• Korean Journal of Weed Science
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• v.30 no.2
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• pp.143-152
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• 2010

Herbicidal characterisitcs of natural product chrysophanic acid were investigated in a greenhouse condition. At early- and middle-stage post-emergence treatments, several grasses and broadleaf weeds appeared to be very susceptible to chrysophanic acid. However, any significant herbicidal activity treated by pre-emergence did not occur at concentration ranges from 31.3 to 1,000 ug $mL^{-1}$. Herbicidal activity of chrysophanic acid estimated by visual injury for large crabgrass was much higher when applied at 7 to 14 days after seeding than at 21 and 28 days after seeding. By post-emergence treatment, chrysophanic acid caused very considerable phytotoxicity on several grasses and broadleaf crops. In herbicidal interaction experiments determined by Colby's method, the effect of chrysophanic acid and caryophyllene oxide tank-mixture showed very high synergistic activity. Although chrysophanic acid did not give any pre-emergence effect, herbicidal spectrum tended to be very wide and strong when treated by post-emergence. These results suggest that chrysophanic acid possesses a possible potential to develop as a natural herbicide.

• The Korean Journal of Pesticide Science
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• v.4 no.2
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• pp.21-28
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• 2000

A new fourty six 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)-N-phenylpro- pionamide derivatives were synthesized and the herbicidal activities against rice plant and barnyard grass with pre-emergence in down land were measured. The structure activity relationships (SAR) between the activities and physicochemical parameters of the substituted(X) N-phenyl group in substrates were analyzed and discussed by Free- Wilson and Hansch method from the basis on the former study (Sung. et. al., 1999). The conditions of selective herbicide activity both the barnyard grass and rice plant are shown that the optimal hydrophobicity, $({\pi})_{opt.}=1.34$ and electron donating with field effect (F<0) of meta and ortho, para-substituted mono or disubstituent on the N-phenyl ring were found to contribute significantly. The herbicidal activities against barnyard grass are roughly the same as the results in up land whereas damage to rice plant in down land more increase than that of up land. Degradation products in water are 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)propionic acid ((A)) (obs. pKa=4.35 & obs. logP=4.77) and 6-chloro-2-benzoxazolone (B) (obs. pKa=8.40 & obs. logP=2.90). These results were supposing that the hydrolysis product of substrates, (A) is comparatively absorbed in rice plant but not in barnyard grass. And it is assumed from the SAR equations that the 2,6-dimethyl-4-methoxymethyl group substituent ($pI_{50}=5.41$, 3g/ha) is selected as the most highest herbicidal activity against barnyard grass in green house.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.34-39
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• 2000

A new fifteen 2,3-dihydro-2-ethyl-2,4,6,7-tetramethylbenzofuran-5-yl substituents in 5-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one derivatives as substrate were synthesized and their herbicidal activities against rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) with post emergence were measured under submerged conditions. The $R_{1}$=methyl substituents, $1{\sim}8$ showed the higher herbicidal activity to the rice plant and barnyard grass. The structure-activity relationships (SARs) on tile herbicidal activity of $R_{1}$ and $OR_{2}$ groups on the azomethine bond in substrates were analysized. From tile results of dicussed SAR, the herbicide activities against rice plant would depend largely on the steric factor, Whereas, in case of barnyard grass, the activities were governed by the hydrophobicity factor. The conditions of selective herbicide activity between the two plant species are assumed that the substrates should nave optimal hydrophobicity ( $(logP)_{opt.}=6.0$), a $R_{1}$ groups of small and a long $OR_{2}$ groups.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.47-51
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• 2000

A some of synthesized 2,3-dihydro-2,2,4,6,7-pentamethylbenzofuran-5-yl substituents in 5-benzofuryl-2-[1-(alkoxyimino)alkyl]-3-hydroxycyclohex-2-en-1-one derivatives as substrates were found to show herbicidal activity against rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) with post emergence under submerged conditions. The substrate with $R_{1}$=methyl substituents, $1{\sim}5$ showed the higher herbicidal activity to the seed, 3 leaf stage of rice plant and barnyard grass. The structure activity relationships (SARs) on the herbicidal activity of $R_{1}$ and $R_{2}$ on the azomethine bond in substrate were analysized. In the condition of $R_{1}$ groups are same, the herbicidal activity against 3 leaf stage of rice plant were governed by the optimal hydrophobicity $(logP)_{opt.}=4.57$. Whereas, in the case of barnyard grass, the herbicidal activities were largely dependent upon the steric effect, $B_{2}$ constant than hydrophobicity. In order to take the selective herbicidal activity between rice plant and barnyard grass, it is assumed that the (S) should be a round shape with higher hydrophobicity (logP>4.57) than optimal value. Also, the $R_{1}$ groups must be small and the $R_{2}$ groups are advisable to be unsaturate.

