Penetration of bean leaves by asulam as influenced by adjuvants and humidity

Penetration of bean (Vicia faba var. Maris Bead) foliage by asulam was found to be affected differently by different surfactants. Some anionic and non-ionic surfactants brought about a significant increase compared with the aqueous control, others were similar to the aqueous control and one caused a significant reduction. High humidity increased asulam uptake and the effect was still further enhanced in the presence of Tween 20. High humidity was also found to influence asulam penetration in the presence of glycerol. With urea, uptake was greater under high humidity conditions and in the presence of Tween 20. A similar enhancement of penetration was found with potassium ethyl xanthate at lower concentrations (0–0.20%) in the presence of Tween 20. On the other hand, reduced uptake resulted at higher concentrations (0.40–1.00%). Tributyl phosphate brought about an increase in penetration at concentrations greater than 0.75%. However, both potassium ethyl xanthate and tributyl phosphate were shown to damage the leaf surface.     

Uptake of aminotriazole from humectant-surfactant combinations and the influence of humidity

Uptake of aminotriazole (3-amino-1,2,4-triazole) by bean leaves (Phaseolus vulgaris var. Canadian Wonder) was not greatly influenced by the addition to the spray solution of dimethylformamide (DMF), ethylene glycol and polypropylene glycol 400 (PPG 400) over the concentration range 1.0–50.0 ml litre^?1. However, the addition of polyoxyethylene 20 sorbitan monolaurate (polysorbate 20) (0.2–1.0 g litre^?1) to spray solutions of the above additives and glycerol (5.0 ml litre^?1; except for DMF, 50.0 ml litre^?1) substantially increased uptake to 80–100% in all cases at 50 ± 10% relative humidity (r.h.). Similar penetration figures were recorded when a range of polysorbate surfactants (polysorbate 20, 40, 60, 80 and 85; 0.2 g litre^?1) were applied to spray solutions containing either dimethyl sulphoxide (DMSO) or glycerol (5.0 ml litre^?1). Humidity was found to have a critical effect upon the humectant-surfactant combinations tested, i.e. DMSO + polysorbate 20, ethylene glycol+ polysorbate 20 and PPG + 400-polysorbate 20 (5.0 ml litre^?1+0.2 g litre^?1). With DMSO + polysorbate 20 the following uptake figures were recorded: < 30% r.h., 3.1 %; 45 ± 10% r.h., 86.8%; 55–65% r.h., 48.2 % and 100% r.h., 0.3%. Similar trends were recorded with all three humectant-surfactant combinations. Further studies revealed that the adverse effect of humidity on DMSO-polysorbate mixtures could be at least overcome partially by regulating the DMSO concentration.     

Penetration of bracken fronds by amitrole as influenced by pre-spraying conditions, surfactants and other additives

