Euwallacea fornicatus (tea shot-hole borer)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Plant Trade
- Wood Packaging
- Impact Summary
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Euwallacea fornicatus (Eichhoff, 1868)
Preferred Common Name
- tea shot-hole borer
Other Scientific Names
- Anisandrus fornicatus (Eichhoff)
- Xyleborus fornicatior Eggers, 1923
- Xyleborus fornicatus Eichhoff, 1868
- Xyleborus perbrevis Schedl, 1951
- Xyleborus schultzei Schedl, 1951
- Xyleborus tapatapaoensis Schedl, 1951
- Xyleborus whitfordiodendrus Schedl, 1942
- Xylosandrus fornicatus (Eichhoff)
International Common Names
- English: shot-hole borer of tea
- French: scolyte du Ceylon theier
Local Common Names
- Germany: teezweig-bohrer
- XYLBFO (Euwallacea fornicata)
Summary of InvasivenessTop of page E. fornicatus should be considered a high-risk quarantine pest. Most of the species in Euwallacea and related genera should be considered potential quarantine pests. This is because members of the tribe Xyleborini (Euwallacea plus related genera) are all inbreeding, with the males generally mating with their sisters within the parental gallery system before dispersal. Thus the introduction of only a few mated females may lead to the establishment of an active population if suitable host plants can be found and environmental conditions are satisfactory. A very wide range of host plants have been recorded for many of the species of Euwallacea and related genera. Any woody material of a suitable size and moisture content may be all that is required. The direct risk of establishment of populations of E. fornicatus into areas of the world outside its present distribution, and particularly into further tropical and subtropical parts of Africa and the Americas, should be considered very serious.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Arthropoda
- Subphylum: Uniramia
- Class: Insecta
- Order: Coleoptera
- Family: Scolytidae
- Genus: Euwallacea
- Species: Euwallacea fornicatus
Notes on Taxonomy and NomenclatureTop of page E. fornicatus was described by Eichhoff in 1868 as Xyleborus fornicatus and in almost all the literature before 1991 it is referred to as X. fornicatus. The genus Euwallacea was described by Hopkins in 1915 and was considered a synonym of Xyleborus until Wood (1980a, 1986) recognized Euwallacea as a distinct genus, on the basis of slight morphological and biological differences. Wood (1989) transferred X. fornicatus to the genus Euwallacea. Schedl (1977) lists Xyleborus ignobilis as a synonym, but this is incorrect (Samuelson, 1981). Earlier references to the species are listed by Wood and Bright (1992), and additional references by Bright and Skidmore (1997, 2002).
DescriptionTop of page Eggs
The eggs of E. fornicatus have not been described. However, the eggs of the related genus Xyleborus are very small, round and translucent, with a smooth surface. They are laid singly or in groups. Freshly laid eggs are pale, but they gradually darken before eclosion.
The larva of E. fornicatus is described by Gardner (1934). The mature larva is about 3.5 mm long and 1.1 mm wide. The head is colourless, about 0.5 mm wide, with the anterior margin nearly straight. The anterior margin of the labrum is nearly straight in the middle, while the posterior margin has a strong median extension. The anterior margin of the epipharynx has a very distinct and regular row of large blade-shaped setae; the internal rods are slightly incurved and the two pairs of setae between the rods are very small and close together, with the anterior pair much more widely separated than the posterior pair. The apical segment of the maxillary palps is stout and distinctly longer than wide. The labial palps are widely separated, with a globular apical segment. Each abdominal segment has two folds on the dorsal surface. The body integument is smooth except for a few scattered minute spicules.
The pupa has not been described.
The adult female of E. fornicatus is very dark-brown to black, 2.0-2.8 mm long, and about twice as long as it is wide. The front of the head is convex, with a slight transverse impression just above the mouthparts. The antennal funicle is five-segmented, and the antennal club is obliquely truncate. The pronotum, viewed from above, is distinctly convex, about equal in length and width, with moderately arcuate sides. The anterior margin of the pronotum is broadly rounded, with about eight equally sized serrations. The anterior area of the pronotum is finely asperate while the posterior area is smooth and minutely punctured.
The elytra are convex and steeply declivous posteriorly. They are about 1.3 times longer than they are wide, with finely indicated striae. The declivous portion of the elytra is moderately steep with the lateral margin finely carinate and the surface bears rows of very small, pointed granules that are arranged in rows inbetween the interstices. The elytral vestiture consists of rows of erect, hairlike, interstrial setae, those on the declivous area are slightly larger.
The small wingless males are 1.5-1.67 mm long (Kalshoven, 1958). They are much less common than the females, and rarely found.
DistributionTop of page There are unpublished records from the USA: Florida (M Thomas, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, personal communication, 2003) in 2002 and 2003, and California (R Penrose, California Department of Food and Agriculture, personal communication, 2004) in 2003. These represent the first introductions of the species to the USA mainland. There are unpublished records from Brunei Darussalam and New Caledonia (RA Beaver, Chiangmai, Thailand, personal communication, 2004). Kalshoven (1981) included Sierra Leone in the distribution of E. fornicatus. However, this is believed to be erroneous. The species has not yet been reliably recorded from the African mainland.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Bangladesh||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Cambodia||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|China||Present||Native||Not invasive||Wood and Bright, 1992; CABI/EPPO, 2013|
|-Guangdong||Present||Native||Not invasive||Yin et al., 1984; CABI/EPPO, 2013|
|-Hong Kong||Present||CABI/EPPO, 2013|
|-Sichuan||Present||Native||Not invasive||Yin et al., 1984; CABI/EPPO, 2013|
|-Tibet||Present||Native||Not invasive||Yin and Huang, 1981; CABI/EPPO, 2013|
|-Yunnan||Present||Native||Not invasive||Yin et al., 1984; CABI/EPPO, 2013|
|India||Present||CABI/EPPO, 2013; EPPO, 2014|
|-Assam||Present||Rajesh et al., 2011; CABI/EPPO, 2013; EPPO, 2014|
|-Karnataka||Present||CABI/EPPO, 2013; EPPO, 2014|
|-Kerala||Present||CABI/EPPO, 2013; EPPO, 2014|
|-Maharashtra||Present||Native||Not invasive||Wood and Bright, 1992; CABI/EPPO, 2013|
|-Tamil Nadu||Present||CABI/EPPO, 2013; EPPO, 2014|
|-Uttar Pradesh||Present||CABI/EPPO, 2013; EPPO, 2014|
|-West Bengal||Present||CABI/EPPO, 2013; EPPO, 2014|
|Indonesia||Present||CABI/EPPO, 2013; EPPO, 2014|
|Israel||Present||CABI/EPPO, 2013; EPPO, 2014|
|Japan||Restricted distribution||CABI/EPPO, 2013; EPPO, 2014|
|-Bonin Island||Present||CABI/EPPO, 2013|
|-Ryukyu Archipelago||Present||CABI/EPPO, 2013; EPPO, 2014|
|Laos||Present||Native||Not invasive||EPPO, 2014|
|Malaysia||Widespread||CABI/EPPO, 2013; EPPO, 2014|
|-Peninsular Malaysia||Present||EPPO, 2014|
|Myanmar||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Philippines||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Sri Lanka||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Taiwan||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Thailand||Present||Native||Not invasive||APPPC, 1987; Beaver, 1990; Wood and Bright, 1992; Waterhouse, 1993; CABI/EPPO, 2013; EPPO, 2014|
|Vietnam||Present||Native||Not invasive||CABI/EPPO, 2013; EPPO, 2014|
|Comoros||Present||Introduced||Invasive||Wood and Bright, 1992; CABI/EPPO, 2013|
|Madagascar||Present||Introduced||Invasive||CABI/EPPO, 2013; EPPO, 2014|
|Réunion||Present||Introduced||Invasive||CABI/EPPO, 2013; EPPO, 2014|
|USA||Restricted distribution||CABI/EPPO, 2013; EPPO, 2014|
|-Hawaii||Present||Introduced||Invasive||Wood and Bright, 1992; CABI/EPPO, 2013; EPPO, 2014|
Central America and Caribbean
|Costa Rica||Restricted distribution||CABI/EPPO, 2013|
|Panama||Present||Introduced||Invasive||Wood, 1980b; CABI/EPPO, 2013; EPPO, 2014|
|Australia||Present||Introduced||Invasive||Wood and Bright, 1992; CABI/EPPO, 2013|
|Fiji||Present||Introduced||Invasive||CABI/EPPO, 2013; EPPO, 2014|
|Micronesia, Federated states of||Present||Introduced||Invasive||CABI/EPPO, 2013; EPPO, 2014|
|Niue||Present||Introduced||Invasive||Beaver and Maddison, 1990; CABI/EPPO, 2013|
|Palau||Present||CABI/EPPO, 2013; EPPO, 2014|
|Papua New Guinea||Present||Introduced||Invasive||CABI/EPPO, 2013; EPPO, 2014|
|Samoa||Present||Introduced||Invasive||Wood and Bright, 1992; CABI/EPPO, 2013|
|Solomon Islands||Present||Introduced||Invasive||APPPC, 1987; CABI/EPPO, 2013; EPPO, 2014|
History of Introduction and SpreadTop of page The species has recently been accidentally introduced to both the Eastern and Western USA. In Florida, it was first found in 2002 in one location in Dade County, in the ornamental tree, Delonix regia, and again in the same location and host in 2003 (M Thomas, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, personal communication, 2003). In California, the species was found in 2003 in Los Angeles County attacking at least four different plant species. These included black locust (Robinia pseudoacacia), Box elder (Acer negundo), Red Alder, Alnus rubra, and California plane tree (Platanus racemosa) (R Penrose, California Department of Food and Agriculture, personal communication, 2004).
Risk of IntroductionTop of page Several other species of Euwallacea with similar habits to E. fornicatus have been imported to tropical and subtropical areas around the world. It is interesting that E. fornicatus is not recorded among the many species intercepted in timber imported to Japan. This is probably because it attacks primarily smaller diameter stems. However, the risk of introduction outside its present geographic range must be considered high. Having been accidentally introduced very recently to both Eastern (Florida) and Western (California) sides of the USA, it seems likely that it will spread further through the southern states, and probably also into Mexico. There is a clear danger of damage to tea plantations in Africa and South America if the species establishes in those regions. One of the fungi with which it may be associated, Ceratocystis fimbriata, is an important plant pathogen with a wide host range. Kühnholz et al. (2003) note that some ambrosia beetles which are normally secondary, and do not attack healthy trees, have started to do so, and discuss the possible reasons for this. E. fornicatus is not known to be specifically listed as a quarantine pest.
Hosts/Species AffectedTop of page Members of Euwallacea and the related genera Ambrosiodmus, Xyleborinus, Xyleborus and Xylosandrus are all ambrosia beetles that feed and breed in a variety of forest trees and shrubs. Depending on the species, they may be found in small branches and seedlings to large logs. All are potentially damaging to agriculture and/or forestry under suitable conditions. Many species, previously considered of only minor importance, may become important pests in agriculture and forestry as a result of the continuing destruction of natural forests and the expansion of forest and tree crop plantations, agroforestry and agriculture.
E. fornicatus attacks a very wide range of host trees. Browne (1961) records the species from 33 plant families, including nearly all the major woody plant families of the Oriental tropics. Danthanarayana (1968) lists 97 species in 35 families, and this list could be further extended. It attacks a wide variety of crop trees, usually attacking cut, stressed or dying, small stems and branches, but primary attacks on healthy plants also occur (Kalshoven, 1958; Browne, 1968). However, healthy plants can sometimes resist attack by exuding gum or latex in which the beetle can become entrapped (Kalshoven, 1958; Danthanarayana, 1968). The species has not yet been recorded from conifers, and attacks on monocotyledonous stems appear to be infrequent. The list of hosts is a small selection only.
