IJERD – International Journal of Environmental and Rural Development (2021) 12-2

Research article
erd

The Current Status of Cassava Producers and Healthy
Cassava Seed Production and Distribution Trial in Vietnam
NIEN CHAU NGUYEN*
Faculty of Agronomy, Nong Lam University, Ho Chi Minh City, Vietnam
Email: nien.nguyen@hcmuaf.edu.vn

TAMON BABA
College of Letters, Ritsumeikan University, Kyoto, JapanHISAKO NOMURA
Faculty of Agriculture, Kyushu University, Fukuoka, JapanKASUMI ITOInternational Center for Research and Education in Agriculture, Nagoya University, Japan
Received 26 January 2021

Accepted 15 November 2021(*Corresponding Author)

Abstract This study discusses the current status of cassava producers in Vietnam, the demandfor healthy cassava seeds, and the potential for a healthy seed production and distribution
system. Owing to the recent spread of Sri Lankan Cassava Mosaic Disease in South East
Asia, the government-led agricultural extension system and the informal cassava production
and distribution system in Vietnam have sought a "health" seed production system. To
improve the existing system and contribute to sustainable cassava production in Vietnam, we
conducted interviews using a structured questionnaire in Dong Nai, Gia Lai, and Tay Ninhprovinces from April to December 2017 and received responses from 182 cassava producers.
The results show that the majority of cassava producers rely on this crop for their income.
Therefore, they are interested in purchasing healthy seeds, and their willingness to pay isstatistically significantly higher than the purchasing price in all three provinces. Based on the
results and the existing cassava production and distribution system in Dong Nai, this project
instituted a monitoring system, polymerase chain reaction testing, and a healthy seedcertification system. This study found that seed producers face several difficulties, including
implementing a monitoring and management system. Thus, there is potential for establishinga healthy cassava seed production and distribution system in Vietnam.
Keywords cassava, seed production and distribution, Vietnam, willingness to pay

INTRODUCTION
Cassava (Manihot esculenta Crantz) is one of Vietnam's three most important food crops, with532,600 ha of cultivated area, an annual average yield of 18.8 tons per ha, and fresh root production
exceeding 10.27 million tons (GSO, 2018). Cassava is grown in as many as 40 of the country's 63
provinces. Vietnam ranks seventh in cassava production in the world (FAO, 2020).
The Sri Lankan Cassava Mosaic Disease (SLCMD) was first reported in Cambodia in 2015
(Wang et al., 2016) and was then found in Tay Ninh in 2018 (Uke et al., 2018). Since then,Vietnamese cassava producers have faced substantial challenges, as the disease drastically decreases
cassava yields (Fargette et al., 1988; Fauquet and Fargette, 1990; Makeshkumar, 2016). According
to Vietnam's Plant Protection Research Institute, the estimated annual cassava yield loss will be
between 12.7 percent and 34.6 percent. The starch content is expected to decrease by 1.02 percent to18.97 percent. SLCMD has spread rapidly using whiteflies as a vector; it is also spread throughinfected stem distribution as cassava can be quickly propagated from stems, which are transported
as "seed" to multiple locations.

