Eggs - elliptical or ovoid in shape, milky-white and shiny when first laid, 0.5-0.8 mm long, 0.25-0.35 mm wide (Bergamin, 1943;Hernandez-Paz and Sanchez de Leon, 1978;Johanneson, 1984).
H. hampei can be detected in the trees and coffee beans.
Tree - inspect the berries and look for a small cylindrical perforation. Look at the lower branches and fallen berries as these may be more likely to be infested. There are numerous sampling methods, many based on counting all berries on 30 or more branches over a hectare and evaluating percentage attack. As yet there is no easy or universal way to relate level of crop attack to future loss at harvest. A figure of 5% infested berries is often used as an economic threshold for field control activities, but more study on this is needed.
Coffee beans - as the perforation on berries may be difficult to see, rub suspect beans between the hands to remove the parchment and look for the perforation. Often a small indentation will be present where the borer started to attack but failed to establish itself.
A trap based on ethanol and methanol has been developed but it also catches many other scolytids. It is useful to monitor emergence flight activity, most notably when rains follow a dry period. French research has renewed interest in trapping as a form of control, initial results have been are encouraging though more research needs to be done to confirm the economic viability of this method (Dufour et al., 1999). Fernandes et al. (2014) found that mass trapping could reduce attacks, but not below an economic threshold.
Related invasive species
- Hypothenemus hampei
Related Farm Practice
- Hosts
- Production
- Monitoring
- Development
- Progeny
- Control
- Inhibition
- Pests
- Diets
- Fluctuations
- Identification
- Tests
- Breeding
- Effects
H. hampei, otherwise known as the coffee berry borer, is the most serious pest of coffee in many of the major coffee-producing countries in the world. The scolytid beetle feeds on the cotyledons and has been known to attack 100% of berries in a heavy infestation. Crop losses can be very severe and coffee quality from damaged berries is poor. H. hampei has been transported around the world as a contaminant of coffee seed and very few coffee-producing countries are free from the borer. Its presence in Hawaii was confirmed in 2010 and Papua New Guinea and Nepal remain free of the pest: in Papua New Guinea an incursion prevention programme was mounted in 2007 (ACIAR, 2013) to reduce chances of invasion from Papua Province (Indonesia). There is no simple and cheap method of control of H. hamepi.
Attack by H. hampei begins at the apex of the coffee berry from about eight weeks after flowering. A small perforation about 1 mm diameter is often clearly visible though this may become partly obscured by subsequent growth of the berry or by fungi that attack the borer. During active boring by the adult female, she pushes out the debris, which forms a deposit over the hole. This deposit may be brown, grey or green in colour.
Infestation is confirmed by cutting open the berry. If the endosperm is still watery, the female will be found in the mesoderm between the two seeds, waiting for the internal tissues to become more solid. If the endosperm is more developed, the borer will normally be found there amongst the excavations and irregular galleries that it has made. The borer sometimes causes the unripe endosperm to rot, most commonly by species Erwinia, causing it to turn black (Sponagel, 1994) and the borer to abandon the berry.
H. hampei is sometimes reported attacking and breeding in plants other than coffee, however there are few convincing published studies of this with supporting expert taxonomic identification. However, a Colombian study (L Ruiz, Cenicafé, Centro Nacional de Investigaciones de Café, Colombia, personal communication, 1994) reports rearing the borer through to adulthood on seeds of Melicocca bijuga and a Guatemalan study (O Campos, Anacafé, Asociacion Nacional del Café, Guatemala, personal communication, 1984) reports the same for Cajanus cajan. Vega et al. (2012) reviewing older little-known literature including that of Schedl (1960), make the case that the African host range may be broader than previously suspected. As there is much current interest in mass production of the borer, further studies of alternative food sources would be of interest. Nevertheless, all field studies of the borer suggest that coffee is the only primary host and that population fluctuations are hence due almost entirely to its interaction with coffee and not to the presence of alternative hosts.