Host Plants and Other Plants AffectedTop of page
|Artocarpus integer (champedak)||Moraceae||Other|
|Bixa orellana (annatto)||Bixaceae||Other|
|Camellia sinensis (tea)||Theaceae||Main|
|Castanopsis (evergreen chinkapin)||Fagaceae||Wild host|
|Ceiba pentandra (kapok)||Bombacaceae||Other|
|Cinchona calisaya (quinine)||Rubiaceae||Other|
|Durio zibethinus (durian)||Bombacaceae||Other|
|Erythrina subumbrans (December tree)||Fabaceae||Wild host|
|Falcataria moluccana (batai wood)||Fabaceae||Main|
|Gmelina arborea (candahar)||Lamiaceae||Main|
|Grevillea robusta (silky oak)||Proteaceae||Other|
|Hevea brasiliensis (rubber)||Euphorbiaceae||Other|
|Litchi chinensis (lichi)||Sapindaceae||Other|
|Macadamia integrifolia (macadamia nut)||Proteaceae||Other|
|Mangifera indica (mango)||Anacardiaceae||Other|
|Persea americana (avocado)||Lauraceae||Other|
|Platanus acerifolia (London planetree)||Platanaceae||Other|
|Psidium guajava (guava)||Myrtaceae||Other|
|Punica granatum (pomegranate)||Punicaceae||Other|
|Ricinus communis (castor bean)||Euphorbiaceae||Main|
|Schleichera oleosa (Macassar oil tree)||Sapindaceae||Wild host|
|Tectona grandis (teak)||Lamiaceae||Other|
|Terminalia catappa (Singapore almond)||Combretaceae||Wild host|
|Theobroma cacao (cocoa)||Sterculiaceae||Other|
Growth StagesTop of page Vegetative growing stage
SymptomsTop of page E. fornicatus bores and tunnels into the stems of the host causing them to break. It results in tea bushes becoming debilitated; recovery is poor. Branches die back after pruning and this leads to sun-scorch.
Repeated attacks by E. fornicatus in successive pruning cycles cause severe chronic debilitation of the tea bushes. The initial attack impoverishes the frame of the bush and the maintenance of the foliage. This causes a drain on the reserves of the bush. The result is poor ground cover, which allows excessive heating of the soil. The long-term effects of E. fornicatus infestation include poor recovery and dieback of the branches after pruning, and sun-scorch of the upper surfaces of the branches after pruning. The dead and moribund wood succumbs to wood rot caused by secondary fungi. Scavenging termites clean up the dead wood, but tend to aggravate the wood rot.
List of Symptoms/SignsTop of page
|Stems / dieback|
|Stems / internal feeding|
|Stems / rot|
|Whole plant / dwarfing|
|Whole plant / plant dead; dieback|
Biology and EcologyTop of page Browne (1961) reviewed the biology and ecology of E. fornicatus in South-East Asia. Muraleedharan (1986) described its biology on tea in India. Wood and Bright (1992) gave several hundred references relating to the biology, habits, taxonomy and control of E. fornicatus.
The major factors that determine the intensity of attacks on tea in southern India are the state of maturity of the branches, the height of pruning, the time of pruning, and the length of the pruning cycle (Muraleedharan et al., 2003). The primary branches formed after pruning are more susceptible to attack, and attack densities are higher in blocks under a longer pruning cycle (Muraleedharan et al., 2003). The distribution of attacks on tea plants is also discussed by Sivapalan (1975).
The female bores a bifurcated or simple tunnel in the twigs and small branches of the host, so that it encircles the stem. If the host is very small, one or two branch tunnels may be constructed. These may be straight or spiral and are often longer than 5 cm.
