Better weed management in bananas

Bananas are an important export from the PhilippinesLower costs and favorable environmental effects when using paraquat: these were the key conclusions from a four-year comparison of weed control methods in bananas, recently completed by the University of the Philippines. The trial was conducted on a commercial plantation on Mindanao, the large southern island of the country. Bananas make a significant contribution to the economy of the Philippines being a major fruit export. New plantations are being established on more sloping land where soil erosion

Description

Displacement of solids (soil, mud, rock and other particles) usually by the agents of currents such as, wind, water, or ice by downward or down-slope movement.

Authoritative On-line References and Resources

http://soilerosion.net/ This site brings together reliable information on soil erosion from a wide range of disciplines and sources. It aims to be the definitive internet source for those wishing to find out more about soil loss and soil conservation.
poses a real threat to sustainable production. Filipino authorities estimate that 623 million tonnes of soil are lost annually from 28 million hectares of land.
Erosion can be reduced by maintaining a vegetative cover on the soil. So, it is important to manage weeds so that they give as much cover as possible to help avoid erosion, but not to allow them to compete with the crop. Two weed control programs were compared. In the field trial, traditional methods of hand weeding and slashing with a machete called a bolo were compared to a monthly spray program in a sequence of two applications of paraquat followed by one of glyphosate. In the latter two years of the trial, these regimes were modified to match changing patterns of weed growth, and weeds were controlled only by paraquat when a threshold of 30% ground cover was breached. Weed control using paraquat reduced soil losses. Low intensity rain = <5mm/h; medium = 5-<10mm/h; high = >10mm/hManaging the weed cover in this way was very successful in reducing soil erosion in both regimes to less than 1 tonne/ha/year, even though plots were laid out on gradients of up to 25%. Also, in bananas the ground becomes covered with decaying leaf material from the crop which helps to protect the soil. Water run-off

Description

The occurrence of surplus liquid (like rain) which originates up-slope and is collected beyond the ability of the soil to absorb it. The surplus liquid then flows away over the surface to reach the nearest surface water (pond, lake, river).

Authoritative On-line References and Resources

US Geological Survey's Water Science School
and soil loss tended to be less from plots sprayed with paraquat, but, as amounts were generally small, these were often not statistically significant.
However, when rainfall events were analysed more closely, the advantages of chemical treatment were clear as the intensity of rain increased. Manual weeding methods that disturb the soil can encourage erosion, damage crop roots and stimulate the germination of new flushes of weeds. In addition to competing with bananas for water and nutrients, weeds can also host pests and diseases. Some broadleaved weeds

Description

The leaves are "broad" as opposed to the "narrow" leaves of grasses. Also called 'dicots' having two seed leaves, while grasses are 'monocots' having one seed leaf.

Authoritative On-line References and Resources

http://www.iwss.info The International Weed Science Society.
prevalent in this study which may reduce yield indirectly and increase the need to use other crop protection products are shown below.

Banana weeds hosting pests & diseases

  • Bidens pilosa is host to Ralstonia solanacearum, which causes moko bacterial wilt, one of the most devastating pathogens to bananas in the Philippines, second only to sigatoka. Infections in the vascular system block transport of water and nutrients.
  • Acalypha indica can harbor nematodes (Meloidogyne spp.), a serious banana pest.
  • Ageratum conyzoides hosts various nematodes and fungal pathogens.
  Earthworms are important indicators of, and contributors to, soil fertility. Populations were studied in each of the four years. There were no differences between numbers of earthworms in manually and chemically weeded plots, indicating that chemical treatment has no adverse impacts on biodiversity

Description

The variety of life in all its forms, levels and combinations. Includes ecosystem diversity, species diversity, and genetic diversity (IUCN, UNEP and WWF, 1991).

Authoritative On-line References and Resources

http://earthtrends.wri.org/ EarthTrends is a comprehensive online database, maintained by the World Resources Institute, that focuses on environmental, social, and economic trends. Statistics on biodiversity indicators are available.
and soil fertility.
Over the whole duration of the trial, using paraquat and glyphosate reduced the cost of weed control by more than 40% compared to the traditional hand methods. Spraying was much quicker and needed only one quarter of the labor required for manual weeding.

Notes

The brand name for the leading paraquat product is Gramoxone