Because of previous taxonomic difficulties in distinguishing this weevil from Sitophilus zeamais, the reference to Sitophilus oryzae in Fiji needs confirmation. They may complete a generation in a month in warm conditions. Photo 4. The female lays a large number of eggs and the larvae feeds on the inner portion of the grain kernels. Used as a fumigant; grain is covered by a tarpaulin or in other ways sealed for the duration of the fumigation. During large infestations, heat and moisture are produced, leading to colonisation by moulds and mites. Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community. Photo 1. Adults are 3-4 mm long, reddish-brown to black (Photos 1&2), with four light reddish to yellowish spots at the corners of the wing cases (Photo 3&4). Very similar in appearance to the Rice weevil with the characteristics described above, except that the insects are longer, adults reaching a length of 3-3.5mm (average 3mm). Primarily because it is not easy to detect whether all the grains are infested, you would do well to wipe out the stocks. The other method of decreasing the number of insects is by the addition of inert dust, like clay and ash to the grain; this causes the insect to die of desiccation. The adults emerge after a further 5-16 days and will live for about 9 months. Locate the source and destroy it by wrapping the foods in heavy plastic bags or in sealed containers, and burn or bury deeply in the soil. These weevils do not bite, nor do they damage wood or furniture. The two species look almost identical without magnification. It must not be used for animal consumption, poultry feed or mixed with animal feed. Rice and Maize weevils are widely distributed in tropical and sub-tropical areas and will be carried to temperate areas on imported commodities. These methods reduce the chances of acute infestation of a granary weevil. At 18-20°C the eggs hatch in 8-11 days to give small, white, legless larvae which feed on the endosperm of the grain. in plastic containers. Harvesting the crop at the earliest when it attains maturity, decreases the chances of harm caused by granary weevil and many other pests in store. Both greater and lesser grain weevils attack cassava. Photo 4. There is a withholding period of 1 day before treated grain can be used for human or stock consumption. On average, adult weevils have a lifespan of two to three months, during which they mate and lay eggs multiple times. Commonly, loss of weight is up to 5%, but severe infestations increase the losses up to 40%. Used as a grain protectant (sometimes with piperonyl butoxide). Perhaps a method to avoid if seed is for growing. Sieving has been used as a method of removing adult weevils, but it is very labour intensive. Maize weevil, Sitophilus zeamais; adult, view from above. The life cycle takes about 5 weeks in the summer, but may take up to 20 weeks in cooler temperatures. The adults also attack damaged grains (Photo 2). Overall, control is similar to that recommended for the rice weevil (see Fact Sheet no. Malathion: apply to walls, floors, and inside of bins used to store the grain. Image Guidelines 5. The pests bore holes into the lot of fresh grains. It is difficult to detect the weevil unless populations are high as it spends most of its life inside grain. There is evidence (from Indonesia) that Sitophilus zeamais is more common on milled rice, and Sitophilus oryzae is more common on paddy (rice in the husk before processing). Note, toys can sometimes be filled with grain and act as a source of infestation; so too can dried flowers. CULTURAL CONTROLIt is most important to dry the grain properly, to keep the storage area clean, and to monitor the grain often and regularly. Neonicotinoids: e.g., imidocloprid. Photo 2. Rice, maize, sorghum, wheat, and cassava. Since, their wing covers are fused together they are unable to fly. Photo 2. Some success has been reported using Bt. READ THE INSTRUCTIONS. The weevil is not a strong flyer, less so than Sitophilus zeamais, and spread to new locations is by adults and larvae on and inside consignments of grain. Heating of the grain, accelerating development of the insects and making the commodity liable to caking, moulding and even germination. Note that identification of Sitophilus zeamais is difficult because of its similarity with Sitophilus oryzae, and needs to be done by a taxonomist. SPECIES CHARACTERISTICS: There is usually a patch of light yellow colour on the front and back of each wing cover. Remove old kernels, and sweep floors, walls, doors, and vents to collect seeds, grain powder and dust, and burn them before storing the new harvest. Insects with cylindrical bodies and a pronounced rostrum (snout) equipped with mouthparts which is used by females as a boring tool; elbowed, clubbed antennae set on rostrum; 4-segmented tarsi. Adults live for several months to a year. Locate the source and destroy it by wrapping the foods in heavy plastic bags or in sealed containers, and burn or bury deeply in the soil. Privacy Policy 8. The maize weevil is very similar to the rice weevil, Sitophilus oryzae (see Fact Sheet no. After deposition of egg the hole is plugged by a gluey secretion produced by female. Look for the faint yellowish or reddish spots on the corners of the wing cases (Photo 4). Development is about 35 days under optimal cnmditions. All larval stages and the pupal stage occur within the grain. Maize weevil, Sitophilus zeamais, clearly showing four light reddish to yellowish spots at the corners of the wing case. Maize, rice, sorghum, wheat, casssava and yam, and also dried stored products, including pasta. Texas A&M Veterinary Medical Diagnostics Laboratory, Texas A&M College of Agrculture and Life Sciences.