Control of Glomerella cingulata f.sp. camelliae with fungicides

A critical test of fungicidal activity against the wound pathogen Glomerella cingulata f.sp. camelliae on camellias involved the application of a conidial suspension to scratches on detached leaves, treated with fungicide 24 h previously. In this test, prochloraz at 250–500 μg/ml a.i. in both EC and manganese WP formulations was highly effective, inhibiting leaf rotting by 90–100% compared with 55% or less in some tests with benomyl, chlorothalonil and captafol at 500–1000 μg/ml and captan at 1200 μg/ml. Prochloraz gave similar protection to leaves when applied to whole plants. Protection was less, especially on older leaves, when wounding and inoculating were delayed by 7 or more days after treatment. Prochloraz did not prevent all infection through comparatively large wounds, e.g. leaf scars, made on stems 24 h after treatment.
Poor control of the disease in a nursery was not due to resistance of the pathogen to benomyl; in vitro tests failed to detect full resistance at this time. Under nursery conditions a statutory policy of destroying infected plants and spraying the remainder with prochloraz or prochloraz manganese (both at 500 μg/ml), alternating with benomyl (500 μg/ml) on a weekly basis apparently prevented spread of the disease to healthy plants.     

THE HERBICIDAL EFFECT OF SOME α-HYDROXY-β,β,β-TRICHLOROETHYLAMINO-1,2,4-TRIAZOLES

Summary. Four α-hydroxy-β,β,β-trichloroethylamino-1,2,4-triazoles were prepared by the reaction of chloral hydrate with the corresponding aminotriazole and tested for herbicidal activity.
The introduction of the α-hydroxy-β,β,β-trichloroethyl group into the aminotriazole molecule increased the activity of the parent compound. The increase in activity was slight with the highly active 3-amino-1,2,4-triazole but was more marked with amino 1,2,4-triazoles of low activity. The symptoms resembled those of the simultaneous action of 3-amino-l,2,4-triazole with chloral hydrate or trichloroacetic acid.     

THE HERBICIDAL EFFECT OF SOME SUBSTITUTED ANILIDES

Summary. The 3,4-dichloroanilides of four herbicidally active and of four inactive or weakly active phenoxyalkanecarboxylic acids were synthesized and tested for herbicidal activity, in order to study the effect of compounds comprising the two characteristic groupings within one molecule. 4-Chloro-2-methylphenoxyacetic acid, 2,4-dichloro-phenoxyacetic acid, 2,4,5-trichlorophenoxyacetic acid and a-[2,4,5-trichlorophenoxy] propionic acid were selected as representatives of active compounds; and phenoxyacetic acid, 2-methylphenoxyacetic acid, 3,5-dichlorophenoxyacetic acid and 2,4,6-trichloro-phenoxyacetic acid as inactive or weakly active compounds.
The compounds were tested in the glasshouse on wheat and white mustard as pre-and post-emergence treatments. The synthesized 3,4-dichloroanilides had no or little herbicidal activity, as compared with the high activity of the known herbicides 3,4-dichloropropionanilide and 2,4-dichlorophenoxyacetic acid. The conclusion can be drawn that the introduction of phenoxy groupings into the acid moiety of the active fatty acid-3,4-dichloroanilides as well as the introduction of the 3,4-dichloroaniline group into the carboxylic group of the active phenoxyacetic acids decreases herbicidal activity. This last phenomenon is probably due to a decreased ability to be hydrolysed.
L'activité herbicide de quelques anilides substituées     

SOME EFFECTS OF DROPLET SIZE AND POSITION ON THE RESPONSE OF LETTUCE TO SUB-LETHAL DOSES OF MCPA

Summary. Senescent, expanded or expanding leaves of lettuce plants were treated individually with MCPA. The subsequent development of auxin-induced symptoms throughout the plants was recorded. The number of leaves affected and the severity of the symptoms increased with application to the less mature leaves. In addition more leaves were affected when the application was made to larger plants than to smaller ones. These results were associated with absorption/translocation differences in the leaves of different ages, and in their spatial relationship to tissues at particularly susceptible stages of development. In further experiments, applications of similar weights of MCPA to lettuce plants in droplet sizes of approximately 100 μ and 500 μ were compared. There were consistent trends for the small droplets to produce greater effects.
Quetques effets de la taille des gouttelettes et de leur position sur la reaction de la laitue à des doses sub-létales de MCPA     

