MINISTRY OF EDUCATION
AND TRAINING
(MOET)
MINISTRY OF
AGRICULTURE AND RURAL
DEVELOPMENT (MARD)
VIETNAM ACADEMY OF AGRICULTURAL SCIENCE
(VAAS)
---------
NGUYEN THE HINH
RESEARCH ON PESTS, DISEASES AND
WEEDS IN THE INTERCROPPING SYSTEMS OF
MONDO GRASS (Ophiopogon japonicus Wall.) AND
OTHER CROPS IN PHU THO PROVINCE
Branch of Study: Plant Protection
Code No.: 62.62.01.12
SUMMARY OF AGRICULTURAL
DOCTORAL THESIS
HÀ NỘI - 2014
The thesis has been completed in:
VIETNAM ACADEMY OF AGRICULTURAL SCIENCE (VAAS)
Scientific supervisors:
1. Prof. Dr. Nguyen Van Tuat
2. Dr. Nguyễn Đình Vinh
Independent Evaluator 1:
Independent Evaluator 2:
Independent Evaluator 3:
This thesis shall be presented before Institutional Thesis Evaluation
Committee at:
Vietnam Academy of Agricultural Science (VAAS)
Date: ... day... month... year
This thesis can be referred at the library of:
Vietnam National Library
Library of Vietnam Academy of Agricultural
Science
1
INTRODUCTION
1.
The demand of the research subject:
Mondo grass is a perennial grass with the scientific name Ophiopogon Japonicus Wall,
which belong to the Ophiopogon genus, Ruscaceae family (Liliaceae family before). The
species of this genus mainly originated from the regions of East, Southeast and South Asia.
Nowadays, the mondo grass is polulated in the world, frequently seen in tropical and semitropical areas. Mondo grass is used as soil coverage plants and ornamental plants in the parks,
office gardens of the countries of China, United States, Gemany, Thailand and Japan. In some
other countries such as Vietnam and China, mondo grass’s tubes and roots are used in making
medicines.
Mondo grass is a crop with many advantages and be able to grow well when
intercropping with other crops. Initial survey on agri-ecological conditions and the market
demand showed that the mondo grass has a huge potential to intercrop in the gardens of fruit
crops and other industrial crops in Northern Mountainous areas. Dispite of the huge potential,
the mondo grass was grown spontaneously by the mountainous farmers without any research
on pests, diseases and other intercropping tactics to maximize the benefits of this crop.
Therefore, the implementation of the research subject “Research pests, diseases and
weeds in the interopping systems of Mondo grass (Ophiopogon japonicus Wall.) and other
crops in Phu Tho province” is highly needed for sustainable intercropping systems in this
province.
2.
The purposes of the research
To study the composition and damage level of pests, diseases and weeds on mondo
grass, tea and pomelo in 02 intercropping systems of mondo grass in tea plantation and
mondo grass in pomelo garden. To research the mondo grass disease (stem rot disease) and
control measures. To study the supression impact of mondo grass to weeds and some
integrated crop management tactics to control weeds in the intercropping systems with
mondo grass. To evaluate the economic and environment benfits of the mondo grass
intercropping systems in Phu Tho province.
3.
3.1.
Scientific and practical values of the research
Scientic value
(i)
The research results contributed to the database of pests and diseases on mondo
grass in Phu Tho province.
(ii)
The research identified the pathogen causing stem rot disease of mondo grass is
the fungus Pythium helicoides Drechsler, through the molecular analysis and DNA
classification, the research found a fungus which has never been found on the mondo grass in
Vietnam. The research showed the description of stem rot disease symptoms and some
2
biological characteristics of the fungus P. helicoides Drechsler, testing of some biological and
chemical control measures on the fungus to enrich the scientific basis for development of the
stem rot disease control procedures on the mondo grass.
(iii) The research studied the impacts of mondo grass intercropping to some major
pests on the main crops (tea and pomelo) in the intercropping systems, initially determined
the suppression impacts of mondo grass on weeds through the physical influence (shading)
and chemical influence (mondo grass root’s powder).
3.2. Practical value
(i)
The results on the pest composition and damage level as well as the experiments
on stem rot disease control measures helped development of some crop protection procedures
to enhance the yields of mondo grass.
(ii)
The results on the influence of mondo grass intercropping on some major pests
and weeds in tea and pomelo plantations helped in development of technical cultural
procedures for the intercropping of mondo grass in the tea and pomelo gardens.
(iii) Analysis on economic and environment values helped in advising farmers on the
benefits of mondo grass intercropping in tea and pomelo plantations in Phu Tho province.
3.3. New findings of the research
Determined the pathogen causing the mondo grass’s stem rot disease is the fungus
Pythium helicoides Drechsler. This fungus has been announced as pathogens in some
crops in the world but this is the first time this fungus was found as the pathogen causing
stem rot disease in mondo grass in Vietnam
Determined some biological characteristics of the fungus Pythium helicoides Drechsler
and experimented some biological and chemical measures to control the fungus in the
laboratory which found the basis for development of the mondo grass’s stem rot disease in
the field.