• Proceedings of the Korean Society of Crop Science Conference
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• 1998.04a
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• pp.139-140
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• 1998

• The Korean Journal of Pesticide Science
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• v.11 no.1
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• pp.52-58
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• 2007

ALA (5-aminolevulinic acid) has been proposed as a tetrapyrrole-dependent photodynamic herbicide and insecticide by the action of the protoporphyrinogen IX oxidase (Protox IX). The present study was conducted to determine growth responses of plant and insects to ALA, biodegradable biopesticidal substance. In the paddy condition experiment, plant height and shoot fresh weight of barnyardgrass (Echinochloa crus-galli) was more reduced by ALA than rice plants, even though both plant species show great phytotoxicity. Hairy crabgrass (Digitaria sanguinalis), a monocot weed, was more sensitive to ALA at 5mM under upland condition when ALA applied on the foliage, compared with soybean (Glycine max) as a dicot crop. ALA solutions were tested for their insecticidal and larvicidal activities against Spodaptera exigua (Hubner) and Tetranychus urticae Koch. by foliar application and leaf-dipping method. The result showed higher insecticidal activity of ALA at 10mM and its mixture with insecticide luferon against S. exigua. Strongest insecticidal activity against T. urticae was observed from the ALA solution at 10mM 72 days after application. This results show that ALA solution had potent herbicidal and insecticidal activities against agricultural pests even though their activities were lower than those of synthetic pesticides.

• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.58-62
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• 2001

New benzenesulfonylurea derivatives possessing ${\beta}$-hydroxyalkyl subgroup were synthesized and found to have interesting herbicidal activity in greenhouse screening.

• Korean Journal of Weed Science
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• v.14 no.3
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• pp.184-191
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• 1994

A zearalenone derivative, methyldihydroxyzearalenone has been isolated from a plant pathogenic fungus, Drechslera portulacae which causes necrosis on the leaves and stem of Portulaca oleracea. It was characterized as 3, 4, 5, 6, 9, 10-hexahydro-8, 9, 16-trihydroxy-14-methoxy-3-methyl-1H-2-benzoxacyclotetradecine-1, 7(8H)-dione on the basis of spectral analysis. Methyldihydroxyzearalenone treatment at $3{\times}10^{-5}M$ inhibited root length of Echinochloa crus-galli and Abutilon avicennae by 35.7% and 72.6% as compared with the control, respectively.

• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.12-17
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• 2001

A new 2,3-dihydro-2,3,4,6,7-pentamethylbenzofuran-5-yl substituents in 5-benzofuryl-2-[1-(alkoxyimine) alkyl]-3-hydroxycyclohex-2-en-1-ones were found to have herbicidal activity against rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-galli) under submerged conditions. The structure activity. relationships (SARs) on the herbicidal activity of $R_1\;and\;R_2$ on the azomethine bond of 2,3-dihydro-2,3,4,6,7-pentamethylbenzofuran-5-yl subsituents were analysized. The conditions of the selective herbicide activity between rice plant (seed) and barnyard grass from the basis on the analysized SARs are assumed that the $R_2$ group of ethyl substituent ($R_1$ ) should have optimal asymmetry parameter, $(L/B_1)_{opt.}=3.96{\AA}$. And also, the $R_2$ groups consist of $C_1{\sim}C_3$ and unsaturated group such as 3-chloro-2-propenyl group was contribution to the herbicide activity.

• Applied Biological Chemistry
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• v.48 no.4
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• pp.394-399
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• 2005

The comparative molecular field analyses (CoMFA) models for the herbicidal activities against barnyardgrass (Echinochloa crus-galli) and rice plant (Orysa sativa L.) by the substituent (R) on the hexahydroisoindol-1-one ring in a series of new 2-(4-chloro-5-(2-chloroallyloxy)-2-fluorophenyl)-3-thioalkoxy-2,3,4,5,6,7-hexahydroisoindol-1-one derivatives were conducted and discussed for selectivity between both plants. The statistical results of the two best models (B2 & R7) showed the best predictability for the herbicidal activities based on the cross-validated value $q_2(r^2cv.=0.529{\sim}0.755)$ and none cross-validated value $({r^2}_{ncv.}=0.937{\sim}0.945)$, respectively. Based on the findings, the predictability and fitness of the model (B2) for barnyard grass was better than that of the model (R7) for rice plant. From the two models and contour maps, it is revealed that the novel selective character for herbicidal activity between the two plants depend on the electrostatic field and steric field for the substituent of ortho-positions on the S-phenyl group as R-substituent in hexahydroisoindol-1-one ring.