Weevils: Facts, Identification & Control
What are Weevils?
Weevils are actually beetles. They belong to the family Curculionidae. There are more species in this family than in any other beetle group. Scientists estimate that there are more than 2500 species of Curculionidae in North America.
Sometimes people get confused and they use the name “weevils” for the white, wiggly creatures they find in the pantry – usually in the flour or the cereal. These are actually larvae of moths or beetles. The adult insects laid their eggs in the flour. The larvae hatched in the flour and they develop into adult insects when they have finished growing.
Weevils are slender or oval-shaped insects. Depending on the species, weevils range in size from about 1/8” to almost 1” in length. They are usually dark-colored – brownish to black. Some have scales or shiny hairs covering part of their bodies. The most distinctive feature of weevils is the shape of their head. An adult weevil has an elongated head that forms a snout. The mouth is at the end of the snout. Some weevils have a snout that is as long as the body.
What Do Weevils Eat?
Weevils feed on plants in the larva stage and as adults. Some weevils can be very destructive to crops. For many years, one of the most destructive weevils was the cotton boll weevil. The Asiatic oak weevil, Cyrtepistomus castanaeus (Roelofs), is found throughout the eastern United States and in California. It attacks many types of hardwood and fruit trees. The black vine weevil, Otiorhychus sulcatus (F.), is found in many parts of the United States. It feeds on a variety of plants, including grapes, strawberries, and some greenhouse plants.
Most weevils are found in fields, gardens, or orchards. A few, weevils attack stored grains and seeds. They can be very destructive and their damage is often very expensive. The most common stored product weevils are the rice weevil, Sitophilus oryzae (L.), the granary weevil, Sitophilus granarius (L.), and the cowpea weevil, Callosobruchus maculates (F.).
However, a few weevils become structural pests. These are the weevils that upset homeowners because they invade homes – often in great numbers. Some of them invade in the fall. They hide during the winter and leave in the spring. Others invade in the summer when the weather starts turning hot. The strawberry root weevil, Brachyrhinus ovatus L., becomes a pest in both spring and fall in many parts of the country. The Egyptian alfalfa weevil, Hypera brunnipennis (Boheman), invades homes in Arizona and California. The Imported longhorned weevil, Calomycterus setarius (Roelofs), is found in the northern section of the United States as far west as Kansas.
Weevil Life Cycle
In spring, the adult weevils lay their eggs on the ground near the host plant. When the eggs hatch, the larvae burrow into the ground and feed on the roots. Since the larvae are underground, people seldom see them.
Many of the larvae spend the winter in the ground and emerge as adults the following spring. However, the adults that emerge during the summer or fall often invade homes for shelter. Some, like the Asiatic oak weevil, are attracted to light, so they are drawn to homes at night. Others may be attracted by the heat from the house.
Weevil Control
Homeowners might not notice weevils when they are gathered on the outside of the home. But if the weevils manage to find an opening and invade the home, the homeowner often finds hundreds of insects crawling on the walls and windowsills.
A vacuum cleaner is a quick way to remove weevils from the walls and furniture. Be sure to take the vacuum outside to empty it so the weevils don’t re-infest the home.
If weevils haven’t invaded, there is time for some prevention. Check outside for any openings that weevils could use to get inside. Look around doors and windows for missing caulk and damaged weather-stripping. Check attic vents and crawlspace vents for torn screens.
The Orkin Man™ can help homeowners manage weevils. He will use Orkin’s exclusive A.I.M. system – Assess, Implement, and Monitor. He will customize the treatment to your home’s situation. By focusing on the source of the problem – outside of the home – he will be able to help keep weevils from invading again.
When weevils invade, they can come in large numbers. Homeowners often feel more confident calling the local Orkin branch office to get The Orkin Man™ to help get weevils out of their home and help keep them out.
Types of Weevils
Boll Weevil – The boll weevil (Anthonomus grandis) is a type of beetle that is known to cause severe damage to cotton crops. The boll weevil measures an average length of six millimeters. It feeds on the buds and flowers of the cotton plant.
Flour Weevil – Wherever flour is present, the beetle known as the flour weevil follows. Rather than whole grains, this beetle can only digest flour. These beetles are not actually weevils.
Rice Weevil – While it is true that the rice weevil is harmless in itself, it hurts human beings on a larger magnitude by compromising food supplies. What it lacks in stinging or biting, it makes up for in causing destruction on a potentially massive scale.
Bean Weevil – Acanthoscelides obtectus is the scientific name of the bean weevil, the farmers’ scourge. Technically, they belong to the cadre of seed beetles and are not true weevils.
Wheat Weevil – Commonly called the granary weevil, the Sitophilus granarius, or wheat weevil, holds notoriety for its destructive potential in agriculture. Historically, it is known as one of the most formidable pests.
Black Vine Weevils – The black vine weevil, Otiorhynchus sulcatus, is believed to be another species that migrated to the United States.
Rose Weevil – The rose weevil is a serious threat to all horticulturists. Its snout can drill through flower buds. These weevils cause irreparable harm by feeding on petals.
White Pine Weevil – Pissodes strobi, or the white pine weevil, is a pest that infests pine and spruce trees.
Cowpea Weevil – True to its name, this pest infests cowpeas and stored soybeans. Cowpea weevils lay eggs on the stored beans that they eat, and the larvae use the beans as food while they develop.
More facts about weevils: