The action of insecticides on neurosecretory neurons in the stick insect, Carausius morosus

The action of insecticides on the spontaneous electrical activity of neurohemal tissue in the stick insect, Carausius morosus, has been studied using extracellular electrodes. The pyrethroid, permethrin, causes a massive increase in the frequency of the spontaneously generated action potentials at concentrations between 5 × 10^?5 and 5 × 10^?8M. Concentrations as low as 5 × 10^?11M are still effective in producing bursting activity.DDT, at concentrations between 5 × 10^?5M and 5 × 10^?6M, produces an overall increase in activity although the bursting activity is less violent than that shown with permethrin. DDT, 5 × 10^?7M, is ineffective at altering the resting pattern.Carbaryl and coroxon cause a transitory increase in electrical activity at 1 × 10^?4M, but are ineffective at 1 × 10^?5M.It is concluded that insecticides could have a direct effect upon the neurohormonal balance in insects.     

Phenylpyrazoles,a new class of pesticide: Effects on neuromuscular transmission and acetylcholine responses

Phenylpyrazoles constitute a newly developed class of chemicals with insecticidal and herbicidal properties. In acute toxicity experiments in rats, near-lethal doses of phenylpyrazoles produce neurotoxic symptoms with an unknown mode of action. We have investigated the effects of two phenylpyrazoles, SLA4722 and SLA4685, in the frog neuromuscular junction and in the clonal muscle cell line BC3H-1. In the frog neuromuscular junction SLA4722 at concentrations ? 10^?5 M caused a pronounced increase in the frequency of miniature endplate potentials (MEPPs). SLA4685 caused a similar increase but was less potent. In the clonal muscle cell line BC3H-1, SLA4685 produced a concentration-dependent block of the acetylcholine (ACh) response (IC₅₀ = 2.4(±0.3) × 10^?5 M). At 10^?6 M a slight potentiating effect of SLA4685 on the ACh response was observed. SLA4722 was less potent in this preparation. The increased transmitter release might, at least partly, be responsible for the excitatory effects of the phenylpyrazoles in intact animals.     

Interference of benomyl and methyl-2-benzimidazolecarbamate (MBC) with DNA metabolism and nuclear divisions in Fusarium oxysporum

Methyl-1-(butylcarbamoyl)-2-benzimidazolecarbamate (benomyl) severely decreased DNA synthesis when applied at 3.5 × 10^?6M during the G1 phase of germinating conidia of Fusarium oxysporum; nuclear divisions were completely inhibited at a fungicide concentration of 10 × 10^?6M. The same concentration applied only after the S phase also completely inhibited the nuclear divisions. This dual interference of benomyl with DNA formation and mitosis might be related to a disturbed phosphorus metabolism.     

Neurophysiological studies of the effects of permethrin upon pyrethroid resistant (kdr) and susceptible strains of dipteran larvae

Permethrin at concentrations as high as 10^?6 had no detectable effect upon neuromuscular transmission at 20-21°C in the body-wall muscles of susceptible larvae of Lucilia sericata and susceptible and resistant (kdr) strains of larvae of Musca domestica. At the higher concentrations of 5 × 10^?6M, muscle cells in all strains and species of larva were slowly depolarised, resulting in failure of neuromuscular transmission when the level of depolarisation corresponded with the peak height of the postsynaptic potentials. Multiple postsynaptic potentials were sometimes obtained in response to a single electrical stimulus to the motor axon. Neither of these effects is considered to result from interference with release of the neurotransmitter or its binding to the postsynaptic receptors. Spontaneous activity in sensory nerve fibres from susceptible larvae was increased followed by intermittent bursting and block at concentrations of permethrin as low as 10^?9M at 20-21°C and 10^?10 at 26°C. Resistant larvae of M. domestica were 1000 times less sensitive, needing concentrations of permethrin as high as 10^?6M at 20-21°C and 10^?7M at 26°C to affect sensory discharge. The results are discussed in relationship to the cause of knockdown by pyrethroid insecticides and to possible changes in the nervous system which may be brought about by the kdr resistance factor.     

