This is about all we have to offer at this time in regard to our variety tests.
We have a problem which I wish to bring before the members of the Association. It is that of controlling the butternut curculio. This insect is very bad on butternut, heartnut and Persian walnuts, with us it does not attack black walnuts or hickories. I fear that it is going to prove hard to control, as the larva is of the boring type, being found inside the green nuts, inside the new growth of the terminals and in the fleshy part of the leaf stems. In these places it cannot be reached by poisons. It appears that we will have to work entirely on the adult beetles. These eat very little and seem to make puncture-like holes, eating little outside tissue but mostly deeper tissues, thus poison will probably have to be applied heavily in order for it to get enough to kill it. D.D.T. is not effective against the apple and plum curculio so probably will not be so against the butternut curculio. It might be effective to apply a heavy coating of D.D.T. bearing dust under the trees so that as the larva drop to the ground to pupate, they will be killed while the adult beetle may be immune to D.D.T., it is not likely that the pupa could survive in heavily impregnated soil.
The adult beetles are present from the time the first leaves appear until late summer. A spray of 4 to 5 pounds of arsenate of lead and 12 to 15 pounds of hydrated lime to 100 gallons of water, applied once a week throughout the early part of the season might prove effective but it will certainly prove expensive.
Planting of the affected varieties at some distance from woodlands and wild butternut trees is helpful in avoiding this insect, but as the trees grow older the pests may build up a population of their own. Some sections of the county may not be affected; I hope so.
Maybe we can get some of our entomologists to work on this insect. Let's put a little pressure on our State Experiment Stations and the U. S. Department of Agriculture. Maybe Mr. Reed can help us.
Another subject I wish to mention is that of hardiness in nut trees. In reading the NNGA reports and in some of the letters I have received, I have found that many people confuse killing of the young leaves in the spring by late frosts, with winter hardiness. In my opinion there is no connection at all. I have seen many trees that were not hurt at all by -34°F. in mid-winter yet had all of their leaves killed by a late frost in the spring. In fact all species and varieties of hickory and walnut will have their leaves killed by a hard frost if the leaves have opened out of the buds; this includes our native wild trees as well as the grafted varieties.
The only hardiness against late spring frosts is the characteristic of leafing out late, thus escaping most of such frosts. Of the different species, the black walnuts seem to be best protected in this way, with the hickories next and the heartnuts and Persian walnuts least protected. Of course there is a considerable varietal variation within each species.
Then the protection we can provide, is to plant nut trees on side hills or other high ground where there is good air drainage, thus avoiding the frost pockets. Of course many want to plant nut trees and have no place except in low frosty sites. To these I say that they can expect to lose an occasional nut crop by these late spring frosts, but that only in exceptional cases will the trees suffer permanent injury. In years when the crops are lost the trees will still be good ornamentals and shade trees. My door yard is quite a frost pocket, yet I have lost only one crop of heartnuts out of four or five crops, no permanent injury to the tree.
Yield and Nut Quality of the Common Black Walnut In the Tennessee
Valley[12]
By Thomas G. Zarger, Tennessee Valley Authority