Eradication of banana moko in dry land areas requires a two-year sanitary break

Based on research results from Embrapa Amazônia Ocidental (AM) in partnership with Embrapa Roraima, scientists recommend a 24-month period for the banana tree health break to restore areas of dry land affected by bacterial wilt or banana moko. The disease is caused by the bacteria Ralstonia solanacearum race 2, a quarantine pest under official control, which is widespread in the states of Amapá, Amazonas, Roraima, Pará, Pernambuco, Rondônia and Sergipe.

Moko is one of the most destructive diseases of banana trees grown in floodplain areas of the Amazon Region, where annual floods are the crucial point for the spread of the bacteria, as flood waters spread the pathogen along rivers, contaminating all plantations downstream of the affected banana plantation.

In the municipalities of Tabatinga and Manicoré, in Amazonas, for example, plantations are affected by the disease, as they are established in the floodplains of the Alto Solimões and Madeira Rivers, respectively. In this case, eradication of the disease is practically impossible, as the areas are flooded every year and the flood waters spread the bacteria.

In dry land areas, the bacteria behaves like a transient soil pathogen, as it survives in this environment for a limited time. It cannot survive in the absence of host plant residues, nor does it produce endospores, which are resistance structures that ensure its survival under environmental stress conditions. After a two-year sanitary break, banana trees from healthy seedlings can be planted again in the area.

There are no resistant cultivars, and chemical control does not work either, because the disease is vascular, inform Embrapa researchers Luadir Gasparotto, Mirza Carla Normando and Daniel Schurt, in Technical Communication 168 “Survival of the bacteria Ralstonia solanacearum race 2,” released this year.

“In dry land areas, the disease only occurs when producers use contaminated seedlings from floodplains for planting. The bacteria is spread by root contact between plants and, within a few months, causes the death of the entire plantation,” explains Gasparotto.

As the spread of R. solanacearum Race 2 for dry land areas is anthropogenic (caused by human action), it can be avoided with exclusion measures, that is, planting healthy seedlings, disinfecting machines and implements used in diseased banana plantations and prohibiting the disorderly movement of vehicles, people and boxes used to transport bananas between plantations.

According to the research, eradication measures have shown good results in banana plantations on dry land, but in order to recommend eradication, it was important to define the survival period of the bacteria in the soil. Therefore, an experiment was carried out for two years at Embrapa, where the survival of banana seedlings of the Prata Anã and PV03-44 cultivars was evaluated in soils infested with the bacteria.

How the experiment was done

In infested trenches, on the day of infestation and at 2, 4, 6, 10, 12, 18 and 24 months after infestation, ten horn-type seedlings of each cultivar were planted. The evaluations consisted of monthly counting, for 24 months, of dead plants or plants showing typical symptoms of moko, such as wilting of leaves and darkening of tissues observed through cross sections of the rhizome and pseudostem. “The results obtained indicate that the bacterium R. solanacearum race 2 survives in infected banana rhizomes for up to ten months in Yellow Latosol type soils and for up to eight months in Argisol type soils”, informs the researcher.

To eradicate the disease, it is important to kill all banana plants. Researchers recommend that no plants be left alive. After all banana plants have died, it is recommended that the area be planted with other crops, such as cassava, manioc, pineapple, papaya and corn, for at least 24 months. During this period, all organic residues from the banana plantation will be decomposed. After a 24-month drought, without banana plants, the same area can be replanted with new banana plants, but with seedlings of known origin that are free of moko.

How to avoid the disease

1. Planting of proven healthy seedlings (certified).
2. Disinfect tools used in thinning, pseudostem cutting and harvesting operations; immersing the material in formaldehyde (1:3) or bleach (1:2) solutions after use on each plant.
3.  Elimination of the heart of the banana tree, as soon as the bunches emerge in varieties with deciduous bracts, aiming to prevent transmission by insects, using the hands to break the rachis.
   
4. Weed control should be carried out by applying herbicides instead of manual or mechanical weeding.
5.  In areas where moko occurs, it is recommended that well-trained people periodically inspect banana plantations to detect diseased plants early.
   

The actions implemented in this research are aligned with the following Sustainable Development Goals (SDGs) of the 2030 Agenda: 2 (Zero hunger and sustainable agriculture), 9 (Industry, innovation and infrastructure), 11 (Sustainable cities and communities), 12 (Sustainable consumption and production), 15 (Life on land) and 17 (Partnerships for the means of implementation).