Chapter X: Section X: Amendments to By-Laws (3)

There is just one other point I want to make. Undoubtedly we need better varieties. The nurseryman realizes this better than anyone else. But when my friend from Brunswick sold his native pecans he got just about as much for them per pound as the southern growers got for their much larger southern seedlings. Several commercial pecan crackers that I asked about this stated that the northern nuts have a better flavor and they produce more kernels per pound. So the size of the kernel doesn't make too much difference, although we all prefer the larger nuts.

Pecans in Northern Virginia

J. RUSSELL SMITH, _Swarthmore, Pennsylvania_

(Extracts from a letter to the NNGA secretary, November 26, 1951)

Having sold my Virginia cabin and the nursery business [Sunny Ridge] I have been down to the nursery for the last month getting rid of trees. A job of digging is one thing and that of packing and shipping is another. The man I had could do one but not both, and competent persons to pick up for either job are not available, so I have been standing in the gap, getting calluses on my hands and getting rid of $16,000 worth of trees.

Now as to facts on northern pecans:

I find the Busseron bears with regularity at Round Hill, Virginia, in a tight bluegrass sod. This pasture is not of high fertility and has had a small amount of commercial fertilizer. It is on a hillside that has probably lost all of its topsoil once or twice in the last hundred years, though not for the last twenty because it has been in grass.

My neighbor, Henry B. Taylor, Hamilton, Virginia, has Busseron, Butterick, Greenriver, Indiana, and Major, all bearing well to heavily.

Unfortunately this year the Greenriver hulls did not open, although the nuts were well filled. Ordinarily I believe they have been dropping their nuts, but not all at once.

Twenty-five years ago I planted some Butterick and Busseron along a stream on a dairy farm on which I was born. There was no regular record of their performance, but I have observed that the Buttericks have had a good crop in 1950 and also in 1951.[6]

I had previously concluded that the Butterick was almost a non-fruiter, and quit propagating it years ago. These especially productive Buttericks are on alluvium near the barn in a permanent pasture where the cattle congregate while waiting for the gate to open to let them into the barn. It is therefore fertilized over and over again with cow drippings.

Mr. Taylor's excellent yields are also produced on trees that are on unusually fertile soil.

My conclusion is that the pecan is a very active feeder, and what it needs is about three times as much fertilizer as is required for any ordinary crop.

It is time somebody better placed than I am made a systematic experiment as follows:

1. Feed pecan trees at least five times as much plant food as the
nuts and leaves use.

2. Injure the trees by hacking the bark to make them bear, and see
how much they can be made to produce by this means.

A Busseron tree in the town of Round Hill stands in a backyard of a friend of mine and they use it, I think, to tie clotheslines to and maybe the boys have had a little fun driving nails into it and it bears every year.[7]

The real find of my observations is a pecan known as All State, which has been wonderfully advertised by one of your fellows.[8] On a catalog it produces a nut two inches long--wonderful. On Mr. Henry Taylor's tree in Hamilton, Virginia, it produces a tiny, symmetrical, pointed nut too small to be contemptible, except for squirrel feed. They might have time to handle the crop.

FOOTNOTES:

[Footnote 6: In the NNGA Report for 1935, Mr. C. A. Reed told of studies of blossoming habits of pecan varieties at Rockport, Indiana, conducted for four seasons in co-operation with Mr. J. F. Wilkinson. There the Busseron was found to be a protandrous variety, shedding most of its pollen, and in some years all of it, before the period of receptivity of its pistillate flowers. "With Butterick ... the order was reversed, as the period of receptivity began first," and it was classified, therefore, as regularly protogynous. "... Furthermore, upon close observation it has been found," he said, that trees of the Butterick variety "develop very few pistillate flowers, and that many of these wither up and drop off, apparently because of inherent weakness. From this, it would appear that light bearing is not necessarily due to lack of suitable or adequate pollen." The Butterick had a record of practically non-bearing performances during the four years (1931, 1932, 1934 and 1935) at Rockport, which is duplicated by its performance records at other locations and other years, so it is generally on the discard list. But when it does bear and mature its nuts it is a good pecan. Mr. P. W. Wang rated it his first choice of northern pecans fruited in China.

