Rice weevils may be considered one of the most important stored products pest or commonly referred to as a pantry pest. They are most alike to granary weevils, however, granary weevils will be more prevalent in cooler climates. So, rice weevils will more commonly be found in warmer regions like in the southern states in the United States whereas granary weevils will more commonly found in the northern states. They are worldwide pests and will be detrimental to grains and stored food products.
Life Cycle and Physical Recognition
Rice weevils undergo a complete metamorphosis and complete all stages of the metamorphosis including the egg, larval stage and the pupa stage until they reach maturity as an adult. Female rice weevils will bore a hole into just one kernel of grain to lay an egg after which she will seal the opening of the hole with a gelatinous material. This exhibits the same behavior and biology as granary weevils. Females are able to lay anywhere between 300-400 eggs in her entire lifetime with egg laying being more sporadic in the cooler seasons and climaxing in the warmer seasons. There are about 4 larval instars that rice weevils undergo before they go into the pupal stage. This requires about 18 days. The pupal stage, or the cocoon stage, will take anywhere between 3-9 days. After adults emerge from the pupal stage, they will remain in the kernel of grain until they are fully developed and their outer shell is hardened. An entire life cycle can be completed in just a month’s time and adults can live for about 3-6 months. In a given year, if all conditions are favorable, there may be several generation overlaps that the weevils can encounter. Adult rice weevils range in size from about 2.5 – 3.5 mm. They are a dark, reddish-brown color with 4 lighter reddish or yellow markings on their thorax. Like granary weevils, they have engravements or indents on their shells and their heads will elongate into a snout or a beak. Unlike granary weevils however, they have fully developed wings are able to fly.
Food and Damage
Rice weevils will usually be found in grain products infesting all kinds of grains that include wheat, oats, corn, rice, barley, and etc. They may also be found inside the home infesting chestnuts, sunflower seeds, ornamental corn, table beans, and etc. Rice weevils may also be found sucking on the juice of some fruits like apples and pears. Rice weevils are sometimes rarely found in macaroni and spaghetti. Larvae will attack whole grains and adults will create holes in them as they emerge from the grain. Fortunately, rice weevils are not known to attack people or pets, nor do they spread disease or damage household furniture.
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