Investigations on fungicides

A number of bis-[(i-formamido-2,2,2-trichloro)ethylamino]-alkanes and their dioxy and dithio analogues were examined for direct and systemic antifungal activity. All compounds showed very low in vitro fungitoxicity and only slight protectant anti-mildew activity when applied as a foliar spray. Certain diamino and dioxy derivatives were, however, systemically active against powdery mildew fungi when applied as a root drench to seedlings of wheat or cucumber; the dithio analogues were inactive. The level of systemic activity shown by these compounds was markedly influenced by the nature of the hydrocarbon ‘bridging’ group.     

Investigations on fungicides: XIV. Fungitoxicity of N-(2,2,2–trichloro-1–methoxyethyl)-formamide and related compounds

From a study of forty compounds related to the systemic fungicide N,N'-bis(1–formamido-2,2,2–trichloroethyl)-piperazine, known as triforine (CELAW524), it was found that a new compound, N-(2,2,2–trichloro-1–methoxyethyl)-formamide, controls Erysiphe graminis on wheat when applied to the roots in sand. A number of N-(2,2,2–trichloro-1–aryloxyethyl)-form-amides and alkyl N-(2,2,2–trichloro-1–arylaminoethyl)-carbamates protect broad beans against Uromyces fabae and wheat against Erysiphe graminis; some of these formamides show slight activity when applied to plant roots.     

Investigations on fungicides

The systemic anti-mildew activity shown by homologous series of alkoxy-, alkylamino- and alkylthio-trichloroethyl formamides when applied to the roots of wheat or cucumber seedlings has been measured. In general the thio compounds were much less active than their oxy and amino analogues. The alkyl grouping giving most activity varied from one series to another and with test method. In cucumber plants the most prolonged protection against mildew was given by the sec-butoxy and sec-butylamino compounds. When inoculated disks of cucumber leaf tissue were floated upon solutions of the compounds, smaller differences in anti-mildew activity were found than when application was made through the roots.     

INVESTIGATIONS ON FUNGICIDES. I. FUNGICIDAL AND SYSTEMIC FUNGICIDAL ACTIVITY IN CERTAIN ARYLOXYALKANECARBOXYLIC ACIDS

Fifty-four aryloxyalkanecarboxylic acids have been examined as systemic fungicides. Of these, four which produced negligible damage in broad-bean seedlings yet conferred systemic fungicidal protection to broad beans against Botrytis fabae and to tomatoes against Alternaria solanixvere studied in detail. The direct fungicidal activity of twenty compounds was assessed against B. fabae and Pythium ultimum. No correlation between fungicidal and systemic fungicidal action toward B. fabae was established. Other possibilities regarding their mode of action as systemic fungicides are discussed. The systemic fungicidal activity of a-phenoxyziobutyric and 2:4:6-trichlorophenoxyacetic acids in beans and of the latter compound in tomato plants was found to depend upon seasonal factors, but for 3-phenoxybutyric and 5-phenoxycaproic acids such variation was not observed. Results obtained in the bean test by two methods of assessment were found to correlate. The potato petiole test (van Raalte) for assessing systemic fungicidal activity was studied and modified. Evidence was obtained that the results might be unreliable owing to toxic effects produced by the compounds on the petiole tissue. Attempts were made to avoid this complication, but when phytotoxicity was eliminated, little fungicidal activity was shown.     

Identification of 1-chloro-2-formyl indenes and tetralenes as novel antistaphylococcal agents exhibiting sortase A inhibition

