The use of separate root and shoot tests in the screening of herbicides for strawberries

The tolerance of strawberries to herbicides was tested by applications to the roots of plants growing in sand and by foliage applications to plants grown in compost, and compared with tolerance in the field. Dimefuron was safe as a foliar application but much more toxic than simazine when applied in sand or in the field. Metamitron caused slight injury as a foliar spray; in sand and in the field it was intermediate in toxicity between simazine and lenacil. At normal rates propachlor was safe as a foliar spray and much safer than lenacil when applied in sand. High rates had no adverse effect in the field. Ethofumesate and pendimethalin caused some temporary stunting when applied to foliage, but were less toxic than lenacil when applied to roots in sand. Field applications of both herbicides at 1–1.5 kg/ha were safe. Foliage sprays of bentazone, oxadiazon and oxyfluorfen severely damaged the sprayed leaves, but these herbicides were less active than lenacil when applied to the roots. In the field they caused severe leaf damage, but by the end of the growing season the plants had recovered. The experiments demonstrated the value of separate root and shoot activity tests for indicating which herbicides merit further field testing.     

Translocation of 14C-glyphosate in johnsongrass (Sorghum halepense L. Pers.) as affected by growth stage and rhizome length

Studies were conducted in the green house on ¹⁴C-methyllabelled glyphosate translocation in johnsongrass as affected by rhizome length and growth stage. The amount of ¹⁴C measured by the liquid scintillation technique in the rhizomes (2-8%) increased with rhizome length (10, 20 or 30 cm) and tended to increase with growth stage (15-30 cm tall, 45-60 cm tall, or at seedhead), but the amount of ¹⁴C per g fresh rhizome weight was almost similar in all cases. Of the total amount applied per plant (0·2 μCi) about 1/3 or less remained on the treated leaf area, while another 1/3 was a absorbed into the treated leaves. Autoradiographs showed that the ¹⁴C label moved to all plant parts, basipetally and acropetally. Migration du glyphosate ¹⁴ C chez le sorgho d'Alep (Sorghum halepense L. Pers.) en relation avec le stage de croissance et la longueur du rhizome Des recherches ont été effectuées en serru sur la migration du glyphosate marqué au ¹⁴C sur le méthyle, chez le sorgho d'Alep, en relation avec la longueur du rhizome et le stade de croissance. La quantité de ¹⁴C mesurée par la technique de scintillation liquide dans les rhizomes (2 à 8%) s'est accrue avec la longueur du rhizome (10, 20 ou 30 cm) et elle a eu tendance à augmenter avec le stade de croissance (Hauteur 15-30 cm, hauteur 45-60 cm ou épiaison), mais la quantité de ¹⁴C par gramme de poids frais de rhizome est restée Presque identique dans tous les cas. Environ 1/3, ou moins, de la quantitéà la surface des feuilles traitées par plante (0,2 μCi), est restéà la surface des feuilles traitées cependant qu'un autre 1/3 a été absorbé dans less feuilles traitées Les autoradiographies ont montré que le ¹⁴C marqueur a migré dans toutes les parties de la plante, dans le sens basipète et dans le sens acropète. Translokation von ¹⁴C-Glyphosat in Johnsongras (Sorghum halepense L. Pers.) in Abhängigkeit vom Wachstumsstadium der Pflanzen und der Rhizomlänge Im Gewächshaus wurden Versuche über die Translokation von ¹⁴C-Glyphosat in Johnsongras (Sorghum halepense L. Pers.) in Abhängigkeit vom Wachstumsstadium der Pflanzen und der Rhizomlänge durchgeführt. An den Rhizomen stieg der Gehalt von ¹⁴C(2–8%), gemessen mit der Flüssig-Szintillationstechnik, mit zunehmender Rhizomlänge (10, 20 oder 30 cm) an und nahm tendenziell auch mit fortschreitendem Pflanzenwachstum zu (15–30 cm und 45–60 cm Sprosslänge oder nach dem Rispenschieben); jedoch blieb die Menge pro g Rhizomfrischgewicht beinahe konstant. Von der insgesamt ausgebrachten Menge pro Pflanze (0.2 μCi) blieben bis zu 1/3 auf der behandelten Blättern absorbiert wurde. Die Autoradiographie zeigte, dass der ¹⁴C markierte Teil in alle Pflanzenteile sowohl basipetal wie auch akropetal transportiert wurde.     

