MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES DOAN THI LUONG THE BIOLOGICAL AND ECOLOGICAL CHARACTERISTICS
Trang 1MINISTRY OF EDUCATION
AND TRAINING
MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
DOAN THI LUONG
THE BIOLOGICAL AND ECOLOGICAL
CHARACTERISTICS AND CONTROL MEASURES OF
PSEUDO-MEALYBUG
Paracoccus marginatus Williams and Granara de Willink
(Homoptera: Pseudococidae) CAUSING DAMAGE ON PAPAYA IN HANOI
Specialization : Plant protection Code : 9 62 01 12
HA NOI - 2019
Trang 2SUMMARY OF AGRICULTURE PhD THESIS
This thesis was completed at Vietnam
Academy of Agricultural Sciences
Scientific Supervisors: Prof Dr Nguyen Hong Son
Reviewer 1:
Reviewer 2:
Reviewer 3:
The thesis will be defended at the Academy-level thesis examination
Council of Vietnam Academy of Agricultural Sciences
At o’clock day month year 201
The copy of this thesis will be found at:
1 National Library of Viet Nam
2 Library of Vietnam Academy of Agricultural Sciences
3 Library of Plant Protection Research Institute
LIST OF THESIS-RELATED PUBLICATIONS
1 Doan Thi Luong, Pham Van Lam, Le Thi Tuyet Nhung, Truong
Thi Huong Lan, “Result of identification of The Mealybug , Pseudococcidae (Homoptera) infesting Papaya around the
suburb of hanoi”, Journal of Plant Protection (6)/2018,
pages 10-14
2 Doan Thi Luong, Le Thi Tuyet Nhung, Nguyen Hong Son, Pham Van
Lam, “Bio-ecological Characteristics of the Papaya Mealybug,
Paracoccus marginatus Williams and Granara de Willink
(Homoptera: Pseudococcidae) under Laboratory Conditions”,
Journal of Plant Protection (6)/2018, pages 3-10
3 Doan Thi Luong, Khuat Thi Phuong, Ho Thi Thu Giang, Nguyen
Hong Sơn, Nguyen Van Liem, “Population dynamic of
Paracoccus marginatus Williams and Granara de Willink
(Homoptera: Pseudococcidae) on papaya in bub-urban of
Hanoi ”, Journal of Agriculture and Rural development
(354+355)/ 2019, pages 310-319
Trang 3intercropped with maize was lower than that on monoculture papaya
(19.1 individuals/leaf and 1.32 individuals/fruit compared with 51.3
individuals/leaf and 5.4 individuals/fruit) P marginatus on
monoculture papaya appeared earlier with density (256.5
individuals/leaf and 4.7 individuals/fruit) always higher than in
papaya rotated with sweet potato (72.1 individuals/leaf and 2.2
individuals/fruit)
1.5 Such cultivation techniques as rotation planting, intercropping
and high pressure watering on the leaves all have the effect of
limiting density of P marginatus The use of lower toxic chemicals
liked Spirotetramat and Pymetrozine (registered for mealybug on
fruit trees) is highly effective in the field (86.42% and 83.8%,
respectively) Rotenone, Abamectin and Petroleum spray oil
(registered to control mealybugs on fruit trees) which can provide
72% control of P marginatus in the field condition, can be used
alternately with Spirotetramate and Pymetrozine for substitution of
chemical pesticides of toxic group 2 that farmers are using commonly
on papaya nowadays but not legally allowed to be used on fruit trees
Spraying pesticides at 1st and 2nd instar nymphs of P marginatus with
a minimum amount of water of 1000 liters/ha and spraying with
pressure compressing pump will bring optimal control
II Recommendations
Control of P marginatus is real difficulty, so it is advised to
apply integrated measures as recommended in conclusion 1.4 and
the proper technique of pesticide use in conclusion 1.5 of this thesis
for ensure of effectiveness Especially for centralised planting
areas, it is advisable to apply appropriate rotation system with crops
that are not the favorable hosts for P marginatus such as corn,
vegetables and beans to reduce accumulation of pseudo-mealybug
INTRODUCTION
1 Reasonale
Papaya is often attacked and damaged by mealybugs, white fly, small spiders, fruit flies, especially damaged by mealybugs Even though, there have been no in-depth studies on insect pests on papaya
as well as on mealybugs on papaya in Vietnam up to date
A comprehensive understanding of the species composition, biological and ecological characteristics of papaya mealybug will