Mr. Reed listed as protandrous Busseron, Kentucky, Major, and Niblack varieties, whereas Butterick, Indiana, and Posey were protogynous. He did not specify in which class the Greenriver fell. Major during each of the four years, had an interval of 1 to 3 days between the last shedding of pollen and the first pistil receptivity; Warrick, an obsolete variety, had some overlap each year as did Indiana and Posey. The Kentucky, a discarded variety, had overlaps the three years it was observed. In two years it was observed, Niblack had staminate and pistillate flowering together one season, and staminate overlapping four days into the period of pistillate receptivity the next. Busseron, Butterick, and Greenriver sometimes had overlaps and sometimes intervals. Reed's conclusion, that "northern varieties of pecan ... appear to be partly or completely dependent upon other varieties for pollen," still holds good, as does his second observation, that "all varieties tend to vary, from year to year with respect to periods of pollen shedding and pistil receptivity." But more records are needed, and any members who have two or more varieties flowering in 1952 can make valuable contributions by taking accurate notes on their habits. There are now newer varieties for which such data are completely lacking, and until more is known, no reliable basis can be had for matching them with the best combinations for adequate cross-pollination.--J. C. McD.]

[Footnote 7: I think the first phase of the suggested experiment has more to recommend it than the second. Perhaps the Round Hill tree gets needed zinc from clotheslines and roofing nails. A more scientific way to apply zinc is to use zinc sulfate in sprays or ground applications, and these are to be used on some trees at Urbana which Dr. Crane diagnosed as zinc-deficient.--J. C. McD.]

[Footnote 8: The Bradley Brothers, who do not court anonymity, are no fellows of the Association or of the University of Illinois. They have been known to sell some kind of grafted pecan trees in recent years, possibly the Stuart or some other variety available from southern wholesale propagators. Mr. Taylor was lucky enough to have his order filled with a southern Illinois seedling which at least is good for the squirrels. We haven't yet seen any All State nuts from Maine or Montana. The Bradley variety is an obsolete southern pecan.--J. C. McD.]

Pecans in the Vicinity of St. Paul, Minnesota

CARL WESCHCKE

About 25 years ago pecan seeds from the most northern natural habitat in Iowa were planted in garden soil here in St. Paul. Most of them were later transplanted in nursery rows at my farm seven miles east of River Falls, Wisconsin. Out of approximately 300 trees, about 40 are still living, of which 25 have grown well. The remainder probably have not found soil conditions to accommodate their natural vigorous growth. Where the trees are in deep soil with sufficient plant food, they have done well, the largest tree being about 10 inches in diameter, and several of these have been bearing nuts for five years. The nuts were immature, however, but in the fall of 1949 about 70 of the best ones were planted in a seed bed and today about 15 living trees of pure pecan parentage represent the second generation.

This evidence is very important, for although the pecan has been almost as hardy as any native tree (such as the bitternut hickory, the butternut and the black walnut), yet the length of season required for the maturing of nuts is a primary factor which would have to be considered in recommending pecans for planting this far north. However, it has been my observation that these pecans have slowly cycled their way into our season, and it is gratifying to notice that this spring many leafed out at nearly the same time that the black walnut vegetated, which of course is much slower than the local butternut. This shows the tremendous adaptability of the pecan, and it is hoped that this ability to adapt itself to soil and climatic conditions will eventually cause it to produce small but edible pecans here in the north.

