Leaf miner – a major problem for palm oil producers

Overview

Results

The team

Related information

So what's the problem?

Palm oil and palm kernel oil are used in products all around the world. A common cooking ingredient in countries where it is produced, palm oil is used extensively in the commercial food industry elsewhere, from margarine and chocolate to cream cheese and oven chips, as well as in cosmetics and increasingly, for use in bio-diesel. As the highest yielding of all oil crops, it is by far the most widely-produced tropical oil, and constitutes thirty percent of total edible oil production worldwide.

The oil palms comprise two species of the palm family and the African oil palm, Elaeis guineensis, is native to West Africa where the processing of oil palm fruits for edible oil has been practiced for thousands of years. In Ghana, oil palm is a valuable economic crop and provides a major source of employment, allowing many small landholders to participate in the cash economy. The yield of plantations is often compromised however, not only by climatic factors such as erratic rainfall but also by pest outbreaks. The oil palm leaf miner (Coelaenomenodera lameensis) is the most serious pest of oil palm in West Africa. Heavy infestations can cause 90% defoliation which can subsequently lead to a 50% reduction in fruit over the following 3 years.

Leaf miner outbreaks are sporadic and difficult to predict and control with pesticides has proven costly and beyond the means of smaller producers. Industrial-scale producers grow oil palms in large plantations and have suffered from severe outbreaks over the years resulting in big impacts on business. The social drive towards more environmentally sound and sustainable plantations has put the use of chemical pesticides under close scrutiny. Awareness of pesticide resistance and health issues through over use of these chemicals have highlighted the need for increased knowledge of the leaf miner and its dynamics and for a move towards more environmentally sustainable integrated pest management methods.

What is this project doing?

Unilever – a large producer of palm oil in Ghana – contracted the CABI E-UK-Lancaster Environment Centre Alliance to carry out a scoping study at their oil palm plantations in Ghana, with a view to improving the management of leaf miner outbreaks by a) identifying key components of current management practices and capturing local knowledge through field visits and interviews with farmers and managers and b) assessing the potential for alternative practices and their suitability for incorporation into the system as part of a sustainable Integrated Pest Management strategy.

The project involved a full review of literature covering leaf miner biology, ecology and control in order to gain a full understanding of the pest and previous research. The team carried out a field trip to the two nucleus Unilever plantations in Ghana to get an understanding of the problem first-hand and met with some of Ghana’s oil palm research scientists from the Oil Palm Research Institute. Following this, a plan of recommended actions was drawn up.

Results so far

CABI undertook the literature review and field trips to Ghana. Here, Unilever showed the scientists around its two oil palm estates, both totalling in the region of 4,000 plus hectares. Private producers with a total of over 4,400 hectares supply additional oil palms to Unilever, these consist of out-grower farms and small holders (usually part of a co-operative) located close to the two central Unilever estates; these were also visited.

Patrols of the Unilever plantations are carried out daily during which leaf miner hotspots are identified and treated. Paper records of these daily checks, along with rainfall and yield data dating back to 1983 had been kept and were made available to the project team. An immediate recommendation was to transfer the data from hard copy to electronic format to allow easier, more comprehensive and less labour intensive analysis. A visit was also made to the Oil Palm Research Institute in Kade, an organisation with in-country expertise of pest management dating back 20 years; as their support and knowledge could prove crucial for the success of any future projects.

The final report was submitted to Unilever, and a general summary of the final recommendations is given below:

Enhance understanding of the biology, ecology and systematics of the pest

A better understanding of the factors that influence the dynamics of leaf miner populations needs to be gained. It is thought that more than one species of Coelaenomenodera could be present and a key step in understanding the pest is its correct identification. Easily transferred identification skills need to be taught to field workers and managers and the factors influencing the impact of natural enemies also need to be investigated.

Maximise conservation biological control and enhance the effect of under-storey species

Growers should review the use of non-selective pesticides that appear to be disrupting the communities of native natural enemies. Also, studies on the influence of non-crop vegetation (or under-storey species) which may enhance natural enemy populations need to be carried out.

Assess the potential for resistance breeding

Unilever should incorporate testing for resistance to leaf miner damage into yield improvement breeding trials and investigate any other resistance enhancing techniques.

Assess the biodiversity supported by different systems

There are currently four growing systems in place: plantation; out-grower; smallholder; and organic. The level of biodiversity present in each of these habitats and its influence upon leaf miner damage needs to be assessed.

Investigate the potential for more rational and environmentally benign insecticide use

Current treatment of leaf miner outbreaks involves the use of a fog-pesticide. Although often an effective killer of leaf miner adults there are various drawbacks associated with this technique. For example, it is harmful to a number of other insects, some of which are natural enemies to leaf miner. A full assessment of alternative chemicals and application methods should be carried out.

Interactions between age-structured pest populations and the predators, pathogens and parasitoids which control them, together with the influences of external factors such as insecticide use and environmental fluctuations all provided an enormous and complex web of dynamics for research. Definitive causes for the occasional outbreaks were beyond the scope of this initial visit. However, it is hoped that by undertaking research along these lines, large producers of palm oil will be able to learn how to manage outbreaks of leaf miner without harming profits or the environment.

Project Manager