Among the many things that we need to know yet about the oak wilt disease and its causal fungus one is outstanding. How does the disease jump from one infection center to healthy trees 200 yards, 2 miles or even 100 miles away? Although spread through root grafts may be controlled by severing root connections, the value of such a control measure is limited as long as the agent or agents responsible for long distance spread remain unknown. The discovery of other methods of spread might result in the development of control measures that are cheaper and less drastic than those known at present.
A great deal remains to be done and research is increasing in the various states concerned. There is reason to believe that oak wilt can be checked before it reaches devastating proportions comparable to chestnut blight which wiped out our American chestnuts.
MR. SLATE: What is the origin of the fungus? Is it a native fungus, or imported?
MR. CURL: Yes, it is a native fungus, as far as we know.
MR. SLATE: Any evidence that the fungus is mutating to make more virulent strains?
MR. CURL: That's something that hasn't been found yet. There are several strains of the fungus, what we call strains, because they will form the sexual stage, and a strain alone will not. There is not too much known about that yet, the strain business.
MR. GRAVATT: Just a word. We had a conference in Beltsville all day Sunday about the recent developments on the oak wilt. There has been very extensive spread in Pennsylvania, Ohio, West Virginia and Maryland this year. We are very much alarmed about the situation. The Chinese chestnut is very severely affected. We have learned that in Missouri. One year there were three Chinese chestnuts killed by the fungus, the next year 60. The oak wilt is a serious threat to the chestnut orchards.
Life History and Control of the Pecan Spittle Bug
STEWART CHANDLER, Associate Entomologist, Ill. Nat. History Survey,
Urbana, Ill., Consulting Entomologist, Southern Illinois University
Since it was a year ago that this subject of spittle bug was first brought to the attention of the Northern Nut Growers Association, it might be well to review briefly the high lights of that report. I told you at the annual meeting at Urbana, something of the life history. There are two broods, one appearing in June and one in July. The adult is a small sucking bug about an eighth to a quarter inch long. The species at that time was uncertain but now has been determined by specialists in that group as Cercoptera achatina Germ. This insect, I reported, is not the same as the one occurring on meadow and other field crops, not only the species but the genus being different. The distribution was found to be in every area where pecans are grown. As to its importance I pointed out that in Illinois it had become very serious in the past three or four years, apparently causing a marked reduction in crop. Control measures were directed against the nymphal stage, which is protected by the spittle which the insect emits continuously while feeding. Three insecticides were tested at Anna, Illinois, Lindane, parathion, and tetra ethyl pyro phosphate, known as TEPP. Lindane proved to be approximately 95% efficient, parathion roughly 60% and TEPP about 10%.