Background

Coffee white stem borer larva © University of Greenwich

Stemborers (Coleoptera: Cerambycidae) are the most important pests of arabica coffee in Asia and Africa. The larvae bore into the stem causing death of young plants. Older plants may survive but yield is drastically reduced and susceptibility to diseases and termites greatly increased. Control methods are limited, and infested trees should be removed and destroyed to prevent infestation of surrounding trees. The cost of replanting and the loss of crop before the new tree starts yielding is such that uprooting of one plant per hectare per year accounts for annual loss of about US $ 8-10 million to the Indian coffee industry.
The coffee white stemborer, Xylotrechus quadripes, occurs in India, Sri Lanka, China and Vietnam. In India, coffee is grown on 300,000 ha, with 90% of this on smallholdings of less than 4 ha, particularly in remote hillside areas. Coffee cultivation provides livelihoods for >400,000 people as well as employment for many others in processing and trade. Furthermore, coffee and the associated shade trees make a major contribution to maintaining ecological balance in poor hillsides, preventing erosion and encouraging biodiversity.
In Africa, the main species is the white stemborer, Monochamus leuconotus, with the yellow stemborer, Dirphya nigricornis, also present. Malawi and Zimbabwe are very minor players in the global coffee supply, but coffee is an important source of foreign exchange for both countries. Malawi produces 5,600 tonnes pa. Around 95% comes from estates but there are 10,000 registered smallholder coffee growers. In a recent survey, over 90% of these smallholders ranked stemborer as the number one problem. Average annual production in Zimbabwe is 10,000 tonnes, almost exclusively arabica. Over 100,000 people depend directly on coffee cultivation for their livelihoods and many thousands more on distribution and marketing.

Objectives
The goal of this project is to produce arabica coffee in a sustainable manner in order to encourage long-term commitment by farmers, particularly smallholders, to the crop.
The project will contribute to this goal by increasing productivity through reducing constraints due to stemborers. This will be done by working with national programmes and coffee growers to:

• identify shortcomings and optimize present practices with currently available technology;
• develop new technologies in pest management, especially use of resistant varieties and biocontrol agents such as parasitoids, fungal pathogens, nematodes and pheromones;
• develop dissemination material and train extension workers in farmer participatory programmes.

NRI will assist in investigations of the use of pheromones against stemborers. The male-produced sex pheromone of X. quadripes has been identified in previous work. Semi-commercial production of lures and traps will be arranged to make possible large-scale evaluation of these for control of the pest in India. The presence and nature of pheromones in M. leuconotus will be investigated in Malawi and Zimbabwe. If appropriate, attraction of host-plant chemicals to stemborers will be studied, along with the role of host-plant chemicals and pheromones in host-finding by parasitoids of the stemborers.


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