ALFALFA WEEVIL, a snout-beetle, or weevil (Hypera postica) of Old World origin. which feeds upon alfalfa, or lucerne (Medicago sativa). Although widely distributed in Eu rope, where its host plant is extensively grown, it attracted little attention until it was accidentally introduced into the United States in the early years of the present century. It appeared sud denly in the vicinity of Salt Lake City, a region where the alfalfa crop is of great importance, multiplied and spread rapidly, caus ing great alarm to the agricultural and live-stock industries. It spread steadily at the rate of from i o to tom. a year, and in 1927 occurred in great numbers through the Great Basin and the Snake river watershed, in large areas of the Colorado and North Platte drainage basins, and in the territory of the Yellowstone and Sacramento rivers. It is a constant threat to the great alfalfa regions to the east, and its spread cannot be prevented by regu lating the production and marketing of the crop, since it feeds on other leguminous plants, some of which are wild.
The adult weevil is dark brown in colour and about -A-in. long. In this stage it passes the winter, usually in crevices in the ground. In the spring the adults begin feeding on the earliest growth of the plant, and lay their eggs either in old, dry stems or in the living stems. In warm weather these eggs hatch in from one to two weeks, and the young larvae begin to feed on the leaves, especially on the opening tips, rapidly skeletonizing them—so rapidly, in fact, that the plant is unable to outgrow the injury. When full grown, the greenish larvae spin loose cocoons from which adults emerge in the summer. The cocoons are found at tached to the stems, in curled leaves or on the ground.
During the first nine years in America, the weevil not only spread rapidly but nearly destroyed the first crop of alfalfa each year. Since then there have been fluctuations in the amount of damage, due probably to climatic changes. Systematic studies have been carried on by the Federal bureau of entomology ever since the insect was first discovered, and important investigations have been made by the official entomologists of Utah and the neighbouring States. Ten species of parasites have been imported from Europe by the Federal experts, and one of these (Bathy plectes curculionis) is thoroughly established and has spread throughout most of the infested territory. In some localities it has been known to kill 90% of the weevil larvae ; but the rate of increase of the weevil is so rapid that even this percentage does not bring about control, and artificial remedial measures must be relied upon. Of the artificial measures, prompt cutting of first crop as soon as it reaches pre-bloom stage ; or spraying or dusting first crop at just the proper time (varying according to conditions) with powdered arsenate of calcium has been found to be the most effective, by which method it is still possible to grow alfalfa with more or less profit, in spite of the weevil. A full account of methods and machinery will be found in Farmers' Bulletin, No. 1,528, U.S. Dept. of Agriculture. (L. O. H.)