Binding of mercury compounds to the chloroplasts in relation to the inhibition of the Hill reaction

The binding behavior of mercuric chloride (HgCl₂), phenylmercuric acetate (PMA), and ethylmercuric chloride (EMC) to the spinach chloroplasts in relation to the inhibition of the Hill reaction was studied at pH 6.8 and 7.8 using ²⁰³Hg labeled compounds. The pH of the reaction medium did not influence the amount of mercury binding of the chloroplast at various mercurial concentrations, but it altered the inhibition curve of the Hill reaction. Between 0–1 × 10^?5M the binding of Hg²⁺ and EMC were similar and increased linearly with the concentration, while the binding of PMA was similar to the binding of Hg²⁺ only at a concentration below 4 × 10^?6M and was less when the concentration was above 4 × 10^?6M. However, the inhibition of the Hill reaction by these mercury compounds was quite different; at pH 7.8, the I₅₀ values for Hg²⁺, PMA, and EMC were 5 × 10^?6, 2.5 × 10^?6, and 2.5 × 10^?6M, respectively, while at pH 6.8, these values were 4 × 10^?6, 4 × 10^?5, and 2 × 10^?4M, respectively. The differential block of electron flow by the mercury compounds at pH 6.8 and 7.8 was further confirmed by electron spin resonance study.     

Biocontrol of sclerotinia stem rot (Sclerotinia sclerotiorum) of soybean using novel Bacillus subtilis strain SB24 under control conditions

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is a major disease of soybean in Canada. Laboratory and greenhouse experiments were conducted to evaluate potential effectiveness of cell suspensions, cell‐free culture filtrates and broth cultures of Bacillus subtilis strain SB24 for suppression of SSR. The SB24 cell suspensions and cell‐free culture filtrates significantly reduced mycelial growth of S. sclerotiorum by 50 to 75% and suppressed sclerotial formation by > 90%. The severity on soybean was negatively correlated (r < ?0·84, P < 0·01) to the concentrations of cell suspension, cell‐free culture filtrate and broth culture applied. The cell suspension and broth culture preparations significantly (P < 0·01) reduced SSR severity by 45 to 90% at concentrations ranging from 5 × 10⁶ to 10⁹ CFU mL^?1. The most effective concentration was 5 × 10⁸ CFU mL^?1 for all three preparations, reducing the severity by 60 to 90%. The B. subtilis SB24 was most effective in reducing disease severity when applied ≤ 24 h before plant inoculation with S. sclerotiorum and a significant effectiveness was observed up to 15 days after plant inoculation. The population density of B. subtilis on soybean leaves decreased by 1·5 to 2·5 log units over 15 days under field conditions, and by 0·8 log units over 5 weeks under control conditions. The decrease in population density was significantly correlated with rainfall in the field (r < ?0·93, P < 0·01), suggesting that the biocontrol bacteria may be washed away by rain.     

Mechanism of herbicidal activity of a new cyclohexane-1,3-dione, tepraloxydim to Poa annua L.