Mondo grass intercropping did not influence the major pests in the tea plantations such as
Empoasca flavescens Fabr., Physothrips stiventris Bagn, Oligonychus coffeae Niet,
Helopentis theivora Waterhouse, Colletotrichum Camelliae Masse, Colletotrichum theae
Petch as well as pests on pomelo plantations such as Phyllocnistis citriella Saintion and
Xanthomonas campestris.
Mondo grass can suppress the weed growth through the physical mechanism (shading)
and chemical mechnism (root powder). This result is in line with the research result of
Lin D., Tsuzuki et al (2003) that the root powder of mondo grass did suppressed the
germination and growth of the weeds in the rice fields. Therefore, mondo grass
intercropping can efficiently control weeds in tea and pomelo plantations.
Initially proposed some mondo grass’s intercropping tactics (optimal planting time,
density and distance between rows) to reach the highest weed control towards the
integrated crop management (ICM) strategies.
3
4.
The thesis structure
The main content consists of 146 pages (excluding the reference and appendices) –
Introduction: 5 pages; Chapter 1: Scientific basis and Document overview – 29 pages;
Chapter 2: Materials, Main research contents and Methodologies – 19 pages; Chapter 3:
Research results and Discussion – 90 pages; Conclusions and Suggestions – 3 pages;
Reference – 23 pages. The thesis consists of 35 tables, 28 pictures and referred to 71
Vietnamese documents and 110 English documents.
CHAPTER 1
SCIENTIFIC BASIS AND DOCUMENT OVERVIEW
1.1. Scientific basis of the research
The mondo grass originated from China and Japan but was introduced into Vietnam
hundred years. The plant adapted well with the climate and soil conditions of many various
eco-agricultural areas from the Central to the North of Vietnam. The mondo grass has many
advantages of a good intercropping plant and high potential to become an important
intercropping crop in the large areas of perennial fruits and industrial crop gardens in
Northern mountainous areas. However, there is no record of research in mondo grass pests as
well as its intercropping systems in Vietnam.
1.2. National and International document overview
1.2.1. International document overview
1.2.1.1.
Research on the mondo grass’s uses
Many research on using mondo grass as the ornamental plants for soil coverage, fens in
family gardens, parks or offices.
Many research and findings on using tubes and roots of mondo grass for making
medicines have been carried out by pharmaceutical researchers in China and other Eastern
countries.
1.2.1.2.
Research on mondo grass pests and control measures
Some research on mondo grass pests have been implemented and the results showed
that the mondo grass was pested by a few species such as scale Pinnaspis carisis Ferris and
snail. Some control measures have been suggested such as spraying soap pesticides to control
scale, using granular bait to control snail.
1.2.1.3.
Research on mondo grass’s disease and control measures
Some fungi have been found as the mondo grass’s
pathogen such as the
Collectotrichum sp. causing yellow leaves, the fungus Fusarium sp. found in roots and stems
of the disease mondo grass plants, the fungi Phytophthora palmivova and Phytophthora
4
nicotiana found in the mondo grass’s nurseries and glass houses, the fungus Pythium
splendens causing mondo grass’s root rot disease. Spraying chemical pesticide Aliette can
control the fungus Pythium splendens. The fungus Pythium helicoides Drechsler has never
found as a pathogen in mondo grass in the world.
1.2.1.4.
Research in the pests on tea, pomelo and the intercropping systems
There are many research in the pests on tea and pomelo crops have been carried out
internationally. There are specific pests for each ecological areas even though some major
pests can be found in most tea growing regions. There are records of over a thousand of
insect and 400 fungi species identified in the world tea growing areas. Many pests and
diseases on pomelo crop have been studied in the countries of Malaysia, Indonesia, China,
Japan, India, Fiji, Philippines and Thailand.
Many international research confirmed the benfits of the various intercropping systems.
However, there is no research results recorded on the influence of the intercropping to pests
and diseases on tea and pomelo crops.
The study of Jey Deputy (1998) showed that the mondo grass can frequently maintain
the completed soil coverage, therefore, well competed with weeds. Lin D., Tsuzuki et al
(2003) recorded that the solution from mondo grass’s root powder could suppress the
germination and growth of weeds in the rice fields without the negative impact to the growth
of rice plant.
1.2.2. National document overview
1.2.2.1.
Research on the mondo grass’s uses
Many national pharmaceutical documents mentioned the mondo grass as a major
ingredient in traditional medicines. Mondo grass’s tube in fact has been used in many
traditional medicines for hundred years in Vietnam.
1.2.2.2.
Research in mondo grass’s pests and diseases and the control measures
There are a few studies recorded on the mondo grass’s pests and diseases. The survey
results of Nguyen Dinh Vinh and Nguyen Thi Thanh Hai (2011) showed that the majority
(72%) of farmers in Phu Tho and Yen Bai provinces mentioned the mondo grass as a crop
with a few pests, only the stem rot disease is the most dangerous which could damage the
crop yield at the dangerous level of 8/10. No research result on the fungus Pythium helicoides
Drechsler as a pathogen causing mondo grass disease in Vietnam has been recorded.
1.2.2.3.
Research in the pests on tea, pomelo and the intercropping systems
Tea and pomelo are the traditional crops in Vietnam, therefore, many studies on their
cultivation tactics, pests and diseases have been found and refered during the document
overview.