Melanin biosynthesis in Pyricularia oryzae: Site of tricyclazole inhibition and pathogenicity of melanin-deficient mutants

Tricyclazole (5-methyl-1,2,4-triazolo[3,4-b]benzothiazole) inhibits melanin synthesis in Pyricularia oryzae at concentrations less than 0.01 μg/ml. The primary site of inhibition in the biosynthetic pathway occurs between scytalone and vermelone. Accumulation of several metabolites derived from melanin precursors along branch pathways is associated with inhibition of melanin biosynthesis. At low tricyclazole concentrations (0.01–1 μg/ml), predominant accumulation of 2-hydroxyjuglone and 3,4-dihydro-3,4,8-trihydroxy-1-(2H)-naphthalenone (3,4,8-DTN) occurs as a result of the primary block between 1,3,8-trihydroxynaphthalene and vermelone. As the concentration of tricyclazole is increased from 1 to 10 μg/ml, flaviolin accumulation is markedly enhanced, whereas that of 3,4,8-DTN and 3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone is depressed, indicating possible secondary sites of inhibition in the main and branch pathways. Five melanin-deficient mutants of P. oryzae that phenotypically resemble the tricyclazole-treated wild-type strain were nonpathogenic or rarely infected two rice varieties. Three of the mutants studied were genetically defective in the melanin biosynthetic pathway at the site blocked by tricyclazole in the wild type. The wild-type strain converted both scytalone and vermelone to melanin; whereas the three mutants and the tricyclazole-treated wild type converted only vermelone to melanin. The data suggest a relationship between melanin biosynthesis and pathogenicity in P. oryzae.     

Comparative inhibition of the juvenile hormone esterases from Trichoplusia ni,Tenebrio molitor, and Musca domestica

Twenty-seven compounds were screened as potential inhibitors of juvenile hormone esterases. Of these compounds O-ethyl-S-phenyl phosphoramidothiolate provided the best inhibition for the cabbage looper, Trichoplusia ni (Hubner), and the yellow mealworm, Tenebrio molitor L., while the juvenile hormone esterases of the house fly, Musca domestica L., were best inhibited by a juvenoid carbamate (1-(m-phenoxy-N-ethyl carbamate)-3,7-dimethyl-7-methoxy-2E-octene). The inhibition patterns of T. ni and T. molitor are similar, while those of M. domestica are relatively different. Further studies on the juvenile hormone and α-napthyl acetate esterases of T. ni showed that they could be differentially inhibited. Diisopropyl phosphorofluoridate and an alkyl trifluoromethyl ketone selectively inhibit the hydrolysis of α-naphthyl acetate and juvenile hormone, respectively, while O-ethyl-S-phenyl phosporamidothiolate inhibits both enzymes. The juvenile hormone esterases of T. ni also appear to be unique enzymes that are selective for juvenile-hormone-like molecules. The in vivo inhibition of T. ni juvenile hormone esterases by O-ethyl-S-phenyl phosphoramidothiolate slows the in vivo hydrolysis of juvenile hormone and results in delayed pupation and malformed larvae that resemble larval-pupal intermediates. Thus, the esterases involved in juvenile hormone metabolism appear to be important in juvenile hormone regulation.     

Physiological actions of dinoterb,a phenol derivative: 2. Effects on isolated plant mitochondria and chloroplasts

Dinoterb, a contact herbicide, affects respiration and photosynthesis of mitochondria and chloroplasts. On mitochondria, at low concentrations, it acts as an uncoupler of oxidative phosphorylation; at higher concentrations, it inhibits the electron transport chains, probably before cytochrome c. On chloroplasts, dinoterb has a stimulatory effect on oxygen uptake in the reduced dichlorophenol-indophenol→methyl viologen couple; however, it is also an inhibitor of the Hill reaction and its site of inhibition is located before plastoquinone, near photosystem II.     

