In vitro screening of some plant extracts against fungal pathogens of mulberry ( Morus spp.)

Twenty one plant species were screened in vitro for their fungitoxic properties against four fungal pathogens viz., Phyllactinia corylea (Powdery mildew), Peridiopsora mori (Brown rust) and Pseudocercospora mori (Black leaf spot) by slide germination method and Myrothecium roridum (Brown leaf spot) by poisoned food technique. Conidial germination of P. corylea was significantly reduced in 5% (w/v) ethanolic extracts all tested plant. Extract of Cassia tora and Cassia sophera completely inhibited conidial germination of P. corylea. Other effective plant extracts inhibited >?90% germination were Allium sativum (99.56%), Ocimum sanctum (97.80%), Moringa oleifera (97.32%). Conidial germination of Pseudocercospora mori was completely inhibited in extract of A. sativum and D. metel. More than 90% inhibition was observed with extract of Holarrhena antidysentrica (93.10%), Adhatoda Zeylanica (91.40%) and Calotropis gigentia (90.40%). Urediniospore germination of Peridiopsora mori was significantly reduced in 19 plant extracts. Extract of A. sativum and D. metel completely inhibited urediniospore germination P. mori. Other effective plant extracts, which inhibited >?90% germination were Calotropis gigentia (99.40%), Targets patula (98.96%), Azadirachta indica (98.85%), Mirabilis jalapa (95.50%) and Chromoleana odorata (90.51%). Maximum inhibition (33.33%) of colony growth of M. roridum was observed with amendment of 5% solvent extracts of D. metel followed by A. sativum (25%), Chromoleana odorata (20%) and Eucalyptus citriodora (16.66%).     

Fungitoxic effects of some leaf extracts against rhizopus oryzae causing tuber rot of potato

Extracts of Cymbopogon citratus, Azadirachta indica (Neem) and Ocimum gratissimum were effective in controlling the growth of Rhizopus oryzae in vitro and in vivo. Neem was found to be the best followed by C. citratus and O. gratissimum. Alcohol extracts of these plant species were more effective than water extracts in reducing the growth of the pathogen in culture and in checking rot development in potato tuber by the fungus. A. indica and C. citratus have considerable disease control potential and their extracts can be exploited as a source of pesticide of plant origin to control the soft rot in stored potato incited by Rhizopus oryzae.     

Inhibitory effect of Tamarindus indica and Carica papaya on egg hatch larva mortality of Meloidogyne incognita

Essentially, the most effective control of plant parasitic nematodes involves the use of synthetic nematicide. However, apart from their very high cost, increased concern on the environment has necessitated a reduction in the amount of nematicides used for nematode control. In view of these, this research work was conducted to evaluate the effects of different concentrations of root extract of Tamarindus indica and Carica papaya at different concentrations S (100% concentration), “S/2” (50% concentration), “S/10” (10% concentration) and “S/100”(1% concentration) in the inhibition of egg hatch and mortality of larva of root-knot nematode, Meloidogyne incognita .The experiment was laid out in a completely randomised design and replicated four times. Combination of equal proportion of T. indica and C .papaya root extract indicated that all the concentrations inhibited egg hatch. The standard solution S of all the selected botanicals were more toxic and effective at (p ≤ 0.05) than the other concentrations. Similarly, combinations of root extracts of T. indica and C. papaya were the most effective of all the selected botanicals in the inhibition of egg hatch and larvae mortality, followed by T. indica root extracts and then C. papaya root extracts.     