5
There are many research works on various intercropping systems in Vietnam. However,
studying on the intercropping systems between mondo grass and other crops is very limited
(Nguyen Dinh Vinh et al, 2007, 2009).
1.2.2.4.
Climate and soil conditions of the research site
Phu Tho is a province with large mondo grass plantations, where the farmers have longterm experience in growing this crop. There are also many mondo grass processing units in
the districts of Ha Hoa and Thanh Ba. Therefore, Phu Tho has large potential in development
of mondo grass, particularly in the areas of unfertile soil, the mondo grass is considered as the
most suitable crop which can maximize the use of land and bring good income to poor
farmers.
CHAPTER 2
MATERIALS, RESEARCH CONTENTS AND METHODOLOGY
2.1. Materials
2.1.1. Laboratory materials
Mondo grass plants (healthy and disease infected) of variety M2 which are polpularly
grown in Ha Hoa district, Phu Tho province. Media for tissue culture are WA, CA, PCA,
PDA, CMA. Chemical pesticides of Ridomil 72 MZ, Viben-C 50 BTN, Aliette 80WP 0,1%;
Copper - Zinc 85 WP and biological pesticides of Trichoderma asperellum, Bacillus
amyloliquefaciens and Streptomyces misionensis. Other common laboratory equipment and
tools.
2.1.2. Field research materials
Tea plantations of Phuc Van Tien variety of 2-4 years with the mondo grass intercropped
between two tea rows; Pomelo gardens of Dien variety of 1 – 3 years intercropped with the
mondo grass.
2.1.3. Research site and duration
Surveys and field research are carried out at Bang Gia commune, Ha Hoa district, Phu
Tho province. The experiments and analysis are implemented at Plant Protection Research
Institute (PPRI). The research duration is from August 2009 to March 2013.
2.2. Research contents
- To study the composition and damage level of pests on mondo grass, tea and pomelo
plants in the two (02) intercropping systems of mondo grass in tea plantations and pomelo
gardens. Comparison of the pests on tea and pomelo plants between intercropped plantations
and non-intercropped plantations in Phu Tho province.
6
- To study specifically the Mondo grass’s stem rot disease: pathogen identification,
some biological characteristics and laboratory testing as well as field trials of chemical and
biological fungicides.
- To survey the composition and damage level of weeds in the two (02) intercropping
systems of mondo grass in the tea and pomelo plantations. The weed suppression mechanism
of mondo grass is also studied.
- To experiment some integrated crop management (ICM) measures for managing
weeds in the intercropping system between mondo grass and pomelo in Phu Tho province.
- To evaluate the economic and environment benefits of the intercropping systems
between mondo grass with tea and pomelo.
2.3. Methodology
2.3.1. Survey and sample collection
Surveys of pests and diseases in the intercropping systems are implemented by the
basic survey methodology of Plant Protection Research Institute (1999-2000). The samples
were sent to PPRI’s specialists for analysis and classification. The damage level is
determined by the pest density or level of leaf damage.
2.3.1.1 Identification of the survey sites
The surveys selected are some communes in Ha Hoa district, Phu Tho province where
mondo grass is popularly grown. To comprehensively survey the mondo grass’s stem rot
disease, the supplementary surveys have been carried out in some other places in Ha Noi and
Bac Giang. The selection of 3 – 5 gardens per location and 5 cross-cutting points per each
garden was inplemented during the survey.
2.3.1.2 Survey methodology for pests and diseases in tea and pomelo plants
For tea pests: Survey frequency is one time per 7 days. The oil tray is used for sampling
green leafhopper and natural enemies. The thrip is collected in the tea buds, the red mite is
collected in the tea leaves; the tea buds eaten by mosquito bugs were counted; the tea leaves
infected with brown blight were collected and the tea buds infected with bud rot disease were
counted for analysis.
For pomelo pests: Survey frequency is one time per two months in the selected young
pomelo gardens. The selection of 20 pomelo plants per garden were made and the collected
pests through catching by net and sampling were sent to laboratory for analysis.
For the mondo grass pests: Carefully watching the mondo grass in the intercropped
plantations to collect pests and diseases for analysis.
The apprearance frequency of the pests below 20% of the samples is rated less popular
(+), 20-50% of the samples is rated popular (++), more than 50% is rated most popular (+++)
7
2.3.2. The assessment methodology of the impacts of mondo grass intercropping to some
major pests in the main crops.
To survey the 06 major pests in the tea plantations (green leafhopper, mosquito bug,
thrip, red mite, brown blight, bud rot) and 02 major pests in the pomelo plantations
(leafminer, black rot). The comparision of the pest apprearance and damages between the
plantations with and without mondo grass intercropping was made. To carefully observe the
growth (height, shading, leaf number) of tea and pomelo plants with and without the mondo
grass intercropping.
2.3.3. Methodology for researching the mondo grass’s stem rot disease
Methodology for identification of pathogen: The Koch’s principles have been followed
[Drenth và Sendall, 2004] including 4 steps: Symptom description and initial clasification;
(ii) Isolation of the disease’s pathogen and identification; (iii) Artificial infection of the
isolated pathogen to the healthy plants and observe the similar disease symptoms; (iv) Reisolation of the pathogen from artificial infected plants and comparison with the intitial
isolated pathogen above. The isolation of pathogen from the disease plants was done through
direct isolation and using trapping methods [Drenth và Sendall, 2004]. The artificial infection
through soil is followed the methodology of Drenth và Sendall (2004).
