Nghiên cứu đặc điểm sinh học, sinh thái của tuyến trùng meloidogyne sp hại cà tím và biện pháp phòng trừ theo hướng quản lý tổng hợp tại lâm đồng tt tiếng anh

There have been several researches about root-knot nematodes parasitised on eggplant, however, very little has been conducted about distribution, as well as biological and ecological cha

MINSTRY OF EDUCATION

AND TRAINING

MINITRY OF AGRICULTURE AND

RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURE SCIENCES

-

TRAN THI MINH LOAN

BIOLOGICAL AND ECOLOGICAL CHARACTERISTICS

OF Meloidogyne sp PARASITISED ON EGGPLANT AND

CONTROL METHODS BY INTEGRATED NEMATODES

MANAGEMENT IN LAM DONG

Specialization: Crop Protection Code: 9620112

SUMMARY OF PH.D AGRICULTURAL THESIS

HA NOI, 2019

The work was completed at: Vietnam Academy of Agricultural Sciences

Supervisor: 1 Asscociate Professor Pham Thi Vuong

2 Asscociate Professor Nguyen Van Ket

Critic 1:

Critic 2:

Critic 3:

The dissertation will be protected before the Institute of Dissertation Boards meets at

(specify the thesis defense at the Institute level) date month year

Maybe find this thesis at:

1 Vietnam National Library

2 Library of Vietnam Academy of Agricultural Sciences

1

INTRODUCTION

1 Rationale

Eggplant is a fruit vegetable and is high nutrient and economical value, developed and expanded

in Vietnam as well as Lam Dong province Although, eggplant is planted and took care easily but, disadvantages of eggplant production are detected by many diseases such as green wilt, leaf spot,

Verticillium wilt and plant-parasitic nematodes

Root-knot nematodes (Meloidogyne spp.) are common pathogens parasitised on most plants

worldwide Among the nematodes discovered in Vietnam, root-knot nematodes is the most serious parasitism and thriving pest in recent years In Lam Dong, root-knot nematodes is one of the major pest parasitised on solanaceae, in generally and on eggplant, as a result, decreasing of quality and yield, increasing other diseases There have been several researches about root-knot nematodes parasitised on eggplant, however, very little has been conducted about distribution, as well as biological and ecological characteristics of root-knot nematodes on Solanaceae and eggplant in Lam Dong to control them For these reasons, we carried out the topic "Research on

biological and ecological characteristics of Meloidogyne sp parasitised on eggplant and methods

control by integrated nematodes management in Lam Dong" to (i) determine root-knot parasitised nematodes species composition on eggplant, (ii) study biological and ecological characteristics, and (iii) provide effective solutions for control root-knot nematodes toward integrated nematodes management in eggplant production in Lam Dong as well as in Vietnam

2 Research aims and objectives

Objectives: the objectives of the research are: (i) to identify species composition root-knot

nematodes parasitised on eggplant, (ii) to determine biological and ecological characteristics of M

incognita, and (iii) to provide proposing methods to prevent them toward integrated nematodes

management, contributing production of eggplant and solanaceace safety, effectively and sustainably

3 Significance

Theoretical significance: The thesis has supplemented new scientific data of species

composition of root-knot nematodes, biological and ecological characteristics, rules of

reproduction, development and parasiticide of M incognita On that basis, effective methods and

solutions to control root-knot nematodes, protecting the environment and contributing to safe production of eggplants safety in Lam Dong was proposed The thesis is a reference for agricultural students, researcher, teacher and sciences

Practical significance: Proposing methods to control root-knot nematodes effectively and

safely, contributing to improved process of the eggplant production toward integrated nematodes management for the purpose of stable, effective and sustainable production in Lam Dong as well

as in Vietnam, particularly, chemical pesticides are abused to control nematodes today This

thesis is also a document to help managers and farmers identifying symptoms of M incognita on

eggplant and decide effectively management solutions of root-knot nematodes

4 Subjects and scope of the research

4.1 Research subjects

The subject of study is root-knot nematodes (Meloidogyne sp.) parasitised on eggplant

4.2 Research scope

Thesis content: Identifying species composition of parasitic root-knot nematodes on

eggplant; Studying biological characteristics of M incognita detected on eggplant; Accessing

some of ecological conditions (soil type, organic fertilizers, rainfall, soil moisture, temperature

