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Biocontrol News and Information
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December 2002, Volume 23 No. 4
- General News
- IPM Systems
- Announcements
- Conference Reports
IPM Systems
This section covers integrated pest management (IPM) including biological control, and techniques that are compatible with the use of biological control or minimize negative impact on natural enemies.
Stemming a Coffee Pest
Coffee stem borers (Xylotrechus quadripes and Monochamus leuconotus), both cerambycid beetles, are now the major pest constraint to arabica coffee production in India (X. quadripes) and Zimbabwe and Malawi (both M. leuconotus) and are inflicting severe economic losses. A new project funded by the CFC (Common Fund for Commodities) with co-financing from national governments aims to meet the urgent need for an effective integrated management package for the pest. The new project, which is being implemented by CABI Bioscience , the Natural Resources Institute, UK (NRI), the Coffee Board of India, the Coffee Research Centre, Chipinge, Zimbabwe and Lunyangwa Research Station, Malawi, recently held its inauguration workshop in Chikmagalur, India.
Losses from the stem borer are cumulative. In addition to crop losses, investment has to be made to establish new plants in place of uprooted ones. As coffee trees take time to come into production, the effects of borer damage are felt for at least 5 years. A survey of the three countries reveals the extent of the problem.
- In Malawi, where coffee is the fourth most important export earner, the borer is the major pest constraint for smallholder coffee farmers, with incidence exceeding 90%.
- In Zimbabwe the borer has led to the uprooting and subsequent replanting of many plantations.
- In south India, where the borer has existed in coffee estates for more than a century, uprooting an average of one infested plant per hectare per year accounts for an annual loss of about US$8-10 million. The borer is the most destructive pest of arabica coffee in the country, and a growing trend to convert from arabica to robusta threatens export earnings.
Damage is caused by larvae, which hatch from eggs deposited in cracks and crevices and under loose scaly bark of the main coffee tree stem and thick primaries. The beetles show an oviposition preference for plants exposed to sunlight. Young larvae feed on the corky tissue just under the bark, which splits making the stem appear ridged. Later, larvae enter the hardwood and tunnel in all directions, even into the roots. Infested trees normally have yellow, wilting leaves, and ejected larval frass and emergence holes can be found on the stems. Severe ring barking of the main roots occurs below ground level, and extends above ground in rejuvenated coffee.
Attack often causes death of young (1- to 2-year-old) coffee and severe wilting of older (3- to 4-year-old) trees. Mature trees are not necessarily killed but, especially in Africa, they become susceptible to termite attack, particularly in the absence of supplemental irrigation during the dry season. In general, infested trees are of poor vigour and yield poorly.
Current management strategies are generally ineffective, or rely on undesirable chemical applications. Cultural control methods include uprooting and burning infested trees, treating the stems during the oviposition period to kill or dislodge eggs and young larvae, catching and killing adults during their period of activity, and maintaining shelter belts in order to shade the coffee bushes. Chemical control includes treatment of stems and primary branches with BHC (or other general insecticides) to reduce the pest incidence.
Biological control of X. quadripes was attempted in Vietnam during the 1920s. Mass rearing and release of the two most easily reared parasitoids found in plantations ( Doryctes strioliger and Sclerodermus domesticus ) led to an increase in parasitism rates, but this was not maintained after releases ceased. The high cost of developing a continuous mass rearing programme led to the work being abandoned.
A variety of control measures are under trial on a local basis in the different countries:
- Maintaining optimum shade.
- Tracing infested plants before flight periods each year by looking for ridges on main stems and thick primaries. Identified plants are collar pruned (and uprooted if the borer has entered the root) and infested material is burned.
- Removing loose scaly bark of the main stem and thick primaries using coir glove or coconut husk, but avoiding damage to the stem, which could kill the coffee or facilitate pathogen entry.
- Spraying/swabbing the main stem and thick primaries during flight periods with Lindane 20EC and a wetting agent.
Given the urgency of the situation and the need to alleviate losses as quickly as possible, the project, in partnership with national programmes and coffee farmers, will assess current measures to identify shortcomings and optimize good practice. It also aims to research and develop new technologies in pest management, concentrating particularly on the potential of biocontrol agents (parasitoids, fungal pathogens and nematodes) and other biologically-based methods including improved agronomic practices, safer pesticides, botanical repellents and pheromones. A participatory approach will be used to maximize dissemination of the knowledge generated in this project.
To achieve the project aims, the collaborating scientists will conduct socio-economic and biological surveys, screen coffee varieties, identify and evaluate potential biological control agents and initiate rearing programmes, and establish field trials to quantify the efficacy and potential of control methods. The dissemination of the project outputs will be enhanced by developing and facilitating improved extension mechanisms through training of trainers and extensionists in farmer participatory approaches.
The project was formally launched on 11 September 2002 at a 4-day Knowledge Workshop held in Chikmagalur in India's main coffee-growing state of Karnataka. Delegates from all the countries involved in the project, including scientists, extensionists and growers from India heard presentations on the history and technical aspects of the stem borer problem and its management with overviews of the problem in each country. All delegates were invited to share their views and participated in group discussions which led to finalized workplans for the first 2 years of the project.
The vast amount of knowledge, experiences and ideas imparted to all at the event will be made more widely available. The proceedings of the workshop will be published and distributed to assist the dissemination of technologies to help other coffee-growing countries not directly participating in the project, but where stem borers are also a problem (e.g. China, Sri Lanka and Vietnam).
With the world coffee industry in crisis, and prices at an all-time low, smallholder livelihoods are under threat as never before, and if the smallholder farming sector is to survive and compete with large plantations, it needs help to solve problems and develop new strategies. In the prevailing conditions, smallholder farmers tend to reduce all inputs including pest control efforts, which leads to reduced quality and quantity, thus further affecting their economic position. The best response to the situation, however, is to concentrate on increasing quality, and adopt tactics that help reduce inputs of dangerous and costly chemicals. Such a strategy will also facilitate entry to new markets, which pay more for environmentally friendly, sustainably produced coffees. This project aims to help smallholders achieve this, and protect them from any future claims that they are insensitive to the increasing environmental awareness of consumer countries.
Contact:
Peter Baker (International Co-ordinator),
CABI Bioscience UK Centre,
Bakeham Lane, Egham,
Surrey TW209TY, UK
Email: p.baker@cabi.org
Fax: +44 1491 829100
Sean Murphy (India Co-ordinator),
CABI Bioscience UK Centre,
Silwood Park, Ascot, Berks SL5 7TA
Email: s.murphy@cabi.org
Fax: +44 1491 829123
George Oduor (Africa Co-ordinator),
CABI Africa Regional Centre,
ICRAF Complex, PO Box 633,
Village Market, Nairobi, Kenya
Email: g.oduor@cabi.org
Fax: + 254 2 522150