Methodology of identification of the mondo grass’s stem rot disease: using the molecular
technology which consists the following steps: (i) Prepartion of the pathogen sources [Drenth
và Sendall, 2004]; (ii) Isolation of DNA [Doyle và Doyle methodology (1987)]; (iii) PCR and
DNA sequencing analysis [Sambrook methodology (1983)]; (iv) Seeking the similar
sequences in Genbank database to identify the pathogen [Using the on-line sofware BLAST
in the NCBI].
Methodology for studying some biological characteristics of the pathogen: To study the
influence of temperature to the fungus growth: the temperature levels popular in the province
were set for the experiment: 14oC, 18oC, 22oC, 26oC, 30oC, 34oC. To study the influence of
the light condition to the fungus growth: continuously 12 hours in light and 12 hours in dark.
To study the influence of pH level to the fungus growth: the pH levels popular in the
provincial soil were set for the experiment: 5,0 - 5,5 - 6,0 - 6,5 - 7,0 - 7,5.
Methodology for the control measures of the mondo grass’s stem rot diease:
- To study the suppression efficacy of the anti-biotic fungus Trichoderma asperellum, vi
khuẩn Bacillus amyloliquefaciens and bacterial Streptomyces misionensis, Streptomyces
aureofaciens, on the growth of the pathogen fungus Pythium helicoides Drechsler in the
invitro condition: the diameter of the pathogen fungus was measured in the experiments.
- To study the control efficacy of chemical fungicides on the pathogen Pythium
helicoides Drechsler: the experiment consists of 5 formula: (i) Ridomil 72 MZ 0,2%; (ii)
Viben - C 50 BTN 0,2%; (iii) Aliette 80WP 0,1%; (iv) Copper - Zinc 85 WP 0,2%; (v)
8
Control: No chemical; Culture the fungus P. helicoides Drechsler in the PDA media and
observe the growth of the fungus. The fungicide efficacy is calculated by Abbott methodology.
- To study the efficacy of the fungicides in the fields: The trial consists of 6 formula: (i)
Spray Aliette 80 WP 0,2%; (ii) Spray Ridomil gold 68 WG 0,3%; (iii) Spray biological
fungicide Trichoderma asperellum; (iv) Spray biological fungicide Streptomyces
aureofaciens; (v) Spray biological fungicide Bacillus amyloliquefaciens; (vi) Control: spray
with water. The narrow trials were arranged by completed random blocks, each plot is 50 m2,
3 replications, the disease levels (%) were monitored before and after treatment (Plant
Protection Research Institute, 1999). The fungicide efficacy is calculated by Henderson-Tilton.
2.3.4. Study the weeds and some control measures of weeds in the intercropping systems
Assessment of the apprearance frequency and the damage level of weeds: To survey
the weeds one per two months. To select 5 cross-cutting points per each plantation, put the
wooden spare 100 x 100 cm and collect all the weeds within the square, bring to laboratory
for cleaning, classification and weigh. Classification of weeds by comparison with the
pictures or consultantion with the specialists. The weed with the apprearance frequency
below 20% is rated (+); from 20-50% is rated (++) and over 50% is rated (+++). The damage
level of weeds is considered by the weight of weeds (more weight resulted to more nutrient
competition with crops). The more weight of weeds, the higher damage levels to crops.
To study the suppression impact of the mondo grass root powder: The experiment
consists of 2 formula by the completed randomization block with 3 replications. The area of
each plot is 50 m2. The dry mondo grass’s root powder is diluted into water at the dose of
50g/m2 and sprayed evenly on all plots [Lin D., Tsuzuki và cộng sự (2003)], the control plot
was sprayed with water. The composition and weight of weeds are monitored at 60 days after
spraying (Plant Protection Research Institute, 1999).
To study the intercropping cultural practices of mondo grass in the pomelo plantations
for weed controlling and enhancing farmer income: The experiments for studying the
influence of mondo grass growing time, density and row distance in the intercropping
systems have been designed. The soil coverage level of mondo grass is measured by square
1m x 1m, which consists of 100 small dots 1cm x 1cm. The dot partly covered is calculated at
50% coverage (the land coverage measurement methodology in the forestry area).
2.3.8. Assessment of the economic, environment and plant protection aspects of the
intercropping systems of the mondo grass in pomelo and tea plantations
To study the economic efficiency of the intercropping systems through the profits
achieved by the mondo grass harvest. To assess the environment impact and plant protection
meaning through the reduction of herbicides and observing of the overall environment and
soil in the plantations.