Relationship between the Spray Droplet Density of Two Protectant Fungicides and the Germination of Mycosphaerella fijiensis Ascospores on Banana Leaf Surfaces

The effect of fungicide spray droplet density (droplet cm^-2), droplet size, and proximity of the spray droplet deposit to fungal spores was investigated with Mycosphaerella fijiensis ascospores on the banana (Musa AAA) leaf surface for two contact fungicides: chlorothalonil and mancozeb. When droplet size was maintained at a volume median diameter (VMD) of 250 μm while total spray volume per hectare changed, M. fijiensis ascospore germination on the leaf surface fell below 1% for both fungicides at a droplet deposit density of 30 droplet cm^-2. At a droplet deposit density of 50 droplet cm^-2, no ascospores germinated in either fungicide treatment. When both droplet size and droplet cm^-2 varied while spray volume was fixed at 20 litre ha^-1, ascospore germination reached 0% at 10 droplet cm^-2 (VMD=602 μm) for both fungicides. At lower droplet densities (2–5 droplet cm^-2 VMD=989 μm and 804 μm respectively), ascospore germination on the mancozeb-treated leaves was significantly lower than on the chlorothalonil-treated leaves. The zone of inhibition surrounding a fungicide droplet deposit (VMD=250 μm) on the leaf surface was estimated to extend 1·02 mm beyond the visible edge of the spray droplet deposit for chlorothalonil and 1·29 mm for mancozeb. The efficacy of fungicide spray droplet deposit densities which are lower than currently recommended for low-volume, aerial applications of protectant fungicides was confirmed in an analysis of leaf samples recovered after commercial applications in a banana plantation. Calibrating agricultural spray aircraft to deliver fungicide spray droplets with a mean droplet deposit density of 30 droplet cm^-2 and a VMD between 300 and 400 μm will probably reduce spray drift, increase deposition efficiency on crop foliage, and enhance disease control compared to aircraft calibrated to spray finer droplets. © 1997 SCI.     

THE COMBINED ACTION OF 3-AMINO-1,2,4-TRIAZOLE AND AMMONIUM THIOCYANATE ON PHOSPHATASE ACTIVITY IN COTTON THISTLE (ONOPORDUM ACANTHIUM L.)

Summary. In phosphatase extracts prepared from untreated leaves of Onopordum acanthium , phosphatase activity was stimulated by amitrole (0·04 M) and ammonium thioeyanate (0·04 M), alone and together. The effect of the mixture of amitrole and ammonium thioeyanate was more than additive in experiments set up at pH 4·0, less than additive at pH 4·6 and roughly additive at pH 5·3 and 5·8. The effect of amitrole alone could be explained simply in terms of the increase in pH it effected.
In leaves harvested 4, 7 and 9 days after spraying rosettes with 1/8 lb/ac (140 g/ha) amitrole and 1/4 lb/ac (280 g/ha) ammonium thioeyanate, alone and together, more than additive or additive increases in phosphatase activity of plants sprayed with the mixture were recorded. These increases are interpreted as being due to increases in the amount of soluble protein.
Inorganic phosphate levels showed different trends with time in plants treated with amitrole alone compared with plants treated with the mixture of amitrole and ammonium thioeyanate.
These interactions between amitrole and ammonium thioeyanate are taken to indicate a possible chemical basis for the increased herbicidal activity of the mixture over amitrole alone.
Histochemical studies on the mature leaves of rosettes showed that phosphatase activity was confined to the vascular tissues while in the very young leaves it was high in the chlorenchymatous tissue and appreciable in the epidermal and hair cells.
Attention is drawn to the strong buffering action of amitrole in the pH range 4·0–5·3. This may be relevant to herbicidal activity, the vacuolar pH of the outer cells of leaves of Onopordum being in the range 4·8-5·2.
L'action combinée du 3-amino-1,2,4-triazole et du thioeyanate d'ammonium sur l'activité de la phosphatase chez Onopordum acanthium L.     