Egg-laying begins as soon as the entrance tunnel is completed. Eggs are laid singly or in small clusters. In Malaysia, egg production continues fairly steadily for about 10 days, after which there is a marked decline, although laying may proceed at intervals for at least an additional 10 days. In Java, broods may include 15-20 individuals (Kalshoven, 1958). In Sri Lanka, the maximum per brood was 34 individuals (Gadd, 1941). In Malaysia, Browne (1961) reported that three galleries in Pajanelia sp. averaged 28.3 individuals per brood.
Males are produced in much smaller numbers, but develop more rapidly than females. The larvae live in longitudinal tunnels in small twigs, and in the transverse branch galleries in larger branches. The female larvae pass through three instars (Gadd, 1941; Browne, 1961).
The larvae pupate together in the tunnels. After emergence from the pupal stage, the young females remain in the galleries for several days, during which time they are fertilized by their brothers. Mated females emerge through the original entrance tunnel and fly to new hosts. They fly during the day and are not attracted to light. In tea plantations they seldom fly higher than 2 m (Judenko, 1956).
The small, deformed males cannot fly and do not normally leave the parental gallery, although they sometimes emerge and crawl on the surface of the bark. Occasionally, these males may enter a gallery made by another female and mate with the females in that gallery system; thus a very small amount of cross-breeding occurs.
In Malaysia, Browne (1961) found that the parent beetle raises only one brood, and dies when her offspring have flown. In the lowlands of Peninsular Malaysia, the life cycle takes 29-33 days. However, eggs continue to be produced for about 3 weeks and it is possible that the emergence of adults from the host may continue for a similar period (Browne, 1961). In southern India, Muraleedharan (1983) reported that the egg, larval and pupal stages lasted 8-10, 21-26 and 10-12 days, respectively. The developmental period varies with altitude, temperature and predation, but most of the new generation emerge about 5-6 weeks after the host is infested.
The ratio of females to males is low compared to many other ambrosia beetles. In Java, it has been estimated as 9:1 (Kalshoven, 1958), and in Sri Lanka as 4:1 (Beeson, 1941) and 3:1 (Judenko, 1956). In Malaysia, Browne (1961) examined several complete broods and reported there were four or five females to each male.
E. fornicatus is closely associated with ambrosial fungi. The fungus is introduced into the gallery by the attacking female and the larvae feed on the developing spores. The spores of the ambrosia fungus are stored in two specialized internal sacs situated anterior to the brain in the head of the adult female E. fornicatus (Fernando, 1960). The spores travel from the sacs through ducts to the buccal cavity and are then deposited in the gallery using the mandibles and maxillae. Early work on the ambrosia fungi (e.g. Speyer, 1923; Gadd and Loos, 1947) should not be relied on, because of problems with fungal taxonomy and contamination of fungal cultures. In southern India, Mouli and Kumar (1988) found the fungus Fusarium tumidum in the tunnels of E. fornicatus in tea branches. Somasekhara et al. (2000) isolated the phytopathogen, Ceratocystis fimbriata, from E. fornicatus in wilting pomegranate trees in Karnataka and Maharashtra. Fusarium bugnicourtii is given as the ambrosia fungus by UPASI Tea Research Foundation, Kerala, India (2003a). The relationship between these fungi and the beetle needs to be investigated further.
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
Notes on Natural EnemiesTop of page The immature stages have few natural enemies. Muraleedharan et al. (1988) recorded no animal natural enemies of E. fornicatus in a survey in southern India, and none appear to have been recorded elsewhere. The female parent remains for much of the time in or near the gallery entrance whilst the immature stages are developing, preventing the entry of potential predators and parasitoids. Provided that the female remains alive and the growth of the ambrosia fungus on which the larvae feed is satisfactory, mortality of the immature stages is likely to be very low. Most mortality is probably during the dispersal of the adults, and during gallery establishment. Adults have been found in the crop contents of the swiftlet (Collocalia fuciphaga) (Beaver and Browne, 1979), and they are predated by lizards, clerid beetles and ants as they attempt to bore into the host tree. Recently, the occurrence of the pathogenic fungus, Beauveria bassiana, on E. fornicatus adults has been noted in Tamil Nadu, India (Selvasundaram and Muraleedharan, 2000).