2.4. Data analysis: The research data are analysed by the software of Excel, IRRISTAT 5.0.
9
CHAPTER 3
RESEARCH RESULTS AND DISCUSSION
3.1. Research pests and diseases in the system of mondo grass intercropped in the tea
plantations
3.1.1. Composition and damage level of mondo grass’s pests and diseases
The survey results of the mondo grass intercropped tea plantations in Ha Hoa district,
Phu Tho province showed that there are 4 mondo grass’s of stem rot (Pythium sp.), fired leaf
(Macrophoma sp.), stunt (not yet identified the cause) and dry leaf tip (not yet identified the
cause) and 3 pests of scale (Pseudaulacaspis cockerelli Cooley), small snail (Achatina fulica)
and leaf hopper (Caelifera sp.). Overall, the mondo grass has a few pests with low damage
level except the stem rot disease which can cause heavy yield losses if no prevention is taken
from the growing time.
3.1.2.Composition and damage level of tea pests and diseases in the intercropping systems
Through the surveys of the tea intercropped with mondo grass in Ha Hoa district, Phu
Tho province, there are 04 insect pests identified including green leafhopper (Empoasca
flavescens Fabr.), mosquito bug (Helopentis theivora Waterhouse), thrip (Physothrips
stiventris Bagn), red mite (Oligonychus coffeae Niet) and 04 diseases including blister blight
(Exobasidium vexans Masse), brown blight (Colletotrichum Camelliae Masse), grey blight
(Pestalossia theae Sawada), bud rot (Colletotrichum theae Petch). Initial assessment showed
that except the blister blight and grey blight have low damage level, other pests and diseases
have medium damage levels and could become epidemics.
3.1.3. Comparison of the mondo grass’s and tea pests and diseases in Phu Tho province
The comparison results showed that the tea’s pests and diseases are different from the
mondo grass’s ones. The observation in the plantations showed that the tea’s pests did not
cause damage to the mondo grass and vice versa, the mondo grass’s pests did not cause
damage to the tea plants in the intercropping system.
3.1.4. Comparison of the damage level of the tea’s major pests in the tea plantations with
and without intercropped mondo grass
The research results showed that the intercropping of mondo grass in the tea plantations
did not cause significant changes of the density of green leafhopper, thrip, red mite as well as
the damage level of mosquito bug. On the other hand, intercropping of mondo grass caused
lightly increase of brown blight and bud rot. The observation results showed that the tea’s
growth (height, shading size, leaf number) was similar between the mondo grass intercropped
tea plantations and the control (without intercropping). Generally, the mondo grass is not
eaten by green leafhopper, thrip, red mite and mosquito bug in the intercropping system.
10
3.2. Research pests and diseases in the system of mondo grass intercropped in the
pomelo plantations
3.2.1. Composition and damage level of the mondo grass’s pests and diseases
The research result showed that the composition of mondo grass’s pests and diseases in
the pomelo plantation was similar to that in the tea plantation. Among the pests and diseases
detected in the mondo grass, the stem rot disease has the medium damage level and could
become epidemic in the favorable weather. Supplementary surveys in the concentrated
mondo grass plantation areas showed that there was the difference in terms of disease levels,
of which, the highest disease level is 9,1%. The disease infection usually caused death of
newly planted mondo grass, which resulted to supplementary seedlings. The disease also
caused partly death of the grown up mondo grass which resulted to the losses of yields.
3.2.2. Composition and damage level of pomelo’s pests and diseases
The result showed that there are 7 pest species including citrus leafminer (Phyllocnistis
citriella Saintion), citrus long-horned beetle (Anoplophora chinensis), red mite (Panonychus
citri), black citrus aphid (Toxoptera aurantii), citrus mealybug (Planococcus citri), citrus tree
borer (Chelidonium argentatum Dalmann), weevils (Hypomeces squamosus Fabr) and 4
diseases of black rot (Xanthomonas campestris), brown rot (Phytophthora citriphora), citrus
scab (Elsinoe fawcettii), greasy spot (Mycosphaerella citri) identified in the pomelo gardens
intercropped with mondo grass. Some pests of citrus tree borer, red mite, black citrus aphid
had low apprearance frequency and caused non-significant damage. Citrus leafminer
appreared more frequently and caused significant damage to young pomelo leaves. Among
the dectected diseases, black rot was frequently found and caused significant damage to the
young pomelo leaves. The remaining citrus scab, brown rot, greasy spot were also found in
the young pomelo plantations in Phu Tho province but caused insignificant damage during
the survey time.
3.2.3. Comparison of the mondo grass’s and pomelo’s pests and diseases in Phu Tho
province
The comparison showed that the composition of pests and diseases of pomelo and
mondo grass is not similar. The observation revealed that the pomelo’s pests did not damage
mondo grass and vice versa, the mondo grass’s pests did not cause damages for pomelo
plants in the intercropping system.
3.2.4. Comparison of the damage level of the pomelo’s major pests in the pomelo garden
with and without intercropped mondo grass
The research result showed that the damage level caused by citrus leafminer and black
rot is not significantly different between pomelo gardens intercropped with and without
mondo grass. Therefore, it is concluded that mondo grass intercropping does not influence the
damage level of the citrus leafminer and black rot to the pomelo plants.
11
3.3. Research in mondo grass’s stem rot disease and control measures
3.3.1 The mondo grass’s stem rot disease’s symptoms
The initial symptom is the stains in young leaf, the junction between leaf and base.
Then, the leaf changes to yellow to dark color and the leaf base is rotten, gently pulling can
separate the upper leaves from the base. During the rainy season, the upper leaves are still
green but the leaf base was already rotten due to high atmosphere moisture. The disease
spreaded from young stem base down to the roots and caused the rotten roots and tubes.