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In Ratanakiri and Battambang provinces in Cambodia and Dak Lak and Tay Ninh provinces inVietnam, informal and self-regulated seed distribution systems are managed by private producers
and traders (Delaquis et al., 2018). Although these systems appear to work well in normal situations,once the stems are infected with SLCMD, the disease can rapidly spread through human factors, suchas traders and transporters, who distribute cassava seeds over a wide range.
In Vietnam, it is essential to understand the current production and stem movement situation,
including the socio-economic condition of cassava producers, to discuss the possibility of healthy
seeds. The seeds are considered healthy if they are not detected positive for SLCMD in thepolymerase chain reaction (PCR) testing. Thus, production and distribution should be carried out
through the market mechanism.
Vietnam has a public extension system founded in 1993, organized into five levels—central,provincial, district, commune, and village or hamlet. All 63 provinces have their own extension
centers (Tokunaga et al., 2018). Furthermore, an official cassava seed production and distribution
system exist in addition to the informal, self-regulated distribution system. As part of the official
system, the Hung Loc Agricultural Research Center (HLARC) in Dong Nai province in southern
Vietnam breeds, produces and distributes cassava varieties. Private producers under HLARC
propagate and distribute these stems among "general producers" who primarily cultivate cassava for
its roots and potential buyers of healthy cassava seeds in the province. This system, however, has nomonitoring methods, nor does it employ PCR testing or have any certification. Hence, there is apotential risk of the distributed stems becoming contaminated with viruses or phytoplasma, further
spreading the disease.
Therefore, since 2016, we have been executing a project titled "Development and Disseminationof a Sustainable Production System Based on Invasive Pest Management of Cassava in Vietnam,
Cambodia, and Thailand," supported by the Japan Science and Technology Agency and the Japan
International Cooperation Agency. This project aims to improve the current cassava seed production
and distribution system centered at HLARC and establish a sustainable production system that uses
healthy seeds. This system can be established by developing a market-based dissemination modelthat supports the private sector, producers, and the government and devising a management system
for invasive cassava diseases and pests. To improve the system, it is essential to first identify cassava
producers' seed preferences, their demand for healthy cassava seeds, and the current situation of
cassava production. However, sufficient information is not yet available.
OBJECTIVE
This study aims to discuss the current status of cassava producers and stem distribution in southern
Vietnam, including their cassava seed preferences. Further, the potentiality of a healthy cassava seedproduction and distribution system is also discussed, and producers' willingness to pay (WTP) for
healthy seeds is estimated. Finally, the improved cassava seed production and distribution systemdeveloped by the project is explained, and challenges are discussed.
MATERIAL AND METHODS
Study Site
A series of semi-structured interviews based on a questionnaire was conducted in southern Vietnam's
Dong Nai, Gia Lai, and Tay Ninh provinces (Fig. 1) from April to December 2017. First, we checked
the government census database and contacted local government offices to determine the cassava
producer population of the provinces; however, we discovered it to be fluctuating. However, thepurpose of the study was to capture the potential for seed production, the selection of seed farmers,
and willingness to pay. Thus, we used purposive sampling with equal selection based on cassava
plantation area to categorize the respondents into three groups: less than 1 ha, between 1 ha and lessthan 5 ha, and more than 5 ha. As a result, the total number of respondents was 182—60 in Dong
Nai, 61 in Gia Lai, and 61 in Tay Ninh.
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The three provinces mentioned above are the primary cassava cultivation areas in Vietnam(GSO, 2018). Tay Ninh and Gia Lai have the largest (64,800 ha) and second-largest (61,600 ha)
cassava production areas among all provinces and produce 2,024,000 tons and 1,207,100 tons,
respectively. Dong Nai stands at the 10th position among the country's 58 provinces and contains
five municipalities with 15,700 ha of cassava production area and 399,700 tons of production. The
main cassava production center in Dong Nai is the Xuan Loc district, and in Tay Ninh, it is the Tan
Chau district. In Gia Lai, the Dak Po and Krong Pa districts are the two leading cassava production
centers. Therefore, these locations were chosen for surveying.