Amitrole (3-amino-l,2,4-triazole) penetration on foliar application to bracken (Pteridium aquilinum) is influenced by pre-spray conditions. With the exception of Triton X-405 all surfactants tested at a concentration of approximately 01% (w/v) viz., Tween 20, Triton GR-5, Triton X-100 and Tergetol NPX, improved penetration by more than 17%. Ammonium thiocyanate and ammonium nitrate both enhanced penetration while ammonium sulphate had no effect. Either phosphoric acid alone or in combination with ammonium nitrate reduced penetration. All humectants used were either deleterious or similar to the water control in their effect. Sucrose was shown to enhance penetration but the difference was not significant. Influence des conditions précédant le traitement, des mouillants et d'autres additifs sur la pénétration de l'amitrole dans le frondes de fougéres La pénétration de I'amitrole (amino-3 triazole-1,2,4) en application foliaire sur la fougére aigle (Pteridium aquilinum) est influenceée par les conditions précédant le traitement. A l'exception du Triton X-405, tous les mouillants essayés à la concentration approximative de 0.1 % (pds/vol), à savoirile Tween 20, le Triton GR-5, le Triton X-100 et le Tergetai NPX, ont augmenté la pézétration de plus de 17 %. Le thiocyanate d'ammonium et le nitrate d'ammonium ont tous deux favorisé la pénétration, alors que le sulfate d'ammonium n'a pas eu d'effets. L'acide phosphorique, seul ou associé avec le nitrate d'ammonium, a réduit la pénétration. Tous les humidifiants utilisés se sont montrds soit néfastes soit analogues dans leurs effets au contrôle de l'eau. Le saccharose s'est révélé susceptible de favoriser la pénétration, mais la difference n'a pas été significative. Einfluss von Vorbehandlungen, Netzmitteln und anderen Zusätzen auf die Penetration von Amitrol in Adlerfarn Die Penetration von Amitrol (3-Amino-l,2,4-trizaol) in Adlerfarn (Pteridium aquilinum) bei Blattbehandiung, wird durch Vorbehandlungen beeinflusst. Mit der Ausnahme von Triton X-405 verbesserten alle geprüften Netzmittel, nämlich Tween 20, Triton GR-5, Triton X-100 und Tergetol NPX bei einer Konzentration von etwa 0,1% (Gew./Vol) die Penetration um mehr als 17%. Ammoniumthiocyanant und Ammoniumnitrat erhöhten die Penetration, wahrend Ammoniumsulfat keine Wirkung hatte. Die Anwendung von Phosphorsäure alleine, oder kombiniert mit Ammoniumnitrat, verminderte die Penetration. Alle verwendeten Substanzen die zur Steigerung der Feuchtigkeit dienen (humectants) waren entweder schädlich oder entsprachen in ihrer Wirkung der Wasserkontrolle. Sucrose verbesserte unbedeutend die Penetration.     

Penetration and establishment of Phakopsora pachyrhizi in soybean leaves as observed by transmission electron microscopy

For over 30 years, it has been known that Phakopsora pachyrhizi is unusual in that it penetrates from urediniospores directly through the leaf cuticle without entering stomates. This unusual mode of penetration suggests that disease resistance mechanisms might exist for soybean rust that do not exist for most rust diseases. As a result, we decided to conduct a histological study using transmission electron microscopy to further elucidate the mechanisms of penetration and early establishment of P. pachyrhizi in soybean leaves. Based on our study, it was concluded that P. pachyrhizi utilizes primarily mechanical force, perhaps with the aid of digestive enzymes, to penetrate the cuticle on the leaf surface. However, the lack of deformation lines in micrographs indicated that digestive enzymes, without mechanical force, are used by the penetration hypha to penetrate the outer and inner epidermal cell walls. Digestive enzymes, again indicated by the lack of deformation lines, are used by haustorial mother cells to breach the walls of mesophyll cells to form haustoria. The possibility exists for eventual determination of the precise roles of pressure and digestive enzymes in the development of soybean rust and elucidation of some of the determinants of resistance and susceptibility to this important plant disease.     

Penetration of bracken fronds by asulam as influenced by the addition of surfactant to the spray solution and by pH