Evaluation of quorum sensing modulation by plant extracts originating from Turkey

Quorum sensing (QS) is a widespread mechanism utilized by both Gram (+) and Gram (?) bacteria for communication and regulation of specific virulence traits and phenotypes due to population density. Plants are known to produce a number of compounds that can inhibit this communication and most of them have been discovered through well-known Chromobacterium violaceum biomonitor strains assays. In this study, we have analyzed 36 extracts, from 26 Turkish plant species, for their effects on bacterial growth and inhibition or induction of QS in the said biomonitoring assay. Four of the crude plant extracts from Tanacetum balsamita L. subsp. balsamitoides (Compositaceae), Epilobium angustifolium L. (Onograceae), Quercus frainetto Ten. (Fagaceae) and Quercus robur L. (Fagaceae) showed QS inhibitory activity and significantly reduced violacein production in C. violaceum. Particularly, ethyl acetate soluble compounds extracted from leaves of Quercus spp. were efficient in QS inhibition without any apparent increase in bacterial growth. On the other hand, extracts from Mentha longifolia subsp. longifolia and Hypericum orientale showed enhanced violacein production, thus increasing QS-dependent behaviour. Our results clearly demonstrate the QS-inhibitory effects of Q. frainetto Ten., E. angustifolium and T. balsamita L. extracts, while two other species showed QS-inducing effects, for the first time.     

Toxic and Antifeedant Effects of Different Pesticidal Plant Extracts against Beet Armyworm (<i>Spodoptera exigua</i>)

The beet armyworm (BAW), Spodoptera exigua (Lepidoptera: Noctuidae) is a highly destructive pest of vegetables and field crops. Management of beet armyworm primarily relies on synthetic pesticides, which is threatening the beneficial community and environment. Most importantly, the BAW developed resistance to synthetic pesticides with making it difficult to manage. Therefore, alternative and environment-friendly pest management tactics are urgently required. The use of pesticidal plant extracts provides an effective way for a sustainable pest management program. To evaluate the use of pesticidal plant extracts against BAW, we selected six plant species (Lantana camara, Aloe vera, Azadirachta indica, Cymbopogon citratus, Nicotianatabacum, and Ocimum basilicum) for initial screening experiment. Four out of six plant species such as A. indica, N. tabacum, C. citratus and O. basilicum showed promising mortality of more than 50%. Therefore, we selected these four plant extracts for the subsequent experiments. Through contact bioassay, A. indica showed high mortality 66.63%, followed by the N. tabacum 53.33%, at 10% w/v concentration. Similarly, N. tabacum showed the highest mortality rate, 66% at 10% w/v concentration, followed by the A. indica 46% through feeding bioassay. Furthermore, the feeding deterrence assay showed that C. citratus had a high antifeedant index (−50) followed by A. indica (−39), and N. tabacum (−28). In living plant assay, the N. tabacum extract showed a low mean damage score 3.6 on living cotton plant followed by C. citratus 4.5 and A. indica 5.5. Hence, extracts of three plant species provided promising results against the BAW, which can minimize the use of synthetic chemicals, particularly for small landholding farmers. Further studies are also required to evaluate the effects of these plant extract against BAW on cotton plants under field conditions to optimize the further use.     

Antifungal activity of herbal extracts against plant pathogenic fungi

The present study was designed to evaluate in vitro antifungal activity of herbal extracts against three plant pathogenic fungi (viz. Rhizopus stolonifer, Botrytis cinerea and Colletotrichum coccodes). Extracts of leaves and rinds of Garcinia indica, rhizomes of Curcuma aromatica, roots of Glycyrrhiza gahliae, leaves of Nyctanthes arbour-tristis and seeds of Vernonia anthelmintica were used for screening. Screening was done using poisoned food technique. Relatively potent extracts were shortlisted from this study and were further assayed to find out their minimum fungicidal concentration (MFC). From the above studies, it was observed that ethyl acetate extract of rhizomes of C. aromatica and unripe fruit rinds of G. indica have shown the lowest MFC values amongst the other tested plant extracts. This study indicates that the potential of these plant extracts in the management of diseases caused by plant pathogenic fungi.     