be the scientific basis to propose measures to manage them effectively and environmentally This thesis will focus the research on "Biological, ecological characteristics and control
measures to control mealybug Paracoccus marginatus Williams
and Granara de Willink (Homoptera: Pseudococidae) damaging papaya in Hanoi"
2 Objective of the research
The the reserach aims to determine species composition of
mealybugs, biological and ecological characteristics of P marginatus damaging papaya and the effective measures to control of P
marginatus, hence, building and proposing protocol to manage P marginatus effectively, economicaly and environmentally in some
papaya growing areas in Hanoi
3 Scientific and practical significance
3.1 Scientific significance
The thesis provided scientific data on species composition of mealybugs on papaya in Hanoi; providing basic biological and
ecological characteristics of P marginatus and the effective control
measures to that insect in papaya growing areas of Hanoi
3.2 Practical significance
The research findings of the thesis are the scientific basis to develop an effective and environment sound protocol for control of
P marginatus
4 New research findings
- It is the first time recorded Paracoccus marginatus Williams
and Granara de Willink (Homoptera: Pseudococcidae) damaging
Trang 4papaya in Vietnam
- Providing new scientific data on biological and ecological
characteristics, especially data on life table, population dynamic of
Paracoccus marginatus in Hanoi, hence updating systematically
scientific data on Paracoccus marginatus on papaya in Hanoi
- Providing scientific data on the effectiveness of feasible
measures including cultivation, mechanical and chemical measures
for effectively and environmentally control of Paracoccus
marginatus on papaya in Hanoi
5 The thesis structure
The thesis is structured in 151 pages, including introduction,
content (3 chapters), conclusions and recommendations with 28
tables of data and 26 figure Reference is made from 107 documents,
including 36 Vietnamese and 71 English documents
CONCLUSIONS AND RECOMMENDATIONS
I Conclusions
1.1 It is the first time recorded P marginatus Williams and
Granara de Willink (Homoptera: Pseudococcidae) damaging papaya
in Hanoi At least 13 plant species belonging to 11 botanical families
in the agricultural ecosystem in the suburbs of Hanoi were recorded
as food plants of P marginatus
1.2 Under stable conditions (25°C and 30°C, 80% RH, and a
photoperiod of 16L:8D) and Taiwan's papaya leaves using as food,
the female of P marginatus has the style of hemimetamorphosis and
the male has hypermorphosis Life cycle is 25.56-30.31 days Female
of P marginatus can reproduce parthenogenetically (although there
are 61.0-61.1% of males in the population) Fecundity is 233.53-462.2 eggs/female Females can live from 14.42 to 21.15 days and male adults can only live from 1.77 to 1.88 days
1.3 At a temperature of 25°C, net reproductive rate (Ro), the intrinsic rate of increase (Rm), the finite rate of increase (λ), mean generation time (Tc) ) and the doubling time (DT), respectively, reached 457,87 ♀/♀, 0.188 ♀/♀/day, 1.19 times, 34.71 days and 3.93 days At 30°C, depending on each parameter, its value can be increased or decreased compared to at 25°C and reached 367,79 ♀/♀, 0,197 ♀/♀/day, 1.22 times, 28.17 days and 3.52 days, respectively There are 11 generations/year in green house
1.4 The density of P marginatus on Hong Phi papaya variety
(the highest density is 255.0-256.5 individuals/leaf and 6.5-7.3 individuals/fruit) is significantly higher than that on dwarf variety (28.2 individuals/leaf and 0.48-0.52 individuals/fruit) The density on 1–year-old papaya (255.0 -256.5 individuals/leaf and 6.5-7.3 individuals/fruit) is higher than that on 2–year-old papaya (53.1-53.8 individuals/leaves and 14,2-14,5 individuals/fruit) The density on intercropped papaya is higher than that on monocultured papaya (83.5 individuals/leaf and 13.2 individuals/fruit compared to 53.1 individuals/leaf and 4.26 individuals/fruit) The density on papaya
Trang 5pesticides including Spirotetramate, Abamectin, Petroleum spray oil