When pulling the diseased plant, roots become black color and tubes totally rotten. The
disease is quickly developed and spreaded in the season between Winter and Spring as well
as in Autumn with the wet weather and rainny. The disease can kill young mondo grass and
caused yellow, rotten leaf and serious reduction of mondo grass yields.
3.3.2. The research in the pathogen isolation of mondo grass’s stem rot disease
Through analysis of the disease samples, the fungi of Fusarium sp. and Pythium sp.
were found in the disease stains. Isolation of pathogens and re-infection into the healthy
plants have been implemented in the laboratory of Plant Protection Research Institute. The
methodogy of using various trapping materials (apple, rose flower, pear, papaya) has been
tested to purify fungus source of Pythium sp. for re-infection and identification. The result
showed that the rose flower is the best trapping materials for purify the pathogen source
Pythium sp. from the disease samples with the isolation ratio at 76,2%.
3.3.3. The artificial infection of isolated pathogens from the mondo grass’s stem rot disease
samples
3.3.3.1. Direct infection to the mondo grass’s leaf base in the laboratory condition
With total 20 fungal sources of isolated Pythium sp., 08 fungal souces of various
morphology have been used for infection. The isolated fungal sources were cultured in the
PDA media and independently infected into the healthy mondo grass’s leaves. The results
have been shown in the table 3.14.
There are 4 pathogen sources of Pythium sp. caused the symptoms similar to the disease
symptoms in the field: after the incubation time from 24 – 32 hours, the infected leaf changed
to the brown color. The remaining pathogen sources did not cause the disease symptoms, of
which, one is Pythium sp. and 3 are Fusarium sp. Therefore, it is concluded that the pathogen
causing the mondo grass’s stem rot disease is the fungus Pythium sp. Although many
pathogen sources of the fungus Fusarium sp. were found in the collected samples, the
experiment result showed that this fungus is not the pathogen of the mondo grass’s stem rot
disease.
12
Table 3.14. Results of artificial infection into the mondo grass leaf (2011-2012)
TT
1
2
Souces of
Pythium sp.
MM 1
MM 2.1
Percentage
(%) of
infection
100
100
Time of
disease
appreared
(hours)
Percentage
(%) of reisolation
Symptoms
24
The leaf tissue changed
brown and the leaf base
rotten
100
28
The leaf tissue changed
brown and the leaf base
rotten
100
100
3
MM 2.2
100
32
The leaf tissue changed
brown and the leaf base
rotten
4
MM 3.2
0
0
0
0
5
MM 5.1
0
0
0
0
6
MM 6
0
0
0
0
7
MM 8
0
0
0
0
100
0
8
MM 26
100
20
The leaf tissue changed
brown and the leaf base
rotten
9
Control
0
0
0
3.3.3.2. Artificial infection of the mondo grass’s stem rot disease in the net house
The 8 pathogen sources have been used to artificially infect the mondo grass plants in
the net houses to confirm the determined pathogen. The result is shown in the table 3.15.
The research result showed that among the pathogens, the fungus Pythium sp. provided
the highest disease infection at 46,6%. The disease symptoms appreared 63 - 86 days after
artificial infection with the incubation time averaged at 77 days. The disease infected more in
the young plants. The symptoms are similar to that of the stem rot disease observed in the
fields of Ha Hoa district – the stem base changed brown then rotten, the young plants died
after disease become serious. The fungus sources of Fusarium sp. did not cause the disease
13
symptoms as that of the mondo grass’s stem rot disease in the fields. It is concluded that the
fungal Fusarium sp. is not the pathogen of the mondo grass’s stem rot disease.
Table 3.15. The artificial infection results of the isolated pathogen sources (Hanoi, 2011)
No
1
2
Pathogens
Disease
rate
(%)
Symptoms
46,6%
63 - 86
The stem base is rotten, gentl
pulling can separate the upper
stem from the base, the whole
stem and roots rotten when the
disease becomes serious.
0
0
Pythium sp.
Fusarium sp.
% of reisolated
samples
Incubation
time (days)
100
No disease symptom
0
To precisely identify which species of Pythium sp. caused the stem rot disease, the
molecular technology has been used to classify the pathogen.
3.3.4. Application of molecular technology in identification of the mondo grass’s stem rot
disease
3.3.4.1. PCR analysis:
All the pathogen sources were extracted DNN through PCR and sequencing analysis.
After fine-tunning, the 4 samples owned the DNA length from s. These sequences contained
the ITS 1 and ITS 2 needed for analysis. The result is shown in the table 3.16.
Table 3.16. The results of DNA analysis for the 4 pathogen sources of Pythium sp. isolated
from the mondo grass’s stem rot disease samples (Ha Noi, 2011)
No
Sample Sequence codes
1
MM1
2
MM2.1
3
MM2.2
4
MM26
1406ZAC000
1406ZAC001
1406ZAC002
1406ZAC003
1406ZAC004
1406ZAC005
1406ZAC006
1406ZAC007
Primer
Sequence
quality
ITS4
ITS5
ITS4
ITS5
ITS4
ITS5
ITS4
ITS5
Good
Average
Good
Average
Good
Average
Good
Average
Readable
sequences (bp)
623
689
689
641
14
3.2.4.2. Searching of the matched sequences from Gen Bank
The online software (Blast search) was used to search the matched sequences, using the
found sequences as the query. The result showed that the 4 pathogen sources are the fungus
Pythium helicoides Drechsler with the preciseness of 99 % overall the compared sequences.
