Probably the most serious enemy of Juglans, in Connecticut at least, is the walnut weevil or curculio, Conotrachelus juglandis LeC. The larvae tunnel in the tender shoots, often ruining the new growth, and they also infest the nuts. The adults feed upon the shoots and leaf petioles. Observations on the different hosts indicate that Juglans cordiformis and J. sieboldiana are preferred, and the most severely injured, followed in order by cinerea, regia, nigra and mandshurica.

Though described as early as 1876, little was known about the life history of this insect until the studies were made at the Station in 1912 by Mr. Kirk and the writer. Formerly it was supposed that this insect attacked and injured only the nuts or fruit, and Dr. Morris in 1909 seems to be the first on record to observe the injury to the shoots of Juglans regia. It was on the trees of Dr. Morris here in Stamford and those of Mr. H. L. Champlain at Lyme that the life history studies were made. There is but one brood each year, and the winter is passed in the adult stage. The beetles appear the latter part of May and feed upon the stems and leaf veins during the egg-laying period, which extends from the last week in May up to August 1st. The eggs are laid in irregular crescent-shaped punctures, similar to those of the plum curculio, and hatch in from six to twelve days, depending upon the weather.

From four to six weeks are necessary for the development of the larvae, and when mature they go into the ground where they remain for about ten days an inch or so beneath the surface. They then pupate, and from sixteen to twenty days later the adult beetles emerge. They fly to the trees and eat small holes chiefly at the base of the leaf petioles, but must early go into winter quarters as they are seldom seen after the first week in September.

This insect occurs throughout the Eastern United States, but seems to cause more injury in Connecticut than has been noted elsewhere. The remedy is to spray the new shoots and under side of the leaves about June 1, with lead arsenate (6 lbs. of the paste in 50 gallons of water), to kill the beetles when feeding on the leaf petioles.

The Nut Weevils.

Balaninus sp.

Several kinds of nuts are attacked and injured by long-beaked snout beetles or weevils belonging to the genus Balaninus, the chestnut probably being the most seriously damaged. All of them feed inside the nuts or fruit during the larval stage, and the larvae are without legs. As both the methods of attack and the life history are similar for all species, they will be considered here in a group. For the sake of distinguishing them, however, their names are mentioned.

Larger Chestnut weevil, Balaninus proboscideus Fabr.
Lesser Chestnut weevil, B. rectus Say.
Hickory nut or Pecan weevil, B. caryae Horn.
Hazelnut weevil, B. obtusus Blanch.
Common acorn weevil, B. quercus Horn.
Mottled acorn weevil, B. nasicus Say.
Straight-snouted acorn weevil, B. orthorhynchus Chittn.
Sooty acorn weevil, B. baculi Chittn.
Confused acorn weevil, B. confusor Ham.
Spotted acorn weevil, B. pardalus Chittn.

All of these weevils pass the winter in the ground in the larval stage, transforming to pupae about three weeks before the adult beetles emerge, which varies from June, when they are usually few and scattering, to September, when they have become abundant. Thus there is a single brood each year, and the larval period lasts from three to five weeks in the nuts and some ten months in the ground, from two to eight inches below the surface.

The control of these weevils is difficult, and ordinary methods such as spraying are not effective. In fact little can be done other than destroying the weeviled nuts, which may be fed to hogs. When first gathered the nuts may be fumigated with carbon disulphide. About two fluid ounces of the liquid should be used for each bushel of nuts and placed in a shallow dish on top of the nuts, which should be enclosed in a tight box or barrel. The period of fumigation should be from 12 to 24 hours. Where nuts are not to be used for seed they may be thrown into boiling water for about five minutes—just long enough to kill the weevils. The nuts are then dried and sold. Most of the weeviled nuts will rise to the surface and may be discarded, but this test is not absolute and cannot be depended on to distinguish the sound from the weeviled nuts.