Controlling Stem Rot Disease in Corn

Controlling stem rot disease in corn can be done genetically, biologically, culturally, technically and chemically.

KOMPAS/VINA OKTAVIA

Corn farmers in Braja Selebah Village, Way Jepara District, East Lampung Regency, Lampung, harvested corn on Friday (8/12/2017). Corn production in Lampung reached 2.4 million tons in 2017. Lampung contributed 8.59 percent of the total national corn production of 27.9 million tons.

Corn is the second main food commodity after rice in Indonesia. The Central Statistics Agency (BPS) noted that corn production in Indonesia in 2023 was 14.46 million tons. However, this figure has decreased compared to the previous year which reached 16.53 million tons.

The production of corn in Indonesia is not only for the needs of the people's food, but also for the needs of animal feed and poultry. Given the high demand for this, the government continues to strive to increase corn production both in terms of intensification and extensification, including expanding the area and assembling new superior varieties.

However, in cultivating corn plants, biotic and abiotic obstacles are often encountered that can hinder increased production. One of the new diseases that often attacks corn is stem rot caused by the bacteria Dickeya zeae. Farmers have complained about this disease in recent years.

Based on pathological characteristics, in corn plants the bacteria Dickeya zeaewas found to be transmitted through soil media. The pathogen inoculum or population of microorganisms can survive 150-270 days in the soil and the disease incubation period ranges from 19-36 days after planting. This bacteria can also spread through irrigation water up to 10 meters.

The symptoms of the attack from this bacteria include yellowing leaves and infected tissue becoming brown, soft, and wet. A strong odor and the presence of dipteran larvae in the decaying tissue are typical signs of this disease. Stem decay occurs in one or two sections or the entire stem, which will eventually dry up.

KOMPAS/FRANSISKUS PATI HERIN

Goris Takene harvested corn in his own garden in Belo Village, Maulafa District, Kupang City, East Nusa Tenggara, on Monday (8/4/2024). The Kupang City Government employee spent his holiday time gardening.

Researcher at the Food Crop Research Center of the National Research and Innovation Agency (BRIN), Suriani, stated that Dickeya zeae can also cause infections in several superior commodities, such as bananas, rice, pineapple and aloe vera. It is recorded that this bacterium is capable of infecting around 22 monocot plant commodities and 24 dicot plant commodities.

Soft rot disease in bananas was first reported in Guangzhou, China in 2009. Meanwhile, the basal stem rot disease in rice began to be reported in the 1980s in several provinces in China with disease incidents ranging from 15 to 100 percent.

The bacteria Dickeya zeae in Indonesia was reported for the first time by researchers in 2002, which was found on aloe vera leaves in the Bogor area, West Java. Meanwhile, in 2020 in Lampung, soft rot disease was identified in pineapple commodities.

Specifically for corn plants, the presence of stem rot disease was first reported by the Mamuju Quarantine in West Sulawesi in 2019. In the same year, Lampung University students also reported the presence of this bacteria in Central Java and Lampung.

In 2023, Suriani and other researchers from the BRIN Food Crop Research Center will again try to explore the distribution of Dickeya zeae. As a result, the presence of this bacteria has been detected in several regions, such as West Sulawesi, Lampung, Central Java, South Sulawesi, Gorontalo, East Kalimantan and Yogyakarta.

KOMPAS/P RADITYA MAHENDRA YASA

Farm workers pass by drying kernels of corn used for livestock feed in Ngabean Village, Boja District, Kendal Regency, Central Java, on Monday (26/2/2024).

According to Suriani, the infection level of stem rot disease in corn reported in other countries such as India has reached 96.65 percent. Meanwhile, in Pakistan, the survey results in 266 regions in the country showed that the incidence of this disease ranged from 9-78.5 percent.

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"We found that in Bone Regency, one of the corn-producing regions in South Sulawesi, farmers have been complaining about stem rot diseases," he said in a webinar entitled "Management of Soil-borne Pathogens and Quality Seed Production in Efforts to Increase National Corn Productivity" on Wednesday (April 17, 2024).

Control mechanism

Suriani explained that in general, efforts to control plant pests (OPT) are carried out through preventive and curative strategies. The preventive strategy is disease control carried out before the appearance of OPT attacks, while curative strategy is carried out immediately after OPT attacks occur.

The first technology that can be applied is the use of stem rot-resistant varieties. However, until now there have been no scientific reports related to the assembly of new superior varieties (VUB) in hybrid or composite corn that are resistant to stem rot attacks, considering that this disease is still relatively new in Indonesia.

Regardless, in 2023, researchers at the BRIN Food Crop Research Center discovered two high-yield, disease-resistant elite hybrid strains. Both strains consistently have low values of Disease Progression Area Under the Curve (LDBKPP) and a protection index of over 50% in the planting season.

KOMPAS/ZULKARNAINI

Corn production in Indonesia has decreased so imports have to return.

"For biological control, in India two genera of bacteria have been reported that are effective in controlling Dickeya zeae, namely Pseudomonas fluorescens, and Bacillus subtilis. "In Indonesia, we are also trying to screen for rhizosphere bacteria to control Dickeya zeae," said Suriani.

From the results of screening 50 isolates of rhizosphere bacteria, 4 isolates were found to have the potential to control the bacteriaDickeya zeae. After that, testing was carried out for Fusarium verticillioides which is one of the pathogens that causes important diseases in corn which can be transmitted through seeds and soil. As a result, 3 isolates were obtained which had the potential to be continued.

"We focused on looking at the ability to fight Fusarium verticillioides because these pathogens sometimes work together to cause stem rot disease. "Sometimes Fusarium infects first, causing wounds and making it easier for the Dickeya zeae bacteria to enter until stem rot disease appears," he said.

Engineering culture

Another control effort that can be done according to Suriani is through technical culture. This effort is carried out by reducing ecosystem suitability, disrupting the continuity of plant requirements, diverting plant populations away from crops, and reducing the impact of plant damage.

"We can create conditions where the land is not suitable for the development of pathogens, such as optimal land tilling. Another important thing is to have balanced fertilization, maintain plant moisture, and avoid planting corn in locations with poor drainage or potential for flood,” he said.

KOMPAS/KRISTIAN OKA PRASETYADI

Corn plants starting to grow taller can be seen on the side of the Outer Ring Road of Gorontalo, Gorontalo Regency, Gorontalo Province on Thursday (30/11/2023). Approximately 400,000 hectares or a third of the land in Gorontalo Province is planted with hybrid corn.

Apart from that, chemical control can also be applied to control stem rot disease. The results of research in India in 2016 reported that copper fungicide in combination with antibiotics could significantly inhibit the growth of the bacteria Dickeya zeae.

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The Head of the Agriculture and Food Research Organization of BRIN, Puji Lestari, stated that maize plants are still a top priority for research because they support national food security, animal feed, and industrial raw materials. Therefore, research related to maize plants is very strategic in helping to support the development of agribusiness.

"We need to anticipate the issues with corn so that we can preserve the potential national production. Corn is a commodity that we have included in our precision breeding platform, and in it, there is management of pests and diseases," he said.