Precocene II metabolism: Comparative in vivo studies among several species of insects,and structure elucidation of two major metabolites

Several species of insects, exhibiting varying responsiveness to the juvenile hormone antagonist precocene II (6,7-dimethoxy-2,2-dimethylchromene), were challenged topically with a tritiated preparation of the title compound. Metabolism of [³H]precocene II was subsequently examined by withdrawing hemolymph samples from treated animals at appropriate time intervals and characterizing the extractable radiolabel chromatographically. Quantitative (or qualitative) differences observed between the respective metabolic profiles were found not correlative with specimen sensitivity to precocene. Production of two heretofore unreported metabolites, identified by spectral and chemical means as O-β-glucosides of 6- and 7-monodemethylated precocene II, was demonstrated in both sensitive and insensitive species. No evidence for the presence of a hemolymphborne, biologically effective “activated metabolite” produced in vivo by precocene-susceptible insects could be found. The latter finding may well argue for in situ bioactivation of precocene at the target tissue(s) by these sensitive insects.     

In vitro metabolism of EPN and EPNO in susceptible and resistant strains of house flies

EPN is twice as toxic as EPNO to house flies from both the Diazinon-resistant strain and the susceptible strain. EPN and EPNO are also eight times more toxic to the susceptible than the resistant strain. This is due to the ability of the resistant strain to metabolize these compounds to a greater extent. Metabolism by the glutathione S-transferases present in the 100,000g supernatant is more extensive than that by the NADPH-dependent microsomal mixed-function oxidases. The glutathione S-transferases are the major route of metabolism for EPN and appear to be the principal mechanism conferring resistance. EPN was metabolized by the microsomal fraction via oxidative desulfuration to the oxygen analog, EPNO, and by oxidative dearylation to p-nitrophenol. EPNO was metabolized by the same system to p-nitrophenol and desethyl EPNO as well as to an unknown metabolite. The soluble fraction metabolized EPN to p-nitrophenol, S-(p-nitrophenyl)glutathione, O-ethyl phenylphosphonothioic acid, and S-(O-ethyl phenylphosphonothionyl)glutathione. The identification of the latter conjugate demonstrates a new type of metabolite of organophosphorus compounds. EPNO was metabolized by the soluble fraction to p-nitrophenol and S-(p-nitrophenyl)glutathione.     

The effect of some Frescon analogs on the aquatic snail,Lymnaea stagnalis: II. Correlation of neurotoxicity to Molluscicidal effectiveness

Although the molluscicide Frescon is a strong neurotoxin to the Lymnaea stagnalis central nervous system in vitro, it is probable that the exposure of the whole animal to this molluscicide fails to result in central nervous system abnormalities: Frescon does not appear to reach the brain in sufficient quantity to disrupt its normal activity. However, only those Frescon analogs found to be neurotoxic were molluscicidal, suggesting some related mode, if not site, of action. Frescon and its analogs may act by affecting excitable tissues other than the nervous system (e.g., the snail musculature) by altering certain functional and/or structural membrane properties.     

An Approach to Forecasting the Incidence of Potato and Cereal Aphids in Scotland1

Many potato and cereal infesting aphids in Scotland are either completely cr partially anholocyclic. This makes forecasting their first appearance and abundance on crops difficult, when compared with holocyclic species such as Aphis fabae Scopoli. This paper describes an analysis of the early movement of nine aphid species, commonly found on potatoes and cereals in Scotland, in relation to winter and early spring climate. Data on their early movement have been extracted from the catches in three of the sjx.12–2.rn suction traps now operating in Scotland in cooperation with the Rothamsted Insect Survey. The particular importance of early spring temperature has been established. The extension of this work to develop a predictive forecast of summer activity of anholocyclic aphid species is discussed. En Ecosse, une forte proportion de pucerons des pommes de terre et des céréales est entièrement ou partiellement anholocyclique. Ceci complique la prévision sur le moment de leur première apparition et sur leur abondance par rapport aux espéces holocycliques telles qu'Aphis, fabae. Cette étude concerne les déplacements précoces de neuf espéces de pucerons retrouveés fréquemment sur les pommes de terre et les céSreales. Les données sur les deplacements ont été obtenues à partir de trois des six piegès à succion de I2,2 m installes en Ecosse en cooperation avec le « Rothamsted Insect Survey », Il est apparu que la température printanière revêt une importance particuliere. Les recherches se poursuivent dam le but d'établir des prévisions sur le développement estival des espèces anholocycliyues de pucerons.