Coffee Berry Borer (Hypothenemus hampei)

Genetics

DNA studies coming out of Kirkendall's lab in Norway suggests that all the CBB from Latin America seem to be genetically very similar but the CBB from Jamaica is slightly different, suggesting that this introduction (in the late 1970s) was maybe directly from Africa or Asia. Considering Jamaica's close affinity with Ethiopia, it is interesting to speculate whether the CBB came from this part of Africa, the country of origin of Coffea arabica.

Cenicafé Colombia has embarked upon a long-term collaboration with Cornell University in the US to genetically engineer resistance into the coffee berry. Ideas include the use of a Bacillus thuringiensis gene or a gene for a protease enzyme. This work is at an early stage and it is expected to take many years before a transgenic plant is available.

Parasitoids

There are four main recognized parasitoids: two bethylids,- Cephalonomia stephanoderis and Prorops nasuta; a eulophid,- Phymastichus coffea and a braconid Heterospilus coffeicola. All are of African origin and the first two are now widely spread throughout Latin America. The third has proved difficult to rear but these problems have now been solved by Jaime Orozco and his staff at Cenicafé (fcjoro@cafedecolombia.com) who is currently producing up to 10,000 per day. Field releases have been made but it is too early to say whether it has established in Colombia.

The fourth parasitoid, H. coffeicola, has never been released anywhere because it has never successfully been reared in the lab. This is a vital step because all coffee insects must be quarantined in a third (non-coffee) country to ensure that spores of coffee berry disease (Colletotrichum coffeanum) are not carried over to countries that do not have the disease. Recently there is renewed interest in H. coffeicola because Ed King of ARS Weslaco believes that it might be possible to mass rear this on an artificial host (i.e. removing the need to keep large and costly CBB cultures). He has already achieved this remarkable feat for Catolaccus grandis, a braconid parasitoid of the bollweevil (Anthonomus grandis) and believes that in principle it would be possible for H. coffeicola.

Mass field releases of C. stephanoderis in El Salvador by Dufour and in Colombia by Aristizábal and Salazar have shown promise as a method of control, though the costs of mass production are still much too high for it to be economic. For this reason there is much interest in mass production techniques using artificial diet for the CBB originally invented by Villacorta of Brazil. Both Cenicafé and Ecosur of Mexico are developing improved versions of the diet.

Entomopathogenic fungi

Beauveria bassiana is the most promising and most studied entomopathogenic fungus, especially in Colombia where the humid conditions make it more likely to succeed than in a drier or more seasonal environment. Field lifetable studies of the CBB in Caldas Colombia which has a continuously humid climate, shows that natural levels of B. bassiana are responsible for up to 80% mortality of adults when they are attacking young berries (> 90 days old) and this means that the fungus is the largest biotic mortality factor for the broca under these conditions.

Applications of the fungus in the field tend to be variable, high mortality of CBB in the entry canal of the berry (80%+) have been achieved but only at uneconomically high doses. At lower doses the mortality is usually between 20 and 50% of CBB adult females entering the berry. Research is currently underway at Cenicafé to improve formulation and application techniques.

Another problem with the fungus is the quality of the marketed product; research at Cenicafé, which routinely evaluates spore quality of private producers, shows that both viability and virulence can vary widely. Hence at this moment, although the fungus shows some promise, its commercial potential is uncertain.

Entomopathogenic nematodes

Relatively little effort has been dedicated to the use of nematodes to control CBB. They would be difficult to apply to coffee trees, but they might be a lot easier to apply to the ground under the trees and the micro-climate might be very suitable for them there. The fallen berries under the tree are known to be a very important reservoir of reinfestation and yet difficult to control either by chemicals, fungi or manual collection and experimental releases of parasitoids suggest that few of them attack fallen berries. Hence what is needed is something that could actively search for an infested berry and tunnel its way into the berry to attack the CBB inside. This is the rational behind an initial feasibility study currently underway at IIP in the UK. Anyone interested in more details should contact Dr Bill Hominick at cabi-iip@cabi.org.

Cultural control studies

Simple hand collection of all ripe and over-ripe berries after harvest to break the cycle and leave little substrate for immigrating CBB is highly recommended and has been widely adopted in Colombia. The problem with this method is that it is very labour intensive and costly where wage costs are high. Exhaustive studies in Colombia by Peralta show that farmers tend to leave many berries after harvest, especially low down on the trees, probably because they don't like stooping to do it. He also showed conclusively that the older the tree, the harder the farmers find it to remove the berries. Experiments are currently being carried out in Colombia to study ways to make this process more efficient, including pruning of lower unproductive branches, application of substances to the ground (urea etc.) to promote rapid decomposition of fallen berries and mechanical removal of fallen berries. Studies on this are still at an early stage.

Chemical control

Most farmers still prefer to use endosulfan though because this is a very toxic substance and workers seldom use protective clothing, likelihood of poisoning is high, especially where intensive methods are used with up to 10,000 trees per hectare. Thus a worker 1.6 m high pushing his way through dense foliage of trees 2 m high with no protective clothing is almost bound to contaminate himself. This is indeed what happens and numerous cases of poisonings, hospitalizations and even deaths have been rumoured though not properly documented. The Jamaican authorities are particularly concerned because of contamination of fresh water and sea around the Kingston area.

Luc Brun in New Caledonia has shown conclusively that the CBB there have developed resistance to endosulfan.

Modelling

Ricardo Cure (Colombia) and Andy Gutierrez (US) have developed a model for both the coffee tree, the CBB and its parasitoids. A paper on this is expected shortly. At Cenicafé Colombia, Bustillo and Prieto are developing a CBB only model and have a prototype for part of the system ready in Pascal. These developments are very welcome because of the complexity of studying a pest on a perennial with several flowerings per year. An accurate model could enable numerous simulations to be carried out, with varying combinations and timings of cultural control, parasitoids, insecticides etc. and thus to help guide researchers in the field on optimal combinations for validatory experiments.

International Workshop

Next year in Tapachula, Mexico from 29th March to 2nd April, there will be an international workshop on many aspects of coffee berry borer research. Further details can be obtained from Juan Barrera at jbarrera@tap.ecosur.mx.

Conclusions

There is a great deal of interesting research being carried out on CBB though it must be admitted that little of it has so far had much impact on farmers' practices. However, from the many lines of research underway it is likely that this will change in the coming years and that simple and effective methods that do not harm the environment or agricultural workers will become available.