DIAGNOSTIC PROTOCOLS FOR REGULATED PESTS Trogoderma granarium Introduction The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae) is a stored product pest of great importance. Its importance lies not only in the capabilities of causing serious damage to stored dry commodities but also that countries having established populations are facing export restrictions. The Khapra beetle is thought to have originated from the Indian subcontinent but has become established in a number of Asian, Middle Eastern, African, and some European countries. It is one of the very few stored product pests that has limited worldwide distribution. T. granarium has very limited ability to spread without human aid as it is unable to fly. It is very important to distinguish between those records which relate to introductions and those of established infestations. The Khapra beetle is established within an area broadly limited north by central Asia, south by the Equator, west by the Sahel of West Africa and east by Myanmar; i.e. the warm dry regions along the Suez route from the Indian subcontinent to Europe. This area includes the southeastern part of the EPPO region. Khapra beetle has been introduced into areas of similar climatic conditions elsewhere particularly the alternative route between India and Europe around Africa. Currently its status in southern Africa is unclear and it may be absent there now. Initially introductions caused severe damage but outbreaks have been local and in most cases have been eradicated. In general, Khapra beetle is only successful in competition with other major stored product pests in conditions of low humidity. It has also established in some areas of unfavourable climate, where it survives only in protected and/or heated environments such as maltings and feedmills, for example in Europe, Korea and Japan. There were multiple introductions to the United States and Mexico but these were eradicated. Hosts The Khapra beetle is a significant stored product pest. It may occur in various dry stored products of primarily vegetable origin. Primary hosts are cereals (rice, wheat, oats, barley, sorghum, maize etc.), cereal products (rolled oats and barley, ground corn, corn meal, wheat flour, bran products, pasta, etc.), pulses (chickpea, soybean, and lentil), various vegetable seeds (cucurbit, capsicum, tomato, etc.), herbs, spices and various nuts (peanut, pecan, walnut, almond etc.). It can successfully complete its lifecycle in copra, dried fruits, various gums and many different dried products of wholly or partial animal origin such as skins, dried dog food, dried blood, dead insects and dried animal carcasses. As a pest it is most prevalent under hot dry conditions where very heavy infestations can develop. In cooler and also in hot and humid conditions it tends to be out competed as a pest by other species such as Sitophilus spp. and Rhizopertha dominica. Commodities stored in bags in traditional warehouses are more at risk from this pest than bulk stored commodities. Biology There are important features of T. granarium biology which enable the pest to survive in harsh conditions. In unfavourable circumstances it is able to maintain its presence in very low numbers in the stores. Khapra beetle can have between one and more than ten generations per year depending on food availability and quality, temperature and humidity. A complete life cycle may be as short as 26 days in an optimum environment, or, as long as 220 days or more in a suboptimal environment. In temperate climates larvae become inactive at temperatures below 50C, so the pest will only survive and breed in protected environments. However, there are two genetic variations of larvae: those which are able to undergo facultative diapausa and those that are unable to do so. Larvae of the first type are stimulated into diapausa by adverse conditions such as low or high temperatures, and/or lack of food. During diapausa their respiration drops to an extremely low level. This leads to problems with fumigation. With such a low respiration rate the gas intake is very low, therefore the rate and/or the exposure time must be increased for successful treatment. Diapausing larvae are also cold hardy and may survive temperatures below -80C. Should favourable conditions return the pest is able to multiply rapidly and causing serious damage to the commodity. For more general information on T. granarium, see Hinton (1945), Lindgren et al. (1955), Pasek (1998), CABI CPC (2005), EPPO/CABI (1997) and Berg (1999). Identity Name: Trogoderma granarium Everts, 1898 Synonyms: T. albonotatum Reiche in Mulsant et Rey, 1868 Trogoderma quinquefasciata Leesberg, 1906 Trogoderma khapra Arrow, 1917 Trogoderma afrum Priestner, 1951 Trogoderma granarium ssp. afrum: Attia & Kamel, 1965 Taxonomic position: Insecta: Coleoptera: Dermestidae, Megatominae Bayer computer code: TROGGA Quarantine status: EPPO A2 list: No. 121 COSAVE: quarantine pest not present Other NPPO: Detection T. granarium has the following developmental stages: eggs on the surface of grain and other