It is my hope, also, that I can use our locally raised pecan seedlings on which to graft our many successful varieties of hickories, which heretofore have been limited to some extent in their usefulness because we had only the local bitternut stocks on which to graft. Whereas the bitternut is an excellent stock for some varieties of shagbark hickory and even for shellbark, as well as pecans and hicans, there would no doubt be an increase in the scope of hickory planting if we had hardy pecan seedlings as understocks. At first, when comparing the growth of the native bitternut seedlings with that of pecans, locally raised in the same soil, it appeared that the pecan was a much more vigorous grower; but experiments with different types of soil and fertilizers indicate that we can get seedlings of certain bitternut hickories to produce from two to three feet of growth in the first year. I have even found several of these same hickory seedlings of two seasons' growth which, when transplanted last fall, are large enough to graft this spring. However, experiments have not proceeded far enough to verify the practical side of this new idea of hickory propagation.

Only one variety of pecan which was among the original seedlings, and which existed as a lawn tree for more than twenty years in St. Paul, was compatible with the bitternut hickory root systems; but enough of this variety of pecan has been grafted on local hickories to demonstrate that this is perfectly feasible as far as the union is concerned. In fact, several of these larger grafted trees have been bearing staminate bloom for two or more years. No nuts have been produced of this Hope variety as yet, and although it has been distributed on the market, it has always been classed as an ornamental rather than a fruiting variety. Of course, the pecan part over-grows the stock. In other words, there is a larger diameter above the union than in the stock below the union. So far, this has not interfered with good growth and hardiness, whereas the black walnut grafted on butternut (which is a similar combination as far as results go) more than thirty years ago in experimental work, indicates that this is a wrong procedure. Very few nuts were ever gathered from grafts of black walnut on butternut, although in most instances they continue to live and thrive.

The pecan here is subject to much the same insect pests as the black walnut, but suffers less from hickory borers and types of insects which seem to be like oak pruners. This might be useful later on in maintaining healthy pecan trunks with hickory tops. Probably the early formation of rough bark, for which the pecan is noted, may be responsible for this. The nuts that have been produced so far have been extremely small, but here again the writer has observed an increase in size over the original nuts that were produced. In some seasons, at least one tree has produced nuts of sufficient size to be good enough for home purposes. They are nothing, however, to compare with any named northern pecans, such as the Major and the Indiana varieties. Practically all of these northern pecans have been tried in our environment, and some have lived for several years. Most of them have died because there was no congenial union of the pecan grafted on our local bitternut stocks. We do, however, have congenial grafts and good living specimens of the Norton and the Burton, which are no doubt some form of hybrid.[9] Hicans that graft well on local bitternut stocks are the Rockville, first in hardiness and for bearing nuts of the usual size for Rockville. They do not mature yet, but it is expected that favorable years will mature these nuts.

Next in hardiness is the Green Bay, and next are Burlington, Des Moines, Bixby, and McCallister. Although making good growth, these have seemed to be too tender for our climate, although we have good living specimens of them and believe that some have begun to bear, particularly the Bixby, unless names of grafts have been mixed up. These latter trees are mostly in the deep woods, and it is hard to get close data on their behavior and bearing.

A Marquardt (which is supposed to be a lost variety of hican) I believe exists on my place, and I have taken it out of the deep woods, where it was grafted nearly thirty years ago from scions direct from J. F. Jones, and have placed scions on stocks in the vicinity of the nursery, where they can be watched. The differences between the scions freshly grafted last spring and the known varieties of Rockville, Green Bay, and Burlington are distinctive. Also the Marquardt (if it is a true Marquardt) last winter indicated much greater hardiness than did grafts made at the same time with Rockville and Burlington varieties. However, it is too early to say for sure whether the Marquardt is represented among my varieties of hicans. The Marquardt grafted on local stocks used by Jones and purchased as individual trees, did not survive. It is assumed in this paper that this discussion would naturally lead to pecan hybrids, rather than staying with the pure blooded pecan this far north, for some of the varieties come very close to being pure pecans, but still, like Norton and Burton, probably are distinct hybrids.

When some of the original seedlings from Iowa were transplanted from the nursery row they were already quite large trees and we did not get all the roots. The portions that were cut off were left in the soil. One of these roots sprouted three trees; one was subsequently moved into the orchard and marked because of its vegetative nature, and a variety of hickory known as the Weschcke was grafted on it. It makes a very good growth, but in most instances our native bitternut stock produces an equally good growth in unions with this particular variety. This particular performance is indicative of things to be expected for this combination in the future.

In conclusion I would say that the pecan is far from being a practical nut tree for our vicinity, and is only a very hopeful dream. But so, also, were the best hickory varieties 30 years ago when I first began my experiments.

FOOTNOTES:

[Footnote 9: The Norton name seems to be shared by a pecan and a hican. The Burton hican from Owensboro, Ky., is presumably a pecan-shagbark cross with an excellent nut, fruitful farther south.--Ed.]

Preliminary Report on Growth, Flowering, and Magnesium Deficiency of Reed and Potomac Filbert Varieties

H. L. CRANE AND J. W. MCKAY[10]

During the course of filbert breeding investigations at the Plant Industry Station, Beltsville, Md., covering a period of approximately 18 years, the leaves of certain seedlings scorched badly in mid or late summer. Certain other trees showed little or no evidence of this disorder. It was thought that, because filberts thrive best under maritime climatic conditions of cool summers and mild winters, this scorch was probably due to high temperatures accompanied by deficient soil moisture.

This breeding work resulted in the introduction in 1951 of the Reed and Potomac varieties, which were produced as a result of crosses between the American filbert, _Corylus americana_, and the European filbert, _C. avellana_. The original trees of these varieties had been under observation for more than 10 years, and their performance had been such as to indicate their suitability for home plantings under eastern conditions. Furthermore, these varieties had shown little or no evidence of scorch and had held their leaves well.

In early spring of 1948, an experimental orchard, consisting of 36 layered trees each of Reed and Potomac, was planted at Beltsville, for the purpose of testing them more fully than had been possible before as to their suitability for eastern conditions. The orchard was designed also for study of their response in tree growth and fruiting to differential fertilizer treatments. Although this experiment has been underway now for only three years, certain of the findings are thought to be of such importance that a preliminary report should be made at this time.

Experimental Plan

The site selected for the orchard is a gentle slope varying from five to 15 percent and providing good air drainage. The soil is a Riverdale (tentative series) sandy loam that had been in orchard grass sod for 10 years before the experiment was begun. Much of the land on the Plant Industry Station farm is now known to be low in available magnesium and potassium. Tree crops, including peaches, pears, and apples, have shown deficiencies of one or both of these elements. The trees were planted 20 feet apart on the contour in pairs, one of each variety in a plot, with six plots in a row. The 36 two-tree plots were in six rows. Thus, the experiment was arranged in a 6 by 6 Latin square and six fertilizer treatments were used. After planting, the trees received frequent cultivation and a uniform application of one pound of 10-6-4 fertilizer. The following spring differential fertilizer treatments were applied: Nitrogen, phosphorus, potassium, complete, nitrogen and potassium, and check. The amounts applied per tree in fractions of a pound were elemental nitrogen 0.2, phosphoric acid, 0.4, and potash 0.2. In the spring of 1950, the amounts applied per tree were doubled; and these same amounts were applied in the spring of 1951. Nitrogen was applied in the form of nitrate of soda, phosphorus as 20 percent superphosphate, and potassium as 50 percent muriate of potash. Strips about six to eight feet wide on each side of the tree rows have been cultivated frequently, but strips of orchard grass sod have been left in the tree row middles to prevent soil erosion. The trees have been sprayed with DDT or parathion or both to control Japanese beetles and mites.

Growth Responses

To determine the growth responses made by the two varieties to the differential fertilizer treatments, diameters of the tree trunks one foot above the soil were measured each spring before growth started. These data are not given here because in 1949 and 1950 there were no significant differences in the growth of the trees as a result of the differential fertilizer treatments. However, trees of the Potomac variety made more growth than those of the Reed variety. At the end of the 1949 and 1950 growing seasons, the average diameters of the tree trunks of the Potomac variety were 16.3 and 25.7 millimeters, respectively; those of the Reed variety were 13.6 and 22.4 millimeters, respectively. The differences 2.7 and 3.3 millimeters, are highly significant. Under the conditions of this experiment, the trees of the Potomac variety are much more vigorous than those of the Reed. The greater vigor of the Potomac trees may account for the fact that they produce suckers much more freely than do trees of the Reed variety. The habit of producing abundant suckers is an advantage in propagating by layering, but it is a disadvantage in orchard trees because the suckers must be removed for optimum nut production. Whether the differences in vigor and suckering habit of the two varieties shown thus far will affect their performance as orchard trees will have to be determined by future observations.