Antibacterial activity of herbal extracts against five plant pathogenic bacteria

The present study was designed to evaluate in vitro antibacterial activity of herbal extracts against five plant pathogenic bacteria (viz. Xanthomonas campestris, Xanthomonas axonopodis pv. punicae, Erwinia spp., Pseudomonas syringae and Xanthomonas citri). Herbal extracts of leaves and rinds of Garcinia indica, rhizomes of Curcuma aromatica, roots of Glyccyrrhiza glabra, leaves of Nyctanthes arbor-tristis and seeds of Vernonia anthelmintica were used for screening. Screening was done using agar well diffusion method. Relatively potent extracts were shortlisted from this study and were further studied to find out their minimum bactericidal concentration (MBC). From the studies, it was observed that extracts of C. aromatica, G. indica and G. glabra have shown lowest MBC values among other tested plant extracts. This study indicates the potential of these potent plant extracts in the management of diseases caused by plant pathogenic bacteria.     

Evaluation of three aqueous plant extracts and Lamdacot in controlling eggplant fruit borer (Daraba laisalis Wlk.) (Lepidoptera: Pyralidae) in north-eastern Nigeria

Field experiments carried out in Dadinkowa, Gombe State, Nigeria, during 2007 and 2008 cropping seasons evaluated the efficacy of three aqueous plant extracts namely neem (Azadirachta indica A.H.L. Juss.), bitter melon (Momordica balsamina Linn.) and siam weed (Chromolaena odorota (L.) King and Robinson) compared to a conventional insecticide, Lamdacot 500EC, in managing fruit borer (Daraba laisalis Wlk.) attack of eggplants in north-eastern Nigeria. The experiments were laid out in a randomised complete block design replicated four times including controls. The results showed that the application of aqueous extracts (5% w/v concentration) of A. indica and M. balsamina at one-week interval during the fruiting stage was effective and at par with the conventional insecticide, Lamdacot, in reducing eggplant fruit borer infestation and fruit damage, as well as the resulting increase in fruit yield. Farmers can therefore adopt the practice of applying 5% w/v concentration of the above aqueous plant extracts at weekly intervals to control fruit borer attack of eggplants in the north-eastern region of Nigeria.     

Feeding inhibition of Helicoverpa armigera （HiJbner） by Eucalyptus camaldulensis and Tylophora indica extracts

Crude leaf extracts of Eucalyptus camaldulensis and Tylophora indica were evaluated for their antifeedancy against Helicoverpa armigera larvae in no-choice bioassays. Cabbage leaf-disc dipped in different concentrations of leaf extracts was used for feeding fifth instars of H. armigera for 24 hours. Ethanol extracts from both the plant species exhibited significant feeding inhibition, activity. The effective concentrations of ethanol extracts that caused 50% reduction in larval feeding （EI50） were 6.9% for E. camaldulensis and 2.8% for T. indica, while these values of hexane extracts were 9.3% and 5.2%, respectively. Compared to the crude leaf extracts, crude alkaloids from T. indica and crude tannins from E. camaldulensis were more potent in reducing larval feedings.     

Integrated management of fusarial wilt of tomato with implementation of soil solarisation

Fusarial wilt of tomato (Lycopersicon esculentum Mill.) is a very common and severe disease occurring in most of the vegetable fields in West Bengal, India. Potenciation and formulation of different fungicidal chemicals and phytoextracts were evaluated against the growth of the pathogen wherein carbendazim (bavistin) and leaf extracts of Azadirachta indica (neem) were recorded to be most effective. Combined treatment with 4 ml neem leaf extract and 1 ml captan (0.01%) or with 4 ml garlic bulb extract and 1 ml captan (0.01%) exhibited 100% growth inhibition of the pathogen. Integrated control of the pathogen with phytoextracts, fungicide and biocontrol agents was carried out. Among the treatments, a combination with extracts of neem, captan (0.01%) and metabolites of Trichoderma harzianum was proved to be superior over the other. Field experiment with three fungicides at 0.5% concentration was carried out in randomised block design where application of bavistin showed up to 62.27% reduction of wilt infection in tomato plants. Soil solarisation of tomato field showed 62.50 and 66.69% reduction of infection during the trial years. However, integration of soil solarisation with the applications of T. harzianum, captan (0.01%) and neem resulted in 100% reduction of infection and thus it was recorded as the most effective treatment in reducing the incidence of the disease.     