Tetralene and indene compounds have shown inhibitory activity against human pathogen, Mycobacterium tuberculosis. Their potential use as antistaphylococcal agent against drug-resistant Staphylococcus aureus has not been explored so far. We determined in vitro antistaphylococcal activity and mechanism of action of these compounds as sortase A inhibitors through in silico analysis followed by biological assays. Tetralene and indene series were tested against S. aureus strains MTCC96, MRSA, and VA30. Three compounds showed significant reduction in MIC in both wild-type and drug-resistant S. aureus strains. In silico absorption, distribution, metabolism, excretion, and toxicity analysis of identified leads and cytotoxicity testing with colorimetric method using Vero and WRL-68 cell lines showed no significant cytotoxic effects. Molecular docking of these molecules with sortase A (PDB: 2KID) showed H-bond interaction with functional site residue Arg197 of sortase A. Sortase A inhibition assay was developed by expressing SrtA_?N from S. aureus strain MTCC96. Tetralene and indene compounds were found to have sortase A inhibitory potential. S. aureus strain MTCC96 treated with these compounds showed surface-sorting inhibition of fibronectin-binding protein and reduction in adherence to host extracellular matrix protein, fibronectin. 1-Chloro, 2-formyl, 6-methoxy, 1-tetralene (Tet-5), 1,5-dichloro, 2-formyl, 1-indene (Tet-20) and 1-chloro, 2-formyl, 5,6-methylenedioxy, and 1-indene (Tet-21) exhibited antistaphylococcal activity along with sortase A inhibition. The results also indicate the possible role of these leads in other reactions essential for cell viability.     

Broad-bean stain and true broad-bean mosaic viruses

Autumn-sown crops of broad beans (Vicia faba L.) in England often contain plants with some leaves characteristically distorted and with a chlorotic mosaic. From some of these plants true broad-bean mosaic virus was isolated in 1959 and 1960 but not in 1965 and 1966. From other plants a similar but distinct virus, which caused staining of the seeds and we call broad-bean stain virus, was isolated in 1960, 1965 and 1966. The two viruses were readily distinguished in serological tests, and in some test plants. Both were seed-borne, and spread in crops, but were not transmitted by several animal species tested as vectors. Both viruses have isometric particles about 25 mμ in diameter. Some of these particles contain about 35% ribonucleic acid, some about 26% and some of those of broad-bean stain virus contain none; these three types of particles had sedimentation coefficients of about 120–130 S, 100 S and 60 S respectively. The ribonucleic acid of each virus had molar base content of G 23%, A 26%, C 18% and U 32%. These two viruses are members of the cowpea mosaic group of plant viruses; broad-bean strain virus was serologically related to cowpea mosaic, F I, red-clover mottle, and squash mosaic viruses. The particles of all these viruses and of true broad-bean mosaic virus were similar in appearance, sedimentation behaviour, and nucleic acid content and composition. The nucleic acid of red-clover mottle virus had a molar base content of G 20%, A 29%, C 20%, U 30%.     

Effects of Short-term Red Radiation and Choline Compounds on Cytokinin Content, Chlorophyll Accumulation and Photomorphogenesis in Wheat Seedlings

Effects of choline compounds (2-chloroethyltrimethylammonium chloride and 2-ethyltrimethylammonium chloride) as well as red radiation (R) pulse on the dynamics of cytokinin changes, growth and chlorophyll (a + b) accumulation were studied during the growth and greening of etiolated wheat seedlings (Triticum aestivum L., var. Mironovskaya-808). The seedlings were grown for 120 h in the dark and then exposed for 72 h to white light. Pre-treatment of caryopses with cholines and pre-irradiation of etiolated seedlings with R inhibited elongation of both coleoptile and first leaf; but the same factors accelerated these growth responses when seedlings were exposed to white light. Chlorophyll (Chl) accumulation and the first leaf appearance from coleoptile were accelerated by the pre-treatments as well. Far-red radiation (FR) reversed all effects of R but choline pre-treatment eliminated partly R/FR photoreversibility. Two compounds with high cytokinin activity (tested on a fresh weight basis by the bioassay with Amaranthus caudatus L.) were found in shoots and first leaves. One of them had R_f, UV absorbance spectrum and the biological activity similar to N⁶-(Δ²-isopentenyl)adenosine. Another cytokinin-like substance was not identified with the used standards. Stimulation of greening by R pulse and cholines was accompanied with accelerated accumulation of both cytokinin-like substances. We conclude that the influence of R and cholines on the concentration of substances with cytokinin activities detected in the leaves might be involved in the stimulation of Chl accumulation.     

