Trogoderma granarium Everts, 1899 - Khapra Beetle

Summary

The khapra beetle is found in hot dry areas. It prefers grain, oilseeds and cereal products but can also develop on animal matter. Larvae feed on grains but the beetle does not bore into the grain. Young larvae feed on damaged grains but older larvae can feed on whole grains. An infestation can start in the field (when the cob is still on the plant) but most damage occurs in storage.

Common Names

Khapra beetle (English); trogoderma du grain, dermeste du grain (French)

Synonyms

Trogoderma khapra Arrow, 1917;Trogoderma affrum Priesner, 1951;Trogoderma quinquefasciata Leesberg, 1906

Taxonomic Position

Phylum: Arthropoda; Class: Hexapoda (Insecta); Order: Coleoptera; Family: Dermestidae

Origin and Distribution

The khapra beetle is thought by some to be native to the Indian subcontinent. It occurs in hot, dry areas and is especially abundant in certain areas of the Middle East, Africa andSouth Asia. It has been spread long distances through the movement of infested grain.

Description

The adults are oval-oblong and are covered in dense hairs. Males are brown to black and females lighter. The antennae are yellowish-brown with a distinct club; its legs are yellowish-brown. Males are 1.4-2.3mm long, 0.75-1.1mm wide; adult females are 2.1-3.4mm long, 1.7-1.9 mm wide. The early stage larvae are yellowish white with a brown head and mature larvae are golden to reddish brown. All stages are very hairy.

Life Cycle

The khapra beetle produces between one and nine generations per year depending on factors such as the host species, temperature, light and moisture. High humidity slows down population increase. Adults live for 12-25 days and females lay between 50-100 eggs. The eggs, which are loosely scattered in host material, hatch in 3-14 days. Larval development usually takes 4-6 weeks during which time they moult 4-15 times. The pupal stage lasts 2-5 days and quiescent adult stage 1-2 days. The larval stage however, can last from a month to a year, if it enters diapause (a dormant phase).

Pest Destructive Stage

Larva. The beetle does not bore into host material but young larvae feed on damaged seed and older larvae on whole grains. Damage can be severe with weight losses of between 5-30% and in extreme cases 70%.

Host Range

Khapra beetles prefer grain, cereal products, particularly wheat, barley, oats, rye, maize, rice, flour, malt and noodles and oilseeds. They can feed on products with as little as 2% moisture content. They can also develop on animal matter such as dead mice, dried blood and dried insects.

Host Lifestage Affected

Pre and post-harvest.

Host Plant Part Affected

Fruits, pods, seeds and grains

Damage Symptoms

Fruits, seeds, grains and pods: internal feeding; visible mould. Shed skins and faeces can also contaminate grain and cause allergic reactions.

Pest Management

Detection methods

Visual inspection can be used but as the beetles crawl into crevices deep into grain stores they can be difficult to detect until numbers become quite large. Pheromone traps can be used to detect khapra beetles at lower densities.

Cultural practices

The severity of a khapra beetle infestation can be reduced by good store hygiene: cleaning the store between harvests, removing and burning infested residues, immersing grain sacks in boiling water, filling in cracks and crevices or fumigating the store to eliminate residual infestations and the selection of only uninfested material for storage. Harvesting the maize as soon as possible after it has reached maturity will reduce the chances of attack by the khapra beetle and other storage pests.

Physical control

The removal of adults and larvae from the grain by sieving can reduce populations but this is very labour-intensive. The addition of inert dusts such as ash and clay to the grain can reduce insect numbers by causing the insects to die from desiccation.

 

Biological pest control
Although the khapra beetle has a number of natural enemies, no biological control agents have been introduced to control this species.

 

Controlled atmosphere
Where suitable infrastructure exists, low oxygen and carbon dioxide-enriched atmospheres can be used to control stored product pests.


Freezing and Heating
Where the infrastructure exists, freezing for several days and heating for 24 hours have proved to be effective control methods for stored product pests.


Botanicals

The use of neem (Azadirachta indica) seed powder mixed into maize appears to be an effective and cheap method to control the pest in stored maize.

 

Chemical control
The khapra beetle is susceptible to all the insecticides normally used on stored food. Fumigation of grain stocks with phosphine or methyl bromide will control existing infestations but will not protect against re-infestation.Pesticides are poisons so it is essential to follow all safety precautions on labels.

Sources of Information and Links

Anonymous (2006). The khapra beetle (Trogoderma granarium Everts, 1898) (Coleoptera: Dermestidae). California Plant Pest Diagnostic Center. http://www.cdfa.ca.gov/phpps/ppd/Entomology/Coleoptera/The_Khapra_Beetle.html (22/12/2010).

Banks H.J. (1977). Distribution and establishment of Trogoderma granarium Everts (Coleoptera: Dermestidae); climatic and other influences. Journal of Stored Product Research 13: 183-202.

Buss L.B. and Fasulo T.R. (2006). Stored Product Pests. UF/IFAS. SW 185. CD-ROM.

Ellis and Hodges (2007). Khapra Beetle Trogoderma granarium. National Plant Diagnostic Network Publication No. 0009. www.npdn.org/webfm_send/460 (accessed 18 June 2011)

Lowe S., Browne M., Boudjelas S. and DePoorter M. (2000). 100 of the World's Worst Invasive Alien Species: A Selection from the Global Invasive Species Database. Invasive Species Specialist Group, World Conservation Union (IUCN).

Szito A. (2006). Trogoderma granarium (insect). GlobalInvasiveSpeciesDatabase.http://www.issg.org/database/species/ecology.asp?si=142&fr=1&sts (22/12/2010).

Editors

Anne M. Akol, Makerere University; Maneno Y. Chidege, Tropical Pesticides Research Institute; Herbert A.L. Talwana, Makerere University; John R. Mauremootoo, BioNET-INTERNATIONAL Secretariat.

Acknowledgments

We recognise the support from the National Museums of Kenya, Tropical Pesticides Research Institute (TPRI) - Tanzania and Makerere University, Uganda. This activity was undertaken as part of the BioNET-EAFRINET UVIMA Project (Taxonomy for Development in East Africa).

Contact

BioNET-EAFRINET Regional Coordinator: eafrinet@africaonline.co.ke