Fig. 1 Survey areas in Vietnam
Theoretical Model
The concept of WTP is derived from the Hicksian welfare measure of compensating variation (CV).
The CV measure asks what compensating payment or offsetting change in income is necessary to
make an individual indifferent to an increase in price. This is often interpreted as the new price set.
The concept can be illustrated by following the standard economic theory of indirect utility function(Bateman et al., 2002), which can be written in the general form:
𝑉 = (𝑌, 𝑃, 𝑄)(1)where (𝑉) describes the economic wellbeing or maximum amount of utility a respondent can derivefrom their income (𝑌), given the prices of goods they face (𝑃) and the level of environmental quality(in this case, getting healthy, clean seeds not infected by pests or disease [𝑄]). WTP is defined as theamount that must be taken away from a person's income while keeping this utility constant:
𝑉 (𝑌 − 𝑊𝑇𝑃, 𝑃, 𝑄1 ) = 𝑉(𝑌, 𝑃, 𝑄0 )(2)where (𝑄0 ) and (𝑄1 ) are the alternative levels of the good or quality indexes (𝑄1 >𝑄0 , indicating that
(𝑄1 ) refers to improved environmental quality).
The WTP was estimated following Mitchell and Carson (1981, 1984), and the payment card
method of contingent valuation was used to estimate the WTP for healthy seeds. Producers wereasked how much they would be willing to pay to obtain a certified healthy cassava seed.
However, an open-ended payment card CVM question can generate a high number of zero
responses (Green et al., 1998). In that case, the distribution of WTP could be censored by the left toa zero value. To address this, Halstead et al. (1991) recommended using the Tobit regression modelas the more theoretically correct econometric model for the open-ended CVM format.
The Tobit regression model considers both the censored and continuous observations in theprocess of estimation. Following Kim and Cho (2002), the Tobit regression model can be expressed
by:
𝑊𝑇𝑃𝑖𝑇𝑜𝑏𝑖𝑡 = 𝑋𝑖′ 𝛽 + 𝑒𝑖

(3)′where 𝑊𝑇𝑃𝑖𝑇𝑜𝑏𝑖𝑡 is the unobserved continuous dependent variable; 𝑋𝑖 is a vector of explanatory
variables; β is a vector of coefficients; ei is an independently distributed error term, assumed to beⒸ ISERD

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normal with zero mean and constant variance σ2 ; and i = 1, 2, . . . . , n denotes individuals in thesample. The observed WTP variable is given by:
𝑋 ′ 𝛽 + 𝑒𝑖.
𝑊𝑇𝑃𝑖 = { 𝑖0𝑖𝑓 𝑊𝑇𝑃𝑖𝑇𝑜𝑏𝑖𝑡 > 0
𝑖𝑓 𝑊𝑇𝑃𝑖𝑇𝑜𝑏𝑖𝑡 ≤ 0(4)

Empirical Model and Hypothesis
The Tobit regression model can be expanded to include the socio-economic variables being
hypothesized to influence producers' willingness to pay for healthy cassava seeds(𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 ). The empirical model is presented in the following:
𝑇𝑜𝑏𝑖𝑡
𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔= 𝛽0 + 𝛽1 𝑔𝑒𝑛𝑑𝑒𝑟 + 𝛽2 𝑇𝑎𝑦𝑁𝑖𝑛ℎ + 𝛽3 𝐺𝑖𝑎𝐿𝑎𝑖 + 𝛽4 𝑡𝑜𝑐𝑎ℎ𝑎 +𝛽5 𝑓𝑢𝑙𝑙𝑡𝑖𝑚𝑒 + 𝛽6 𝑒𝑥𝑝𝑒𝑟𝑖𝑒𝑛𝑐𝑒 + 𝛽7 𝑐𝑎𝑡𝑖𝑚𝑒𝑠 + 𝛽8 𝑐𝑎𝑚𝑎𝑖𝑛 + 𝛽9 𝑙𝑎𝑏𝑜𝑟 +𝛽10 𝑑𝑎𝑐𝑡𝑢𝑎𝑙𝑝𝑢𝑟𝑐ℎ𝑎𝑠𝑒 + 𝛽11 𝑑𝑤𝑖𝑙𝑙𝑖𝑛𝑔𝑛𝑒𝑠𝑠 + 𝛽12 𝑑𝑠𝑡𝑒𝑚𝑠𝑢𝑝𝑝𝑙𝑖𝑒𝑟 + 𝑒𝑖