Antifungal Activity of Aqueous Extracts of the Leaves of Cowparsnip and Comfrey

We found that extracts from the leaves of medicinal comfrey and cowparsnip strongly inhibit the germination of Erysiphe graminisconidia and uredospores of Puccinia graminis. Spraying wheat seedlings with these extracts, in contrast to the irrigation of soil, markedly diminished infection in plants with powdery mildew. Antifungal activity in vitroand protective activity (when plants were sprayed) correlated with the level of phenolic compounds in these extracts. Experiments with healthy plants have demonstrated that the photosynthetic apparatus of wheat plants is stimulated by extracts. Spraying seedlings with the extracts resulted in an increased rate of O₂evolution calculated per unit of chlorophyll, an increase in the ratio (F_M– F_T)/F_Tin the experiments that recorded slow fluorescence induction, an increase in the relative light intensity of band A, and a decrease of relative intensity of band Cin experiments with thermoluminescence of wheat leaves. These results provide evidence that the protective activity of comfrey and cowparsnip extracts is associated with their action on the pathogenic fungus and with the activation of natural defense reactions of the host plant.     

Peptidomimetic 2-cyanopyrrolidines as potent selective cathepsin L inhibitors

Cathepsins have been found to have important physiological roles. The implication of cathepsin L in various types of cancers is well established. In a search for selective cathepsin L inhibitors as anticancer agents, a series of 2-cyanoprrolidine peptidomimetics, carrying a nitrile group as warhead, were designed. Two series of compounds, one with a benzyl moiety and a second with an isobutyl moiety at P₂ position of the enzyme were synthesized. The synthesized compounds were evaluated for inhibitory activity against human cathepsin L and cathepsin B. Although, none of the compounds showed promising inhibitory activity, (E)N-{(S)1-[(S)2-cyano-1-pyrrolidinecarbonyl]-3-methylbutyl}-2,3-diphenylacrylamide (24) with an isobutyl moiety at P₂ was found to show selectivity as a cathepsin L inhibitor (Ki 5.3 μM for cathepsin L and Ki > 100 μM for cathepsin B). This compound could act as a new lead for the further development of improved inhibitors within this inhibitor type.     

Growth retardant activity of paclobutrazol enantiomers in wheat seedlings

The resolved enantiomers of paclobutrazol appeared to have different primary modes of action as plant growth retardants in rht3 (tall) wheat seedlings. 2S,3S-Paclobutrazol reduced shoot growth more effectively than root growth, whereas the opposite was the case with the 2R,3R-enantiomer. Low concentrations (0.03–1.0 M) of 2S,3S-paclobutrazol specifically inhibited gibberellin A₁ (GA₁) production in Rht3 (dwarf) seedlings without affecting shoot growth, confirming that inhibition of GA biosynthesis is the primary mode of action of this enantiomer. Reductions in shoot growth of rht3 (tall) wheat treated with 2S,3S-paclobutrazol were associated with reductions in GA₁ content, an effect that could be reversed by gibberellic acid (GA₃) application, showing that GAs are important regulators of light-grown shoot growth in wheat. The inhibition of root growth of wheat seedlings following treatment with 2R,3R-paclobutrazol was associated with a decline in de novo synthesis of major sterols, a decrease in stigmasterol: sitosterol ratio and an accumulation of the 14-methyl sterol, obtusifoliol. Concentrations >3 M 2S,3S-paclobutrazol also affected de novo sterol production in wheat roots, suggesting that root growth is more responsive to interference with sterol than GA biosynthesis. There was a decline in abscisic acid (ABA) content in Rht3 (dwarf) shoots treated with relatively high concentrations of 2S,3S-paclobutrazol but no effect with its optical isomer.     

Alleviation of Fusarium oxysporum induced oxidative stress in wheat by Trichoderma viride

Trichoderma viride (Pers.) pre-inoculated wheat seedlings infected with Fusarium oxysporum Schlecht. (co-stressed) did not show wilting symptoms compared to Fusarium infected seedlings. Antagonistic activity of T. viride could be demonstrated against Fusarium infection by dual culture experiment. After seven days post infection, morphological and physiological parameters such as, root and shoot length, fresh and dry weight, relative water content, total soluble protein, total chlorophyll and carotenoid contents were observed to be increased in co-stressed compared to Fusarium infected seedlings. Accumulation of hydrogen peroxide was enhanced in Fusarium infected tissues compared to co-stressed. Trichoderma mediated activation of antioxidant enzymes such as, catalase, guaiacol peroxidase, ascorbate peroxidase, superoxide dismutase in co-stressed seedlings indicated their involvement in enhanced resistance against Fusarium infection, which is suggestive of playing crucial role in mitigating cellular toxicity developed due to excess H₂O₂. Thus, Trichoderma pre-inoculation protected wheat against Fusarium infection by stabilising oxidative stress.     

