Fear No Weevil
Celebrated in song, folklore, and statuary, the boll weevil—scourge of the American cotton industry—is perhaps the best known agricultural pest in the United States. But not so for its weevil cousins, a lacuna that E. Richard Hoebeke, a taxonomic and survey entomologist recently retired from the Department of Entomology, is looking to remedy with the help of Kent Loeffler, photographic specialist in the Department of Plant Pathology, in the forthcoming book An Illustrated Identification Guide to the Adventive (Non-Native) Weevils (Curculionoidea) of North America.
Specifically, Hoebeke and co-author James LaBonte, a taxonomic entomologist with the Oregon Department of Agriculture, hope to enable specialists and others to accurately recognize North American non-native weevils.
Like the boll weevil, which emigrated from Mexico to Brownsville, Texas, and beyond, many of the 3,200 North American species of weevil are not native to our fauna, either unintentionally introduced via commerce and a traveling public, or deliberately released for weed biocontrol.
Because of their great diversity, ability to thrive in any climate, association with virtually all plants, and a burgeoning global marketplace, weevils are especially successful hitchhikers to all of the world’s continents. The accidental introduction of exotic weevils into North America has occurred since early colonial days. And although a large number of weevils introduced into North America, or soon to be on the continent’s shores, are innocuous and apparently cause no measurable damage to plants, many are serious plant pests, such as the feared Japanese Pear Weevil (below).
The number of described weevil species on the planet is calculated to be about 62,000, with the total number of existing species likely approaching 220,000, meaning that entomologists have described just over a quarter of the diverse population of this important and largest group of herbivorous beetles.
What follows is imagery of the wonderful weevil as captured for the forthcoming book.
Rhynchites heros (“Fruit Weevil”, “Peach Weevil”, “Japanese Pear Weevil”, “Japanese Apple Curculio”)
Native to East Asia (Japan, Korea, Taiwan, and some parts of China). Not yet known from or established in North America. This species represents a serious threat and great concern to American agriculture.
Common on apple throughout Japan, but also sometimes causes serious damage to pear, and attacks peach, plum, loquat, and other fruits. There is usually one generation a year. Rhynchites heros larvae live within the fruit and can survive between 18 and 50 days feeding on and developing within the fruit.
Curculio elephas Gyllenhal
Native to south and central Europe and northern Africa (Algeria). Not yet known from or established in North America.
Feeds on the seeds (nuts) of chestnuts and oaks. Adult weevils emerge from the soil in late summer to early fall and cause feeding damage by piercing nuts with their long, slender snout. After feeding, female weevils turn around and deposit one to several eggs in each nut through the feeding hole. Upon hatching, the larvae or “grubs” consume the “meat” of the nut. After feeding inside the nut for about a month, the larvae chew their way out of the nut and enter the soil to pupate.
Eurhinus magnificus Gyllenhal
No Common Name
Native to Mesoamerica (Belize, Costa Rica, Guatemala, Honduras, Mexico, Nicaragua, and Panama). First reported in Florida in 2002 (Broward County). Collected again in 2003 near Homestead (Miami-Dade County). Also intercepted in shipment of bananas from Costa Rica in 2004. In 2005, all life stages collected repeatedly in Broward and Miami-Dade Counties. Appears to be established in southeastern portion of state. Probably inadvertently imported into Florida via living plants or plant products.
Adults feed on outer layers of plant stems, within cavities in stems and leaf petioles, and on leaf blades at portion of leaf attachment to petiole. Larvae induce galls on stems of Cissus spp. (Vitaceae). Only verified host in Florida is C. verticillata. Although sometimes planted as an ornamental, C. verticillata is a prolific perennial vine and generally considered a weedy species. Eurhinus magnificus not known to be a pest of commercial grapes and not considered a threat to Vitis spp. However, additional studies are needed to determine if other grape cultivars might be susceptible.
Anthonomus grandis Boheman (“Cotton Boll Weevil or Boll Weevil”)
Native to Central America and Mexico; migrated into the United States from Mexico. First appeared in the U.S. in Texas (near Brownsville) in 1892 and reaching Alabama in 1915. By the mid 1920s, it had entered all cotton-growing regions in the U.S.
The cotton boll weevil is considered a key pest of cotton in the eastern United States. These weevils overwinter under leaf litter, in woods, among weeds, and along fencerows surrounding cotton fields. Adults feed on terminal shoots of cotton seedlings and immature cotton bolls, while larvae feed inside the boll, eventually destroying the plant. Also a serious pest in South America.
Coniatus splendidulus (F.) (“A Tamarisk Weevil”)
Native to the Mediterranean region and Asia. In North America, presently known only from a few localities in Arizona. The species has been found in Gilbert (Maricopa County), as well as along the Santa Cruz River from Marana (NW Pima County) to Amado (Santa Cruz County).
A potential biological control agent of tamarisk or saltcedar (Tamarix spp.) in the West. The weevils were imported and released to control the spreading of Tamarisk in riparian areas. The larvae live on the surface of the twigs and spin a protective cage to pupate.
Cryptorhynchus lapathi (L.) (“Poplar-and-Willow Borer”)
Native to and widespread in Europe and Asia. First reported in New York in 1882 and in British Columbia in 1923. Now found throughout southern Canada and in the northern half of the United States from northern California eastward to the Carolinas.
Attacks species of Salix (willow) and Populus (poplar). Larvae riddle stems of young trees in plantations throughout north-central North America. Complete girdling kills the tree above the injury.
Cylas formicarius (F.) (“Sweet Potato Weevil”)
Native to the Old World; accidentally introduced into the southern United States, Hawaii, Greater Antilles, Central America, Australia, and Japan. The sweet potato weevil can be found throughout the coastal plain of the southeastern U.S. from North Carolina to Texas and Hawaii. In the Caribbean it is found in Cuba, Puerto Rico, Jamaica, Dominican Republic, Haiti, Guyana, St. Kitts-Nevis and in Central America—Mexico and Panama.
Cylas formicarius is considered the single most important pest of sweet potato (Ipomoea batatas) in countries where it occurs. Weevil infestation ranges from 20 to 50% on many farms and can even reach to 100% depending on the season and variety. Higher infestation occurs during dry seasons. Weevil damage to tubers causes heavy losses. The larvae feed in the tubers and the adults feed on the stem and leaves.