and Pymetrozine with various sprayers such as hand compressing
sparyer, hand pre-compressed sprayer and motor compressed sprayer
The result showed that when spraying with the conventional hand
compressing sprayer the efficacy of insecticides decreased
significantly compared to that when sprayed by pre-compressed
sprayer (49.70 - 62.87% compared to 68.88 - 81.98%) When
spraying by motor sprayer, the pesticide efficacy was not improved
even decreased compared to spraying with hand compressing sprayer
and pre-compressed sprayer
Chapter 1 LITERATURE REVIEW AND SCIENTIFIC BACKGROUND
OF THESIS 1.1 Scientific background
The diversity of ecological and farming system (intensive, intercropping, rotation, varieties and farming techniques) has a very complex impact on insect community on papaya, including mealybugs Therefore, the determination of mealybug composition, biological and ecological characteristics, population
dynamic and control measures against P marginatus are an
important scientific basis to develop effective control measures of this most common and important insect pest in Vietnam
1.2 Oversea research findings on Paracoccus marginatus 1.2.1 Research on classification, distribution and damage of Paracoccus marginatus
1.2.1.1 Classification of P marginatus
According to Williams and Granara, papaya mealybug P
marginatus belongs to the Kingdom Animalia, Phylum Arthropoda,
Class Insecta, Subclass Pterygota, Order Homoptera, Suborder Sternorrhyncha, Superfamily Coccoidea, Family Pseudococcidae,
Genus Paracoccus, Species P marginatus Williams and Granara de
Willink
1.2.1.2 Origin, distribution and invasion of the papaya mealybug Paracoccus marginatus
Papaya mealybug, P marginatus native to Mexico, Central
America and distributed in tropical Americas, began to invade out of the natural distribution area since 1992 and quickly became an invasive alien species in many islands in the Caribbean, Central America and South America Up to now, it has been recorded in 5 biogeological regions of the world: neotropical, nearctic, oceania/ Australia, oriental/Indo-Mala and Afrotropical (Ben-Dov, 2012; Heu
et al., 2007; Meyerdirk et al , 2004; Miller et al., 1999; Muniappan
et al., 2006, 2008)
Trang 61.2.2 Study on morphological characteristics of Paracoccus
marginatus
Morphological characteristics of adult, egg and nymph of P
marginatus were described in Al-Helal et al (2012), Mani
Chellappan et al (2013b), Miller et al (1999), Sharma et al (2013),
Tanwar et al (2010), Walker et al (2003), Wu et al (2014),
1.2.3 Study on biological and ecological characteristics of
Paracoccus marginatus
Details of the biology and ecology of P marginatus can be
found in the literature of Amarasekare et al (2008a, 2008b),
Hintenou et al (2015), Mani Chellappan et al (2013b), Thangamalar
et al (2010) and Walker et al (2006)
1.2.4 Research on control of Paracoccus marginatus
Control of P marginatus by integrated pest management
measures including phytosanitary, cultivation and manual,
bio-control with using botanical and chemical pesticides (Banu et al.,
2010; Galanihe et al., 2010; Krishnan et al., 2016; Mani et al., 2012;
Muniappan, 2014; Saengyot amd Burikam, 2011; Seni and
Chongtham, 2013; Sharma et al., 2013; Tanwar et al., 2010;…)
1.3 Research on Paracoccus marginatus on papaya in Vietnam
1.3.1 Detection of Paracoccus marginatus in Vietnam
P marginatus was firstly recorded in Vietnam on cassava (Le
Thi Tuyet Nhung et al., 2014, 2015) So far there has been no
publication regarding this species on papaya
1.3.2 Morphological characteristics of Paracoccus marginatus
Research results on the species composition of mealybugs
(Pseudococcidae) were published by Nguyen Thi Chat (2008),
Nguyen Thi Chat et al (2005), Pham Van Lam (2013), Le Thi Tuyet
Nhung et al (2018),… but very limitation of their morphological
characteristics were described
1.3.3 Biological and ecological characteristics of Paracoccus
marginatus
So far, there have been no research on biological and ecological
characteristics of P marginatus in Vietnam
3.4.2.2 Effect of pesticides to control P marginatus on the field
