Habitat
Khapra beetle occurs almost exclusively in closed environments in agricultural and urban areas. In agricultural areas it is associated primarily with silos, storages and animal holding facilities. In urban environments it is found within human dwellings (synanthropic) and in stores, food stores, malt houses, seed processing plants, fodder production plants, dried milk factories, merchant stores and stores of packing materials (used sacks, bags, crates).
It is found in hot, dry conditions, predictably in areas which have a mean temperature greater than 20°C and relative humidity below 50% for at least four months of the year.
Distribution
Trogoderma granarium originated from the Indian subcontinent and now is established throughout the warm dry regions of the Middle East, Asia and the Indian subcontinent.
The khapra beetle has been introduced into areas with similar climatic conditions, especially the alternative route between India and Europe around Africa. Initially, these introductions caused severe damage but outbreaks have been local and in most cases have been eradicated or died out. New incursions in developed countries are quickly eradicated, sometimes at great expense.
Damage
Khapra beetle will feed on most dried plant or animal matter. It can feed on products with as little as 2% moisture content and can develop on animal matter such as dead mice, dried blood and dried insects. Its preferred grain and cereal products are wheat, barley, oats, rye, maize, rice, flour, malt and noodles.
It also feeds on:
- soybeans, lentils, dry peas, grain sorghums, cowpea and corn
- rolled and ground barley, ground corn, ground dog food, rolled oats, dried orange pulp, ground rice, and cracked and ground wheat bran
- peanuts, pecans, walnuts and almonds.
Other commodities that often serve as hosts include:
- bread, dried coconuts, cornmeal, crackers, white and wholemeal wheat flour, pasta, dry baby food, pearl barley and wheat germ
- rat and mouse baits, snail pellets.
Impact
If khapra beetle infestations are left undisturbed in stored grain they can cause significant weight loss and may lead to significant reduction in seed viability. Weight loss can be 5-30% and in extreme cases 70%.
Larvae typically attack the embryo point or a weak place of grain or seed, but will attack other parts during heavy infestations. Young larvae feed on damaged seeds, while older larvae are able to feed on whole grains.
Khapra beetle can also damage dried animal products. Large numbers of larval skins and setae (hairs) may cause dermatitis and/or allergic reactions. Larvae wander in and out of sacked material, weakening the sacks, which may ultimately tear.
Due to their resilience and ability to survive without food for years, an infestation can stay undetected in cleaned warehouses and silos. Once the facility is refilled with dry commodities the khapra beetle population can explode and cause significant damage in a short period of time.