A hot bath for the suckers!

An effective treatment against nematode and weevil pests of banana and plantain

Plantain plant with three sword suckers, field trial on IITA campus, Ibadan, Nigeria. Photo by A. zumFelde, IITA.
Plantain plant with three sword suckers, field trial on IITA campus, Ibadan, Nigeria. Photo by A. zumFelde, IITA.

Banana and plantain (Musa spp.) are important food crops for millions of people all over the world. The banana is the most popular fruit in the world and number one in international trade. The FAO estimates that over 100 million t of banana and plantain were produced worldwide in 2007. In sub-Saharan Africa (SSA), over 70 million smallholder farmers depend on the two crops for their food and income.

Banana and plantain production is greatly constrained by pests and diseases that lead to annual losses of millions of US dollars. The most important pests are nematodes (several species) and weevils (Cosmopolites sordidus) that are found in the soil and roots.

Nematodes attack the roots, hampering the uptake of nutrients from the soil and drastically reducing yield. In severe cases, they topple the whole plant. Weevils, on the other hand, attack the plant’s underground corm, weakening the plant and causing stem breakage. Average production losses from nematodes are estimated at 30% of the harvests of highland banana in East Africa and can exceed 60% for plantain in West Africa.

These two pests are spread from one farm to another through the planting of infested suckers. Farmers can avoid infesting their farms by ensuring that they plant disease- and pest-free suckers, such as those derived from tissue culture. These are, however, out of reach for the millions of small-scale farmers in sub-Saharan Africa.

Farmers dipping peeled suckers in boiling water. Source: D. Coyne, IITA.
Farmers dipping peeled suckers in boiling water. Source: D. Coyne, IITA.

Research has shown that peeling and treating the suckers in hot water, at 50 °C, can effectively remove both nematodes and weevils and their eggs. This method has worked successfully for commercial farms and organized cooperatives but not for small-scale farmers. This is because a thermometer must be used to ensure precision and the right temperature and this is not readily accessible to the farmers in SSA.

IITA’s scientists Danny Coyne and Stefan Hauser have developed an easier method that is just as effective by simply immersing the peeled or unpeeled suckers in boiling water for 20–30 seconds.

The counting
The duration of 20–30 seconds can be achieved by simply counting from 1 to 30. Farmers can also use small objects, such as pebbles, to mark the time: picking the pebbles one by one and placing them in a small container. The counting takes about 1 second/item but farmers can check the time for more accuracy.

This technique has proven to be friendly to small-scale farmers and is better than the hot water treatment at 50 °C as the time taken to treat a sucker is reduced and the measurement of the temperature and timing is simplified. It effectively disinfects suckers of various sizes without affecting their germination

Plantain field planted with suckers treated in boiling water. Photo by A. zumFelde, IITA.
Plantain field planted with suckers treated in boiling water. Photo by A. zumFelde, IITA.

The method is radical and requires skill and care when it is promoted to farmers who may be sceptical at first. The scientists recommend the use of a demonstration plot to introduce the technology and convince farmers to adopt it. They must keep within 30 seconds as otherwise they risk damaging the suckers, especially those that are small-sized.

Although the technology requires a fuel/energy source and the process has to be followed precisely, it is definitely a much easier method to use than the hot water treatment.

Using boiling water to treat the suckers has the potential to improve banana and plantain productivity by eliminating the two pests.