Comparative bioactivity of selected extracts from Meliaceae and some commercial botanical insecticides against two noctuid caterpillars, <Emphasis Type="Italic">Trichoplusia ni</Emphasis> and <Emphasis Type="Italic">Pseudaletia unipuncta</Emphasis>

Plant-derived extracts and phytochemicals have long been a subject of research in an effort to develop alternatives to conventional insecticides but with reduced health and environmental impacts. In this review we compare the bioactivities of some plant extracts with those of commercially available botanical insecticides against two important agricultural pests, the cabbage looper, Trichoplusia ni and the armyworm, Pseudaletia unipuncta. Test materials included extracts of Azadirachta indica (neem), A. excelsa (sentang), Melia volkensii, M. azedarach (Chinaberry) and Trichilia americana, (all belonging to the family Meliaceae) along with commercial botanical insecticides ryania, pyrethrum, rotenone and essential oils of rosemary and clove leaf. Most of the extracts and botanicals tested proved to be strong growth inhibitors, contact toxins and significant feeding deterrents to both lepidopteran species. However, there were interspecific differences with T. ni generally more susceptible to the botanicals than the armyworm, P. unipuncta. All botanicals were more inhibitory to growth and toxic (through feeding) to T. ni than to P. unipuncta, except for M. azedarach which was more toxic to P. unipuncta than to T. ni. Athough, pyrethrum was the most toxic botanical to both noctuids, A. indica, A. excelsa, and M. volkensii were more toxic than ryania, rotenone, clove oil and rosemary oil for T. ni. As feeding deterrents, pyrethrum was the most potent against T. ni, whereas A. indica was the most potent against the armyworm. Based upon growth inhibition, chronic toxicity, and antifeedant activity, some of these plant extracts have levels of activity that compare favorably to botanical products currently in commercial use and have potential for development as commercial insecticides.     

Screening of plant extracts for organic management of downy mildew of sorghum

Antipathogenic potential of 38 plants was evaluated in the form of aqueous extracts against Peronoclerospora sorghi, causing downy mildew of sorghum. Conidial suspension and plant extracts were mixed individually and allowed to stand for 5 min and then used to inoculate the host by sprout-dip method. The sprouts thus inoculated were grown in pots, and the disease incidence was observed. Eight plant extracts (Cicer areatinum, Datura metel, Croton sparsiflorus, Parthenium hysterophorus, Nerium oleander, Chromolaena odorata, Duranta repens and Oxalis latifolia) at 20% concentration performed at par with chemical fungicide (Mancozeb 75%) by exhibiting total suppression of disease incidence to 0%, when compared with 64.1% of negative control. Organic management of air-borne inoculum of downy mildew of sorghum is feasible and preferable when compared with chemical control methods, considering human and environmental health concerns. The use of water extract keeps the technology simple so that it can be directly prepared and used by the farmers. Short-listing of eight most effective water extracts would help in self-reliance of farmers, reducing their dependence on commercial products.     

Fungitoxic properties of selected South African plant species against plant pathogens of economic importance in agriculture

Thirty‐nine plant species, representing 20 families from the subclasses Rosidae, Asteridae, Commelinidae and Liliidae, were collected from the Blyde River Canyon Nature Reserve, Mpumalanga, South Africa. Crude extracts were prepared and bioassayed, at equal concentrations, for their antifungal potential by determining the inhibitory effects on the mycelial growth of seven economically important plant pathogenic fungi. Statistically significant differences between plants and plant parts were observed as well as the resistance of different fungi to treatment with different plant extracts. The most significant mycelial growth inhibition was obtained with extracts from two species of the subclass Liliidae, namely Aristea ecklonii and Agapanthus inapertus. The crude extract of A. ecklonii performed best of all extracts as it totally inhibited the mycelial growth of all seven of the plant pathogenic test organisms and outperformed the inhibition by a broad spectrum synthetic fungicide (carbendazim/difenoconazole). Crude extracts of A. inapertus showed complete inhibition of four and strong inhibition of the remaining three plant pathogenic fungi. Although not as efficient as the previous two species, the extract of Anisopappus junodii, from the subclass Asteridae, also showed promising antifungal activity by completely inhibiting mycelial radial growth of two and strongly inhibiting that of the remaining five fungi.     

