Weevils are a diverse group of beetles, recognized by their distinctive elongated snouts. These insects are primarily herbivores, consuming a wide array of plant matter throughout their life cycles. With over 60,000 known species globally, weevils are found in numerous environments, from agricultural fields and gardens to household pantries, and their diets vary significantly among species.
Common Weevil Food Sources
Weevils consume a broad spectrum of plant-based foods, often categorized by habitat. Many species are pantry pests, infesting stored grains and products. For example, rice weevils (Sitophilus oryzae) and granary weevils (Sitophilus granarius) commonly target items such as rice, corn, wheat, oats, rye, barley, pasta, flour, cereals, and dried beans.
Other weevil species are significant agricultural pests, feeding on field crops. The boll weevil (Anthonomus grandis) primarily feeds on cotton buds and flowers, causing substantial damage. Root weevils, like the black vine weevil (Otiorhynchus sulcatus), target the roots and foliage of plants such as strawberries, rhododendrons, and various ornamentals.
Understanding Weevil Feeding Habits
Both adult weevils and their larval stages, often referred to as grubs, actively feed, though their methods and preferred food parts differ. Adult weevils feed externally on plant foliage, stems, or the surface of stored goods. Larvae are internal feeders, tunneling into grains, stems, or roots where they develop.
Weevils use their distinctive snouts for feeding and preparing egg-laying sites. The female weevil bores a small hole into a grain kernel or plant tissue, depositing a single egg. She then seals the hole, allowing the larva to hatch and feed protected within the food source. This internal feeding mechanism can lead to significant damage, including holes in grains, wilting plants, stunted growth, and damaged fruits or seeds. Their feeding activities can render stored food unfit for consumption and severely reduce crop yields.
Signs of Weevil Activity
Detecting a weevil infestation often involves observing specific indicators of their feeding and presence. In stored food products, visible damage includes small holes in grain kernels, flour, or pasta, which are exit points for emerging adults. Fine dust, known as frass, which consists of weevil droppings and chewed food particles, may also be present inside or outside food containers.
Adult weevils may be seen crawling in stored food containers or on shelves. In severe infestations of stored grains, a musty or slightly sour odor can become noticeable. For weevils affecting plants, symptoms include notched or ragged edges on leaves, particularly from adult feeding. Plants may also show signs of wilting, yellowing, or stunted growth, indicating larval feeding on roots or weakened stems. Digging around affected plants might reveal weevil grubs in the soil.