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Weed management


Weed management

Weeds

Photo by Nicolas Fégeant, UGPBAN

Weed management consists in removing the weeds that compete with the banana plant for resources and favour the development of parasites. Controlling weeds is particularly important in the first few months after plantation when the banana plants are small and there's little shade. In commercial plantations where banana plants are grown on bare soil, sowing a ground cover can reduce the use of herbicides.

Chemical control

The use of herbicides to control weeds dates back to the 1970s. But herbicides are not only toxic, there also persist in the soil. Moreover, their uncontrolled use can lead to soil erosion, loss of organic matter and a reduction in the soil's biological activity. In the 1980s, certain production zones along Costa Rica's Caribbean coast had to be abandoned because of that reason. Herbicide use is now better controlled. Applications should be conducted at the most appropriate time and respect the recommended doses.

Herbicides

Two types of herbicides are used in commercial plantations: contact herbicides (e.g. paraquat) and systemic herbicides (e.g. glyphosate, glufosinate ammonium).

Contact herbicides only destroy the plant's aerial parts that come in contact with the product. They will eliminate annual plants, but since the root system is not affected, perennial weeds will grow back. The volume needed is also high (200 to 400 liters per hectare). They are best used at the beginning of a production cycle.

Systemic herbicides destroy the entire plant and the volumes needed are lower, a maximum of 100 liters per hectare. Systemic herbicides are recommended for established plantations.

Herbicide application

The herbicide should be applied in a fine layer when the climatic conditions are favourable and before the weeds have started producing seeds. The equipment must be in good condition and calibrated. It's important to be precise to avoid spraying the banana plants, the naked soil or the useful cover crops.

Backpack spayers are the most commonly type of equipment used. They are especially useful to reach hard-to-access areas. Drift and an uneven distribution of the herbicide are more common with sprayers in which the pressure is maintained by operating a hand pump, than with sprayers that can maintain a constant pressure.

A combustion engine backpack sprayer or a pressure regulating nozzle can ensure a constant pressure and improve the efficiency of the application. Low-volume sprayers can distribute pur or concentrated products, thereby reducing the volumes applied.

The drop size can have an effect on several parameters. Large drops reduce drift and evaporation. Small drops, on the other hand, have a better penetration. The type of nozzle will affect the spray angle, the droplet spectrum, the drop size, drift, the operating pressure and the type of herbicide[1].

Type of nozzle
ADI drift reduction nozzle
 
CVI anti-drift nozzle
 
AVI anti-drift nozzle
 
APM ceramic inserted deflector nozzle
ATR hollow cone nozzle
 
Spray angle
Droplet spectrum
Drop size
Medium
300-400 µm
Large
400-600 µm
Large to very large
500-600 µm
Very large
>600 µm
Fine
<150 µm
Drift
Low
Very low
Very low
Low
High
Recommended pressure
2-4 bar
1.5-3 bar
3-5 bar
1.3 bar
3-20 bar
Contact herbicide
Excellent
Good
Good
Excellent
Excellent
Systemic herbicide
Excellent
Excellent
Excellent
Good
Good

Selective chemical control

Instead of applying herbicide indiscriminately, the operator can target which plant to remove and which to maintain. This practice not only reduces the volumes of herbicide applied, it also favours the establishment of a natural plant cover that will not interfere with the banana plants. Examples of such species are Geophila macropada, Galactia striata, Evolvulus nummularis and Murdania nudiflora. This cover will provide services such as reducing erosion and leaching, or limit the development of weeds that may compete with the banana plants or be hosts to pests and pathogens.

Manual and mechanical weeding

Manual weeding is labour intensive but requires little equipment. Besides being slow, it can damage the banana plant, transmit pathogenic bacteria ou contribute to weevil build-up.Weeding should start one meter away from the pseudostem to avoid damaging the plant.

Mechanical weeding is possible in plantations in which the bananas have been planted in double rows. Having a larger alley allows mechanization. Using light equipment prevents soil compaction. There is a need to develop equipment better adapted to more environmentally-friendly situations.

Cover crop

Main page on cover crop

Weeds can also be controlled by planting a ground cover  that will prevent the growth of weeds without negatively impacting banana yields[2][3]. Some of these species can also have an allelopathic effect[4][5].

References

1. Institut Technique Tropical. Weed management. Manuel du planteur. ITT, France.
2. Tixier, P., Lavigne, C., Alvareza, S., Gauquier, A., Blanchard, M., Ripoche, A. and Achard, R. 2011. Model evaluation of cover crops, application to elevens pecies for banana cropping systems. European Journal of Agronomy 34(2):53-61.
3. Dorel, M., Tixier, P., Dural, D. and Zanoletti, S. 2011. Alternatives aux intrants chimiques en culture bananière. Innovations Agronomiques 16:1-11.
4. Dore, T., Sene, M., Pellissier, F., Gallet, C. 2004. Approche agronomique de l'allelopathie. Cahiers Agriculture, 13(3):249-256.
5. Bais, H.P., Weir, T.L., Perry, L.G., Gilroy, S., Vivanco, J.M. 2006. The Role of Root Exudates in Rhizosphere Interactions with Plants and Other organisms. Annu. Rev. Plant Biol. 57:233-66.

Further reading

Control de malezas en plantaciones bananeras mediante el uso de coberturas nobles produced by Augura, Colombia's association of banana producers.

Also on this website

Musapedia pages on pesticide-reducing practices:

 

This page is part of a series initiated by a grant from the Ministère français de l'agriculture, de l'agroalimentaire et de la forêt to the World Banana Forum.White