Characterization of new photosynthesis-inhibiting imidazolidine derivatives. 1. Interpretation of post-emergence herbicidal performance from photosynthesis-inhibiting activity and systemicity

An attempt was made to account for quantitatively measured herbicidal performance of foliage-applied 5-hydroxy-3-methyl-2–oxo-imidazolidine-1-carboxamide derivatives by their photosynthesis-inhibiting activity and systemicity. Photosynthesis-inhibiting activity was estimated from the increase of chlorophyll fluorescence intensity in Chlorella vulgaris Beijer cells measured by a microplate scanner, and systemicity was also evaluated by computer-aided chlorophyll fluorescence imaging. The highest herbicidal performance was recorded for N-cyclohexyl-5-hydroxy-3-methyl-2-oxo-imidazo～idine-l-carboxamide, a compound with the second strongest photosynthesis-inhibiting activity and intermediate systemicity. Though neither photosynthesis-inhibiting activity nor systemicity showed significant correlation with the actual herbicidal performance in simple regression analyses, a high predictability was found for a multiple regression on both parameters as two independent variables, suggesting that these two factors work cooperatively in the field performance.     

Use of ELISA for assessing major gene resistance of potato leaves to Phytophthora infestans

Hypersensitivity and susceptibility of potato leaflets of different genotypes to Phytophthora infestans were distinguished using ELISA. Estimates of pathogen growth indicated that an intermediate reaction sometimes occurred. Visual symptoms of disease were not always closely related to the pathogen content (mycelium, μg fresh weight) of leaflets estimated by ELISA. Leaflets inoculated with 1000 zoospores in a droplet had to be incubated for at least 6-8 days at 15 C before reliable estimates of the reaction by ELISA could be determined. Increasing the inoculum load improved the differentiation between hypersensitivity and susceptibility.     

Design and Development of a Disc-Windmill Atomiser for Aerial Applications1

For greater efficiency in aerial applications of pesticides it is essential to get a greater fraction of the emitted formulation to the true biological target To achieve this and at the same time ensure that environmental pollution is a minimum requires the use of a narrow droplet spectrum of the correct mean size. The best atomisers currently made for aircraft use produce at best only about 40 % of the emitted volume in sizes within 25 % of the desired size and in many cases the percentage is far smaller. A simple spinning disc atomiser has been designed at Cranfield which operates in the filament mode of droplet formation at flow rates many times greater than the usual maxima for these devices. This improvement is achieved by using a high velocity radial airflow in the region of atomisation. This same air, arising from the forward speed of the aircraft, is used to rotate the disc by shaping it to be a high solidity windmill. Test results show that a 5 cm diameter disc will atomise up to 11/min into droplet sizes from 80 μm to 300 μm VMD, depending upon the chosen blade setting, and that, for any given blade setting, up to 80 % of the emission will be within ± 25 % of the mean size. It is anticipated that mass production of the atomiser will commence in 1983.     

THE HERBICIDAL ACTIVITY OF 2-AMINO-3-CHLORO-1,4-NAPHTHOQUINONE

Summary. An investigation was made of a now herbicide, 2–amino-3–chloio-1,4–naphthociuinone (ACNQ,), which appears to be promising for the control oi Echinochloa crus-galli (L.) Beauv. in transplanted paddy rice [ Oryza sativa L.).
In pot experiments in the glasshouse, seedlings of Echinochloa at different stages of growth were killed by ACNQ, at doses equivalent to 2–4 kg/ha (applied as granules) if they were submerged, but not if the shoots emerged above water. Activity was increased more by raising the level of water in the pot than by increasing the dosage. Emergent rice seedlings were little affected by ACNQ, up to 8 kg/ha, and the observed selectivity is considered to be due mainly to differences in plant height in relation to depth of water.
In laboratory experiments with rice seedlings grown without soil, the activity of ACNQ again increased with the depth of solution. Conversely, at a standard solution depth, there was a reduction in damage with advancing stage of growth, and the chemical had little effect once the leaf tip was above the solution surface.
The rate of leaching of ACNQ. through a sandy soil was slow and, at a dose of 2 kg/ha, persistence was about 15 days.
In evaluating new herbicides for paddy rice it is suggested that screening tests arc necessary on submerged as well as non-submerged plants.
Activité herbicide de la 2–amino-3–chloro-1,'4–naphtoquimne. I. Activité herbicide et profondtur de de l'eau     

Treatments to control Phoma and Alternaria infections of brassica seeds

The screening of chemicals using agar plate tests for activity against cultures of Phoma lingam, Alternaria brassicicola and A. brassicae is described. Most fungicides which were inhibitory to growth at 20 μg/ml or less showed eradicant activity when used as seed treatments. Selected on this basis, thiabendazole, applied as a slurry at 2–5 g a.i./kg seed, showed excellent eradicant activity against seed-borne Phoma but not Alternaria when tested under laboratory, glasshouse and field conditions. Triarimol, tridemorph and azepine-A2151, nuarimol, fenarimol and imaza-lil although effective in agar plate tests against Alternaria and Phoma were phytotoxic when applied to seeds at rates sufficient to eliminate these fungi, Iprodione and fenpropimorph inhi bited the growth of the fungi at concentrations of 0.625 to 4 μg/ml and subsequent treatment of infected seeds at 1.25–2.5 g a.i. fungicide/kg seed with these fungicides proved effective against all three pathogens. Neither chemical adversely affected germination or emergence.     