Means of Movement and DispersalTop of page Natural Dispersal
Adult females fly readily and flight is one of the main means of movement and dispersal to previously uninfected areas. Of more importance, however, is the movement of infested woody material in timber, ship dunnage and crating. Numerous species of Euwallacea and related genera have been taken in port cities from discarded ship dunnage, and in similar circumstances.
Both adults and larvae of E. fornicatus are dependent on the growth of the fungus on the walls of the gallery system in the wood for their food (Beaver, 1989). The fungus is transmitted by the female in a mycangium. In E. fornicatus this consists of mandibular pouches (Fernando, 1960). 'Contamination ' of the mycangia by the spores of pathogenic fungi is possible. Spores of pathogenic fungi can also be transported on the cuticle of the beetle, although their chance of survival there is much less than in the mycangial pouch. E. fornicatus is associated with the spread of the pomegranate wilt, Ceratocystis fimbriata, in southern India (Somasekhara and Wali, 2000; Somasekhara et al., 2000).
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Bark||adults||Yes||Pest or symptoms usually visible to the naked eye|
|Stems (above ground)/Shoots/Trunks/Branches||adults; eggs; larvae; pupae||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Wood||adults; eggs; larvae; pupae||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|True seeds (inc. grain)|
Wood PackagingTop of page
|Wood Packaging liable to carry the pest in trade/transport||Timber type||Used as packing|
|Loose wood packing material||Fresh twigs or branches||Yes|
|Solid wood packing material with bark||Fresh unseasoned wood||Yes|
|Solid wood packing material without bark||Fresh unseasoned wood||Yes|
|Wood Packaging not known to carry the pest in trade/transport|
|Processed or treated wood|
Impact SummaryTop of page
|Fisheries / aquaculture||None|
ImpactTop of page E. fornicatus has been a serious pest of tea in Sri Lanka and parts of southern India for nearly 100 years (Cranham, 1966). It seriously affects about one-third of the tea acreage in Sri Lanka, although it does not occur in tea above an altitude of 1300 metres. E. fornicatus is a relatively minor pest of tea in South-East Asia. Waterhouse (1993) notes that the species is locally important in Malaysia.
There is little precise information about the crop loss caused by E. fornicatus or other tea pests. In Sri Lanka, the loss of crop caused by E. fornicatus in 1953-1955 was estimated as 8-9% and possibly over 20% (Portsmouth, 1956). Cranham (1966) considered these estimates were reasonable. In Sri Lanka, the level of attacks by E. fornicatus is related to the pruning cycle, and negatively correlated with the crop size in the preceding month (Sivapalan, 1977).
In southern India (Karnataka and Maharashtra), E. fornicatus has recently become a serious pest of pomegranate. Somasekhara and Wali (2000) found that damage caused by the wilt fungus, Ceratocystis fimbriata, which is vectored to some extent by the beetle, caused monetary loss worth Rs. 67.45 lakhs during 1996-1997 and Rs. 26.9 lakhs during 1999-2000. Attacks in Maharashtra are positively related to humidity, and negatively related to temperature (Mote and Tambe, 2000a).
Also in Kerala, Mathew (1985), Mathew and Nair (1986), and Nair and Mathew (1988) consider that E. fornicatus is a major pest of Albizia falcataria, and a potentially serious pest of Gmelina arborea, both of which are fast-growing forest plantation trees.
Prevention and ControlTop of page
In Sri Lanka and south India, several tea varieties have been developed that show at least partial resistance to E. fornicatus (Jayasuriya, 1979; Rao, 1979; Thirugnanasuntharan and Jayachandran, 1989).
The high concentrations of caffeine found in some tea clones inhibit or prevent the growth of the ambrosial fungus, with which E. fornicatus is closely associated. Kumar et al. (1995) reported that tea clone TRI 2023, which is only slightly susceptible to E. fornicatus, accumulates higher concentrations of caffeine than clone TRI 2025, which is more susceptible to E. fornicatus.
