Sustainable management of coffee green scales in Papua New Guinea

• PNG Coffee Industry Corporation, Papua New Guinea
• University of New South Wales, Australia

Coffee is the largest earner of foreign exchange within the PNG agricultural sector (> 43% of PNG agricultural exports and 10% of total exports). Primarily produced by smallholders in the highlands (397,000 families and 85-90% production in 2003), with few management inputs, productivity is hampered by inadequate pest management as well as by deficiencies in quality management and marketing.
With the latter problems being addressed by other ACIAR projects, this project is developing and fostering uptake of biological control and other integrated strategies for coffee green scale (CGS - Coccus celatus De Lotto and C. viridis (Green) (Hemiptera:Coccidae)), a pest capable of causing up to 50% yield reduction in some instances. The scale insects colonise leaves and stems of the plant, closely adhering to them. Although immobile, they avoid attack by natural enemies because they are guarded by ants that drink their honeydew, the partially digested plant juices that flow quickly through the digestive tract of the pest. The quality of bean is likely to be affected by CGS, since quality depends on bean density and during ripening there is often a critical shortage of nutrients to fill the bean sufficiently before harvest comes.
In consultation with smallholders, the PNG Coffee Industry Corporation (CIC) has confirmed the urgent need to develop and introduce integrated management systems for coffee green scale. Currently the European Union (EU) is supporting CIC to develop capacity for research in IPM and biological control of CGS, but this effort (provision of facilities, equipment, training, access to parasitoids) needs the complementary R&D supplied by this project.

Objectives of this project are:
to document baseline information on the distribution, impacts, biology and control of CGS in the coffee-growing zones of PNG;
to evaluate biological and other control methods of CGS, taking into account grower information;
to develop regional and national strategies for wider evaluation and implementation of CGS control.

The project is developing an integrated management strategy for coffee green scale (CGS) in PNG based on cost-effective control methods suitable for smallholder farmers. Project members seek a better understanding of the pest species and why it is causing such a problem. They are then establishing the best short-term strategy for control, based on currently available methods. This will be followed by development of a long-term sustainable strategy, based as much as possible on use of natural and cultural control methods.
The project team is fostering the engagement and commitment of smallholders into these strategies, and ensuring that they harmonise with any overall strategic plans for PNG coffee and any mandatory certification requirements for export coffee. PNG researchers and extensionists are receiving contingency planning and skills training, focused on green scale control, parasitoid introduction and assessment.