Inhibition of Rust Diseases of Cereals by Metabolic Products of Verticillium chlamydosporium

Verticillium chlamydosporium produced in submers culture several antifungal and/or phytotoxic compounds which were detected in a bioassay by using the pathogen-host system Puccinia coronata and oat seedlings. The antifungal compounds were also tested against P. recondita on wheat and P. sorghi on corn seedlings. The production of the active metabolic compounds highly depended on the nutrient solution (peptone-Czapek [PC] and malt extract [ME]) and on the fermentation times. Cell-free filtrates of PC-cultures of the fungus were highly phytotoxic; the fungitoxic and phytotoxic compounds were heat-labile and dialyzable. The ethyl acetate extracts of the PC-culture filtrates contained only the antifungal active substances. The antifungal compounds in ME-culture filtrates proved to be heat-stable, could be dialyzed and extracted with ethyl acetate. Ethyl acetate extracts of PC- and ME-culture filtrates at concentrations of 500 μg/ml reduced rust disease incidence by up to 80 % compared to the control treatment. Further studies with extracts of ME-culture filtrates displayed a distinct protective but no systemic activity. The extract interfered with the development of several infection structures of the rust fungi, mostly with the growth of germ tubes as well as with the formation of the aappressoria and haustorial mother cells. Three rust-active fractions were obtained by preparative layer chromatography on silica gel. One of these fractions exhibited phytotoxic activity. The most active antifungal fraction is identical with the macrolid antibiotic monorden which caused a desorientated spiral growth in P. coronata germlings on oat leaves.     

Bisphosphonic acids as effective inhibitors of Mycobacterium tuberculosis glutamine synthetase

Inhibition of glutamine synthetase (GS) is one of the most promising strategies for the discovery of novel drugs against tuberculosis. Forty-three bisphosphonic and bis-H-phosphinic acids of various scaffolds, bearing aromatic substituents, were screened against recombinant GS from Mycobacterium tuberculosis. Most of the studied compounds exhibited activities in micromolar range, with N-(3,5-dichlorophenyl)-2-aminoethylidenebisphoshonic acid, N-(3,5-difluorophenyl)-2-aminoethylidene-bisphoshonic acid and N-(3,4-dichlorophenyl)-1-hydroxy-1,1-ethanebisphosphonic acid showing the highest potency with kinetic parameters similar to the reference compound – L-methionine-S-sulfoximine. Moreover, these inhibitors were found to be much more effective against pathogen enzyme than against the human ortholog. Thus, with the bone-targeting properties of the bisphosphonate compounds in mind, this activity/selectivity profile makes these compounds attractive agents for the treatment of bone tuberculosis.     

Photosynthesis and Activity of Ribulose Bisphosphate Carboxylase of Wheat and Maize Seedlings during and following Exposure to O(2)-Low, CO(2)-Free N(2)

Seven day old wheat and maize seedlings were exposed to 1300 or 2000 microeinsteins per square meter per second photosynthetically active radiation in CO₂-free air for 3 hours with either 1% O₂ in N₂ or N₂-only and then returned to normal air of 340 microliters per liter CO₂, 21% O₂ in N₂. Activity of the ribulose bisphosphate carboxylase and amount of the substrate, ribulose 1,5-bisphosphate, were measured during and following the CO₂-free treatments as was photosynthetic CO₂ fixation. Photoinhibition of photosynthesis was observed only with wheat seedlings following the N₂ only treatment. During the CO₂-free treatments, the levels of RuBP rose during all experiments except when wheat was photoinhibited. The activity of the ribulose bisphophate carboxylase, measured directly upon grinding the leaves, declined during the CO₂-free conditions. The carboxylase total activity increased in minutes in the leaf during and following the CO₂-free treatments. The specific activities of the wheat carboxylase went from 0.16 to 1.06 micromoles CO₂ fixed per milligram protein per minute while the maize carboxylase varied from 0.05 to 0.36 micromole CO₂ fixed per millogram protein per minute. This suggests that in these seedlings considerable inactive carboxylase must be stored in a form not activatable in extracts by CO₂ and Mg²⁺. Possible mechanisms of regulation of photosynthesis by the ribulose bisphosphate carboxylase must consider not only the amount of active enzyme, but the amount of enzyme which the plant can make activatable upon demand.     

