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The cassava mosaic disease appeared more than a year ago but it has not been able to be controlled up to now

Worrying pests

Cassava mosaic disease has appeared in the province since June 2018, but until now this disease has not been completely prevented but has developed complicatedly.

According to the provincial Department of Agriculture and Rural Development, only two months after the first outbreak, nearly 380 hectares of cassava in the province have been infected with cassava mosaic disease. In late 2018, the cassava mosaic disease tended to gradually decrease as farmers started to focus on prevention and control. However, in early July this year the area infected with cassava mosaic disease has increased dramatically. At present, statistics indicate that more than 450 hectares in the province has been infected with cassava mosaic disease.

Cassava mosaic disease is caused by viruses and transmitted by mealybugs or spread by pathogens in cassava stem cuttings. The yield of the cassava plants that are infected with mosaic disease will drop sharply and 100% of the yield will mostly be gone. More dangerously, the varieties that are being infected are those producing a high yield and planted by the province’s farmers like HL-S11, KM 140, KM 60, and SM 937-26.

Meanwhile, the epidemic of fall armyworms on corn plants has appeared in the province since early May. Though fall armyworms have just appeared, they have done enormous damage to corn growers. The Head of the Plant Quarantine Station, Mr. Nguyen Trang Thinh, said: “Fall armyworms were confirmed to appear in the northern provinces in February, 2019 for the first time. Then, this harmful exotic species quickly spread to a lot of localities throughout the country. The transmission route has not yet been known, but due to the fact that fall army worms have a development of butterfly and can fly far and spread widely. Worms tend to appear in the fields of the young corn plants of 20 to 35 days, especially on the corn plants in the stage of bursting 3 to 7 leaves.

“Unlike other previous pests, fall armyworms have a destructive power and a fast speed of causing damage to plants. The results of surveys show that there is only one grown-up worm on each head of a corn plant, but after only a few days they can bite and eat up all the young leaves at the top and leave a huge amount of poo”, Mr. Thinh said.

In fact, after just over 2 months of its appearance, fall armyworms have up to now inflicted more than 400 hectares of corn in the province.

The risk of disease outbreaks is high

Director of the provincial Department of Agriculture and Rural Development, Huynh Thanh Vinh, said: “For cassava mosaic disease and fall armyworms, scientists have not been able to find out the most effective specific remedy. For cassava mosaic disease, only cassava varieties with a high resistance to diseases have been found but no disease-tolerant varieties. Similarly, for fall armyworms recommendation is still preventing and using manual measures to eliminate the disease as soon as it appears.

Fall armyworms on corn plants are still raging and causing substantial losses to farmers

Assessing the risk of mosaic disease outbreaks, Mr. Nguyen Trang Thinh said, the disease is likely to spread widely mainl due to the fact that farmers have still used the old infected varieties of cassava for cultivation and that a lot of farmers have still had their habit of re-using cuttings in their fields to reduce costs whereas they are unaware that most of the old varieties of cassava have been infected. If this issue continues, the risk of outbreaks of this disease in the near future is very high.

According to the provincial Department of Agriculture and Rural Development, fall armyworms are a new species of insects that has appeared in the country for the first time and so no specific research has been done and solutions have been put forward mainly based on reference materials from abroad. Therefore, no precautionary effects have been brought about. In addition, farmers have not taken all the precautionary measures in their fields at one time and corn crops are cultivated at different times, which results in the fact that after this corn field is sprayed and then grown-up worms move to and damage other fields. Therefore, the area that is prevented from this type of pests has not decreased considerably.

To minimize the level of damage caused by pests, Deputy Director of Plant Protection Department at the Ministry of Agriculture and Rural Development Le Van Thiet said, farmers are recommended not to use cassava variety HL-S11 as this variety is very susceptible to diseases and will be infected immediately after being grown, which will create great losses to crop yield. Particularly, cassava variety KM94 is recommended to use by the Ministry of Agriculture and Rural Development since it is a disease-tolerant variety and despite the fact that though this variety has a low rate of flour, the possibility of being sick won’t be great and its yield won’t decline considerably. “In fact, the rate of infected cassava plants in the areas where farmers use cassava variety KM94 falls dramatically”, said Thiet.

For fall armyworms, Mr. Thiet said, the most attentive thing is that in the coming time farmers must visit their fields regularly to detect and deal with outbreaks soon and effectively. The local force of agriculture and plant protection officials should be active to conduct inspections to early detect and prevent diseases effectively. In particular, biological measures to prevent fall armyworms should be encouraged to use.

According to the Department of Agriculture and Rural Development, to prevent cassava mosaic disease, the provincial Plant Protection Department of disease-free cassava varieties KM140 and KM225 on an area of 92 ha in Xuan Loc district (two models) and Long Thanh district (2 models).

These models have adopted such measures as using yellow sticky traps to control mealybugs, spraying plant protection products to prevent their, and having “mealybug and cassava samples” tested during the monitoring period and before and after the harvest period to determine sick cassava varieties. Also, during the piloting period cassava plants of four models have developed and grown well; the effectiveness of sticky yellow traps is from 10 to 214 bugs per trap; and no infected cassava plants have been found out. At present, farmers have harvested 59 hectares with the average yield of 26 to 33 tons per ha and this source of disease-free varieties is expected to be provided for production activities.

To prevent and control the epidemic, the Chairman of the provincial People’s Committee has just sent documents on how to prevent and control cassava mosaic disease and fall armyworms to the Departments of Agriculture and Rural Development; Science and Technology; Information and Communications; and Industry and Trade; Provincial Public Security; People’s Committees of districts and cities; and provincial agencies, newspapers, and radio and television stations.

Accordingly, to promote the prevention and control of cassava mosaic disease and fall armyworms on corn plants, the Chairman of the provincial People’s Committee assigned the provincial Department of Agriculture and Rural Development to host and coordinate with concerned departments and sectors and localities to monitor the cultivation of corn and cassava to provide directions for varieties, crops, and farming methods against cassava mosaic disease and fall armyworms; further conduct investigations to early detect the areas infected with cassava mosaic disease and fall armyworms as well as introduce precautionary and preventative measures according to the Plant Protection Department’s technical process for prevention and control of cassava mosaic disease and fall armyworms; direct the agricultural promotion system to focus on disseminating propaganda information to and providing training in prevention and control measures for farming households; don quick tests of plant protection products with high efficiency against fall armyworms as a basis for giving recommendations to farmers; investigate and discover varieties of cassava with great resistance against mosaic disease to show farmers how to replace severely-infected varieties; and continue to apply the models of making disease-free cassava varieties and ensure that disease-free varieties are put into cultivation.

Duy Minh (T. C)