Location: Identifying species composition, affecting ecological conditions on root-knot

nematodes and open field experiments were conducted in three vegetable growing areas in Don Duong, Duc Trong and Da Lat in Lam Dong province Greenhouse experiments were conducted

in the Department of Agriculture and Forestry, Dalat University In vitro experiments including idetification of root-knot nematodes, extractation vermiform root-knot nematodes from soil and

root, lilfe cycle of M incognita were carried out in Plant Protection Laboratory, the Department

of Agriculture and Forestry, Dalat University and laboratories of Nematology Department, Institute for Agricultural and Fisheries Research (ILVO), Flanders, Belgium

5 Novel contributions of the thesis

This thesis makes contributions:

(i) To provide some new data of species composition of root-knot nematodes

(Meloidogyne spp.), biological and ecological characteristics of M incognita detected on

eggplant in Lam Dong province

(ii) To propose methods to control root-knot nematodes detected on eggplant in Lam Dong according to integrated nematodes management to decrease damage; to reduce using chemical pesticides; to complete the protocol of eggplant production following safety and organic cultivation in Lam Dong as well as in Vietnam

CHAPTER 1 LITERATURE REVIEW

1.1 Overview

Eggplant (Solanum melongena) is a fruit vegetable with high economic value In over the

world, there were about 1.6 million hectares growing eggplant In Vietnam, eggplant is grown in recent years and becomes popularly in many areas throughout the country In Lam Dong, eggplant was planted reaching about 1,944 ha, with an average yield of 47.6 tons/ha in 2017 Growing eggplant can bring high income but unstable, because eggplant is a susceptible

crop to many diseases, insects and nematodes, in which, Meloidogyne spp are an important group

of plant parasites reduced eggplant yield and quality Root-knot nematodes are the most important and common pest worldwide, causing economic damages of agricultural crops in tropical and subtropical areas Root-knot nematodes were reduced eggplant yield up to 95% (Di Vito, 1986)

There are many species of root-knot nematodes detected on eggplant, in which two species M

incognita, M javanica detected in South Asia, Nepal and India, three species M incognita, M arenaria and M javanica detected in Egypt

Until now, very few surveys have been conducted and evaluated the role of root-knot nematodes on crops in Vietnam, mainly focused on some industrial perennial plants Some survey reported the species composition of root-knot nematodes on vegetables in South of Vietnam and Lam Dong provine in the 1990s However, there is no report studying root-knot nematodes on eggplant

On over the world, there have been a number of studies involves the different ecological

conditions such as temperature, humidity, climatic factors affecting life cycle of M incognita on

eggplant as well as control methods However, in Vietnam, there are no research results of

1.2.1.1 Research history, distribution and damage thresholds of root knot nematodes in agriculture

Root-knot nematodes are obligate parasites which can be found in varieties of plants play

an important role in agriculture They caused serious economic losses in agriculture The earliest report of observation of plant parasitic nematodes was in the mid-18th century (1743) when Needham observed pests on wheat by microscope However, until the middle of the 19th century, root-knot nematodes had been identified morphological characterictics clearly

Typical symptoms of root-knot nematodes are many galls on the root system M incognita,

M javanica and M arenaria are the major of root-knot nematodes, in which, M incognita is the

most important plant parasitic nematodes Like other plant pathogens, root-knot nematodes cause estimated crop yield decline According to Taylor and Sasser (1978), for infected areas, without control methods, crop yield may be drop to 24.5% - 85.0%

1.2.1.2 Classification and identificationy root knot nematodes

Root-knot nematodes (Meloidogyne) belongs to kingdom Animalia, phylum Nematoda

Potts, 1932; class Chromadorea Inglis, 1983; order Rhabditida Chitwood 933; suborder

Tylenchida Thorne, 1949; family Meloidogynidae Skarbilovich, 1959; genus Meloidogyne Goldi,

1987 Initially, technique identification of root-knot nematodes is mainly based on morphological characteristics, describes perineal pattern characteristics of females and the length of second-stage juveniles However, at the end of the 20th century, root-knot nematodes is identified by isozyme analysis and molecular identification methods