Dispersal of Pseudocercosporella herpotrichoides and Pyrenopeziza brassicae spores in splash droplets

Splash dispersal of conidia which differ in shape and size, those of Pseudocercosporella herpo ichoides (needle-shaped, 52×2 μm) and Pyrenopeziza hrassicae (cylindrical, 12×3 μm), was studisd by allowing 5 mm drops to fall 13 m on to suspensions (depth 0.5 mm, concentration 120, 000 spores/ml) of each. The resulting splash droplets were collected on photographic film. The pattern of spore dispersal with distance and the distribution of spore-carrying droplets and spores within droplet-size categories were similar for both fungi. Regressions of square root spore number) on droplet diameter gave lines with slopes of 0.0138 for P. herpotrichoides and 0.0167 for P. brassicae.     

Biology and control of Polystigma ochraceum, the cause of almond red leaf blotch

Polystigma ochraceum is a major leaf pathogen of almond in Fars Province of Iran. Over a 4-year study period it was found that ascospore discharge began at flowering and continued for 4–5 weeks. The maximum discharge occurred at petal fall. The incubation period was estimated to be 4–5 weeks under experimental conditions. Although the mature ascospores could produce short germ tubes in distilled water or water agar, the fungus could not be cultured or grown on conventional media from either ascospores, pycnidiospores or stromatic tissues under laboratory conditions.
Of several systemic and non-systemic fungicides evaluated under field conditions, triforine at 100–400 μ/ml was most effective. Other fungicides which significantly reduced leaf infection were, in order of efficacy, copper oxychloride (2000 μg/ml), copper hydroxide (2000 mUg/ml), Bordeaux mixture (10 000 μg/ ml) and mancozeb (2000 μg/ml). Carbendazim and thiophanate methyl (500 μg/ml) increased the level of infection. One application of the fungicide at petal fall and then two at 14-day intervals were found to be effective in reducing the disease.     

具有除草活性的小麦根腐病菌发酵条件优化

通过单因子试验和正交试验对小麦根腐病菌菌株进行了发酵条件优化,以提高其活性物质的产量。结果表明:最适合小麦根腐病菌产毒的培养基是察氏培养基;该培养基的最佳碳源为葡萄糖,氮源为氯化铵,无机盐为氯化钾、磷酸氢二钾、硫酸镁和硫酸亚铁;发酵培养基各组分的最佳配比为:葡萄糖2.0%,氯化铵0.25%,氯化钾0.05%,磷酸氢二钾0.025%,硫酸镁0.025%,硫酸亚铁0.000 5%;有利于提高菌株活性物质产量的培养条件为初始pH7.0,转速为130r/min,温度为28℃,培养时间为5d,装液量为120mL/250mL,接种量为6%。小麦根腐病菌菌株发酵产物具有良好的热稳定性和光稳定性,在弱酸性及中性条件下较稳定。发酵条件优化后提高了小麦根腐病菌的除草活性。     

THE GROWTH IN VITRO OF MICRO-ORGANISMS IN THE PRESENCE OF SUBSTITUTED PHENOXYACETIC AND PHENOXYBUTYRIC ACIDS

Summary. The growth has been tested in vitro of selected species of fungi, yeasts, bacteria, actinomycetes and green algae in the presence of the acetic and α-butyric acid forms of MCPA, 2,4–D and 2,4,5–T. The results show that at concentrations approximating to field rates of application, these chemicals were harmless. At much higher concentrations (above 500 ppm), however, the α-butyric acids were found to be highly toxic whereas the acetic acids has no effect on growth.     