Antifungal activity of several medicinal plants extracts against the early blight pathogen (Alternaria solani)

The antifungal activity for several medicinal plants against the early blight fungus (Alternaria solani) has been investigated. These plants were Syrian marjoram (Majorana syriaca), rosemary (Rosmarinus officinalis), Greek sage (Salvia fruticosa), roselle (Hibiscus sabdariffa) and cotton lavender (Santolina chamaecyparissus). The inhibitory effect of these extracts on the radial mycelial growth as well as on spore germination was measured in vitro at various concentrations of crude extract (0.5 g dry plant powder/ml medium). Extracts of M. syriaca and H. sabdariffa were most effective causing total inhibition of mycelial growth and spore germination at 8–10% concentration. Extract of R. officinalis also caused total inhibition of the above two parameters but at double the concentration (20%). Extracts of S. fructicosa and S. chamaecyparissus produced relatively moderate antifungal activity. At 25% concentration, these extracts showed an incomplete inhibition in mycelial growth being around 75–85% and 70–90%, respectively. However, at this same concentration both plant extracts produced total inhibition of spore germination. Results of this study indicated that both extracts of M. syriaca and H. sabdariffa were strong inhibitors of this fungus and to levels comparable to standard fungicides. Further studies are required to determine the effect of these extracts in vivo to evaluate their potential as natural treatments for this disease.     

Induced resistance against Alternaria brassicae blight of mustard through plant extracts

An experiment was conducted to study the effect of plant extracts on soluble sugar, soluble phenol and defence-related enzymes response against Alternaria blight in mustard crop. The efficacy of six selected plant extracts (5 and 10%) used as foliar sprays at 60 and 70 days after sowing and mustard leaves was used for investigation. The results indicate that soluble phenol and sugar content in mustard leaves significantly increases in response to spraying of Azadirachta indica seed kernel, Calotropis procera and A. indica leaf extracts. The soluble protein, viz. peroxidase, polyphenol oxidase and phenylalanine ammonia lyase content, was higher in mustard leaves sprayed with C. procera leaves extract, A. indica seed kernel and Allium sativum bulb extract.     

Evaluation of antifungal potential of Marchantia polymorpha L., Dryopteris filix-mas (L.) Schott and Ephedra foliata Boiss. against phyto fungal pathogens

Methanol and flavonoid extracts (free and bound) of Marchantia polymorpha L., Dryopteris filix-mas (L.) Schott and Ephedra foliata Boiss. were screened against three fungal plant pathogens: Alternaria solani, Fusarium oxysporum and Rhizoctonia solani. The extracts from D. filix-mas and E. foliata showed >80% of mycelial inhibition of A. solani whereas M. polymorpha and D. filix-mas (rhizome) completely inhibited the mycelial growth of R. solani when tested at highest concentration (5 mg/ml). Inhibition of spore germination of fungi (A. solani and F. oxysporum) was observed to be 100% by most of the extracts at 10 mg/ml. Moreover, plant extracts were found effective in increasing seed germination and seed vigour simultaneously thereby decreasing the percentage of pathogen infection. The results of the present study reveal that the plants screened possess the potential to inhibit the crop fungal pathogens and further investigation is required to explore the biologically active constituents of these plants and to use them as natural plant protectants for agriculture.     

Antifungal activity of some plant extracts on some pathogenic fungi

The inhibitory activity of five plant extracts viz. Artemisia absinthium L., Rumex obtusifolius L., Taraxacum officinale Weber ex Wiggers, Plantago lanceolata L. and Malva sylvestris L. were evaluated against the mycelial growth of three fungi Alternaria alternata (Fr.) Keissler, Penicillium expansum Link ex Thom. and Mucor piriformis Fisher that cause rot diseases in fruits and vegetables resulting in low yield and quality of fruits and vegetables. Results revealed that all the concentrations of plant extracts brought about significant inhibition in the mycelial growth of these pathogenic fungi. However, the highest concentration caused maximum inhibition in the mycelial growth followed by lower concentrations of plant extracts. The extract of A. absinthium leaves at highest concentration (S) proved highly effective in inhibiting the mycelial growth of all these pathogenic fungi followed by other plant extracts. These plants thus may have potential as the new natural fungicide for management of fungal rot diseases.     

