.58% and adults with 86.00% mortality values of A. plutellae as compared to the low mortality values of 42.14% for the pupae and 32.11% for the adults of P. xylostella, with the same concentrations and bioassay methods. The LC₅₀ values of GCSC-BtA were 0.3402, 0.5516 and 1.2405, 1.9480mg/ml for the pupae and adults of P. xylostella and A. plutellae, respectively, while the LC₅₀ values for cypermethrin were 1.5652, 2.3471 and 0.1096, 0.1152mg/ml, respectively. GCSC-BtA was found more toxic to the pupae and adults of P. xylostella and safer to the pupae and adults of A. plutellae than cypermethrin. The possibilty of using GCSC-BtA against P. xylostella under partial control by A. plutellae in vegetable fields is discussed.     

三种植物次生物质对B型烟粉虱羧酸酯酶活性及其对药剂敏感度的影响

采用人工饲料添加法,研究了不同浓度的槲皮素、2-十三烷酮和葫芦素B 3种植物次生物质对B型烟粉虱Bemisia tabaci羧酸酯酶(CarE)活性的影响,同时比较研究了用3种植物次生物质处理后敌敌畏、脱叶磷、灭多威、乐果和氧乐果5种药剂对CarE 的抑制中浓度(I50)的变化。结果表明: 0.01~1.0 mg/mL的槲皮素对B型烟粉虱成虫CarE活性均具有明显的诱导增加作用,最高为对照的4.32倍; 0.1和0.5 mg/mL的2-十三烷酮处理使CarE活性比对照分别下降了22%和58%; 0.75~30.0 mg/L的葫芦素B对烟粉虱CarE活性均表现为抑制作用;用1.0 mg/mL的槲皮素处理24 h后,敌敌畏和脱叶磷对烟粉虱CarE的I50值分别增加为对照的20.05和3.16倍; 3.75 mg/L 的葫芦素B处理后,敌敌畏和灭多威对CarE 的I50值分别增加为对照的25.94、2.45倍; 1.0 mg/mL的2-十三烷酮处理后敌敌畏、脱叶磷和乐果对CarE 的I50值分别降低了89%、83%和90%。     

Biological characteristics and life tables of Neoseiulus umbraticusChant (Acari, Phytoseiidae) at three constant temperatures

The development time, survival and fecundity of the generalist predatory mite, Neoseiulus umbraticusChant, were determined at 20, 25, and 30°C and 65±10% RH. N. umbraticus females completed development in 9.7, 8.0 and 5.9 days, respectively, using a diet of all life stages of Tetranychus cinnabarinus Boisduval. Total developmental times of males were relatively shorter at 25 and 30°C than at 20°C. In general, preoviposition, oviposition, and postoviposition periods of N. umbraticus shortened as temperature increased. The longest survival rate of N. umbraticus of 80.5 days occurred at 20°C, followed by 67.0 and 57.6 days at 25 and 30°C, respectively. Mated females laid an average 0.9, 1.3 and 1.4 eggs per female per day and 33.1, 44.0 and 43.6 eggs over their entire lives at 20, 25 and 30°C, respectively. The sex ratios of this species were 0.57, 0.57 and 0.54 female (female+male) at 20, 25 and 30°C, respectively. The intrinsic rate of increase (r_m) became greater with rising temperatures from 0.123 at 20°C to 0.180 at 30°C. The net reproduction rate (R_o) was highest at 25°C (25.0 females/female) and lowest at 20°C (18.8 females/female), while T_o decreased with increasing temperatures, from 23.8 days at 20°C to 17.5 days at 30°C.     

