Developmental status of duku stem-canker in Jambi

Dead molt disease or duku stem-canker disease has been widely discussed in several studies. Some suspect it is caused by Phytophthora palmivora, or Ceratocystis fimbriata, and possibly Botryodiplodia spp. In the last decade, studies and discussions in control efforts have been carried out. Control studies using biological control strategies continue to be carried out, especially in the South Sumatera region, as well as control studies using pesticides have also received a lot of attention, but the control results have not reached a satisfactory stage. There are still many duku plants that have experienced widespread mortality. Finally, we will discuss about the research that has done into developing effective and sustainable control strategies.


Duku and the dead molt disease
Duku (Lansium domesticum L.) is a tropical fruit plant that grows throughout the archipelago and is thought to have originated in the regions of Sumatra, Java, and Borneo which are indicated by presence of wild duku species there.Moreover, duku is also found in Malaysia (known as langseh), Philippines (known as lanzone), Thailand (known as longkong), and Vietnam (known as bon-bon) [1].
There are excellent duku on the island of Sumatra, including duku Komering from South Sumatera, and duku Kumpeh from Jambi [1].These two duku became famous for their abundant fruit, until they were marketed in the capital city of Jakarta [2].In general, both of them are known as duku Palembang, although they come from various regions in South Sumatera and Jambi.This is understandable because the history of South Sumatera Province and Jambi Province used to be still incorporated in the Southern part of Sumatra [3].The income from the duku proceeds is quite large.For example, in the Kumpeh area of Jambi Province, the duku season generally runs for 3 months, can provide an average farmer income of 9 billion for farmers, and provide business opportunities for 500 duku fruit traders [4,5].
Around the last 20 years, there have been disturbances in the duku farming, with the intensity of a plant disease that decreases in production, and followed by the death of plants [3,4,6].In early 2014 a massive death of duku along the Komering River watershed in Ogan Komering Ulu (OKU) District was reported by most local newspapers and some national newspapers.In total, more than 2,000 of the most popular cultivar trees, the Komering duku, died.The symptoms first appeared at the beginning of the rainy season in October 2013.Most of the dead duku were affected by partial flooding to a depth of about 20 cm for about a month from late December 2013 to January 2014.However, some affected duku were found in non-flooded locations, indicating infectious diseases too [7].
Based on the characteristics of the symptoms and causes, the disease is actually an advanced cankerstem disease.Diseases can decrease yields and even lead to the death of plants.The typical symptoms of canker-stem duku disease that known as dead molt disease lies in the stem.The bark of the affected 1297 (2024) 012007 IOP Publishing doi:10.1088/1755-1315/1297/1/012007 2 plant trunk will dry out and peel off starting from the bottom.On the woody part under the peeling bark, found a mass of white fungal spores.Symptoms on the woody part are indicated by the presence of black spots, which are increasing in number [6].The expansions of the trunk that dry out and peel off in bark very quickly.If only part of the side of the stem peels off, then it gets to the twigs and the leaves will become dry.If the expansion of the bark dries out to the perimeter of the stem, then the whole leaf will turn yellow and dry out, the leaves of the plant fall off, and finally the duku dies [8] as in figure 1. Young of duku that are less than 10 years old will die in less than a month after showing symptoms on the stem, while plants older than 10 years may die within 2-3 months after symptoms develop on the stem [3].
Recently, as reported by the daily newspapers Jambi, and South Sumatera in September 2022, the disease is increasingly widespread and increasing number of duku deaths.Muaro Jambi Regency, Jambi Province experienced a large number of duku deaths.In the Ogan Komering Ulu Regency of South Sumatera Province, duku farmers have been unable to harvest in the past two years, due to duku crops experiencing many deaths [9].