Asulam (methyl(4-aminobenzenesulphonyl)carbamate) does not penetrate rapidly on foliar application to bracken (Pteridium aquilinum). Its performance is therefore erratic if rain follows immediately after spraying. The addition of the surfactant polyoxyethylene sorbitan monolaurate (Tween 20) increased spray retention and doubled penetration of asulam by the bracken frond. Concentrations of Tween 20 greater than 01 % (w/v) gave no further increase in penetration and pH had no effect. Pénéetration de l'asulame dans les frondes de fougiré: influence de l'addition d'un mouillant a la bouillie herbicide et du pH L'asulame (méthyl(4-aminobenzinsulfonyl)carbamate) ne pénètre pas rapidement lorsqu'il est appliqué par voie foliaire sur la fougére (Pteridium aquitinum). En conséquence, son efficacité est irrégulière s'il plcut immédiatement apres le traitement. L'addition d'un mouillant, le Tween 20 ou monolaurate de polyoxyéthylène sorbitol a augmenté la rétention de la pulvérisation et a doublé la pénétration de l'asulame dans les frondes de fougères. Les concentrations de Tween 20 supérieures à 0,1 % (pds/vol) n'ont pas augmenté la pénétration et le pH s'est montré sans effet. Der Einfluss von Netzmittetzusatz und pH auf die Penetration von Asulam in Wedel des Adterfarns Asulam (N-(4-Amino-benzolsulfonyl)-carbaminsäure-methyl-ester) dringt in Adlerfarn (Pteridium aquilinum) bei Blattapplikation nicht schnell ein. Deshalb ist seine Wirkung unzuver-lässig, wenn es unmittelbar nach der Spritzung regnet. Der Zusatz des Netzmittels Polyoxyäthylensorbitanmonolaurat (Tween 20) erhöhte die Retention der Spritzbrühe und verdoppelte die Penetration von Asulam in die Adlerfarnwedel. Höhere Konzentrationen von Tween 20 als 0,1 % (Gew./Vol.) steigerten die Penetration nicht und das pH spielte keine Rolle.     

Phytoalexin production in French bean leaves infected by botrytis cinerea

French bean (Phaseolus vulgaris) leaves were inoculated with three pathogenic and two nonpathogenic isolates ofBotrytis cinerea and the infected tissues, containing either spreading lesions or lesions limited in size, were investigated for the presence of phytoalexins. In most cases phaseollin, phaseollidin, phaseollinisoflavan, the phaseollin metabolite, 6a-hydroxyphaseollin, and a few unidentified antifungal compounds were found; phaseollin was predominant. The concentration of phaseollin accumulating in leaves infected by the nonpathogenic isolate BC-5 was about twice as high as that in infections produced by pathogenic isolates. In contrast, leaves infected by the nonpathogenic isolate BC-6 only contained low concentrations of phaseollin.Our data do not provide strong evidence that phaseollin is the principal factor that limits lesion development.Samenvatting Bladeren van boon (Phaseolus vulgaris) werden geïnoculeerd met drie pathogene en twee niet-pathogene isolaten vanBotrytis cinerea, als gevolg waarvan zich uitbreidende lesies, resp lesies van beperkte omvang ontstonden. Deze lesies werden samen met een omringend groen gedeelte onderzocht op de aanwezigheid van fytoalexinen. Hiertoe werden deze stoffen geëxtraheerd uit drooggevroren bladmateriaal, en gezuiverd m.b.v. kolomchromatografie over Sephadex LH-20 (Tabel 1) en dunnelaag-chromatografie (Tabel 2). Kwantitatieve analyse vond plaats d.m.v. in situdensitometrie.In de meeste gevallen werden phaseolline, phaseollidine, phaseollineïsoflavaan, een omzettingsprodukt van phaseolline, nl. 6a-hydroxyphaseolline, en enkele onbekende fungitoxische stoffen aangetoond (Fig. 1). Phaseolline was het meest voorkomende fytoalexine (Fig. 2 en 3). De concentratie van phaseolline in bladeren geinfecteerd met het niet-pathogene isolaat BC-5 was ongeveer tweemaal zo hoog als in bladeren geïnfecteerd met een pathogeen isolaat (isolaat BC-1, BC-3 en BC-4). Daarentegen bevatten bladeren die met het niet-pathogene isolaat BC-6 waren geinfecteerd slechts lage concentraties phaseolline.De hoeveelheden phaseolline en 6a-hydroxyphaseolline, omgerekend per lesie, namen snel toe in zich uitbreidende lesies van isolaat BC-1, terwijl de toenamesnelheid van deze stoffen afnam in lesies van isolaat BC-5, die beperkt van omvang bleven (Fig. 4).De resultaten geven geen duidelijke aanwijzingen dat phaseolline de belangrijkste remmende factor zou zijn bij het beperkt blijven van lesies.     