The result shown in the table 3.17.
Table 3.17. The result of searching the matched sequences from the Genbank through the
online software Blast (2012)
No.
Sample
Results of searching from Genbank
Determined
species
Query code
Comparison
length (%)
Matching ratio
(%)
Pythium helicoides
HQ643383
100
99
02
MM2.1 Pythium helicoides
HQ643383
100
99
03
MM2.2 Pythium helicoides
HQ643383
100
99
04
MM26
HQ643383
100
99
01
MM1
Pythium helicoides
15
3.3.4.3. Classification structural analysis
Pythium helicoides-HQ643383
MachMon1
HQ643383
MachMon1
Pythium
helicoides-AY598665
MachMon2.1
AY598665
Pythium
helicoides -AB217659
MachMon2.1
1
MachMon2.2
AB217659
helicoides-AB108057 Pythium
MachMon2.2
100 Pythium
2
helicoid
MachMon26
AB108057
es
Pythium
helicoides-AB108057
MachMon26
Pythium helicoides-FJ348741
AB108057
Pythium helicoides-AB108032
FJ348741
56
Pythium helicoides-AB108051
AB108032
Pythium helicoides-AB1080345
AB108051
Pythium
helicoides-HQ643383
AB1080345
Pythium cinnamomi-GU191211
HQ643383
Pythium vexans-GU931701
GU191211
GU931701Pythium arrhenomanes-HQ643471
Pythium aphanidermatum-HQ643439
HQ643471
100
57
20
Pythium
HQ643439myriotylum-HQ643704
HQ643704
Diagram 3.12. Classification structural analysis based on the ITS of 4 fungal sources
Oomyces isolated from the disease mondo grass
3.3.5 Morphology of the fungus Pythium helicoides Drechsler
Observation of the fungus P. helicoides Drechsler through the microscopes showed that
the fungal spown has white color, spongy, no wall along the spown and the round sporages
developed on the top or middle of the fungal spowns.
3.3.6. Influence of some environment conditions to the growth and development of the
fungus Pythium helicoides Drechsler
The result showed that the fungus P. helicoides Drechsler can adapt with a large range
of pH from 5 to 8 and the various light conditions as well as the most suitable temperature
from 25 - 350C, which matched the weather conditions of Spring in Phu Tho province.
Therefore, the possibility of stem rot disease epidemic outbreak in the Spring is rather high
when widely growth of mondo grass in Phu Tho province.
16
3.3.7. Research the measures to control mondo grass’s stem rot disease
3.3.7.1-2. Result of experiment on the suppression efficacy of the biological pesticide
Trichoderma asperellum and anti-biotic bacteria to the fungus Pythium helicoides Drechsler
in the laboratory conditions:
The experiment resulted that the biological pesticide products
Trichoderma
asperellum and antibiotic bacteria Streptomyces misionensis, Streptomyces aureofacien,
Bacillus amyloliquefaciens brought the high efficacy in the suppression of the fungus P.
helicoides Drechsler at the high rate of 75%.
3.3.7.3. Field trials of some chemical fungicides to the fungus Pythium helicoides Drechsler
in the laboratory conditions:
The chemical fungicides such as Aliette 80WP 0,1%, Ridomil 72 MZ 0,2%, and Viben
- C 50 BTN 0,1% provided the controlling efficacy to the fungus P. helicoides Drechsler
more than 78%. The chemical Copper - Zinc 85 WP 2% brought the low controlling efficacy
of 31,9%. The result is presented in the table 3.23.
Table 3.23. The controlling efficacy of some chemical fungicides to the fungus Pythium
helicoides Drechsler (PPRI, Hanoi, 2012)
Diameter of colony
No
1 day
2 days
Controlling efficacy
(%)
Chemical fungicides
1
Ridomil 72 MZ 0,2%
0,0
0,0
100
2
Viben - C 50 BTN 0,2%
0,0
0,6
93,3
3
Aliette 80WP 0,1%
0,8
2,0
78,1
4
Copper - Zinc 85 WP 0,2%
3,6
6,1
31,9
5
Control (Water)
5,6
9,0
0
CV (%)
3,2
1,6
3.3.7.4. The trial results of controlling efficacy of some biological and chemical fungicides to
the mondo grass’s stem rot disease in the fields:
The trial result showed that the biological pesticide products of Streptomyces
aureofaciens, Bacillus amyloliquefaciens, Trichoderma asperellum delivered the medium
suppression efficacy as high as 63% and 69% after 3 months and 6 months relatively.
However, the biological fungicides do not deliver the satisfactory impacts in the cases of
epidemic outbreaks due to the slow action. The result is presented in the table 3.24.