1.2.1.3 Biological and ecological characteristics of root-knot nematodes

There are many stages growth and development of root-knot nematodes changing in different shapes which could be called sexual dimorphism Females are the pear-shaped, less moving into the root The first-stage juveniles (J1) are within the eggs The second-stage juveniles are worm shape, move in the soil After infecting roots, the second-stage juveniles (J2) develop into the third juveniles (J3) and the four juveniles (J4), then swollen to adult females or form males moving in the soil Usually, root-knot nematodes development depends on species, host and temperature In general, life cycle is 15 days to 70 days

Root-knot nematode are detected on different varieties of crop with the different ways The density of root-knot nematodes in soil depends on soil type and ecological climate conditions Species composition and nematode density in soil are related to 65% of rainfall and 58% of soil temperature Soil texture and structure also affects nematodes density Sandy are more favorable than clay The density of nematodes in soil is related to organic materials added to soil In general, growth, density and survival of root-knot nematodes depend on the host, ecological conditions such as temperature, soil moisture, organic content and soil texture

1.2.1.4 Methods control root-knot nematodes

Using control methods aims to limit harmful effects of nematodes on crop, stabilize yield

and quality, bring high economic efficiency There are 6 control methods of root-knot nematodes

to protect crops including: crop rotation, sanitation, resistant varieties, biological methods, physical methods and nematicide Integrated nematode management is studied and implemented

to efficiently control nematodes and reduce using nematicide

of M arenaria, M cynariensis, M graminicola, M incognita, M javanica, M exigua, M

cofeicola, M enterolobii, M hapla and M daklakensis which belonged to genus Meloidgyne,

family Heteroderidae, suborder Tylenchina and order Tylenchida Studies of investigating and classification of root-knot nematodes in Vietnam were mainly based on morphological methods

In 2005, identifying nematodes by molecular methods was first applied, but there was no results

of Meloidogyne identification In 2012, M graminicola and M incognita were identified by molecular methods In 2018, Trinh et al were identified new species called M daklakensis based

on morphological characteristics, genes and mitochondrial ADN-based identification

The study of root-knot nematodes was first published basing on biological characteristics of

M arenaria parasitised on rice, M incognita, relationship between M incognita, Rotylenchulus reniformis and Tylenchorhynchus brassicae and damage thresholds parasitised on tomato and

tobacco However, there are not any reports about biological and ecological characteristics of root-knot nematodes parasitised on eggplant

1.2.2.2 Methods control root-knot nematodes

In Vietnam, the first report method to control of root-knot nematode was in 1981, followed

by reports about control methods for root-knot nematodes on black pepper and vegetable grown

in Ha Noi Control methods of root-knot nematodes in Vietnam were also carried out basing on the most popular methods on crops such as rice, tobacco, coffee, black pepper, Chinese cabbage and salad Control methods include crop rotation, resistant varieties, physical methods, biological methods, chemical methods and integrated nematodes management However, there have been publishing methods to control root-knot nematode parasitised on eggplant in Vietnam as well as Lam Dong

CHAPTER 2 METHODOLOGY 2.1 Research time

Research period was from 2014 to 2017

2.2 Materials, equipments and instruments

Materials were eggplant variety of TN525 Green King; sandy clay (49% sand, 10% limon and 41% clay) and clay (32% sand, 1% limon, 67% clay) and river sandy (70% sand, 20 % limon and 10% clay); nylon bags and pots; organic amendments and Yara NPK fertilizer 15-15-15; chemicals for specimens; sampling tools, sieve and laboratory equipment

2.3 Research content

- Conducting to survey, collect samples, identify species composition, recognize symptoms,

to determine damage threshold and to observe density change of root-knot nematodes

(Meloidogyne spp.) in open field parasitised on eggplant in Lam Dong

- Studying biological and ecological characteristics of M incognita detected on eggplant in

Lam Dong

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- Studying methods to control root-knot nematodes (M incognita) following integrated

nematode management

- Building protocol of integrated nematodes management (M incognita) parasitised on

eggplant in Lam Dong

4.1.1.2 Investigation of the main nematodes parasitised on eggplant in the field

Samples were collected from 85 households On the field, an random area was chosen about 100m2 Surveying from 5 points according to diagonal rules was to determine main pest and diseases in open field based on typical symptoms on the stem, leaf, fruit of eggplant (Daunay, (2008); Srinivasan (2009)