(5)where the dependent and independent variables are defined in Table 1, 𝛽0 𝑡𝑜 𝛽12 are coefficients,and 𝑒𝑖 is the error term ~𝑁 (0, 𝜎 2 ).
The study hypothesizes that older producers, experienced producers, producers with larger land
areas devoted to cassava, producers with more family members engaged in cassava production, andproducers who would like to be healthy seed producers will have higher 𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 .
RESULTS AND DISCUSSION
Status of Cassava Producers in Southern Vietnam
Table 1 shows the socio-economic situation of the respondents. Among the cassava producers
surveyed, 86 percent were men and the rest were women; the average age of the respondents was
48.63 years. Their total cassava plantation area was 2.90 ha. Sixty percent of the respondents werefull-time producers and had an average of 23.82 years of general farming experience. They had
planted cassava 11.43 times on average, and 63 percent of them cited cassava production as theirmain source of income.
Table 1 Descriptive summary
Variables
genderage
DonNai
TayNinGiaLaitocahafulltime
experiencecatimescamainlabor
dactualpurchasedwillingness
dstemsupplier(1=male, 0=female)(years)Province (Don Nai=1, otherwise=0)
Province (Tay Nin=1, otherwise=0)
Province (Gia Lai=1, otherwise=0)
Total cassava cultivated area (ha)General farm working status (1=full time,
0=part time)Years of farming experience (years)
Number of cassava plantings done before
2016/2017 cycle (times)
Cassava as main income source (1=yes, 0=no)
Number of family members engaged in cassava
farming
Purchased seeds for the 2016/2017 cycle(1=yes, 0=no)
Want to buy healthy seeds (1=yes, 0=no)
Want to be a producer of healthy seed (1=yes,
0=no)Note: N=182Ⓒ ISERD

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Mean
0.86
48.63
2.01

Std. dev.
0.35
10.48
0.82

Min.
0
23
1

Max.
1
70
3

2.90

2.55

0.4

17

0.60

0.49

0

1

23.82

9.67

2

50

11.43

6.38

0

31

0.63

0.49

0

1

2.10

0.97

1

7

0.27

0.44

0

1

0.66

0.48

0

1

0.35

0.48

0

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The average family consisted of 4.51 members, of which 2.10 were engaged in cassava farming.
This information shows that our respondents were introduced to cassava production recently, and forsome of them, it has become an important cash source, making it a sort of family business. In otherwords, they depend on cassava production for a living. In addition, 27 percent of the respondents
purchased seeds for the 2016/2017 farming cycle, and 66 percent of them were interested inpurchasing healthy seeds if they were available in the market; moreover, 35 percent of the producers
wanted to make a business of producing healthy seeds.
Cassava Varieties
The cassava varieties used by the producers are shown in Table 2. Since these producers can cultivate
different varieties simultaneously, the total number is not equal to the number of respondents.
Whereas 17.4 percent of the respondents mentioned the variety of cassava they cultivated as"Unknown," others answered with specific variety names. In Dong Nai, KM325 (21 cases) andKM140 (20 cases) were preferred. In Tay Ninh and Gia Lai, KM419 and KM94 were the major
cassava varieties. Although this study could not confirm their claimed variety, it was found that theKM series was the most popular choice in southern Vietnam.
Table 2 Cassava varieties used by producers
Varieties
KM419
KM94
KM325
KM140
KM98-5
KM95
KM98
KM505
KM96
Unknown