Assessment of potential antagonists for anthracnose (Colletotrichum gloeosporioides) disease of mango (Mangifera indica L.) in North Western Ethiopia (Pawe)

Mango (Mangifera indica L.) is considered as one of the most popular fruits among millions of people in the tropical area and increasingly in the developed countries. Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most important pre- and post-harvest disease of mango. The objective of this research was to evaluate the prevalence of different promising antagonistic Trichoderma and Bacillus spp. on phyloplane of mango in Ethiopia and to evaluate their antagonistic potential against the pathogen. A total of 19 mango fields were surveyed and anthracnose affected all fields. Culture studies on potato dextrose agar for evaluation of antibiosis activity of Trichoderma spp. and Bacillus spp. revealed that they have inhibitory and lytic effect on C. gloeosporioides, which is an indication of their potential biocontrol agent for management of mango anthracnose as an alternative to chemical control. Significant differences (p?<?0.05) were observed among Bacillus isolates in causing lysis of pathogen mycelium, when inoculated on actively growing colony of C. gloeosporioides. Maximum reduction in growth rate of pathogen was observed with Bacillus spp. (B50), which restricted the growth to 2.7?mm compared to 8.3?mm in the control with 67.5% efficacies. There were similar effects (p?<?0.05) among Trichoderma spp. in formation of inhibition zones and lysis by varying degrees up to 59.7% efficacies in reducing linear growth of the pathogen in dual culture.     

Evaluation of plant extracts as an antagonist to mycelial growth of Mycosphaerella fijiensis morelet

Three plant extracts (rice husk, wood and bamboo) at different concentration were evaluated in vitro as an antagonist to mycelial growth of Mycosphaerella fijienesis on different culture media using spread plate and mycelia dry weight method. The plant extracts had significant effects on the mycelial growth of Mycosphaerella fijiensis. Rice husk extract at concentration of 1, 1.5, 2.5 and 5% completely inhibited the mycelia growth of M. fijiensis in malt extract broth (MEB) and at 2.5 and 5% on malt extract agar (MEA). Wood extract at concentration of 1 and 1.5% inhibited the mycelial growth of M. fijiensis and completely at concentration of 2.5 and 5% on MEA. Although complete inhibition was only observed at 5% concentration on MEA for bamboo extract, the evaluated plant extracts could be recommended for the control of M. fijiensis on a large-scale farming.     

Endophytic bacteria from Datura metel for plant growth promotion and bioprotection against Fusarium wilt in tomato

Nine non-pathogenic bacterial isolates, recovered from Datura metel organs and able to colonise the internal stem tissues of tomato cultivar Rio Grande, were screened for their ability to suppress tomato Fusarium wilt disease caused by Fusarium oxysporum f. sp. lycopersici (FOL), and to enhance plant growth. S33 and S85 isolates tested were found to be the most effective in decreasing Fusarium wilt severity by 94–95% compared to FOL-inoculated and untreated control. A significant enhancement of growth parameters was recorded on tomato plants inoculated or not with FOL. Both isolates were characterised and identified using 16S rDNA sequencing genes as Stenotrophomonas sp. str. S33 (KR818084) and Pseudomonas sp. str. S85 (KR818087). Screened in vitro for their antifungal activity towards FOL, these isolates led to 38.7% and 22.5% decrease in pathogen radial growth and to the formation of an inhibition zone of 12.75 and 8.37?mm respectively. Stenotrophomonas sp. str. S33 and Pseudomonas sp. str. S85 were found to be chitinase-, protease- and pectinase-producing strains but unable to produce hydrogen cyanide. Production of indole-3-acetic acid-like compounds, phosphate solubilising ability and pectinase activity were investigated for elucidating their plant growth-promoting traits and their endophytic colonisation ability.