2.4.1.3 Sampling

Soil and root samples were taken according to the W-pattern from 85 eggplant fields in Lam Dong Samples were stored in a thermostatic cabinet at a temperature of 15oC

2.4.1.4 Extraction root-knot nematodes from soil and root samples

Activity second-stage juveniles were extracted from soil and root by modification Baermann funel The sample was incubated in the funnel for 48 hours at room temperature Activity second-stage juveniles were counted by stereo-microcopes with 4X magnification

2.4.1.5 Determining the ratio of root damage and root gall-index

Root gall-index was assessed by the degree of infection from 1-10 according to Zeck (1971), Bridge and Page (1980)

Determining the incidence of root knot nematodes

Incidence of root knot nematodes(%) =𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑟𝑒𝑝𝑒𝑎𝑡 𝑓𝑖𝑒𝑙𝑑𝑠 𝑠𝑢𝑟𝑣𝑒𝑦𝑒𝑑

𝑇𝑜𝑡𝑎𝑙 𝑓𝑖𝑒𝑙𝑑 𝑠𝑢𝑟𝑣𝑒𝑦𝑒𝑑 100

Determining the frequency of species occurrence

Frequency of species occurrence(%) = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑖𝑚𝑒𝑠 𝑒𝑛𝑐𝑜𝑢𝑛𝑡𝑒𝑟𝑒𝑑 𝑠𝑢𝑟𝑣𝑒𝑦

𝑇𝑜𝑡𝑎𝑙 𝑜𝑓 𝑡𝑖𝑚𝑒𝑠 𝑠𝑢𝑟𝑣𝑒𝑦𝑒𝑑 100

Determining ratio of root infestation

Ratio of root infestation (%) = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑟𝑜𝑜𝑡 𝑖𝑛𝑓𝑒𝑐𝑡𝑒𝑑

𝑇𝑜𝑡𝑎𝑙 𝑜𝑓 𝑟𝑜𝑜𝑡 𝑠𝑢𝑟𝑣𝑒𝑦𝑒𝑑 100

2.4.1.6 Extraction with perineal pattern females

Females of Meloidogyne were dissected out from the root galls by using forceps under

compound microscope and transferred 20 females to 0,9% NaCl

2.4.1.6 Cut perineal patterns

Females were cut with a sharp knife and the body content was cleared away from the internal surface of the cuticle The cuticle of the posterior third of the body was trimmed down to

a small piece containing vulva, anus and tail tip Perineal patterns were sealed with a coverslip

by nail varnish

2.4.1.7 Making specimens

How to make temporary and long-term specimens was been according to Bezooijen (2006)

and Ravichandra (2010)

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2.4.1.8 Examinations of morphological features

Morphological features included the perineal pattern, stylet morphology, and distance from the base of the stylet knobs to the dorsal esophageal gland, length of second-stage juveniles, males, females by Bel-capture ruler

2.4.1.9 Identification root-knot nematodes by molecular

Root-knot nematodes were identified by molecular basing on primer of tropical root-knot

nematodes group

2.4.2 Biological and ecological characteristics of root-knot nematodes (M incognita) detected

on eggplant

2.4.2.1 Culturing and purifying species

Root-knot nematodes (M incognita) were cultured and purified on tomato roots in

B5-Gamborg semi-liquid media

2.4.2.2 Studying morphological and biological characteristics (life cycle, ratio of hatching of M incognita) in the laboratory

Morphology characteristics and development stages of M incognita were observed at

temperature about 24±1oC with 3 different soil moisture at 30 - 40%, 40 - 50%, 50 - 60% Roots were stained to describe morphology characteristics and development stages Roots were stained

by fuchsin acid Ratio of hatching was determined by counting the number of the second-stage juveniles formed on the total of hatching eggs in 3 different environments including distilled water; extracts of 1-month eggplant roots; 6-month eggplant roots