A biochemical mechanism for the gene-for-gene resistance of tomato to Cladosporium fulvum

Model experiments were carried out with the tomato varieties Moneymaker (no resistance genes), Leaf Mould Resister No. 1 (resistance gene Cf 1), Vetomold (resistance gene Cf 2) and V 473 (resistance genes Cf 1 and Cf 2) and various physiological races ofCladosporium fulvum. Leaking of³²P from labelled leaf disks, was obtained on infiltration with high molecular weight excretion products from incompatible races ofC. fulvum but not with those from compatible races. These products were obtained by Sephadex G-25 gel filtration of culture filtrates.The observations are in line with our hypothesis that the gene-for-gene relation existing between tomato andC. fulvum is based on interaction of specific fungal excretion products with specific receptors in the host which may be located in the cell membrane. The presence of these fungal compounds is supposed to be controlled by four avirulence genes (A₁, A₂, A₃ and A₄) and that of the receptors by the four resistance genes (Cf 1, Cf 2, Cf 3 and Cf 4). Results obtained from experiments with tomatoes Cf 1, Cf 2 and Cf 1 Cf 2 suggest that leakage followed by the hypersensitivity reaction occurs whenC. fulvum races possessing a specific avirulence allele penetrate into a host carrying the corresponding resistance allele.It is not yet clear why growth ofC. fulvum is stopped when leakage of the host tissue resulting in the hypersensitive reaction takes place. No compound toxic toC. fulvum is present or is formed in homogenates of tomato leaves.Samenvatting Modelproeven werden uitgevoerd met de tomatenvariëteiten Moneymaker (geen resistentiegenen), Leaf Mould Resister No. 1 (resistentiegen Cf 1), Vetomold (resistentiegen Cf 2), V 473 (resistentiegen Cf 1 en Cf 2) en verschillende fysiologischen rassen vanCladosporium fulvum. Bladponsjes van radioactief gemerkte bladeren (gemerkt met³²P) werden geïnfiltreerd en geïncubeerd met cultuurfiltraatfracties (fractionering over Sephadex G-25) vanC.fluvum. Waargenomen werd dat ponsjes, behandeld met cultuurfiltraat van een niet compatibeleC.fulvum, een grotere uitlek van radioactief gemerkt materiaal te zien gaven dan in de, gevallen waarin een compatibele schimmel werd gebruikt.Deze waarnemingen stemden overeen met onze hypothese dat de gen-om-gen relatie die bestaat tussen tomaten enC.fulvum, gebaseerd, is op een interactie van specifieke schimmelprodukten met specifieke receptoren in de plantencellen, mogelijk in de membranen. De produktie van de specifieke stoffen door de schimmel zou worden bepaald door vier avirulentiegenen (A₁, A₂, A₃ en A₄), en de aanwezigheid van de specifieke receptoren in de plantencel door de vier resistentiegenen Cf 1, Cf 2, Cf 3 en Cf 4.De waarnemingen, verkregen uit de proeven met de tomaten Cf 1, Cf 2 en Cf 1 Cf 2, doen vermoeden dat de uitlek een gevolg is van een overgevoeligheidsreactie die optreedt, indien een fysio vanC.fulvum, dat een specifiek avirulentie allel bezit, een gastheer binnendringt die beschikt over een bijpassend resistentie allel.Het is tot nu toe niet duidelijk waarom de groei vanC.fulvum stopt indien, uitlek op gaat treden als gevolg van de overgevoeligheidsreactie. In homogenaten van tomatenbladeren werd geen stof gevonden die de groei vanC.fulvum remt.     

Influence of mixed biocide GCSC-BtA on the pupae and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host. Plutella xylostella (L.) (Lep., Plutellidae)