Tepraloxydim [(EZ)‐(RS)‐2‐{1‐[(2E)‐3‐chloroallyloxyimino]propyl}‐3‐hydroxy‐5‐perhydropyran‐4‐ylcyclohex‐2‐en‐1‐one] showed high activity against annual bluegrass (Poa annua L.), which is relatively tolerant to sethoxydim [(±)‐2‐(1‐ethoxyiminobutyl)‐5‐[2‐(ethylthio)propyl]‐3‐hydroxycyclohex‐2‐en‐1‐one]. Absorption and translocation rates of tepraloxydim and sethoxydim were higher in P. annua than in Setaria faberi, but the absorption and translocation patterns of tepraloxydim in the two plants were similar to those of sethoxydim. Metabolic rates of tepraloxydim and sethoxydim in P. annua and S. faberi were found to be similar. The concentration for 50% inhibition (I₅₀) of acetyl‐coenzyme A carboxylase (ACCase) with tepraloxydim was approximately 3 × 10^?6 mol L^?1 for P. annua and 7 × 10^?7 mol L^?1 for S. faberi. For sethoxydim, the I₅₀ was found to be 2 × 10^?6 mol L^?1 with the enzyme of S. faberi, while sethoxydim showed a slight effect on ACCase from P. annua activity, even at 10^?4 mol L^?1. The strong inhibition of ACCase with tepraloxydim is considered to be the major factor contributing to the high herbicidal activity against P. annua. Measuring the whole plant growth response, the ratio of the tepraloxydim I₅₀ dose of P. annua to that of S. faberi (P/S) was found to be 2.4, while the P/S ratio of sethoxydim and a tepraloxydim analog with a propyl chain at R₂ were 56.3 and 73.3, respectively. The herbicidal activity against P. annua was remarkably influenced by the length of the R₂ alkyl chain, while the effect on S. faberi was not affected. Acetyl‐coenzyme A carboxylase from P. annua also exhibited a higher resistance to the tepraloxydim analog with a propyl chain than to tepraloxydim. These results suggest that a binding site structure of cyclohexane‐1,3‐diones in the ACCase differs between P. annua and S. faberi.     

Response of maize (Zea mays L.) inbred lines and hybrids to chlorsulfuron

Twenty inbred maize lines, raised in a growth chamber, were treated with 0 or 1 ng g^?1 of chlorsulfuron which caused a variable reduction in root-length. In a second experiment, all crosses (reciprocals included) among two tolerant lines (T: Va85 and Mes44) and two susceptible lines (S: B73 and B79) were raised in a growth chamber together with the parental lines and exposed to 0,0×5 or 1 ng g^?1, The interaction of reciprocal effects x rates was not significant for all traits, The T × S hybrids showed an intermediate response between the T × T and S × S responses for root-length and dry weight. Interaction (hybrids vs. parental lines) × rates was not significant for all traits. These results indicate that susceptibility to chlorsulfuron is not controlled by extra-nuclear factors and that additive gene actions prevail. Four crosses (one T × T, two T × S and one S × S) were further investigated at nine rates from 0 to 1 ng g^?1. The responses confirmed the intermediate behaviour of T×S hybrids, resulting in a GR₂₀ of 0×07, 0×55 and 0×94 ng g^?1 for S × S, T × S and T × T, respectively. In a third experiment, the four crosses previously considered were grown in the field with parental lines and treated at five rates from 0 to 1·12 g a.i. ha^?1. Effects on shoot height and dry weight were consistent with root effects found in growth chamber experiments.     

Effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on photosynthesis and respiration of Nitella dactyl cells

Long-term experiments with dactyl cells of Nitella flexilis showed that the herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) at a concentration of 1 × 10^?5M affected not only O₂ evolution in the light but also O₂ uptake in the dark. The inhibition of O₂ production was transitory, but dark respiration did not recover. DCMU induced the formation of giant mitochondria which disappeared before cell death. It was concluded that the algicidic effect of 1 × 10^?5M DCMU on N. flexilis, but not necessarily the elongation of mitochondria, was due to the inhibition of mitochondrial respiration and not of photosynthesis.     

Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armyworm Spodoptera exempta (walker) following topical treatment with the compound

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with pre- cocene II. [3H]-Precocene II penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6–8% of the applied dose. A maximum titre of precocene of 1.1 × 10^?4 _M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11–3, 4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 × 10^?4 _M at 4 h suggesting metabolism via the 3, 4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6- and 7-(O)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to prevent the establishment of a high titre of precocene. This, however, did not affect the corpora allata in this insect, whereas in a sensitive species that has been studied by other workers, necrosis of the glands would have resulted. Alternative explanations for insensitivity are discussed.     