2.4.2.3 Studying ecological conditions affected to density of root knot nematodes

Preparing free-disease plants

Seeds are sterilized and sown on sterilized substrates in the greenhouse

Nematode inoculation in pots in the greenhouse

The second-stage juveniles of M incognita were extracted from tomato roots cultured in the laboratory Initial population of M incognita was inoculated about 2000 individuals/pot

Effect of soil moisture, rainfall, temperature on M incognita in the field

The experiment was conducted in the open field grown eggplant TN 252 Green King variety

in Suoi Thong B village, Da Ron communes, Don Duong district in Lam Dong provine Secondary data of temperature and rainfall during 2014-2017 was collected from meteorological stations of Thanh My, Don Duong and Da Lat Soil moisture is determined by weigh method The density of the second-stage juveniles was determined a 30-day period during three continuous

seasons to assess correlation between the density of the second-stage juveniles of M incognita

and rainfall, temperature and soil moisture

Effects of soil conditions (particle composition and organic content in soil) on density

of root-knot nematodes

Analysis of soil texture

Analysis of soil texture was deternined according to Bouyoucos (1962) and named based

on soil triangle Correlation of sand content and density of second-stage juveniles in the soil was assessed

Effect of different organic amendments on root- knot nematodes M incognita parasitised on eggplant

Experiments were carried out in the green house Meterials included organic amendments such as chicken manure, pig manure, goat manure, cow manure, commercial organic fertilizer and eggplant “TN252 Green King” Comparison between the 5 treatments with control was

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carried out, each repeated 3 times in clay pots Root-knot nematodes (M incognita) were

inoculated at 3 weeks planting Soil and root samples were taken from 6 planting pots and mixed

to collect mixture samples Experimental measures included density second-stages juveniles in soil and roots, ratio of root galls, number of galls, flowers, fruits and eggplant yield

Evaluation of eggplant varieties on root-knot nematodes

The experiment was carried out in pots, in sandy clay, including six eggplant varieties including Thailand No.1, TN252 Green King, F1-033 local, black fruit NV123, Runako and Com

Xanh, repeated 3 times Inovation second-stages juveniles of M incognita after 3 weeks planting

Soil and root samples were mixed from 6 pots to a mixture sample Experimental measures were density of the second-stages juveniles in soil and roots, root-gall index, number of flowers, fruits and ratio of fruiting

2.4.3 Control methods root-knot nematodes (Meloidogyne incognita) detected on eggplant following by integrated nematodes management in Lam Dong

These experiments was conducted using eggplant ‘TN 252 Green King’ in the open field in

Da Ron, Don Duong in Lam Dong The experiments were repeated 3 times Planting density was about 17,000 plants per hectare Care and irrigation were the same in all treatments Experimental measures included density of the second-stage juveniles in soil at the time of 30 days, 60 days,

90 days planting and the end of harvesting; density of the second-stages juveniles in roots; effective control of root-knot nematode calculated by Henderson - Tilton formula; ratio of root

infected, root gall index and eggplant yield

2.4.3.1 Cultivation methods to control root-knot nematodes

Experimental treatments included: (i) crop rotation between eggplant with tung ho, cabbage,

chili peppers, sweet corn, (ii) intercropped with the common bean Phaseolus vulgaris and

eggplant

2.4.3.2 Physical methods to control root-knot nematodes

Experimental treatments included: (i) soil solarization (after harvesting the previous crop, plowing and drying the soil for 4 weeks); (ii) Keep soil dried (after harvesting the previous crop, plowing, every 7 days upsetting soil, keep soil dry out and soil moisture lower than 35% in 4 weeks); (iii) Covered with dark plastic (after harvesting the previous crop, deep plowing at least 25cm, irrigating and covering by plastic for 4 weeks); (iv) Burning soil (after harvesting the previous crop for 2 weeks, plowing the soil, making rows, covering a thin layer of 5-7cm husk into the planting groove, then a layer of 5cm thick soil, burning anaerobic, irrigating to soil moisture after 48 hours); and (v) Control (after harvesting the previous crop, did not using any method in soil, keeping for 4 weeks, plowing soil and making row for ready to plant)

2.4.3.3 Biologicial methods to control root-knot nematodes

The experimental treatments included: Jianon Chitosan super (Chitosan); Vineem 1500 EC