This paper deals with the influence of the mixed biocide GCSC-BtA on the pupal and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host, Plutella xylostella (L.) (Lep., Plutellidae). The results show that mortalities of the pupae of P. xylostella in the direct-dip bioassay were 84.67%, that of the adults in the residue bioassay at 1.2500mg/ml concentration of GCSC-BtA were 78.00% which were significantly higher than the mortality values for the pupae with 54.62% and adults with 48.13% of A. plutellae. In contrast, cypermethrin showed extremely high toxicity to the pupae with 94.58% and adults with 86.00% mortality values of A. plutellae as compared to the low mortality values of 42.14% for the pupae and 32.11% for the adults of P. xylostella, with the same concentrations and bioassay methods. The LC₅₀ values of GCSC-BtA were 0.3402, 0.5516 and 1.2405, 1.9480mg/ml for the pupae and adults of P. xylostella and A. plutellae, respectively, while the LC₅₀ values for cypermethrin were 1.5652, 2.3471 and 0.1096, 0.1152mg/ml, respectively. GCSC-BtA was found more toxic to the pupae and adults of P. xylostella and safer to the pupae and adults of A. plutellae than cypermethrin. The possibilty of using GCSC-BtA against P. xylostella under partial control by A. plutellae in vegetable fields is discussed.     

Changes in susceptibility of bean leaves (Phaseolus vulgaris) to Sclerotinia sclerotiorum and Botrytis cinerea by pre-inoculative ozone exposures

The effects of ozone on the susceptibility of leaves ofPhaseolus vulgaris toSclerotinia sclerotiorum andBotrytis cinerea have been investigated. Seedlings of one ozone-sensitive (Pros) and five relatively ozone-insensitive cultivars (Gamin, Precores, Groffy, Narda, Berna) were exposed to different ozone concentrations (0, 120, 180 and 270 g m^–3) for 8 h. One day after the exposures, primary leaves were detached and immediately inoculated with spores of either pathogen suspended in water or in a 62.5 mM KH₂PO₄ (Pi) solution. Visible ozone injury differed between the cultivars and increased with increasing ozone concentration. On the leaves of non-exposed plants, spores of the pathogens suspended in water caused very few lesions, whereas fungal pathogenicity was stimulated by addition of Pi to the inoculum. Ozone-injured leaves of all cultivars exhibited lesions after inoculation of the leaves with the pathogens suspended in water, and the number of lesions was positively correlated with the level of ozone injury for either pathogen and cultivar. The increase in susceptibility of bean leaves in response to increasing ozone concentrations was greater forB. cinerea than forS. sclerotiorum when spores were suspended in water, but was similar when the spores were suspended in Pi.In general, the number of lesions following inoculation with spores in Pi increased with increasing ozone concentration. However, the number of lesions in the ozone-insensitive Groffy was reduced by an exposure to 120 g m^–3 but increased with higher concentrations. This pattern of susceptibility response to the pathogens was not found in the other ozone-insensitive cultivars and, thus, did not appear to be related to the inherent ozone-insensitivity in bean.     

Effects of different high constant and alternating temperatures on the development and prey consumption of Dicyphus tamaninii Wagner (Heteroptera, Miridae) with Aphis gossypii Glover (Homoptera, Aphididae) as prey

The present work aimed to study the effects of high constant and alternating temperatures on the development and prey consumption by Dicyphus tamaninii Wagner (Het., Miridae) with Aphis gossypii Glover (Hom., Aphididae) as prey.Results showed that the predator was able to successfully develop and reach the adult stage, on average, after 20.1 () and 20.6 () days at a temperature of 30 ± 1 °C with A. gossypii as prey. On the other hand, it was not able to develop at 35 ± 1 °C, here all N₁ instars used at the beginning of the experiments had died even before moulting to N₂ instar. At alternating temperatures of 25/15 ± 1 °C, the predator reached the adult stage 23.7 () and 23.5 () days after egg hatching, whereas when the temperatures were increased to 35/22 ± 1 °C, it took a significantly shorter period: 20.6 () and 20.9 () days. In general, the highest mortality occurred during the first two nymphal instars. The total percentage mortality during development from N₁ to adult stage was 30 % and 100 % at the constant temperatures 30 ± 1 °C and 35 ± 1 °C, respectively. At the alternating temperatures of 25/15 ± 1 °C, it was lowest with 16.5 %, while at 35/22 ± 1 °C, it was 20 %.The results of the experiments on prey consumption showed that an individual D. tamaninii consumed during its development to adult stage at 30 ± 1 °C an average of 442.2 (), 433.6 () aphids. At the constant temperature of 35 ± 1 °C, the average daily prey consumption started with 4 aphids and decreased continuously till it approached nil on the 9th day, where all predatory nymphs died. At the alternating temperatures of 25/15 ± 1 °C, the total prey consumption during development was, on average, 359.3 () and 297.0 () aphids, while at 35/22 ± 1 °C it was 348.5 () and 334.0 () aphids. The effect of the four temperatures on the prey consumption by D. tamaninii during the first 10 days after emergence was also studied. At a constant temperature of 30 ± 1 °C, a total of 446.4 () and 372.0 () aphids were consumed, compared to 40.6 () and 39.0 () at 35 ± 1 °C. At alternating temperatures of 25/15 ± 1 °C, the predatory adult consumed, on average, a total of 267.0 () and 207.0 () aphids. Increasing the temperature to 35/22 ± 1 °C resulted in a higher prey consumption by the adult predator, reaching 351.5 () and 267.7 () aphids over the same period.In conclusion, results indicated that D. tamaninii is a promising predator of the melon aphid at a temperature spectrum ranging from 15 ± 1 °C up to 35 ± 1 °C.     