Following the discovery of the entomopathogenic fungus, Beauveria bassiana, attacking E. fornicatus adults in Tamil Nadu (Selvasundaram and Muraleedharan, 2000), the strain of the fungus involved has been developed as a means of biological control. It significantly reduces the beetle population, and is now available commercially as a wettable powder (UPASI Tea Research Foundation, 2003b).
A further recent development is the use of an alternative attractant to lure the beetles away from the tea bushes. UPASI Tea Research Foundation (2003a) suggests the use of cut stems of Montanoa bipinnatifida (Asteraceae) placed in infested plantations to attract the beetles, which may later be killed by burning the stems.
The decision to use chemical control is influenced by the difficulties of application (E. fornicatus feeds deep in the wood of infested branches), the cost and environmental concerns. The insecticides that may be used include fenvalerate, deltamethrin, quinalphos and cypermethrin (Muraleedharan, 1995).
Deltamethrin, applied during the peak activity time of E. fornicatus, in the second and third years of the 3-year pruning cycle of tea, significantly reduced infestation levels (Muraleedharan and Radhakrishnan, 1994). In India, both fenvalerate and cypermethrin, sprayed on tea plants at different concentrations reduced E. fornicatus infestation to 5%, compared with an infestation rate of 33% for plants that received no treatment (Muraleedharan et al., 1992). Selvasundaram et al. (2001) found that Lambda-cyhalothrin 2.5 EC was more effective in reducing E. fornicatus populations than fenvalerate. Against attacks on pomegranate, Mote and Tambe (2000b) found that chlorpyrifos at 0.1% applied as a paste to the tree trunk were the most effective and economical insecticides for the control of the pest. Addition of geru (red soil) and copper oxychloride to the insecticides increased the control of insect pests.
The effect of potassium acetate and zinc acetate, when applied at concentrations of 0.5, 1.0 and 1.5 g/bush, 4, 8 and 12 months after pruning, on the incidence of E. fornicatus on mature tea plants was studied by Ranasinghe and Wickremasinghe (1988) in Sri Lanka. The number of pupae and adults in treated plots was significantly reduced for up to 21 months after pruning. Earlier studies by Wickremasinghe and Thirugnanasuntheram (1980) indicated the same effect; the mechanism of action of potassium acetate was thought to be related to its conversion to saponins and/or sterol analogues that interfere with pupation.
Soil applications of granular systemic insecticides proved ineffective against E. fornicatus in India (Mote and Tambe, 1990).
Recent changes in cultural practices in tea plantations in Sri Lanka have increased yields but have intensified pest problems, particularly the damage caused by E. fornicatus. The most important damage caused by E. fornicatus is to the primary branches (those generally removed in low pruning but left in high pruning), therefore low pruning every two to three pruning cycles has been recommended (Sivapalan and Delucchi, 1974).
Integrated Pest Management
IPM programmes combining cultural and chemical control have been developed and implemented, especially in southern India (Muraleedharan, 1995).
UPASI Tea Research Foundation (2003a) summarizes the recently published suggestions and recommendations for the control of E. fornicatus in India. These include attention to pruning height, adding fertilizer to pruned fields, spraying of entomopathogenic fungus, use of alternative attractant, and chemical treatment.
ReferencesTop of page
APPPC, 1987. Insect pests of economic significance affecting major crops of the countries in Asia and the Pacific region. Technical Document No. 135. Bangkok, Thailand: Regional Office for Asia and the Pacific region (RAPA).
Beaver RA, 1989. Insect-fungus relationships in the bark and ambrosia beetles. Insect-fungus interactions. 14th Symposium of the Royal Entomological Society of London in collaboration with the British Mycological Society [edited by Wilding, N.; Collins, N.M.; Hammond, P.M.; Webber, J.F.] London, UK; Academic Press, 121-143
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