Catalase activity as a potential vital biomarker of fish intoxication by the herbicide aminotriazole

The objective of this study was to investigate the effects of the herbicide 3-amino-1,2,4-triazole (AMT) on the activities of catalase and lactate dehydrogenase (LDH) in blood (plasma and erythrocytes) and eight solid tissues of goldfish, Carassius auratus. Injection of goldfish with AMT (0.5 mg/gww AMT in 0.9% NaCl) resulted in a significant decrease in catalase activity 24 h post-injection in most tissues investigated. In white and red muscle, kidney, heart, liver, brain and erythrocytes the activity of catalase decreased by 61%, 69%, 64%, 48%, 40%, 27% and 26%, respectively, in comparison to the values seen in animals injected with physiological saline (0.9% NaCl). However, the activity of LDH decreased only in red muscle (by 19%) after AMT injection, whereas in plasma it increased by 137%. Protein carbonyl levels, a measure of oxidative damage to proteins, did not change in plasma in goldfish injected with AMT and total hemoglobin levels in AMT-injected fish, although lower compared with uninjected controls, did not differ from values in saline-injected controls. It is proposed that catalase activity in erythrocytes and white muscle might be usefully developed as a potential marker for fish intoxication by aminotriazole and other related herbicides.     

The influence of light and dark on attack of bean leaves by Alternaria zinniae

Bean leaves inoculated with spores ofAlternaria zinniae showed small purplish brown lesions after incubation in light for 3 days. After incubation in darkness for 1–3 days necrotic spots were formed, the size of which increased with increasing length of the period of incubation in darkness. Application of culture filtrates ofA. zinniae to the leaves caused the same symptoms as did inoculation with spore suspensions.Samenvatting Bonebladeren, geïnoculeerd met sporen vanAlternaria zinniae, vertoonden na 3 dagen incubatie in het licht kleine paarsbruine lesies (Fig. 1A). Na incubatie gedurende 1 tot 3 dagen in het donker ontstonden necrotische vlekken (Fig. 1B), waarvan de grootte toenam met de lengte van de incubatieperiode in het donker (Tabel 1).Toediening van cultuurfiltraten vanA. zinniae aan de bladeren veroorzaakte dezelfde symptomen als inoculatie met sporensuspensies.De grotere vatbaarheid van bonebladeren voor deze schimmel in het donker is waarschijnlijk te wijten aan een verhoogde gevoeligheid voor een toxische stof, mogelijk zinniol, gevormd doorA. zinniae.     

Pectic enzymes associated with phosphate-stimulated infection of French bean leaves by Botrytis cinerea

Botrytis cinerea readily produced polygalacturonases and pectin esterases in shake cultures of Richards' medium containing orthophosphate and no pectinaceous material or galacturonic acid.In inoculum droplets containing glucose and KH₂PO₄ or glucose and Na-ATP, which were used to evoke a susceptible reaction in French bean leaves,B. cinerea produced pectic enzymes. However, in inoculum droplets containing glucose but lacking phosphate, used to evoke a resistant reaction, activities of pectic enzymes remained low. As the enzyme activities already increased during the penetration stage of the infection process, it is assumed that these phosphatestimulated activities of pectic enzymes are, at least partially, responsible for the phosphatestimulated susceptible interaction between French bean leaves andB. cinerea.Electrophoresis in pectin-polyacrylamide gels showed that two polygalacturonases with a high isoelectric point value were associated with the penetration stage of the infection process.Samenvatting Botrytis cinerea vormde vlot polygalacturonasen en pectineësterasen in schudculturen in Richards' medium dat wel orthofosfaat maar geen pectineachtig materiaal of galacturonzuur bevatte.In inoculumdruppels met glucose +KH₂PO₄ of met glucose + Na-ATP, waarmee een vatbare reactie in bonebladeren kon worden opgewekt, vormdeB. cinerea verschillende pectolytische enzymen. In inoculumdruppels met glucose maar zonder fosfaat, waarmee een resistente reactie werd teweeggedbracht, bleeff de activiteit van pectolytische enzymen gering.Aangezien de enzymactiviteiten al begonnen toe te nemen tijdens de binnendringingsfase van het infectieproces, wordt verondersteld dat deze door fosfaat gestimuleerde activiteiten van pectolytische enzymen althans ten dele verantwoordelijk ziijn voor de door fosfaat gestimuleerde vatbare interactie tussen bonebladeren enB. cinerea.Elektroforese in pectine-polyacrylamidegels liet de toename zien van twee polygalacturonasen met een hoog isoëlektrisch punt tijdens de binnendringingsfase van het infectieproces.     