It was shown from small scale trials that, athough the efficacy to
control P marginatus by pesticides was significantly lower than that in
the Lab Test, all chemicals provided high and stable efficacy (from 80.27% to 87.32%) after 7 days of spraying Of which, Cypermethrin + Chlorpyrifos Ethyl brought the highest efficacy of 87.32%, followed by Carbosulfan (86.5%) Both low toxic pesticides Spirotetramat and Pymetrozine showed high potency, respectively 86.42% and 83.8% Biological and botanical pesticides also showed a high potency from 66.83% to 78.01%, of them, Abamectin achieved the highest effect 78.01%, then Petroleum spray oil and Rotenone achieved 72.8% and 72.57%, respectively, at 7 days after spraying
Observation from large scale experiments conducted with 05 pesticides including: 2 low-toxic chemicals selected from common registered pesticides to control mealybugs on fruit trees and 03 bio and botanical pesticides also indicated that at 10 days after spraying, the effectiveness of Spirotetramate reached the highest of 84.79% Biological and botanical pesticides have good and prolonged efficacy (67.95% - 76.96%)
3.4.2.3 Efficacy of pesticides against different developmental stages
of Paracoccus marginatus
Experiments to determine the efficacy of Spirotetramat and
Pymetrozine to control P marginatus at different instar indicated that
both insecticides are highly effective for control 1st and 2nd instar
nymph of Paracoccus marginatus at 7 days after spraying The
efficacy is gradually reduced when apply against 3nd instar
3.4.2.4 Efficacy of pesticides applied with different water volume to control Paracoccus marginatus
The efficacy pesticides to control P marginatus after 7 days of
spraying was highest when spraying at 1000 liters/ha compared to
600 and 800 liters/ha
3.4.2.5 Efficacy of pesticides applied with different sparyers to control Paracoccus marginatus
Experiments were conducted to investigate efficacy of 4
Trang 7marginatus is significantly decreased compared to density in plot
washing at by compressor spraye rat 1000lit/ha in 1 day only
Therefore, this method can be applied to manage P marginatus when
the density is low
3.4.2 Chemical application
The use of pesticides is a last measure when efforts to apply
other measures are not likely to prevent the outbreak of P
marginatus According to the list of pesticides allowed to be used in
Vietnam, issued together with the Ministry of Agriculture and Rural
Development’s Circular No 03/2018 / TT-BNNPTNT dated
February 9, 2018, there are currently no pesticides registered to use
for control of P marginatus on papaya Meanwhile, in production,
farmers have to choose different types of mealybug on other crops,
including chemical pesticides belong to toxic group 2 that are not
allowed using to control mealybugs in fruit trees This research has
focused on assessment of 14 pesticides, including 8 chemical
activities (including 6 active ingredients are commonly used by
farmers in papaya growing areas and 2 low-toxic active ingredients
selected from common registered pesticides to control mealybugs on
fruit trees such as Spirotetramat; Pymetrozine), and 6 bio- and
botanical pesticides selected from popular registration pesticides to
control mealybugs on fruit trees
3.4.2.1 Effect of pesticides to control P marginatus in laboratories
- For chemical pesticides: all tested chemicals brough 86-100%
efficacy to control P marginatus, the highest is Carbosulfan (100%),
followed by Pyridaben+Abamectin (97.33%) Two commonly
registered low-toxic chemical pesticides can control 97.33% and
94.67% P marginatus
- For bio- and botanical pesticides: Observations indicated that
after 3 days of spraying, the pesticides brough a relatively high
efficacy of to control P marginatus (70.67% - 81.33%) Among the
experiment, two pesticides provided high efficacy over 80%
(Abametin and Petroleum spray oil)
1.3.4 Control of Paracoccus marginatus on papaya
To date, no researchs on control of P marginatus has been
conducted in Vietnam
CHAPTER 2 MATERIALS, CONTENTS AND METHODS OF THE STUDY 2.1 Location and time of study