Isolation of Ceramides from Tagetes patula L. Yellow Flowers and Nematicidal Activity of the Fractions and Pure Compounds against Cyst Nematode,Heterodera zeae

Investigation of yellow flower extract of Tagetes patula L. led to the identification of an aggregate of five phytoceramides. Among them, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]icosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]heneicosanamide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]docosanamide, and (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tricosanamide were identified as new compounds and termed as tagetceramides, whereas (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tetracosanamide was a known ceramide. A steroid (β‐sitosterol glucoside) was also isolated from the subsequent fraction. The structures of these compounds were determined on the basis of spectroscopic analyses, as well as chemical method. Several other compounds were also identified by GC/MS analysis. The fractions and some commercial products, a ceramide HFA, β‐sitosterol, and stigmasterol were evaluated against an economically important cyst nematode, Heterodera zeae. Ceramide HFA showed 100 % mortality, whereas, β‐sitosterol and stigmasterol were 40–50 % active, at 1 % concentration after 24 h of exposure time, while β‐sitosterol glucoside revealed no activity against the nematode.     

Synthesis and antiproliferative activity of some steroidal lactams

Using cholesterol as starting material, a series of 6-substituted-3-aza-A-homo-3-oxycholestanes and 6-substituted-4-aza-A-homo-3-oxycholestanes were synthesized by the oxidation, reduction, oximation, Beckman rearrangement and condensation reaction. These synthesized compounds displayed a distinct cytotoxicity against MGC 7901, HeLa and SMMC 7404 cancer cells. Our results revealed that the structures of functional groups at position-6 on the steroidal ring are crucial for the IC₅₀ value of antiproliferative activities of these compounds and the cytotoxic activity against MGC 7901 and SMMC 7404 cells was not significantly different between 4-N-lactams and 3-N-lactams when its 6-substituted group was a carbonyl or a hydroximino, but all 3-N-lactams showed a higher cytotoxicity against HeLa cells than 4-N-lactams. In particular, compounds 6, 8, 9 (IC₅₀6: 6.5 μmol/L; 8: 7.7 μmol/L; 9: 5.6 μmol/L) were even more cytotoxic than cisplatin to HeLa cells (positive contrast, 10.1 μmol/L). The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs.     

Isolation and Structural Determination of the Antifouling Diketopiperazines from Marine-Derived Streptomyces praecox 291-11

Marine derived actinomycetes constituting 185 strains were screened for their antifouling activity against the marine seaweed, Ulva pertusa, and fouling diatom, Navicula annexa. Strain 291-11 isolated from the seaweed, Undaria pinnatifida, rhizosphere showed the highest antifouling activity and was identified as Streptomyces praecox based on a 16S rDNA sequence analysis. Strain 291-11 was therefore named S. praecox 291-11. The antifouling compounds from S. praecox 291-11 were isolated, and their structures were analyzed. The chemical constituents representing the antifouling activity were identified as (6S,3S)-6-benzyl-3-methyl-2,5-diketopiperazine (bmDKP) and (6S,3S)-6-isobutyl-3-methyl-2,5-diketopiperazine (imDKP) by interpreting the nuclear magnetic resonance and high-resolution mass spectroscopy data. Approximately 4.8 mg of bmDKP and 3.1 mg of imDKP were isolated from 1.2 g of the S. praecox 291-11 crude extract. Eight different compositions of culture media were investigated for culture, the TBFeC medium being best for bmDKP and TCGC being the optimum for imDKP production. Two compounds respectively showed a 17.7 and 21 therapeutic ratio (LC₅₀/EC₅₀) to inhibit zoospores, and two compounds respectively showed a 263 and 120.2 therapeutic ratio to inhibit diatoms.     

