Loading...
 

Deleafing


Deleafing

Deleafing blade

Photo by Nicolas Fégeant, UGPBAN 

Deleafing is the sanitary removal of leaves, or parts of them, that are infected with black leaf streak (BLSD). Banana leaves being the only source of inoculum of BLSD, and the capacity to produce ascospores being higher in living leaves than in cut leaves laying on the soil, less ascospores will be released. Deleafing increases the efficiency of fungicide applications and has been shown to reduce the premature ripening[1]. However, it involves a trade-off between the removal of infected leaves and the preservation of a minimum leaf surface area to ensure an adequate development of the bunch until harvest. Studies have shown that the weight of the bunch is not appreciably affected when the number of leaves between flowering and harvest is between 5 and 7[2][3].

Methodology

Sanitary deleafing

Sanitary deleafing consists in the surgical removal of part of a leaf. It generally follows the order of apparition of the symptoms: the tip, the left blade and the right blade. The removed leaves are generally at stages 5 or 6 of the disease (also stage 4 if the density of spots is high), these stages being the most visible. A weekly deleafing is recommended.  It's also recommended to deleaf before the application of fungicides to avoid the selection of resistant strains. All the plants must be examined, even the suckers.

The trade-off between removing the entire leaf and removing only the infected part depends on the severity of the disease and the rate of deleafing:
  • For infections that cover less than 30% of the leaf area, it's preferable to remove the infected part;
  • When more than 40% of the leaf area is infected, it is recommended to remove the entire leaf.

Early deleafing

This method consists in the weekly removal of the leaf tip (about 20 cm) of one of the 5 oldest leaves before the appearance of necroses[4][5]. It is complementary to sanitary deleafing and is particularly useful in areas where the conditions are favourable to the development of BLSD or during the rainy season.

Deleafing at flowering

This method consists in systematically removing the 3 oldest leaves at flowering. This strategy has a strong impact on the plant's leaf area. It anticipates, but does not replace sanitary deleafing since symptoms can appear on other leaves before harvest.

Deleafing residues

The cut leaves should not stick to the base of the plant or the sucker, to avoid contamination. Infected leaves being sources of inoculum even when they have been cut and left on the soil, it is recommended to accelerate their decomposition. If the scientific community does not agree which side of the leaf should face the soil, it agrees that piling them reduces spore dispersion. Two methods need further testing in commercial plantations to evaluate their efficiency:
  • The regular application of various products (e.g. glyphosate, chlorotalonil, bacteria, molasses, urea) in order to accelerate decomposition. Mixed results have been obtained, except for the weekly application of urea (5 or 10%) which has given interesting results[6][7][8].
  • Composting the leaf and crop residues between the rows could reduce inoculum and bring nutrient and organic matter to the soil. The effect remains to be evaluated.

Troubleshooting

New necroses appeared after the removal of the tip and right blade. The entire leaf will need to be removed during the next round.
New necroses appeared after the removal of the tip and right blade. The entire leaf will need to be removed during the next round.
Presence of BLSD on the suckers. All the plants, including suckers, need to be looked at and subjected to deleafing if symptoms are present.
Presence of BLSD on the suckers. All the plants, including suckers, need to be looked at and subjected to deleafing if symptoms are present.
Botched partial removal as the infected part remained attached to the leaf. Tools need to be sharp and operators should ensure that the infected part is actually removed.
Botched partial removal as the infected part remained attached to the leaf. Tools need to be sharp and operators should ensure that the infected part is actually removed.
Photos: Nicolas Fegeant, UGPBAN

Impact

A study conducted in Guadeloupe at a time when only Mycosphaerella musicola was present, showed that although deleafing reduced the weight and diameter of fruits harvested at 900 degree-days, their green life was significantly increased[1]. In highly infested plots, leaf removal increased the green life from an average of 7.7 days to 45.8 days. The authors also note that intense deleafing (leaving less than 3 leaves on a plant) negatively impacts fruit weght. However, leaving 5 or more leaves should not significantly affect yield. Since the presence of necrotic tissues during the last month of fruit growth seems to be responsible for the physiological changes linked to early ripening, the authors suggest that in severe infestations, yield losses could be reduced by deleafing one month before harvest.

References

1. Chillet, M., Castelan, F.P., Abadie, C., Hubert, O. and De Lapeyre De Bellaire, L. 2013. Necrotic leaf removal, a key component of integrated management of Mycospaerella leaf spot diseases to improve the quality of banana: the case of Sigatoka disease. Fruits 68(4):271-277.
2. Daniells, J.W., Lisle, A.T. and Bryde, N.J. 1994. Effect of bunch trimming and leaf removal at flowering on maturity bronzing, yield, and other aspects of fruit-quality of bananas in North Queensland. Australian Journal of Experimental Agriculture 34:259-265.
3. Vargas, A., Araya, M., Guzman, M., Murillo, G. 2009. Effect of leaf pruning at flower emergence of banana plants (Musa AAA) on fruit yield and black Sigatoka (Mycosphaerella fijiensis) disease, International Journal of Pest Managagement,55:19-25.
4. Chica, R., Herrera, M., Jiménez, I., Lizcano, S., Montoya, J.A., Patiño, L.F., Rodríguez, P.A. and Ruiz, L.H. 2004. Impacto y manejo de la Sigatoka negra en el cultivo de banano de exportación en Colombia. p.53-62. In: Orozco-Santos, M., Orozco Romero, J., Robles-Gonzáles, M., Velázquez-Monreal, J., Medina-Urrutia, V. and Hernández-Bautista, J.A. (eds.). Proceedings of Reunión Internacional ACORBAT, Oaxaca (MEX), 2004/09/26-10/01. Publicación especial del XVI reunión internacional ACORBAT. ACORBAT, Oaxaca (MEX).
5. Martinez-Acosta, A.M., Castaneda-Sanchez, D.A., Bornacelly-Horta, H. and Merchan, V. 2006. La poda trempana, practica en el manejo integral de la Sigatoka negra en banano. Proceedings of the XVII International Meeting of ACORBAT. Joinville, Brazil, October 15-20. Pp. 690-697.
6. Guzman, M. and Romero, R. 1995. Determinacion del efecto antiesporulante de diferentes compuestos sobre Mycosphaerella fijiensis. p. 46. In: Informe anual 1994. Departamento de Investigacion y Diversificacion Agricola CORBANA (Corporacion Bananera Nacional). San Jose, Costa Rica.
7. Villalta, R. and Guzman, M. 2005. Capacidad de esporulacion de Mycosphaerella fijiensis en tejido foliar de banano depositado en el suelo y efecto antiesporulante de la urea. Resumen, p. 14 In: 1er Congreso Cientifico Tecnico Bananero Nacional. Pococi, Limon, Costa Rica.
8. Guzman, M., Calvo, CM., Ovando, R. and Vargas, R. 2005. Evaluacion preliminar del efecto de la aplicacion de bacterias, melaza y urea sobre la degradacion de hojas de banano y la esporulacion de sigatoka negra en hojas a nivel de suelo. pp. 54-56. In: Informe anual 2004. Direccion de Investigaciones Agricolas CORBANA (Corporacion Bananera Nacional). San Jose, Costa Rica.

Also on this website

Musapedia pages on pesticide-reducing practices:

Further reading

Deleafing banana plants to control sigatoka by Australia's Queensland Department of Agriculture, Fisheries and Forestry

 

This portal was initiated by a grant from the Ministère français de l'agriculture, de l'agroalimentaire et de la forêt to the World Banana Forum.White