- Laboratory, green house of Plant Protection Research Institute
- Papaya growing areas in 03 communies of Hanoi: Phung Thuong commune (Phuc Tho district), Dan Phuong commune (Dan Phuong district), Di Nau commune (Thach That district)
- Research period: 2015 - 2018
2.2 Research content
- Surveying papaya insect pests and determining the main pests of papaya in Hanoi
- Determining biological and ecological characteristics of papaya
mealybug P marginatus in laboratory
- Study on population dynamic and factors affecting the population
density of P marginatus on papaya in the study area
- Research on IPM measures of P marginatus on papaya
2.3 Materials and tools for research Materials
The source of P marginatus used in the study was collected from
papaya orchards in Hanoi
The Hong Phi - Taiwanese papaya variety was used to feed P
marginatus in lab experiments
Two varieties (Hong Phi papaya – Taiwan and high yielding dwarf papaya –Thailand) were used in field study
Tools and equipments
Stereo microscope: Carl Zeizz Stemi 2000-C and microscope: Carl Zeizz Promostar with a maximum magnification of 1000 times
Air - controlled insect rearing chamber: DAEYANGETS model GC-101B (RGX-400E brand) with temperature, humidity and light control system Other
Trang 8laboratory equipment: insect-proof plastic boxs, petri boxes, tubes, insect needles,
lame, lamen, plastic pots, insect netting cages, green houses, quills, blotting paper,
sample containing jars, nylon bags,
Chemicals
96% alcohol, KOH, H2SO4, alcohol acid, clove oil, canola glue, some
pesticides to control mealybugs, etc
2.4 Research methodology
2.4.1 Method of surveillence the species composition of papaya
pests and determining the main pests of papaya in Hanoi
2.4.1.1 Method to survey pests on papaya
Following the survey method of the Plant Protection Research
Institute (1997) and the National Technical Regulation on methods
of survey and detection of plant pests QCVN 01- 38: 2010/
BNNPTNT The interval between two surveys is 14 days on a
fixed day of the month
2.4.1.2 Method to identify of papaya pests
Follow the method of Watson (2007), and identify their
scientific name according to keys of Williams and Willink (1992),
Williams and Watson (1988, 1990) Lame specimens after
identification have been to verify by Dr Natalia von Ellenrieder
(from the Center for Pest Control in California Department of
Agriculture and Food) The scientific name of other pests collected
on papaya were determined by viẹtnamese taxonomists
2.4.2 Method of studying morphological, biological and ecological
characteristics of papaya mealybug P marginatus in laboratory
2.4.2.1 Study on morphological characteristics
Observing 30 individuals with a hand-held and stereoscope
microscope for the egg/egg sac and the length, width of the egg
(mm), egg color, body length and width, number of beard burns
2.4.2.2 Research on biology and ecology characteristics
Following the method of Amarasekare et al (2008a) with
improvements to suit the experimental conditions P marginatus
were individualy raised in air - controlled chamber (model
RGX-400E) at 25ºC, 30ºC, 80% RH and photoperiod of 16L:8D Observing
3.3.4 Effect of rotation on the density of P marginatus on papaya
In Thach That, farmers usually grow monoculture papaya or 1 year old papaya rotated with potatoes, chilli, vegetables, etc
Observation showed that in monoculture gardens, P marginatus
began to appear on leaves from 5 March 2017 with a low density, an average of 0.8 individuals/leaf Then increased, especially increasing rapidly from mid-April and peaking first time from 29 June 2017 to 6 July 2017 (with 39.3 - 39.8 individuals/leaf, 4.8 - 6.3 individuals/fruit) and second time at 19 October 2017 (with 256.5
individuals/leaf, 4.7 individuals/fruit) When rotation with potato, P
marginatus started to appear on papaya leaves later with lower
density (0.30 individuals/leaf) and then increased rapidly from the end of April and the get the first peak from 29 June 2017 to 6 July
2017 (with 21.3 - 22.5 individuals/leaf, 2.9 - 3.5 individuals/fruit) and second pick at 19 October 2017 (with 72.1 individuals/leaf, 2.2 individuals/fruit)