Interactive effects of diluent pH and calcium content on glyphosate activity on Panicum repens L. (torpedograss)

Summary. Solutions of glyphosate containing 0–5 mM calcium, both with buffering (pH 4, 6 or 8) and without, were sprayed onto Panicum repens L. (torpedograss) foliage. Growth inhibition of the treated foliage was poorly correlated with inhibition of shoot regrowth from rhizomes. Therefore, when evaluating long term control of perennial grasses regrowth data should be utilized. Spray solution pH, calcium and glyphosate rate influenced herbicidal activity on torpedograss. Calcium affected glyphosate activity on torpedograss except at the highest herbicide rate (4·48 kg ha⁻¹). Optimum herbicidal activity on torpedograss was achieved with soft water (i.e. no calcium), however, when calcium was present in the spray solution a pH of 6 reduced its antagonistic effects.     

EFFECTS OF TEMPERATURE AND SOIL TYPE ON THE PHYTOTOXICITY OF TRIFLURALIN

Summary. Wheat, oats, and green foxtail were grown at day-night temperatures of 32–16, 27–16, or 16–16°C in the growth chamber. The caryopses were planted at depths of 2·5 or 6·3 cm, and trifluralin was incorporated in the surface 5 cm of soil. The results indicated that the phytotoxicity of trifluralin was somewhat greater when plants were grown at day-night temperatures of 32–16°C than at a temperature regime of 16–16°C. A further study in the greenhouse indicated that the phytotoxicity of trifluralin was dependant upon soil properties. In general, the toxicity of trifluralin to both wheat and green foxtail appeared to decrease with an increase in the organic matter content of the soil.
Effets de la température et de la nature du sol sur la phytotoxicité de la trifluraline     

THE ADSORPTIVE BEHAVIOUR OF ACID AND ESTER FORMS OF 2,4-D ON SOILS

Summary. The adsorption of acid, n-butyl, and iso-octyl ester forms of 2,4-D (2,4- dichloiophenoxyacetic acid) was studied for several Canadian prairie soils. The k values for the acid ranged from 0·09 to 1·30 and were correlated to the soil organic matter and not to the clay content. The Q , values (μg adsorbed/g of organic matter) for the acid were 7–2±l. The n-butyl and the iso-octyl esters hydrolysed to the acid form in the aqueous medium and this process was accelerated in the presence of the moist soil. Consequently, the k values for the esters, using slurry type adsorption experiments, or their distribution coefficients, using leaching columns, could not be determined. It was concluded that the adsorptive behavior of the two esters in moist soil was similar to that of the acid form.
Comportement des formes actde, et ester du 2,4-D quant à leur adsorption dans tes sols     

EVALUATION OF PARAQUAT AND DIQUAT FOR WEED CONTROL IN RUBBER

Summary. In Malayan rubber plantations where the weed flora was dominated by grasses paraquat was superior to diquat as a herbicide. At the rates needed to give satisfactory grass weed control paraquat also gave an adequate control of broad-leaved weeds.
The rate of paraquat needed varied between 0.75 and 1.25 lb/ac depending on the weed flora and the growth stage of the rubber trees. In young rubber 1.0–1.25 lb/ac gave 8–10 weeks' control, but in mature rubber there was only 20% recovery 6 months after an application of 0.75 lb/ac. Where weed regrowth was very rapid after the initial spray, as in the case of Paspalum conjugation in young rubber, a second application some 2–3 weeks after the first was an advantage. The volume of water in which it was applied was not critical.
Rain falling soon after application did not reduce the herbicidal activity of paraquat. Paraquat did not injure rubber trees providing it was not sprayed onto green tissue and this feature combined with its inactivation by soil made it safe to use from a very early stage in the growth of the rubber trees.
L'évaluation du paraquat et du diquat pour la lutte contre les mauvaises herbes dans les plantations de caoutchouc     

Droplet Formation and Deposition1

At the EPPO Conference in Belgrade on 1970 the author reported on work showing that small, uniform, and non-volatile droplets appeared to offer the prospect for greatly reduced dosages of pesticides by both providing a more effective deposit and by controlling drift. Three recent studies provide further evidence for this hypothesis, which questions the very principles on which our present spraying practices are based. However, the deposition of droplets by the external forces of wind and gravity imposes lower limits on the droplet sizes capable of being used. These are 30 μm for insecticides and fungicides (except in the case of flying insects) and 150 μm for herbicides, since the droplets require sufficient energy to impact themselves on the target. Electrostatic charging of droplets promises to free us from these size constraints by providing the droplet with a depositional force of its own, allowing it to impact on any surface. Electrostatics, however, is solely a force of deposition and thus must be balanced with the forces required for spray dispersion so that the droplets can penetrate the crop canopy and/or be transported to the target