The best remedies are (1) clipping off and burning the nests when small, and (2) spraying the foliage with arsenical poison.
Inconspicuous nests containing small caterpillars are often found at the ends of the new shoots of _Juglans regia_, seriously injuring them, and sometimes killing the trees. One small tree two feet high was killed, and thirty-five pupae were found in the nests at Dr. Morris' farm in 1912. The adult is a small gray moth with a wing expanse of about three-fourths of an inch. There are three broods each season in Connecticut, the larvae appearing about June 1, July 10 and August 18.
By spraying the foliage with lead arsenate (3 lbs. in 50 gals. water) this insect can be controlled. One application should be made about June 1, followed by a second about July 10.
Though this insect is thought to be _Acrobasis caryae_ Grote, it is often difficult to distinguish some of these species in this genus without a knowledge of their food habits and seasonal life histories. We possess such knowledge regarding this species which we have studied and reared in Connecticut, but it is lacking in connection with adult specimens in the United States National Museum labeled _caryae,_ which superficially seemed identical with ours. Further study, therefore, may prove this to be an undescribed species. There are other bud-worms attacking nut trees, especially in the southern states, where they cause considerable damage to pecans.
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.