3.4 IPM measures of Paracoccus marginatus damage on papaya 3.4.1 Cultivation measures
3.4.1.1 Using tolerant varieties
The surveillence indicated that density of P marginatus on the
high yielding dwarf variety is significantly lower than that on Hong Phi variety So that, using dwarf papaya variety is advised to limit the
density and damage of P marginatus, hence limitation use of pesticides
3.4.1.2 Intercropping
It was also found from population dynamic study that when
intercropping with maize, the density of P marginatus was much lower than that of monoculture gardens, while the density of P
marginatus in intercropping with bananas was higher than that of
monoculture papaya Thus, to limit the damage of P marginatus,
farmers should not be recommended to intercrop bananas in papaya garden as it has been practicing in some localities
3.4.1.3 Watering on the leaves with a high pressure pump
When washing the leaves with water at 2000 or 3000 liters/ha
by high pressure pump during 2 consecutive days, the density of P
Trang 93.3.2 Population dynamic of Paracoccus marginatus on papaya at
different ages
The regular observation on 1-year-old papaya indicated P
marginatus appears on leaves from early March and on fruits from
early May, forming two peaks of density in late June to early July
and mid-October Where as, P marginatus occures year-round on
2-year-old papaya, but only forming two peaks (in late June and
mid-October to early November) on the leaf The density at the first peak
is many times higher than that at the second peak The density of P
marginatus in the one-year-old papaya garden is always higher than
that on the two-year-old papaya
3.3.3 Population dynamic of Paracoccus marginatus in
monoculture and intercropped gardens
When intercropping with banana in Phuc Tho district, the P
marginatus population is low during January to March but higher
than that in the monoculture garden of papaya (from January to
May) Then the density began to increase from the beginning of April
(earlier than monoculture garden) and formed two peaks on June 29,
2017 (with 49.1 individuals/leaf, 6.22 individuals/fruit) and on 9
Nov 2017 (with 83.4 individuals/leaf, 13.2 individuals/fruit),
markedly higher than density in the monoculture garden (peaked on
29 June 2017 at 16.2 individuals/leaf, 1.6 individuals/fruit, and on 2
Nov 2017 at 53.1 individuals/leaf, 4.26 individuals/fruit)
When applying maize intercropped in papaya garden at Thach
That, P marginatus population during the period from January to
mid-May was low, averaging of 2.2 - 5.5 individuals/leaf, 0.1 - 1.3
individuals/fruit After that, the density began to increase, forming
two peaks: pick 1 from June 22 to June 29 2017 (with 8.7 - 9.5
individuals/leaf, 0.8 - 1.96 individuals/fruit), and pick 2 at November
9 2017 (with 19.1 individuals/leaf, 1.32 individuals/fruit),
significantly lower than the density in monoculture orchard (peak 1
from June 22 to 29 2017 at 16.1 - 16.2 individuals/leaf, 8.7 - 9.5
individuals/fruit, and peak 2 on November 2 2017 at 51.3
individuals/leaf, 5.4 individuals/fruit)
the life cycle; population development criteria such as net reproductive rate (Ro), the intrinsic rate of increase (Rm), the finite rate
of increase (λ), mean generation time (Tc) and doubling time (DT),
and adjusted with formular of Birch (1948) and Kakde et al (2014)
2.4.3 Method of studying on population dynamic and factors affecting the population densities of Paracoccus marginatus
Carried out on two papaya varieties: Hong Phi (Taiwan) and high yielding dwarf (Thailan) at various conditions suchs as: plant age (1 year and 2 years old); planting mode (monoculture, intercroping and rotating with potato) Observation was followed survey method of Plant Protection Research Institute (1997)
2.4.4 Method for research on IPM measures of Paracoccus marginatus on papaya
2.4.4.1 Research on cultivation measures
The research was conducted with 3 control measures including (i) using resistant papaya varieties (Hong Phi and high yielding dwarf papaya); (ii) intercropping with bananas and maize and (iii) rotating with potatoes The effectiveness of eah control measure was based on