Challenging the larvae of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> and assessing the immune responses to nematode-bacterium complex

Helicoverpa armigera is a strong insecticidal resistance developed insect pest. The understanding of its innate immune responses to emerging biocontrol agent entomopathogenic nematode-bacterial complex can provide an opportunity to control this insect in an environmentally benign manner. Study was focused on role of hemocytes changes and PO activity in Steinernema abbasi-Xenorhabdus indica challenged larvae of H. armigera over the time. Total cell count changed effectively from 10.2?±?1.81?×?10⁵ to 15.5?±?3.3?×?10⁵ cells/mm³ upto 9 h and reduced distinctly up to 8.0?±?2.49?×?10⁵ cells/ mm³ in 24 h. PO activity inclined significantly and was recorded highest at 9 h (24.67?±?1.08?×?10² units) and lowest at 24 h (14.34?±?0.74?×?10² units) in total hemolymph with a similar pattern in plasma and the cellular fraction. Phenoloxidase activity in total and cellular component of hemolymph was positively correlated with prohemocytes, granulocytes and oenocytoids. Study showed the hemocytes and PO accounted as active immune responses against nematode infection. The results provide the first insight to understand the hemolytic activity, quick immunosuppression responses of S. abbasi-X. indica and vulnerability of H. armigera.     

Is sulfotep a proctolin receptor antagonist?

Proctolin-induced, dose-dependent (10^?8-2 × 10^?6 M) contraction of the isolated foregut of Schistocerca gregaria was antagonised non-competitively by sulfotep (2 × 10^?6-10^?5 M). A higher dose of sulfotep (5 × 10^?5 M) caused restoration of the proctolin dose-response curve to its control value. Neostigmine (10^?5 M) caused non-competitive inhibition of proctolininduced tissue contraction. Increasing the dose of neostigmine to 10^?4 M restored the proctolin response to control values. Sulfotep (10^?5 M) and neostigmine (10^?4 M) caused inhibition of acetylcholinesterase (AChE) activity in tissue homogenates obtained from guts pretreated with either drug for 20 min. The stimulatory effect of sulfotep (5 × 10^?5 M) on proctolin-induced gut contraction was abolished by pretreatment of tissues with atropine (10^?6 M). Under these conditions, 5 × 10^?5 M sulfotep caused further antagonism of the action of proctolin. The results suggest that sulfotep is a proctolin receptor antagonist in the locust foregut. However, higher concentrations inhibit tissue AChE activity, thereby allowing endogenous acetylcholine to activate muscarinic receptors. This leads to enhanced tissue contractility which masks the antagonistic effect of sulfotep on proctolin-induced contraction.     

Effect of 2,4,5-T and picloram on the regeneration of blackberry (Rubus procerus P.J. Muell) from root segments