Causes of the disease
Several studies have been conducted to study the incidence of the disease in South Sumatera Province, and Jambi Province.The three main studies on the incidence of this disease, namely research in Jambi in 2005, it is suspected that this disease was infected by Phytophthora palmivora on the basis of similarity of symptoms with stem-canker on durian, so that the disease of death molting duku in Jambi is often called stem-canker disease [5].Then continued in the 2009 study and is still in the estimation of the cause of the disease P. palmivora.Then in 2014 it was detected with a morphological and Postulate Koch approach, and followed by molecular tests, information on the main pathogen of duku stem-canker was obtained in Jambi i.e.P. palmivora, which has a kinship with P. palmivora strain_2 durian from Thailand [3].Meanwhile, research in South Sumatera on duku that are symptomatic of twig death and followed by the death of duku in Ogan Komering Ilir (OKI) area carried out field observations and morphological analysis along with molecular analysis obtained information, the main pathogen in duku plants in OKI is Botryodiplodia theobromae [10].Other research on symptomatic of bark decay, wood discoloration, and wiltiness in duku plants was deeply analyzed in Ogan Kemering Ulu (OKU) region.The approach by morphological analysis and testing of Postulate Koch, and continued with molecular analysis showed the main pathogens in wilt disease the deadly one is Ceratocystis fimbriata which has a close kinship with C. fimbriata isolate CMW21127 in Acacia plants in Indonesia [7].

Ecological and environmental aspects
The discussion of ecological and environmental aspects related to plant disease epidemics becomes very important, given the basic theory in the disease triangle, the successful infection of pathogens against hosts that vulnerable, must be met with the availability of ecological and environmental support [10; 11].The incidence of this disease follows the polyetic cycle [12] that is, pathogens found in the tropics and infecting perennial plants can also develop following repeated cycles, but it is not clear when the incidence of the plant infection is.Environmental factors have an influence on the development of the incidence of this duku stem-canker disease.Micro-weather elements such as soil temperature, and air humidity have a noticeable effect on causing an increase in the epidemic rate of duku stem-canker with a positive correlation.Air temperature has a significant effect on the epidemic rate of stem-canker with a negative correlation [13].The soil content factor also affects the development of this disease.The content of organic materials such as C-organic, Phosphorus, Potassium, Calcium, Magnesium, and Zinc can reduce the severity of this disease [14], the availability of nutrients in a balanced manner and the adequacy of nitrogen elements also increases the resistance of duku to pathogen infections [15].
Likewise, the content of other organisms in the soil also affects the development of duku disease.Populations of antagonistic fungi, and mycorrhizal fungi are negatively correlated to the incidence of stem-canker disease [16].The agronomic character present in some duku clones also affects the incidence of duku disease.The agronomic characteristics that marks resistance is that the leaves are longer, the yield and number of fruits are more, the heading is larger, and the branches are more numerous.All of these characteristics are indicators found in older duku trees, with high productivity.Therefore, it is assumed that plant resistance is part of the phenomenon of avoiding disease [17].

Disease control
Several activities in order to reduce the initial population of a pathogen or disease have been carried out as well.The eradication of symptomatic plants, and the wise use of pesticides is the most important part of reducing the initial population of a disease.This includes control activities through reducing the growth rate of pathogens, which is expected to reduce the infection rate and at the same time to reduce of disease development rate.The control time is often the factor that determines the implementation of the control application.A time function that directly gives pathogens, and diseases have opportunity to develop, however in disease control has a real ability if carried out as quickly as possible, according to calculate the concept of integrated pest control.

Based on biopesticides and biocontrol agent studies
The use of pesticides in disease control has been carried out trials in Batanghari Regency, Jambi Province [6].This activity approach by reducing the initial population of pathogens or diseases.The method used by means of pesticide infusion in the root tissue.If the intensity of the disease is still small, this means of control will be effectively carried out.The weakness in this control is that if the rapid rate of disease, results in the unable to apply pesticides for large quantities and large areas.The use of Bordeaux solution, or California solution has also been tested in duku cultivation in Muaro Jambi Regency, Jambi Province [18].The obstacle that arises is the estimation of the loss of other useful fungi in the soil.The use of organic pesticides (biopesticides) is also carried out in the control of this disease with an approach to reducing the pathogen population.The application of organic fertilizers enriched with biopesticides (made from phosphate solvent bacteria, and Plant Growth Promoting Rhizobacteria / PGPR or Plant Growth Promoting Fungi / PGPF) has been carried out in OKI Regency South Sumatera.Meanwhile, the application of biopesticides and bioagents is still at the pilot level for farmer [19,20].

