Cassava mosaic disease outbreak in Nghe An

4ha/7.5ha of cassava newly planted by Mr. Tran Van Nham's family (Thanh Ngoc, Thanh Chuong) were infected with mosaic disease and had to be uprooted. Photo: Thanh Phuc

In the 2022 cassava crop, Mr. Tran Van Nham's family in Yen Xuan hamlet, Thanh Ngoc commune, Thanh Chuong district contracted 7.5 hectares of public land of the commune. There is a cassava factory in the area, the price of raw cassava has been high in recent years, at times up to 2,000 VND/kg, each hectare of cassava brings in a profit of 20-25 million VND, so he boldly converted the land area he had just bid to grow cassava. However, 7.5 hectares of cassava had just sprouted from the ground when mosaic disease appeared sporadically, and up to now, 4 hectares of cassava have been infected.

Mr. Tran Van Nham said: “41 million VND in land rent and nearly 200 million VND in capital, fertilizer, labor, and land preparation were poured into 7.5 hectares of cassava. Now, more than half of the infected cassava area must be uprooted and destroyed, losing hundreds of millions of VND. Now, we also have to spend money on hiring workers to uproot and treat pathogens on the planted area. Another problem is where to get disease-free cassava seeds to plant new ones, and it is not in time for the season. Meanwhile, the land area is hilly and far from water sources, so it cannot be converted to other crops.”

Cassava leaves curled up, shriveled and stopped growing just 20cm above the ground. Photo: Thanh Phuc

Faced with the cassava mosaic disease appearing in the locality, Thanh Chuong district has organized inspection teams to survey cassava growing areas. At the same time, it has issued official dispatches to urge, direct and guide functional agencies, local authorities and cassava growing households to promptly uproot, destroy and treat infected cassava areas.

Mr. Le Van Quang, Director of the Agricultural Service Center of Thanh Chuong district, said: “The total cassava area in the district is currently 2,000 hectares. Of which, the main varieties are KM94, CT11, in addition to NA94... Currently, cassava mosaic disease has appeared in Thanh Ngoc, Thanh Hoa, Thanh Nho communes... with a total infected area of ​​about 15 hectares. Of which, the severely affected area is 2.5 hectares, the average area is 5.5 hectares, and the lightly affected area is 6.5 hectares.

There is currently no specific medicine for this disease, so the only way is to remove, destroy and treat the disease at its root to avoid spreading to other areas. At the same time, we need to propagate and train people to detect the disease early, how to treat it, and arrange for specialized staff to coordinate with agricultural staff of the cassava starch processing factory to inspect and monitor the growing areas.

After being removed, many cassava growing areas are left empty because they do not know what to plant instead, especially in areas far from water sources. Photo: Thanh Phuc

In Tan Ky, in the 2022 cassava crop, the entire district has planted 2,400 hectares of cassava, but up to 1,700 hectares have been infected with mosaic disease. Currently, people are focusing on uprooting, destroying and treating the soil.

Ms. Dang Thi Van, Deputy Head of the Agriculture Department of Tan Ky district, said: "In the 2021 cassava crop, the whole district had 2,000/3,500 hectares of cassava infected with mosaic disease, with a sharp decrease in productivity. This year's cassava crop, many areas that had just sprouted were infected with the disease and had to be uprooted and destroyed, causing great losses for farmers, with some households losing hundreds of millions of dong."

According to preliminary statistics from the provincial Department of Crop Production and Plant Protection, the whole province has planted nearly 10,000 hectares of raw cassava, but more than 2,000 hectares of cassava have been infected with mosaic disease. At this time, cassava has just grown about 15-20cm above the ground, the main source of the disease is in the tree trunk, in the infected cuttings, in the near future, when the sun rises, whiteflies will develop strongly, then certainly, the area infected with mosaic disease will increase rapidly if not handled thoroughly and promptly.

People are massively expanding their acreage but have not paid attention to choosing seed sources and effective farming techniques. Photo: Thanh Phuc

According to experts' analysis, the main source of cassava mosaic disease is the use of diseased cassava varieties for planting. Therefore, controlling the spread of the disease according to infected varieties and using disease-resistant varieties is the most important issue at present. However, cassava varieties are currently floating, mainly due to people leaving their own seeds, asking for seeds from each other, but there is no reliable source of seeds, and the source of seeds has not been controlled to be disease-free or not.

Faced with the widespread outbreak of cassava mosaic disease, some localities such as Anh Son and Tan Ky are currently testing a model of disease-free cassava varieties on a number of areas, from which they will be widely replicated. At the same time, people in growing areas are encouraged to share disease-free varieties within the community. People with disease-free varieties should share with people whose cassava fields are diseased; absolutely do not import cuttings from other places, as it is difficult to control pathogens.

Currently, the need for disease-free seed sources is very urgent. While waiting for new varieties to be widely propagated, people need to share clean seed sources with each other. Photo: Thanh Phuc

Currently, the Agricultural Genetics Institute is propagating new disease-free varieties such as HN1, HN36, HN80, HN97 as a source of seeds for localities. However, before the new disease-resistant varieties are widely propagated, people need to strictly follow professional techniques for preventing cassava mosaic disease, not massively expand the area and share clean seed sources with each other.

Measures to prevent and control mosaic disease on cassava:

-Cassava should not be grown continuously for many years on one land and absolutelyDo not replant cassava on land infected with mosaic disease but switch to other crops..

-Select and plant cassava varieties that are not or very rarely infected with mosaic disease such as: KM94, KM95... Do not take cuttings of cassava varieties that have recently been infected with mosaic disease to replant and do not plant cassava varieties of unknown origin.

-Proactively spray insecticide to kill whiteflies to prevent disease outbreaks., spread by drugs such as: Pymetrozine (Chess 50 WP, chessar 50 WG, Sagametro 50WG, Schezgold 500WG...)

-Depending on the severity of the disease and the period when the cassava plant is infected, it should be treated according to the instructions of the Department of Crop Production and Plant Protection. In particular, it is necessary to note:Uproot and destroy all infected cassava areas to ensure safety for the remaining area.