A convenient ‘one-pot’ synthesis and in vitro microbiological evaluation of novel 2,7-diaryl-[1,4]-diazepan-5-ones

A convenient method for the ‘one-pot’ synthesis of novel target molecule 2,7-diaryl-[1,4]-diazepan-5-ones from the respective 2,6-diaryl-piperidin-4-ones was catalyzed by NaHSO₄.Al₂O₃ heterogeneous catalyst in dry media under microwave irradiation in solvent-free conditions. Moreover, the catalyst could be recovered and re-used up to 4 times after washing with ethyl acetate. They were evaluated for potential antibacterial activity against Staphylococcus aureus, β-Haemolytic streptococcus, Vibreo cholerae, Salmonella typhii, Escherichia coli, Klebsiella pneumonia, Pseudomonas and antifungal activity against Aspergillus flavus, Aspergillus fumigatus, Mucor, Candida albicans and Rhizopus. Structure-Activity Relationship (SAR) led to the conclusion that, of all the compounds 25–32 tested, compound 30 exerted strong in vitro antibacterial activity against S. aureus, S. typhii, and Pseudomonas and all the compounds 25–32 were less active against E. coli, whereas all the compounds 25–32 displayed potent in vitro antifungal activity against all the fungal strains used, except compound 30, which was more effectual against Mucor.     

Cytotoxicity and DNA Topoisomerase Inhibitory Activity of Benz[f]indole-4,9-dione Analogs

A series of benz[f]indole-4,9-diones, based on the antitumor activity of 1,4-naphthoquinone, were synthesized and evaluated for their cytotoxic activity in cultured human cancer cell lines A549 (lung cancer), Col2 (colon cancer), and SNU-638 (stomach cancer), and also for the inhibition of human DNA topoisomerases I and II activity in vitro. Several compounds including 2-amino-3-ethoxycarbonyl-N-methyl-benz[f]indole-4,9-dione showed a potential cytotoxic activity judged by IC₅₀<20.0 μg/ml in the panel of cancer cell lines. Especially, 2-hydroxy-3-ethoxycarbonyl-N-(3,4-dimethylphenyl)-benz[f]indole-4,9-dione had potential selective cytotoxicity against lung cancer cells (IC₅₀=0.4 μg/ml)) compared to colon (IC₅₀>20.0 μg/ml) and stomach (IC₅₀>20.0 μg/ml) cancer cells. To further investigate the cytotoxic mechanism, the effects of test compounds on DNA topoisomerase I and II activities were used. In a topoisomerase I-mediated relaxation assay using human placenta DNA topoisomerase I and supercoiled pHOTI plasmid DNA, 2-amino-3-ethoxycarbonyl-N-(4-fluorophenyl)-benz[f]indole-4,9-dione had the most potent inhibitory activity among the compounds tested. However, most of the compounds showed only weak inhibition of the DNA topoisomerase II-mediated KDNA (Kinetoplast DNA) decatenation assay, except for 2-amino-3-ethoxycarbonyl-N-(4-methylphenyl)-benz[f]indole-4,9-dione and 2-amino-3-ethoxycarbonyl-N-(2-bromoehtyl)-benz[f]indole-4,9-dione with a moderate inhibitory activity. These results suggest that several active compounds had relatively selective inhibitory activity against toposiomearse I compared to toposiomerase II. No obvious correlation was observed between the cytotoxicity of the individual compound and the inhibitory activity of DNA relaxation and decatenation by topoisomerase I and II, respectively, in vitro.     

A laboratory method of screening fungicides for systemic activity against Bretnia lactucae

A soil-free in vivo laboratory technique is described for the detection of systemic anti-fungal activity against Bretnia lactucae, a representative of the Peronosporales. This system is not subject to some of the complications encountered with in vitro and glasshouse experiments. Two new compounds (prothiocarb and LS 73–1038 (Nina)) were found to have high systemic activity against B. lactucae using this technique and it was confirmed that zineb also has some systemic effect. Streptomycin sulphate and DPX-3217 showed some activity but were phytotoxic. Dowco 269 was phytotoxic and showed no activity against B. lactucae. None of these chemicals showed any significant vapour activity.