Dong Nai
5
7
21
20
1
0
0
0
1
5

Tay Ninh
48
8
1
1
2
0
0
1
0
2

Gia Lai
13
9
1
1
6
4
2
0
2
25

Total
66
24
23
22
9
4
2
1
1
32

Percent
35.9
13.0
12.5
12.0
4.9
2.2
1.1
0.5
0.5
17.4

Note: N=184

Among the respondents, 72.5 percent did not purchase cassava seeds for planting or replanting
and instead used stems from the previous cycle. Of the remaining producers, 52.0 percent bought
stems from their neighbors or relatives. These community-level stem exchanges are dominant in
Vietnam and Cambodia (Delaquis et al., 2018). Another 46.0 percent bought stems from seed dealers
because they wanted to explore new varieties with higher starch content. In Dong Nai, one cassava
producer bought stems from the HLARC. Based on our interviews, most seed dealers were from the
Tay Ninh province. This fact is consistent with a previous study's finding that Tay Ninh is "the highly
commercialized 'cassava seed basket' of Southern Vietnam" (Delaquis et al., 2018).
Healthy Cassava Seed and Distribution System
We also asked the respondents whether they would purchase healthy stems if they were available inthe market, and 65.9 percent of the producers answered yes, of which the percentages for Dong Nai,
Tay Ninh, and Gia Lai were 23.08, 18.68, and 24.18, respectively. In contrast, 28.03 percent of
producers would not purchase healthy stems, of which the percentages in Dong Nai, Tay Ninh, and
Gia Lai were 4.95, 14.84, and 8.24, respectively. Another 6.05 percent of producers would like tohave more information about the growth status, yield, and starch content of healthy varieties before
making a decision.
Further, we found that the respondents' WTP for healthy cassava seeds was significantly higher
than the actual purchasing seed price in all three provinces (Table 3). Thus, we confirmed that there
is a potential market for healthy cassava seeds.
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Table 3 Purchase, seed price, and WTP for healthy cassava seeds by province
Purchase for cassava seed
% (producers)
Yes
No
Other
23.08
4.95
4.95
Dong Nai
(42)
(9)
(9)
18.68
14.84
0.00
Tay Ninh
(34)
(27)
(0)
24.18
8.24
1.10
Gia Lai
(44)
(15)
(2)
Note: Price in VND, 22500 VND ~ 1 USD
Province

Mean of seed price(95% C.I.)

Mean of WTP(95% C.I.)

18546(16837-20255)
11528(8418-14637)
12593(10578-14607)

24091(19630-28552)
22875(17140.45-28609.55)
17500(15841-19159)

t statistic
2.61
4.2
3.64

Table 4 presents the factors that influence producers' 𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 . The results show thatthe number of cassava plantings done before the 2016/2017 cycle influences 𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 .
When we run the pair-wise regression, older producers, producers with larger cassava land area,
producers with more family members engaged in cassava production, and producers who would liketo be healthy seed producers had higher 𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔 at the statistically significance level of
p<0.10. However, the effects of these individual factors diminish with the number of times they had
previously planted cassava. There was a strong correlation between number of years planting cassava
and age, so we excluded age. Apart from that there were no other strong correlations. Thus, we canconclude that when producers are experienced with cassava cultivation, they understand theimportance of purchasing healthy seeds and perhaps the high risk of purchasing unknown seeds that
could spread pests and disease. You may as well say that older people prefer to purchase healthycertified seeds.
Table 4 Determining factors that influence producers' WTP
𝑊𝑇𝑃ℎ𝑒𝑎𝑙𝑡ℎ𝑦𝑠𝑒𝑒𝑑𝑙𝑖𝑛𝑔

VARIABLES
gender

2,551(3,153)
2,008
TayNinh(2,632)-2,364
GiaLai(2,463)
464.4
tocaha(362.3)-392.7
fulltime(2,071)10.84
experience(106.7)313.8
catimes(161.6)-395.5
camain(1,975)-710.3labor(907.2)-1,541
dactualpurchase(2,158)
7,635
dwillingness(7,407)2,659
dstemsupplier(1,979)9.803e+07
var(e.willprice)(1.298e+07)
9,355
Constant(9,918)114
Observations
Note: *** p<0.01, ** p<0.05, and * p<0.10, respectivelyⒸ ISERD

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Thus, following the current situation and the existing cassava production system centered at the
HLARC, our project tested the healthy seed production system. We did so because the organization
has played an important role as a cassava center, and producers and traders in Dong Nai and Tay
Ninh provinces buy cassava seeds from the HLARC (Fig. 2). As a "stock seed production field," theHLARC produce healthy seeds after careful field monitoring and PCR testing, and it sold seeds tothree producers in Dong Nai province in 2018 (Producer A, Producer B, and Producer C). These
producers found business prospects in healthy cassava seed production and were trained periodicallyon how to monitor cassava fields and to execute such monitoring by themselves. They also received
pest and disease information packages and were expected to become proficient at healthy seedproduction.