(neem - azadirachtin); Abuna 15GR (saponin); Biosune one (Trichoderma harzianum,

Trichoderma viride and other microorganism) and control

2.4.3.4 Chemiscial methods to control root-knot nematodes

The experimental treatments included: Tervigo 020SC (Abamectin), Cazinon 10GR (Diazinon), Vifu-super 5GR (Carbosulfan), Map Logic 90WP (Clinoptilote) and control

2.4.4 Building a model of control root-knot nematodes (Meloidogyne incognita) according to integrated nematodes management detected on eggplant in Lam Dong

The previous crop was Tung Ho After harvesting, cleaning the fields, plowing and drying for 4 weeks, then making rows Cow manure putting down with an amount of 40m3/ha were

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incubated with 10 kg/ha probiotics containing T harzianum Irrigating and using plastic covered

on rows, keeping them for 7 days to allow fungi multiplied biomass rapidly, then planting after 7 days After 10 days planting, eggplant was putted down chicken manure with amount of using about 300kg/ha The area of the model was 500 m2 compared to farmers' handling

Evaluation of economic efficency of the model and control methods

Calculation of production costs included costs for fertilizers, pesticides and labor Calculating total income based on yield and price which was assumed about 2,000 VND per kilogram (price assumed if profit was the lowest), the efficient economic was calculated as following:

Total income (thousand VND) = selling price per kg x yield

Total costs = cost of seed + cost of labor + cost of fertilizer + cost of plant protection + cost

CHAPTER 3 RESEARCH RESULTS AND DISCUSSION 3.1 Cultivation methods and control nematode parasitited on eggplant of farmers in the studied area

3.1.1 Survey of traditional cultivation of eggplant farmer in the studied area

Cultivation and control methods root-knot namtodes detected on eggplant of farmers in the

studied area

Table 3.1&3.3 The area and yield of eggplant varieties were grown widely in open field

(Lam Dong, 4/2014-6/2017) Eggplant varieties Ratio

of grown (%)

Density (plants/ha)

Yield (tons/ha)

Infestation level (%)

Yield losses (%)

Season of the highest nematode populations

Oval fruit Japanese 11.76 25,000 36,60 48.00 20.41 Rainy season

F1-033 local variety 3.53 19,000 78.33 33.33 Trivial

losses

There was 7 varieties planted in Lam Dong, TN252 Green King was the most planted variety, accounting for 56.47% of the total, average yield was 92.72 tons/ha and density was 17,000 plants/ha, followed by the Runako variety accounted for 12.94% of total, average yield was 35.90 tons/ha, density was 25,000 plants/ha The lowest ratio belonged to Com xanh variety, just only 1.18% and the yield was just about 35.00 tons/ha

Only 34.11% farmers checked pest and disease status of nursery stock and only checked the surface parts such as fungal disease on leaves or stems If the nursery stock was not managed

Soil treatment and eggplant parasitic nematode control methods of farmer

Table 3.4 Treatment of soil by farmers in Lam Dong (4/2014-6/2017) Treatment methods Ratio application (%) Dose

All surveyed farmers used lime before planting to treat soil for controlling pathogens and some insects caused disease of eggplant, accounted for 100% for surveyed farmers Chemical methods were also commonly used, accounting for 62.35% Commercial chemicals were used such as Nokaph 10GR (30.82%), Map Logic 90WP (5.88%), Basudin 10% granular (8.0%) and Binhtox 1.8EC (17.64%) Up to 67.06% of surveyed farmers used physical methods such as fallow, did not plow, covering with dark nylon Only 5.88% of surveyed farmers used biological methods for controlling disease in soil About 11.76% of surveyed farmers did not use any treatment methods except liming According to farmers, chemical methods were the most

effective brought the highest profits

76.46% of surveyed farmers recognized symptoms of stunted plant, roots galls, low uptake nutrition, they changed the ways to provide fertilizer for eggplant by diluting fertilizer then irrigating directly to roots or spraying on the foliar instead of putting down into soil as before Only 5.88% of surveyed farmer using Tervigo 020SC sprayed on their roots to control root parasitic nematode

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Fertilizers used and feritilizer dosage used in eggplant cultivation

Table 3.6 Using fertilizer of eggplant farmers (Lam Dong, 4/2014-6/2017)