stored products; larvae (5-11 instars) in stored products (larvae in diapausa may be found in packing material or within storage structure); pupae in stored products, in the last larval skin; adults in stored products. Methods to detect T. granarium infestations include inspection (physical and visual search) and use of food baits or, more importantly, pheromone traps. Often the infested material contains larvae only. There are three reasons for this: (1) adult longevity can vary between 12-25 days on average although it can be as long as 147 days in unfavourable conditions, while larval longevity is 19 –190 days (it can be up to 6 years shoud larvae go to diapausa); (2) most of the Dermestid larvae occurring in the stored product will partially or wholly consume dead adults; (3) adults are usually present when conditions are favourable for population growth. Larval skins are usually not consumed so their presence is a clear indication of a possible active infestation. Larvae are extremely cryptic by nature. It is particularly so in the case of diapausing larvae that can stay inactive in cracks and crevices for periods of time where they are very difficult or nearly impossible to locate. Searches for this pest are particularly difficult in cases of low level infestations. In addition to the obvious food sources the potential hiding places should also be inspected. In contrast to most other stored product pests the Khapra beetle prefers hot and dry areas. During inspection efforts should be concentrated in these areas. Larvae of Trogoderma species are very crepuscular and populations can persist in small quantities of residues that may occur within a structure or mode of transport. Larvae in diapausa can survive long periods without food. For diapausing larvae it is important to search under flaking paint and rust, piles of dirt, in empty packaging materials such as hessian bags, tarpaulins, and corrugated cardboard. Larvae are often hiding behind wall panelling, under internal lining, between floorboards, under insulation, on dry ledges, electrical cable trays and conduits, switch boxes, stores and kitchens etc. Larval skins become airborne very easily therefore it is always important to check window sills, grilles of venting holes, and spider webs for their presence. Rodent traps containing baits should be always inspected. Khapra beetle infestations can be recognised by (1) the presence of the pest (especially feeding larvae and cast skins) and (2) symptoms of infestation. The short-lived adults are sometimes not seen. Damage to the commodities can be a warning sign, but often it is a result of the feeding of other common stored product pests. Early instar larvae of this pest feed on broken or damaged kernels, whereas older larvae feed on whole kernels. Larvae usually feed first on the germ portion of cereal seeds and then on the endosperm. The seed coat is eaten in an irregular manner. Larvae can occasionally be found as deep as 3-6 m in bulk grain. In the surface layers of the infested stored product numerous cast larval skins are present, and these are often covered with long hairs. Infested material is also polluted with frass, larval skins and broken setae. During stored product inspections of commodities from areas where T. granarium is indigenous or known to be established, particular attention should be paid to the presence of various developmental stages of the pest, cast larval skins and signs of damage. Samples of the suspect products have to be visually inspected in a well-lit area, using a 10x magnification hand lens. If no signs of Trogoderma infestation are found then larger quantities of the product should be passed over sieves with aperture sizes relevant to the particle size of the products. Usually sets of sieves of aperture sizes 1.0, 2.0 and 3.0 mm are used. The sifted material collected on particular sieves should be placed in Petri dishes and examined under at least 10x but preferably greater than 25x magnification through a stereoscopic microscope to detect the pest. This sieving technique allows the detection of various developmental stages of the pest. However, some larvae feeding within grains may remain undetected. Therefore, it may become necessary to heat samples to 40oC to drive pests out of the grains. Visual inspection is preferential because sieving can easily destroy or seriously damage dead adults and larval skins rendering the identification very difficult or impossible. Insects found during quarantine, routine or monitoring inspections of warehouses, ships and cargo containers should be carefully picked up with small forceps or collected using an aspirator (“pooter”). One of the most important requirements is that the inspector should collect multiple specimens of the pest. Identification of larvae is difficult, and if the dissection of a single specimen is not successful and serious damage occurs to the mouthparts then exact identification is impossible. Specimens should be placed, in a sturdy plastic or glass container or jar (McCartney bottle) containing 70% alcohol.