The duration of life cycle of rice weevil and number of generations completed in a year depends upon the weather conditions, like temperature and humidity. Distribution: It is a serious pest not only of paddy and rice but almost of all cereals and their products. Inside the grain kernel, the egg hatches into a young larva which migrates toward the centre of the grain kernel. The pronotum is barely shorter than the elytra. During its life span of 5 months, it lays a total of about 250-400 eggs. What are the damages caused by Sitophilus oryzae. Some external features can be used to differentiate … In fact, it is the commonest pest that one encounters in all kinds of stores. The pupa does not feed. [CDATA[ TOS 7. A female may lay as many as 300 to 550 eggs in 4-5 months. Before pupation it may pass through pre-pupal stage for 1-2 days. A pair of stout mandibular jaws is present at the extremity of the rostrum. Journal of Economic Entomology. Rice weevils are good flier as it has been known to fly from go down to the nearby fields, where it infests the ripe grains. Rice weevils are the most destructive pests of stored grain and they completely destroy the grain. Larva: They feed inside the grain kernel for 18 days. Rice Weevil (Sitophilus Oryzae): Distribution and Life History! These insects do not bite nor damage wood. Feeble sexual dimorphism exists. It is easily confused with the similar looking maize weevil. Eggs are laid singly in a prepared hole in the grain and then covered with waxy plug. (Wayback in 1763 it was known as Calandra oryzae.). Explain the stages in the life cycle of rice weevil. Sometimes, they are also found infesting beans, sunflower seeds and dried corn. The emerged adults are ready to mate and begin their generation. A fully matured grub makes a pupal cell inside the grain and pupates. These species are identical externally and can only be distinguished by examination of genitalia. The body color appears to be brown/black, but on close examination, four orange/red spots are arranged in a cross on the wing covers. Copyright 10. Female rice weevils lay between 300 to 400 eggs and 2-3 eggs in the grain. Egg: Rice weevil lays its eggs in crevices of kernels or dust. Due to many droppings of rice weevils the products can be stale and of bad quality. Content Guidelines 2. The treatments are without toxic chemicals which can be applied as an organic fumigation solution. The adult emerges out through the hole of emergence. The harm they cause is destruction of the seeds they infest. The pupal stage lasts for 3-6 days (July-September) but in unfavourable conditions (winter and summer months) it may extent up to 20 days. The damage caused by them may extent up to 50% of the total grain stored in a particular go down. It is a serious pest not only of paddy and rice but almost of all cereals and their products. Sitophilus Oryzae is usually found in grain storages and processing plants. Behavioral responses to food volatiles by two species of stored-product Coleoptera, Sitophilus oryzae (Curculionidae) and Tribolium castaneum (Tenebrionidae). There is generally no external evidence that the larvae have been eating until when the adult weevil chews through the seed coat and emerges. They can exist anywhere where physical conditions for growth are favourable and the grain is left undisturbed for some time. Sorghum In Maharashtra, India, some hybrids and varieties of sorghum were less susceptible to attack by S. oryzae than local varieties (Borikar and Tayde, 1979). Larvae: apodus is white and legless. The adults formed after pupation bores its way out of the grains. The size of the newly bored adult weevil is directly proportional to the size of the grain in which the larval period has been spent. They can exist anywhere where physical conditions for growth are favourable and the grain is left undisturbed for some time. Genus – Sitophilus . Rice weevils pretend death by drawing their legs close to body and remaining silent even when disturbed. However, this pest is particularly common in warm countries. Previous years questions with explanations...for all competitive exams, Dampness which may even cause germination, Repackaging material into new infection-free containers, Placing the products in the freezer for several weeks may help to kill adults and larvae. Content Filtrations 6. These two weevils exhibit closely morphological and ecological resemblance making difficult their proper identification and recognition of their distribution in grain‐producing regions. Distribution of the related weevil species Sitophilus oryzae and S. zeamais (Coleoptera: Curculionidae) in farmer stored grains of China. In Indian conditions, 5-7 generations of this weevil is generally completed in a year. They have three pairs of legs and their bodies are divided into head, thorax and abdomen. Adults may also, feed upon flour (milled cereals) but the larvae cannot develop in it unless the material is caked. The adult rice weevil lives at a temperature of 28 º C for about 3 months, and at 20 º C they live 5-7 months. Emergence holes of the rice weevil are smaller than those of the granary weevil, and tend to be smooth and round. The tiny, white, fleshy, legless grubs with yellowish- brown head and biting jaws bores down into the grain, feeding on its starchy content and hallowing it out leaving the shell intact. Inside the seed, its cuticle hardens and matures. Sitophilus Oryzae is also called as Rice weevils. Attack is evidenced by, //