Environmental factors
Studies of the environment show that appropriate environmental modifications are possible to reduce the intensity of the disease.Aspects of the biological environment can begin with the development of mycorrhizal fungi, and antagonistic bacteria can become more competitive with pathogens, and at the same time may help increase the growth rate and health of the duku [14,18].The study of the most influential land characteristics for optimum duku production, showed that the soil pH is the main factor in reducing soil support for duku productivity [21].It is possible to utilize modifications of the soil environment, with continuous adjustment of the pH simultaneously with the application of fertilizers in the duku plantation.Other non-living environmental aspects may be modified, to increase the resistance of duku to pathogenic infections while suppressing the development of pathogens.Among them, weather factors consisting of air temperature, air humidity, and soil temperature have an influence on the development of duku stem-canker in Jambi [13].If the modification of air temperature and air humidity by measuring pruning the canopy of the duku plant can be part of the disease control strategy duku stem-canker.Become scrutiny with soil fumigation that can control soil-borne pathogens.The application of biofumigants to suppress the growth of soil-borne pathogens while being able to increase soil temperature which results in more effective control [22].

Participation of all levels of society
It is undeniable that the support of the farming community in control efforts is part of the integration of disease management.Engineering analysis of supporting subsystems in duku farming centers, the active role of the community is needed in the management of duku plantations [20,23].The implementation of the duku management program implemented by the government must be welcomed by the community with willpower to improve governance and cultivation.[24][25] [26][27] [5][28]

Preparation of duku seeds in a generative and vegetative manner, and enriched with mycorrhizal fungi and antagonistic microorganism
This activity is a combination of generative propagation of seeds and vegetatives by inoculation at a certain age.In addition, the growing medium is prepared by enriching organic matter and antagonistic microorganisms, and mycorrhizal fungi [15,16].

Utilizing plants of the family brassicaceae as biofumigans of soilborn pathogens
Soil-borne disease control will become more effective using soil-related control applications.Biofumigants are fumigant compounds obtained from plants of the family Brassicaceae, which undergo decomposition and hydrolysis.When the leaves and stems of the Brassicaceae family are decomposition, it will produce additional nutrients stored in the soil, while producing Glucosinolates (GSL) subsequently undergoing hydrolysis with the myrosinase enzyme into isothetianate (ITS) which is highly toxic to nematodes [22,25,28], inhibiting the growth of the bacterium Pseudomonas marginafis causing soft blight [26], controlling mace root disease (Plasmodiophora brassicae) in caisin [24], is also effective in controlling soil-borne pathogens [27].

Improving plant health by managing healthy duku cultivation
As stated in the front, community participation in the management of duku disease, especially in Jambi Province, is very necessary.Because the more and more duku farming communities involved will produce a good control effect, and can simultaneously break the cycle of development of pathogens and duku stem-canker disease [23].The application of no. 1 and no. 2 combined with the behavior of the farming community in managing duku plantation will further make duku healthy, and can be expected to restore the glory of duku in Jambi.

Conclusion
Duku stem cancer has threatened duku cultivation and caused a decrease in production to plant death.As a result, various efforts must be made to preserve the existence of duku, including the supply of healthy seedlings enriched with beneficial microorganisms as a support for growth and biocontrol of pathogens, the use of biofumigants, and the behavior of farming communities in the management of duku plantations.The combination of these efforts as integrated management can improve the health and quality of products, thereby restoring the popularity of Jambi Duku.