Chevalier (cited in Le Pelley, 1968) found Coffea liberica almost immune to H. hampei followed by C. excelsa, C. dewerei, C. canephora and C. arabica in increasing order of attractiveness to the borer. Villagran (1991) found that. H. hampei had difficulty in penetrating the hard exterior of C. liberica berries. However, Roepke (in Le Pelley, 1968) states that C. liberica is preferentially attacked. Extensive studies by Kock (1973) reported C. canephora variety Kouilou (or Quoillou) is attacked less than the Robusta variety.
Villagran (1991) found C. kapakata supporting very significantly fewer immature stages of the borer than other varieties and some tendency for C. arabica variety Mundo Novo also to support fewer progeny. Olfactometry tests by Duarte (1992) showed C. kapakata to be significantly less attractive. C. kapakata appears to be one of the most resistant coffee species currently known but this is not a commercial variety and neither the berries nor the plant resemble a coffee plant to the casual observer.
Romero and Cortina-Guererro (2004) in laboratory studies in Colombia found no difference in levels of antixenosis (deterrence to attack coffee in field tests) of various coffee varieties (including C. arabica Caturra, various Ethiopian accessions as well as C. liberica). However Romero and Cortina-Guererro (2007) did find differences in antibiosis (expressed as fecundity) with Ethiopian accession CC532 and C. liberica both yielding significantly fewer borer progeny.
Gongora et al. (2012) confirmed the inhibitory effects of C. liberica through a functional genomics study using ESTs libraries, cDNA microarrays and an oligoarray containing 43,800 coffee sequences. The results allowed for a comparison of C. liberica vs. C. arabica berry responses to H. hampei infestation after 48 h. Out of a set of 2500 plant sequences that exhibited differential expression under H. hampei attack, twice the number were induced in C. liberica, than in C. arabica. One of the identified biochemical pathways was the one that leads to the production of isoprene. The authors studied the effect of isoprene on H. hampei by monitoring the development of the insect from egg to adult, using coffee-artificial diets amended with increasing concentrations of isoprene. Concentrations of isoprene above 25 ppm caused mortality and developmental delay in all insect stages from larva to adult, as well as the inhibition of larvae moulting.
Hence it seems certain that varying amounts of resistance or antibiosis to the borer exists within species of Coffea. Such resistance to attack or even moderate antibiosis is worthy of further study because an increase in development time and/or decrease in fecundity could have a pronounced effect on infestation levels. Conventional breeding to introduce such inhibition from outside the Arabica genome might be difficult however, hence genetic engineering may be increasingly considered in the future.
A team of CIRAD scientists were the first to succeed in producing a transgenic coffee plant with Bt resistance to leafminers but there is no information about its effect on H. hampei (Leroy et al., 2000). Scientists from Brazil and Colombia (Barbosa et al., 2010) transformed C. arabica by introducing an enzyme inhibitor from the common bean (Phaseolus vulgaris). Beans have evolved an amylase enzyme inhibitor (or ‘starch blocker’) to make them less palatable to attacking insects. They demonstrated that crude seed extracts from genetically transformed C. arabica plants expressing the α-amylase inhibitor-1 gene (α-AI1) under the control of the common bean P. vulgaris seed-specific promoter PHA-L, inhibited 88 % of H. hampei α-amylases during in vitro assays. Since then, offspring from these GM coffee plants have been cultivated under greenhouse conditions to study the heredity, stability and expression of the α-AI1 gene. Subsequently Albuquerque et al. (2015) carried out in vivo assays of H. hampei development in berries of the transformed plants. A 26-day assay showed that the lifecycle of H. hampei was still completed, though significantly fewer offspring developed than on non-transformed control beans. Other tests showed that gene expression occurred only in the endosperm tissue. Commercial interest in developing transgenic coffee resistant to pests and diseases is still low however and might meet considerable consumer resistance.