Spray drift as influenced by meteorological and technical factors

BACKGROUND: The objective of this study was to investigate spray drift from a conventional field sprayer as influenced by meteorological and technical factors, and to provide spray operators with data on which to base sound judgements when applying pesticides. The study was conducted in grazing fields and cereal crops. RESULTS: Interpreting the results from 15 field trials under varying meteorological conditions using different boom heights and driving speeds indicates that, during normal spraying conditions, the most decisive factors influencing the total spray drift (TSD) will be boom height and wind speed, followed by air temperature, driving speed and vapour pressure deficit. One important finding was that TSD (within the encompassed range of meteorological conditions and a boom height of 0.4 m) could be expressed as a simple function of the fraction of droplets ≤ 100 µm. In cereal crops: TSD = 0.36 + 0.11× [fr. (d ≤ 100 µm)] and in grazing fields, TSD = 1.02 + 0.10× [fr. (d ≤ 100 µm)]. In most cases a fraction of the airborne drift passed over the 6 m sampling mast located 5 m downwind of the spray swath. CONCLUSIONS: Under specified conditions, the present results indicate a simple relation between the total spray drift and volume fractions of droplets ≤ 100 µm. Given the nozzle type, it was concluded that the most decisive factors determining TSD are wind speed and boom height. Evaluating the relative importance of the meteorological and technical factors contributes to increasing knowledge in this field of research. Copyright © 2011 Society of Chemical Industry     

喷雾助剂对氟啶虫胺腈在富士苹果叶片表面润湿和持留的影响

为明确喷雾助剂在苹果园化学防治中的作用,采用表面张力、接触角和最大稳定持留量等分析了GY-T12、NF-100和迈润等3种喷雾助剂在达到临界胶束浓度 (CMC) 时对22%氟啶虫胺腈悬浮剂药液的表面张力及其在苹果叶片表面润湿性能和持留量的影响。结果显示:当添加的3种喷雾助剂达到其CMC时,氟啶虫胺腈药液表面张力降低至27.64~35.64 mN/m;根据水滴在苹果叶片表面的接触角小于或大于90°判定苹果叶片近轴面为亲水性表面、远轴面为疏水性表面,添加助剂使药液在近轴面和远轴面30 s的静态接触角分别降低23.2°~41.3°和68.0°~93.5°,同时使亲水性近轴面黏附功降低5.36~12.56 mJ/m2,而黏附张力增大9.27~11.26 mN/m,在疏水性远轴面黏附功与黏附张力分别增大27.45~36.66 mJ/m2和47.55~53.28 mN/m,对改善远轴面的黏附润湿性更显著;药液表面张力和最大稳定持留量存在抛物线状函数关系,当表面张力为40.89 mN/m时,持留量达最大值12.53 mg/cm2;3种助剂中,NF-100和GY- T12可显著增加药液持留量,且GY-T12对靶标害虫苹果黄蚜有显著增效作用。本研究结果表明,在苹果园应用时应依据预期目标选择适当的喷雾助剂,并通过调节药液表面张力使其处于适宜范围以增加药液持留量、提高对靶标害虫的毒力。     

Effect of inoculum composition on infection of French bean leaves by conidia of Botrytis cinerea