Fig. 2 Healthy cassava seed distribution system centered at HLARC
The project faced several challenges. In the existing system, the HLARC issues seeds to
producers for free, along with necessary tools such as production techniques, fertilizers, andchemicals, because it does not have enough fields to test new varieties and wants producers to
propagate and test them. Although, as part of our project, we wanted the HLARC to "sell" seeds to
producers so that our system could work in a market-based manner in future, the producers who used
to get seeds for free from the HLARC did not want to "purchase" them. In addition, producers weremore interested in "higher starch content" than "healthy" seeds. It was complicated to make themunderstand how healthy seeds are essential for sustainable production.
Furthermore, the monitoring system needed to produce healthy seeds had not been properly
implemented by the seed producers from the beginning. Our project provided them with information
packages and training on pests and diseases, including how to treat them, and tried to train them tomonitor cassava fields to avoid infections, pests, and their spread. As cassava has grown well for along time without monitoring, seed producers were averse to the idea of monitoring their fields. This
prevented the early mitigation of infected seeds when SLCMD spread in Dong Nai province in 2018.
Consequently, although the HLARC and seed producers inspected their fields and removed
suspicious seeds about two months after the planting in which the infection was detected, its spreadbecame worse in the province. Even the higher level of monitoring afterwards failed to completely
contain the spread of the infection.
Facing these challenges, however, Producer C produced healthy seeds for at least three cycles
and sold them to general producers, whereas Producers A and B stopped production. The reason forthis was that they were both producers in Dong Nai. Producers A and B were not following themonitoring protocol because the disease was not found in Dong Nai in the same year as in Tay Ninh.
Consequently, when the producers found their cassava infested, they could not continue harvesting
healthy cassava as the disease rapidly spread to other provinces, including Dong Nai. In contrast,
Producer C had predicted the status of SLCMD. Therefore, he followed the protocol and his cassava
production remained healthy. Although there is room for improvement in the monitoring done by
Producer C, the current findings show that our healthy seed production and distribution systemfollowing the existing system could work. To develop the system, it is essential for HLARC and the
project to provide every possible assistance to seed producers, teach them the importance ofmonitoring and management of healthy seeds for sustainable cassava production, and effectively
implement a monitoring and management system.
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CONCLUSION
This study analyzed the current status of cassava producers, their demand for healthy cassava seeds,
and the potential of a healthy seed production and distribution system in Vietnam. Cassava producers
depend on cassava production for their livelihood and tend to use varieties that are predominant intheir communities. In addition, they have a preference for the KM series, which indicates that thevariety is well-accepted as a healthy seed in the area. A production and distribution system of healthy
seeds has a potential market because the respondents in all three provinces were interested inpurchasing healthy seeds, and their WTP was statistically higher than their actual seed purchasing
price. Our project created a healthy seed production system in Dong Nai province. Although there
were many challenges, such as low awareness among seed producers about the importance offollowing the monitoring protocol and the rapid spread of SLCMD, one seed producer succeeded inpropagating healthy seeds by monitoring their production. Considering the existing system andproducers' preferences, we continue to explore ways to implement an efficient monitoring andmanagement system to mitigate the impact of SLCMD and distribute healthy seeds.
ACKNOWLEDGEMENTS
This research was supported by the Science and Technology Research Partnership for Sustainable
Development (SATREPS) in collaboration between the Japan Science and Technology Agency (JST,JPMJSA1508) and the Japan International Cooperation Agency (JICA).
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