Northern Nut Growers Association Report of the Proceedings at the 44th Annual Meeting / Rochester, N.Y. August 31 and September 1, 1953

by Unknown

It is our thought that if some effort were made to bring to this assembly, a digest of what has been done to control the Hickory weevil, we might arouse enough interest to carry on some experiments.

If, at the conclusion of this paper, we can get enough discussion, we will be able to avail ourselves of the knowledge and experiences of others who have made attempts to control this pest, it would be to our advantage.

The Pecan weevil of the south and the Hickory weevil are identical and we learn the following from the experiments carried out by G. F. Moznette, Bureau of Entomology, U.S.D.A.

Pecan weevil damage is of two types—(1) that resulting from attack before the shell-hardening period in July and August and causing all affected nuts to drop, and (2) that resulting from attack after kernel formation and usually causing the shuck of infested nuts to stick tight to the shell instead of opening normally. Weevil-injured nuts of the second type contain grubs which destroy the kernels, or they contain holes about one-eighth inch in diameter which mature grubs have bored and through which they escaped after destroying the kernels. The first type of damage often passes unnoticed and is due to the feeding of early emerging weevils, which puncture the immature nuts with their long lancelike beaks to feed on the juices within. Since all nuts punctured in this way before the shell-hardening period drop to the ground, the entire crop may be lost if weevils are abundant and the crop is light. Such damage may be heavy even when a large crop is attacked. The second type of damage is generally noticeable at harvest-time in October and November, and in seasons when large numbers of weevils have been present practically the entire crop may be wormy at harvest.

Since the weevils do not feed very much on the outer surface of developing pecan nuts, stomach poisons applied to trees have been of little practical value in control. In 1944, however, laboratory tests showed that DDT could kill the adults, and that it was worthy of field trial.

Field tests were made at Fort Valley, Georgia, with DDT and the conclusions drawn from these tests show that the effectiveness of two applications of DDT at the rate of 6 pounds of a 50-percent wettable powder to 100 gallons of water in reducing harvest infestations to 1 percent gives rise to the hope that this treatment, applied for several seasons, will eliminate a pecan weevil infestation in an orchard, or will reduce it to such an extent that spraying every year will not be necessary.

The time of the first application of DDT cannot be based on the time of the first drop of nuts, because other pecan insects also cause the nuts to drop during July and August. However, pecan growers who wish to make the effort can time the first application accurately by spreading a sheet on the ground beneath an infested tree and lightly jarring the branches to dislodge the weevils. When the weevils are disturbed they fall and "play possum" and can be easily collected. When a minimum of six weevils can be taken by jarring the branches on any one tree, it is time to make the first application.

While the above will probably give an indication as to what can be done, using DDT to control the Hickory weevil, for those who have large plantings and can afford the expensive spraying equipment necessary, it will be necessary to look farther for control methods for the small orchard, where expensive equipment is not feasible.

The following is part of a letter from Dr. C. C. Compton, Entomologist for the Julius Hyman and Company.

"It is our thought that since DIELDRIN is so highly toxic to Curculionids it might be possible to take advantage of the habits of this insect and control it by spraying the soil surface. The larval stage of this insect leaves the nuts and enters the soil sometime in the fall. It is believed that the larvae penetrate the soil rather deeply, to a depth of perhaps a foot or more and remain in the soil over winter. In the spring or early summer the larvae transform to adults and emerge to lay their eggs. In some regions at least the adults do not emerge until the second year after the larvae enter the ground.