There has been little disease among my Persian walnuts except that in wet seasons leaves and nut shucks are sometimes attacked by a fungous blight. In the city there has been no insect injury worthy of note. In the country, adjacent to wooded areas, insect injury is sometimes serious. Pests include spittle bugs, stink bugs and other insects that attack young leaves and tender growth. These check the leaders and cause late multiple growths that may fail to mature and hence winterkill.
In such locations the butternut curculio also attacks and destroys the young nuts. Avoid wooded areas if choosing a site for a Persian walnut orchard.
The most destructive pest with which I have had to contend has been the large black-bird or purple grackle. Oddly enough they are much worse in the city than in the country. As soon as the young are grown, about the middle of June, they appear in flocks and attack the nuts of the Persian walnut. At first, before the shell has hardened, they penetrate the nut apparently for the nectar which is the substance of the immature kernel. When the shell can no longer be penetrated they continue to eat away the husk, which is equally fatal to the nut. This continues until late in July, when the squirrels take over. Fortunately squirrels are highly allergic to a bullet from a 22 rifle.
In pointing out some of the hazards encountered in growing Persian walnuts in the East the writer has not intended to be discouraging but helpful. Persian walnuts of good quality can be grown in this section; full understanding of the factors involved make it possible, I believe, to grow them successfully on a commercial scale.
Varieties of Persian Walnuts in Eastern Iowa
Ira B. Kyhl, Sabula, Iowa
There are a great many varieties of Persian walnuts, many of which originated in the region of the Carpathian mountains and other parts of Europe and a few varieties in the United States and Canada.
I believe that some varieties now grown in the United States and Canada which originated in Europe may have come from the same tree as they appear to have the same shape, thickness of shell and flavor. I have as many as four varieties that are identical.
The Persian walnut has always been my favorite nut. I started with 2 or 3 varieties and now have 35 or 40 varieties and 200 trees most of which are doing well. Some are superior in hardiness and vigor.
In eastern Iowa at 42 degrees N. latitude minimum winter temperatures vary from 25 to 32 degrees below zero. Usually the minimum is 12 to 15 degrees below zero, but last winter it was 25 degrees below zero for several days. Only the hardier varieties will endure -25 degrees without injury, but -12 to -15 does not injure any variety very much.