Inoculation of leaves of French bean (Phaseolus vulgaris) with sprays or small drops of a suspension of conidia ofBotrytis cinerea gave rise to spreading lesions, lesions remaining restricted in size or to no visible necrosis. The type of reaction depended on the composition of the inoculum. In studies with drop inoculations with buffered inocula some of the factors involved were analyzed. The formation of spreading lesions depended on pH, type and molarity of the buffer, presence of glucose, and concentration of conidia in the inoculum. If the phosphate buffer used in most of the inocula was replaced by monobasic phosphate, similar results were obtained. The reactions were not influenced by the proportion of K⁺ or Na⁺ ions in the phosphate buffer. Inoculations with conidia suspended in a solution of 0.067 M phosphate buffer (pH 5.0) or monobasic phosphate and 0.11 M glucose always evoked a susceptible reaction, i. e. the formation of spreading lesions.     

作物叶片表面自由能及喷雾助剂对农药药液在5种作物叶片上润湿性能的影响

为了解不同作物叶片表面润湿性能,科学选用助剂提高化学防治水平,采用光学视频接触角测量仪分别测定了小麦、玉米、辣椒、大豆和苹果5种作物叶片的表面自由能及其分量,进一步测定了2%甲氨基阿维菌素苯甲酸盐微乳剂和20%阿维·杀虫单微乳剂两种药液液滴在添加Silwet 408和GY-Spry两种喷雾助剂后其在5种作物叶片上的接触角。结果表明：5种作物叶片正反面表面自由能差异较大,表面自由能最大和最小的分别为辣椒叶片(54.12、45.08 mJ/m2)和小麦叶片(3.76、6.42 mJ/m2);同种作物叶片正反面表面自由能均有差异,其中辣椒叶片正反面和大豆叶片正面自由能以极性分量占主导,表现出亲水性,小麦、玉米、苹果叶片正反面及大豆叶片反面自由能以色散分量占主导,表现出疏水性。在2%甲氨基阿维菌素苯甲酸盐微乳剂5 000倍液和20%阿维·杀虫单微乳剂750倍液中分别添加两种助剂后,药液液滴在5种作物叶片上的接触角均有不同程度降低,其中添加Silwet 408后两种药液接触角分别降低82.63%～100%和85.07%～100%,添加GY-Spry后分别降低0～57.54%和10.96%～59....     

Droplet evaporation and spread on waxy and hairy leaves associated with type and concentration of adjuvants

BACKGROUND: Adjuvants can improve pesticide application efficiency and effectiveness. However, quantifications of the adjuvant‐amended pesticide droplet actions on foliage, which could affect application efficiencies, are largely unknown. RESULTS: Droplet evaporation rates and spread on waxy or hairy leaves varied greatly with the adjuvant types tested. On waxy leaves, the wetted areas of droplets containing crop oil concentrate (COC) were significantly smaller than those containing modified seed oil (MSO), non‐ionic surfactant (NIS) or oil surfactant blend (OSB), whereas the evaporation rates of COC‐amended droplets were significantly higher. On hairy leaves, COC‐amended droplets remained on top of the hairs without wetting the epidermis. When the relative concentration was 1.50, the wetted area of droplets with NIS was 9.2 times lower than that with MSO and 6.1 times lower than that with OSB. The wetted area increased as the adjuvant concentration increased. MSO‐ or OSB‐amended droplets spread extensively on the hairy leaf surface until they were completely dried. CONCLUSION: These results demonstrated that the proper concentration of MSO, NIS or OSB in spray mixtures improved the homogeneity of spray coverage on both waxy and hairy leaf surfaces and could reduce pesticide use. Published 2011 by John Wiley & Sons, Ltd.     