The formation of roots and shoots on root segments of Rubus procerus P.J. Muell was prevented by soaking the segments for 24 h in a 10^?4M solution of 2,4,5-T or a 10^?5M solution of picloram. Shoot numbers were significantly increased after treatment with 10^?9M and 10^?10M 2,4,5-T, but picloram did not cause a significant increase in shoot numbers. Measurement of the concentration of 2,4,5-T in the extracambial tissue showed that roots treated with 10^?4M 2,4,5-T contained 5× 10^?8 mmole 2,4,5-T per mg dry weight, and by extrapolation, roots treated with 10^?9M 2,4,5-T contained 2× 10^?10 mmole/mg dry weight. Action du 2,4,5-T et du piclorame sur la régénération de la ronce (Rubus procerus P.J. Muell) è partir de fragments de racines La formation de racines et de tiges è partir de fragments de racines dc Ruhus procerus P.J. Muell a été supprimée par trempage des fragmenls pendant 24 heures dans une solution a 10^?4M et de 2.4,5-T, ou dans une solution 10^?5M de piclorame. Le nombre de pousses s'est accru significativement après traitement avec le 2,4,5.-T è 10^?9M et 10^?10M, mais le piclorame n'a pas provoqué d'accroissemcnt significatif du nombre de pousses. La mesure de la concentration de 2,4,5-T dans le tissu extra-cambial a montré que les racines trailées avec du 2,4,5-T è 10^?4M contenaient 5×10^?8 mmole de 2.4,5-T par mg de poids sec et par extrapolation, quc les racines traitées avec du 2,4,5-T k 10^?9M devaient contenir 2 × 10^?12 mmole/mg de poids sec. Die Wirkiing von 2,4,5-T und Picloram auf den Wuchs der Wurzehegmenten von Bromheeren (Rubus procerus P.J. Muell). Die Bildung von Wurzeln und Sprossen aus Wurzelsegmen-ten von Ruhu.i procerus P.J. Muell wurde durch 24-stündiges Einlegen der Wurzelstücke in 10^?4M 2,4,5-T bzw 10^?5M Picloram verhindert. Die Anzahl neugebiideter Sprosse wurde nach Einlegen in 10^?9M und 10^?10M 2,4,5-T, nicht jedoch durch Picloram, signifikant erhöht. Im extracambialen Gewebe von Wurzeln, die mit 10^?4M 2,4,5-T behand-elt worden waren, wurden 5×10^?8mMol 2,4,5-T je mg Trockengewiclu bestimmt. Durch Extrapolation wurde ermittclt. dass mit 10^?9M 2,4,5-T behandelte Wurzeln 2× 10^?12mMol/mg Trockengewicht cnthielten.     

Effects of benomyl,carbendazim and thiophanates on respiration and oxidative phosphorylation of Fusarium oxysporum and Saccharomyces cerevisiae

Benomyl [methyl 1-(butylcarbamoyl)-benzimidazol-2-ylcarbamate] (350 × 10^?6 M) decreased the respiration rate of Fusarium oxysporum conidia by 50% during germination. This inhibition was maintained at least 24 h after the treatment had begun. The treatment did not modify the relation between incubation time and respiration rate. Carbendazim [methyl benzimidazol-2-ylcarbamate], thiabendazole[2-(thiazol-4-yl)benzimidazole], thiophanate [1,2-di-(3-ethoxycarbonyl-2-thioureido)benzene] and thiophanate-methyl [1,2-di-(3-methoxycarbonyl-2-thioureido)benzene] were assayed using isolated mitochondria of Saccharomyces cerevisiae. These four compounds decreased mitochondrial respiration and oxidative phosphorylation rates to different extents when they were applied at a concentration of 250 × 10^?6 M . Thiophanate-methyl was the most effective since it completely suppressed the mitochondrial respiratory control at 75 × 10^?6 M .     

Pyrethroid insecticides: Potent,stereospecific enhancers of mouse brain sodium channel activation

Deltamethrin and NRDC 157, pyrethroid insecticides that produce different poisoning syndromes in mammals, enhanced veratridine-dependent, sodium channel-mediated ²²Na⁺ uptake in mouse brain synaptosomes. Concentrations producing half-maximal enhancement were 2.5 × 10^?8M (deltamethrin) and 2.2 × 10^?7M (NRDC 157). This effect was stereospecific: The nontoxic 1S enantiomers had no significant effect on veratridine-dependent activation. At high deltamethrin concentrations, enhancement was maximal at 5 × 10^?5?1 × 10^?4M veratridine. Pyrethroid enhancement was completely blocked by 5 × 10^?6M tetrodotoxin, and neither pyrethroid affected ²²Na⁺ uptake in the absence of veratridine at concentrations up to 1 × 10^?5M. The relative potencies of deltamethrin and NRDC 157 in the synaptosomal sodium channel assay agree well with their relative acute toxicities to mice when administered by intracerebral injection. These findings demonstrate that pyrethroids exemplifying both characteristic poisoning syndromes are potent, stereospecific modifiers of sodium channel function in mammalian brain.     