Type of

fertilizer

Ratio of use (%)

0.3 - 1.0 tons/ha

Every ten days Scattering around root

0.2 tons/ha

Every ten days Irrigating around root after 5

months planting Foliar

Scattering around root

Scattering around root and between rows

Survey results show that 100% of eggplant farmers used organic fertilizers and NPK, phosphate and potassium fertilizers However, fertilizer types and dosage were different Up to 94.11% of surveyed farmers used foliar and nitrogen fertilizers to put down for eggplant

3.1.2 Symptoms and the major eggplant pests and diseases in Lam Dong

Common eggplant diseases included green wilt, Verticillium wilt, anthracnose and mosaic

disease All diseases exposed symptoms on leaves, fruits, but none symptoms on roots and none galls

Eggplant insects included leaves and fruit insects and thrips palm These insects damage on leaves, stems and fruits of plants, but not detected in root system

There were seven genus nematodes infected eggplant root system including

Helicotylenchus, Tylenchus, Meloidogyne, Criconemella, Pratylenchus, Rotylenchulus and Longidorus In which, Helicotylenchus were encountered with 100% of eggplant fields Next,

genus of nematodes was Tylenchus, achieved 91.76%, following Meloidogyne with 83.52%

Longidorus was the least parasitic nematode only 2.35% The highest nematode density belonged

to Meloidogyne (667 individuals/50cm3 soil), followed by Helicotylenchus with 570

individuals/50cm3 soil Density of Rotylenchulus was the lowest with only 16 individuals/50cm3 This proved that root-knot nematodes played an important role for yield losses

Typical symptom of root-knot nematodes was the appearance of numerous galls on the roots With the serious damage, galls were enlarged, even forming large swollen on the main roots Symptoms of root-knot nematodes above-ground were differently recognized, especially when plants were young When eggplant was 3-4-month age, root gall index was approximately

6, symptoms were recognized by stunted, yellow leaves, small and fewer fruits Below-ground symptoms exposed in the period of about 6-8 months after planting This was the time that eggplant have been ready for harvest, growth and resistance of the plant were reduced, root system was old, less forming new roots and lower uptake nutrition

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3.1.3 D ensity of root -knot nematodes (Meloidogyne spp.) detected on eggplant in Lam Dong

Table 3.9 Second-juvenile stages density of Meloidogyne sp in soil and roots and infestation

level (Lam Dong, 4/2014-6/2017)

Density of second-juvenile stages Average of

year

Average in rainy season

Average in dry season Density of J2 in soil (individual/50cm3 in soil) 1455 1750 827 Density of J2 in roots (individual/5 g root) 728 939 331 Damage level according to farmer estimated (%) 4.04 5.13 2.85 Yield losses (%) 12.41 14.89 7.19 During the year, density of second-juvenile stages in soil was 1455 individuals/50cm3, in roots was 728 individuals/5g of roots In the dry season, nematodes density was lower than average of year, the density of the second-juvenile stages was just only 827 individuals/50cm3 in soil lower than 628 individuals/50cm3 in soil that of average year and 331 individuals/5 g roots

in roots lower than that of 397 individuals/5g in roots of average year

Figure 3.12 Correlation between damage thresholds and yield crop (Lam Dong, 4/2014-6/2017)

Damage level of root knot nematodes was higher, eggplant yield losses was more, they have been non-linear correlation according to the cubic equation (y = 0.02 + 3.09x-2.41x2 + 0, 49x3)

In eggplant field, if root gall index of root knot nematode was 1-3, the yield would be not reduced When symptoms of root-knot were recognized visibly on roots such as stunting, fertilizer was used much higher, flowers and fruits would be reduced, yield losses would be higher Meanwhile, eggplant roots were more than 60% of root galls, approximately 6 root-gall index, estimated yield losses up to 40 - 50%

Density of the second-stage juveniles of root-knot nematodes in soil ranged from 500 individuals/50cm3 to 1500 individuals/50cm3 in soil In the 71 surveyed samples, there were 6 soil samples with density of second-stage juveniles ranged of 2000 - 3000 individuals/50cm3, 4 soil samples with density higher than 3000 individuals/50cm3