Effects of different high constant and alternating temperatures on the development and prey consumption of Dicyphus tamaninii Wagner (Heteroptera, Miridae) with Aphis gossypii Glover (Homoptera, Aphididae) as prey

The present work aimed to study the effects of high constant and alternating temperatures on the development and prey consumption by Dicyphus tamaninii Wagner (Het., Miridae) with Aphis gossypii Glover (Hom., Aphididae) as prey.Results showed that the predator was able to successfully develop and reach the adult stage, on average, after 20.1 () and 20.6 () days at a temperature of 30 ± 1 °C with A. gossypii as prey. On the other hand, it was not able to develop at 35 ± 1 °C, here all N₁ instars used at the beginning of the experiments had died even before moulting to N₂ instar. At alternating temperatures of 25/15 ± 1 °C, the predator reached the adult stage 23.7 () and 23.5 () days after egg hatching, whereas when the temperatures were increased to 35/22 ± 1 °C, it took a significantly shorter period: 20.6 () and 20.9 () days. In general, the highest mortality occurred during the first two nymphal instars. The total percentage mortality during development from N₁ to adult stage was 30 % and 100 % at the constant temperatures 30 ± 1 °C and 35 ± 1 °C, respectively. At the alternating temperatures of 25/15 ± 1 °C, it was lowest with 16.5 %, while at 35/22 ± 1 °C, it was 20 %.The results of the experiments on prey consumption showed that an individual D. tamaninii consumed during its development to adult stage at 30 ± 1 °C an average of 442.2 (), 433.6 () aphids. At the constant temperature of 35 ± 1 °C, the average daily prey consumption started with 4 aphids and decreased continuously till it approached nil on the 9th day, where all predatory nymphs died. At the alternating temperatures of 25/15 ± 1 °C, the total prey consumption during development was, on average, 359.3 () and 297.0 () aphids, while at 35/22 ± 1 °C it was 348.5 () and 334.0 () aphids. The effect of the four temperatures on the prey consumption by D. tamaninii during the first 10 days after emergence was also studied. At a constant temperature of 30 ± 1 °C, a total of 446.4 () and 372.0 () aphids were consumed, compared to 40.6 () and 39.0 () at 35 ± 1 °C. At alternating temperatures of 25/15 ± 1 °C, the predatory adult consumed, on average, a total of 267.0 () and 207.0 () aphids. Increasing the temperature to 35/22 ± 1 °C resulted in a higher prey consumption by the adult predator, reaching 351.5 () and 267.7 () aphids over the same period.In conclusion, results indicated that D. tamaninii is a promising predator of the melon aphid at a temperature spectrum ranging from 15 ± 1 °C up to 35 ± 1 °C.