Comparison between the penetration characteristics of methyl bromide and ethanedinitrile through the bark of pine (Pinus radiata D.Don) logs

BACKGROUND

Ethanedinitrile (EDN) is a fumigant being commercialized worldwide as an alternative phytosanitary treatment to methyl bromide (MB) for forest products. The penetration characteristics of MB and EDN were measured through the bark of wooden blocks (100 × 100 × 50 mm) cut from the upper (average bark thickness 5 ± 2 mm) and lower (average bark thickness 25 ± 5 mm) trunk of recently felled pine (Pinus radiata D.Don) trees. Doses of 48 g m⁻³ MB and 50 g m⁻³ EDN were applied to chambers at 10 and 20°C for 10 h.

RESULTS

Penetration of MB was influenced by the interaction between fumigation time and temperature, with concentrations increasing at a higher rate at 20°C compared with at 10°C. After 10 h, an average concentration of 8.05 ± 0.89 g m⁻³ had penetrated the bark of log sections at 20°C, whereas 5.20 ± 0.89 g m⁻³ was measured at 10°C. By contrast, the factors examined in this study did not significantly impact the penetration of EDN. Concentration × time (CT) values for MB under the bark were 35.20 ± 2.30 g h m⁻³ at 10°C and 55.85 ± 9.58 g h m⁻³ at 20°C; whereas for EDN, CT values were 19.50 ± 6.80 g h m⁻³ at 10°C and 19.08 ± 4.10 g h m⁻³ at 20°C.

CONCLUSION

MB can achieve a higher concentration under the bark of log sections during simulated fumigations, but all of the factors examined affected the ability of MB to penetrate the bark of wooden blocks. By comparison, the penetration of EDN through the bark is more consistent than MB under laboratory conditions. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Effect of CGA 123407 as a safener for pretilachlor in rice (Oryza sativa L.). Recordings of elongation rates of single rice leaves

The elongation rates of single attached leaves of rice (Oryza saliva L.) were recorded. The effect of pretilachlor on the elongation rates and the safening effect of CGA 123407 [4, 6-dichloro-2-phenyl-pyrimidine] were evaluated. Both chemicals were applied to the roots in a nutrient solution. Pretilachlor reduced leaf elongation in concentrations as low as 300 μg^?1 (9–6 × 10^?7 M) but. for combination trials with the safener, 3 mg 1^?1 (9–6 × 10^?6 M) was used. in combination with pretilachlor the safener prevented damage in very low concentrations. The ratio of pretilachlor to safener, 30:1, was sufficient when both chemicals were given to roots in nutrient solution, although for field work the ratio of 3:1 is recommended. The safener alone did not influence the elongation rate of rice leaves in the concentrations used. When pretilachlor was given to the roots and CGA 123407 to the shoot, some delay in the herbicidal action was recorded but even with high concentrations of the safener no continuous safening effect was achieved. CGA 123407 was also effective when given previous to the herbicide. This proved true even with a 2-day interval between safener uptake and application of the herbicide. When pretilachlor was given first, the safener effected recovery to various degrees when given 1–4 days after the herbicide application. When pretilachlor was given for a limited period of time only (1–3 days) and was subsequently removed from the nutrient solution, recovery of the plant occurred. It is speculated that the safener either helps this recovery or else competitively prevents the herbicide from occupying the sites of action or from keeping them occupied for a long period of time.     