17
Table 3.24. The controlling efficacy of some biological pesticides against the mondo
grass’s stem rot disease (Phu Tho, 2013)
No
Trial formula
1
Trichoderma asperellum
Streptomyces
aureofaciens
Bacillus
amyloliquefaciens
Controlc(water)
CV (%)
2
3
4
Before
treatment
Disease
ratio (%)
0,7
After treatment
3 months
6 months
Disease Efficacy Disease Efficacy
ratio (%)
(%)
ratio (%)
(%)
2,7
63,0
3,3
69,2
1,3
3,3
75,7
4,0
79,9
1,3
4,7
65,3
5,3
73,3
0,7
7,3
25,7
0
10,7
24,2
0
The chemical fungicides such as Ridomil gold 68 WG 0,3% and Aliette 80 WP 0,2%
brought the disease control efficacy more than 70% after 1 month. The controlling impact of
Aliette 80WP still remained in the fields after 2 months while the efficacy of Ridomil Gold
68WG reduced after 2 months since spraying. Overall, these 2 chemical fungicides delivered
the fair suppression impacts and quick action, which can be efficient in the cases of epidemic
outbreak. The trial results are presented in the table 3.25.
Table 3.25. The controlling efficacy of some chemical fungicides to the mondo grass’s
stem rot disease in the fields (Phu Tho, 2013)
Before
treatment
No
Trial formula
After treatment
1 month
Disease
ratio (%)
Disease
ratio (%)
Efficacy
(%)
2 months
Disease Efficacy
ratio (%)
(%)
1
Spray Aliette 80 WP 0,2%
4,8
5,7
70,3
5,7
73,6
2
Spray Ridomil gold 68 WG
0,3%
3,8
2,9
75,0
4,8
63,2
3
Control (water)
3,8
15,2
17,1
11,7
20,6
CV (%)
3.4. Some measures for controlling the weeds in the intercropping systems
3.4.1. The composition and popularity of the weeds in the intercropping system between
mondo grass and tea
18
The weed composition is very diversified in the tea plantations including many annual
and perenial weeds. After 3 years of studying the tea plantations grown in the feralit soil in
Ha Hoa district, the 15 weed species have been identified including Digitaria marginata
Link, Imperata cylindrica PB, Commedia nudiflora L., Zigodium scandans, Cyperus
rotundus L., Cyclosorus parasiticus, Ageratum conyzoides L., Paspalum conjugatum L.,
Cynodon dactylon Pers, Celtella asiatica Urs, Panicum repens L., Bellis perennis,
Eupatorium odoratum L., Oxalis cornicullata L., Lygodium sp., Centranthera
cochinchinensis L.. The most popular weeds are Commedia nudiflora L, Ageratum
conyzoides L, Bellis perennis, Centranthera cochinchinensis L; the popular weeds are
Cyperus rotundus L., Paspalum conjugatum L, Celtella asiatica Urs, Panicum repens L and
the less popular weeds are Imperata cylindrica PB, Digitaria marginata Link, Lygodium sp..
The weeds are well grown in the spring including Commedia nudiflora L, Cyperus rotundus
L., Bellis perennis, Panicum repens L. The perennial weeds well gorwn the whole year are
Imperata cylindrica PB, Lygodium sp., Paspalum conjugatum L.. The Ageratum conyzoides
L. grown strongly in the season of autumn-winter and the Centranthera cochinchinensis L.,
Bellis perennis died in the winter but germinated in the next spring. Therefore, in the tea
plantation always consists of many weed species with the various levels of growth and
damage.
3.4.2. The damage level of weeds in the tea plantations
The monitoring of the weed weight in the tea plantations showed that the weeds grown
faster than the young tea plants. After 2 months, the weed weight is 0,73 kg/ m2, the peak was
reached at 1,41 kg/m2 after 7months. The weeds strongly competed with the young tea plants
and become the environment for tea’s pests and dieseases. The comparison showed that after
7 months of intercropping, the tea plantations intercropped with the mondo grass always had
the weed weight lower than the tea plantations without mondo grass intercropping. When the
mondo grass grown up, the leaf shading had larger soil coverage, which compressed the weed
growth significantly, particularly the annual weeds such as cỏ cứt lợn, cỏ vừng và hoa cúc
dại. Therefore, the mondo grass intercropping reduced the weeds significantly in the
comparison with the non-intercropped tea plantations.
3.4.3. The composition and popularity of the weeds in the pomelo platations intercropped
with the mondo grass
The survey results showed that there are 24 weed species in the pomelo plantations
intercropped with the mondo grass including Digitaria marginata Link, Imperata cylindrica
PB), Commedia nudiflora L., Cyperus rotundus L., Ageratum conyzoides L., Paspalum
conjugatum L., Cynodon dactylon Pers, Celtella asiatica Urs, Panicum repens L., Bellis
perennis, Oxalis cornicullata L., Centranthera cochinchinensis L., Eclipta alba Hassk,
Zigodium scandans, Jussiaea repens, Tadehagi triquetrum L. Ohashi, Eleusine indica,
Lophatherum gracile Brongn, Eupatorium odoratum L., Achyranthes aspera L., Portulaca
oleracea L., Marsilea quaurifolia L., Scoparia dulcis Linn. Of which, 05 species of
- Xem thêm -
.PDF 
27 
183 
105 