Substances in dead plant tissue that stimulate infection of French bean leaves by Botrytis cinerea

Spreading lesions were found in primary leaves of French bean after inoculation with pieces of dead bean tissue on which a droplet of a suspension ofBotrytis cinerea conidia was placed, and after inoculation with conidia suspended in a diffusate from dead tissue. After fractionation of aqueous extracts from dead bean leaves, the infection-stimulating activity was confined to the fractions containing sugars and phosphate esters.The infection-stimulating activity and the concentrations of carbohydrates and orthophosphate in extracts of liquid N₂-killed bean leaves varied slightly with the manner and degree of senescence. No consistent correlation, however, was observed between infection-stimulating activity and concentration of particular components. This was also true for extracts from other dead bean tissues. The stimulation of infection exhibited by extracts from dead flowers of different plant species, however, was closely correlated with the orthophosphate concentration.Inocula containing only orthophosphate and sugars in the same concentrations as found in the extracts, did not stimulate the infection to the same extent as the extracts did. It is concluded that, in addition to simple carbohydrates and orthophosphate, one or more other compounds in the extracts are involved in the stimulation of infection.Samenvatting In primaire bonebladeren onstonden zich uitbreidende lesies na inoculatie met stukjes dood boneweefsel waarop een druppeltje van een suspensie van conidiën vanBotrytis cinerea was aangebracht, maar ook na inoculatie met condiën in een diffussat van dood weefsel. Na fractionering van waterige extracten van dode bonebladeren bleek de infectiestimulerende activiteit gebonden te zijn aan de suiker- en fosfaatesterfracties.De infectiestimulerende activiteit en de concentraties van koolhydraten en orthofosfaat in extracten van met vloeibare N₂ gedode bonebladeren varieerden enigszins met wijze en mate van veroudering. Er werd echter geen vaste correlative waargenomen tussen infectiestimulerende activiteit en concentratie van bepaalde stoffen. Dit gold ook voor extracten van andere dode boneweefsels. De infectiestimulatie teweeggebracht door extracten van dode bloemen van verschillende plantesoorten was evenwel nauw gecorreleerd met de orthofosfaatconcentratie.Inoculatie met sporensuspensies waaraan orthofosfaat en suikers waren toegevoegd tot de concentraties gelijk waren aan die in de extracten, gaf veel minder infectie dan die met sporen gesuspendeerd in de extracten zelf. Daarom wordt geconcludeerd dat naast eenvoudige koolhydraten en orthofosfaat een of meer andere stoffen in de extracten betrokken zijn bij de stimulatie van de infectie.     

Inactivation of triforine by u.v. and sunlight on glass and on leaves of bean plants

Triforine is sensitive to u.v. and sunlight. The photochemical inactivation rate was higher in aqueous solution than in the solid state. In aqueous solution 50% of triforine was inactivated after 3 h irradiation with u.v. light and after 30 h exposure to sunlight. Eighty hours were necessary to decompose 25% of triforine in the solid state with sunlight on glass. The half life of triforine residues on the leaves of bean plants was about 60 h when exposed to solar irradiation. The inactivation of triforine by u.v. light and sunlight was accelerated in the presence of the sensitising chemicals riboflavin and xanthene; however, rhodamine B (C.I. 45170) showed only a small photosensitising activity.     

Effects of Aureobasidium pullulans on numbers of lesions on dwarf bean leaves caused by Alternaria zinniae

Inoculating dwarf bean leaves with spore suspensions ofAureobasidium pullulans one day before or simultaneously with inoculations made withAlternaria zinniae significantly decreased numbers of lesions caused by the latter fungus. Delaying inoculation withA. pullulans until 1 day after that withA. zinniae lessened the effect on lesion numbers. Increasing numbers ofA. pullulans spores progressively decreased numbers ofA. zinniae lesions. Three of five isolates ofA. pullulans decreased lesion numbers caused byA. zinniae. AlthoughA. pullulans restricted the germination ofA. zinniae on dwarf bean leaves, it had no effect when on cherry agar. Few viable propagules ofA. pullulans were recovered from dwarf bean leaves when examined 7 days after application.