Hydrolysis of the pyrethroid insecticide fenpropathrin in aqueous media

The hydrolysis of [¹⁴C] fenpropathrin ( I ) [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] was studied in buffer solutions at pH 1.9–10.4, and in natural river and sea water at 25, 40, 55 and 65°C under laboratory conditions. The hydrolysis of I proceeded predominantly through neutral (pH independent) and base-catalysed processes in the regions below pH 3.9 and above pH 7.0, respectively, whereas both reactions occurred between pH 3.9 and 7.0. The rates of hydrolysis of I in buffer solutions were similar to those in one sample of river and one sample of sea water. If this obtains generally, it may be expected that the half-life of I in natural waters, normally within the range pH 5–9, will range from 1.54 to 1080 days at 40°C, 11.3 to 8520 days at 25°C and, by extrapolation of the data obtained in buffer solutions, 106 to 83 000 days at 10°C. The rate constants for hydrolysis of I in aqueous media can be expressed by: Where log k_N = 9.60–(5.56 × 10³ T^?1) and log k_B = 7.32–(2.56 × 10³ T^?1). The calculated rate constants were in good accord with the observed values in buffer solutions. Cleavage of the ester linkage was more rapid than hydration of the cyano group at any pH and temperature tested.     

Actions of sodium hypochlorite and hydrogen peroxide on seed dormancy and germination of wild oats, Avena fatua L.

Sodium hypochlorite (NaOCl) can release dormancy of imbibed wild oat (Avena fatua L.) seeds. Treatments found effective included (i) immersing intact seeds in 800 mm NaOCl for 1 h followed by incubation on 5 × 10^?4m gibberellin A₃(GA₃); (ii) immersing dehulled seeds in 800 mm NaOCl for 1 min followed by incubation on 5 × 10^?4m GA₃; (iii) immersion of dehulled seeds in much lower concentrations of NaOCl, e.g. 13 4 mm for 3 h followed by incubation on water; or (iv) incubating dehulled seeds on a low concentration of NaOCl. Based on the concentrations of each of the reagents required to produce equivalent responses, NaOCl is approximately 4–6 times more effective than hydrogen peroxide (H₂O₂) in triggering the onset of germination, and 6 times as effective in causing growth inhibition in the roots. These results suggest the modes of action of NaOCl and H₂O₂ in the termination of dormancy reside in a modification of the properties of the hull and seed coat membranes, and in the provision of additional oxygen to the seed.     

绿僵菌对草坪灰翅贪夜蛾和粘虫的毒力及田间防治效果

测定了从草坪灰翅贪夜蛾上分离的绿僵菌(Metarhizium anisopliae)对灰翅贪夜蛾和粘虫的毒力,采用时间-剂量-死亡率模型分析了绿僵菌对灰翅贪夜蛾和粘虫的毒力。结果表明绿僵菌对灰翅贪夜蛾和粘虫的剂量效应常数分别为0.69和0.66;在孢子含量1×10^6～7个／mL高剂量下接种,灰翅贪夜蛾和粘虫幼虫在接种第7天和第8天累积死亡率达100％;在孢子含量1×10^3～4个／mL低剂量下,接种后第10天达到死亡高峰。在孢子含量1×10²个／mL下的累积死亡率分别为6％和4％。绿僵菌对灰翅贪夜蛾和粘虫致死剂量是时间的函数,对灰翅贪夜蛾第5天和第7天的LC₅₀为孢子含量2.1×10⁶和3.5×10⁴个／mL,在孢子含量10⁷～10⁵个／mL下的LT₅₀分别为4.15、5.1、6.18、7.7 d;对粘虫第5天和第7天的LC₅₀为孢子含量1.55×10⁷、2.39×10⁵个／mL,在孢子含量10⁷～10⁵个／mL下的LT₅₀分别为4.4、5.4、6.4、7.8 d。在草坪禾草上喷洒绿僵菌孢子含量1×10⁶个／mL,5、7、10 d后对粘虫的防治效果分别为46.4％、65.8％、71.4％,对灰翅贪夜蛾的防效分别为47.6％、66.0％和79.6％。绿僵菌制剂孢子含量为1×10⁵个／mL对两种害虫的防治效果相近。