the survey of P Marginatus population dynamic on the field as
described in section 2.4.3
2.4.4.2 Research methods on effective of manual measures
Proceed with a high-pressure watering technique to wash away
P marginatus on papaya leaves through large scale experiment on
the field, no replicates and 300 m2/plot The experiment was conducted in Di Nau (Thach That, Ha Noi) on 2 years old papaya orchard Treatments included different watering regimes with 3 categories: (i) volumes of 1000, 2000 and 3000 liters/ha; (ii) two sprayers: high-pressure nozzles and compressors sprayer; and (iii) one time watering and 2 times within 2 days, and non-watering as checking plot Water was sprayed evenly on the under and upper surfaces of the leaves at 15.00-18.00 pm
Surveying the density of mealybugs before and after watering 7 days Adjusting the efficacy by the Henderson-Tilton formula
Trang 102.4.4.3 Research methods on pesticides use
The study was conducted with the following contents
- Surveying the efficacy of pesticides currently used by farmers
and alternative bio & botanical pesticides to control P marginatus
through Lab tests and small/large scale experiments on the field
- Determining effective techniques to use pesticides such as suitable
dosage, application timing, water volume and spraying tools
Adjusting the efficacy by the Abbot formula for Lab tests and
Henderson-Tilton formula for field trials
2.5 Data statistix methods
Field data were statistixed with Excel and statistical Window
software
CHAPTER 3 FINDINGS AND DISCUSSION 3.1 Species composition of papaya pests and main pests damaged
papaya in Ha Noi
3.1.1 Species composition of insect and mite pests damaging papaya
Have been 8 species belonging to 8 different families of 6 insect
and mite orders collected and identified, similar to the number of insects/
mites found on the papaya in Vietnam until 2013 (Pham Van Lam,
2013) However, the majority of insect species (6 species) in this study
did not coincide with those recorded on papaya before 2013
3.1.2 Identifying the scientific names of pests collected on papaya
It was showed by using the taxonomy keys of Williams (2004),
Williams and Watson (1988) that the characteristics of the mealybug
species collected on papaya in Hanoi belonging to genus of Paracoccus
Ezzat & Mc Connell Folloing the identification key of Williams and
Willink (1992), the mophology characteristics observed on Lam
sampled, are coincided with characteristics of P marginatus Williams
and Granara de Willink species (Figure 3.1) After identification,
specimen of mealybug species was sent to the Pest Identification Center
of the California Department of Agriculture and Food for
re-3.3 The population dynamic and factors affecting the density of
Paracoccus marginatus on papaya in the study area 3.3.1 Population dynamic of Paracoccus marginatus on papaya
The survey showed that on high yielding dwarf papaya variety,
the density of P marginatus was always much lower and more stable than that in Hong Phi variety at both study sites Density of P
marginatus on leaf is always significantly higher than that on fruit The
density of P marginatus is highest at the end of October and early
November when the temperature is not so lower and little heavy rain
occured The density of P marginatus is lowest in August when
prolong and strong rainy comes (Figure 3.13; 3.14; 3.15 and 3.16)
This is similar with the research results of Walker et al (2003)
According to these authors, the heavy rainfall severely reduced the
population density of P marginatus
Figure 3.13 Population dynamic
of P marginatus on leaves of
various papaya varieties at Phuc Tho (Ha Noi) in 2017
Figure 3.14 Population dynamic
of P marginatus on leaves of
various papaya varieties at Thach That (Ha Noi) in 2017
Figure 3.15 Population dynamic
of P marginatus on fruits of
various papaya varieties at Phuc Tho (Ha Noi) in 2017
Figure 3.16 Population dynamic
of P marginatus on fruits of
various papaya varieties at Thach That (Ha Noi) in 2017