Flowering Response

Each year at the height of the flowering period, each tree in the experiment was rated on the catkins it carried. So far, there has been no effect of the differential fertilizer treatments on the production of catkins. However, there have been very highly significant differences between the Potomac and the Reed. In 1950, only four of the 36 Reed trees produced catkins, whereas 32 of the 36 Potomac trees flowered, and approximately half of them were heavily loaded. In 1951, the number of Reed trees producing catkins was 12 of the 36, whereas 35 Potomac trees flowered. The amount of pistillate flowering during the two years was small on both varieties and not greatly different; this indicates that their nut-bearing potentialities may be about the same. The amount of pollen produced by the Reed variety has always been considered ample for cross-pollinating the Potomac, even though the former has been a light producer of catkins.

Records of dates of flowering of the two original trees over a 10-year period, and of these young orchard trees over a 3-year period, show that there is great variability in time of flowering, depending upon the sequence of weather events each season. Fertilizer treatments have had no measureable effect. The trees have shed pollen as early as January and as late as April, and stigma receptivity sometimes has continued intermittently for two months. The average period of flowering at Beltsville is the last week of February to the first week in March. Both varieties have flowered at the same time under all seasonal conditions observed. This means that additional pollinators will not be necessary when the varieties are planted together in an orchard.

Symptoms of Scorch

The visible symptoms of scorch do not begin to appear under conditions at Beltsville until about the middle of July or later. The first symptom is fading of the green color, especially around the margins of the leaf blade. Sometimes this chlorosis results in blotches, which may extend for a considerable distance from the margin towards the mid-rib. This stage is of short duration, as the tissues of marginal chlorotic areas or those of the blotches soon die, roll up, and turn brown. Some leaves show yellow blotchiness over most, if not all, of the surface and this may develop into brown patches of dead tissue or the yellow leaves may fall before the tissues die. The older leaves, those at the base of a shoot, are generally the first to show chlorosis and scorch, and the terminal leaves are the last to show such symptoms. On severely affected trees all the leaves on a shoot may be scorched at the time scorching is observed. Severely affected trees drop part or all of their leaves prematurely. The leaves dropped are those that are scorched or that show yellow blotches. Such trees do not make satisfactory growth, they set few nuts, and the nuts are usually poorly filled at harvest. The symptoms of scorch on filbert leaves are similar in many respects to magnesium-deficiency symptoms on apple (1, 5, 6)[11] and tung leaves (3).

Leaf Analyses[12]

No differences in appearance of the trees as regards leaf scorch were noticed the first year after the differential fertilizer treatments were applied. However, in late July and early August of the second season, severe leaf scorch developed on the trees that had received potassium alone or nitrogen plus potassium, and scorch developed to some extent on the check trees. On August 15, 1950, leaf samples for chemical analyses were taken from each tree in all replications and composited by treatments into six samples. The data on the chemical composition of the leaves as affected by the differential fertilizer treatments are given in table 1.

These data show that the fertilizers applied to the trees were taken up by them and that the composition of the leaves was significantly affected. The trees in treatments 2, 3, and 6, which did not receive nitrogen in the fertilizer, had lower percentages of nitrogen in the leaves than those from the other plots. Their light green color indicated that in the middle of August they were deficient in nitrogen when its concentration was 2.3 percent or less.

=Table 1. Chemical composition (oven-dry basis) of filbert leaves collected August 15, 1950, from fertilizer experiment, Beltsville, Md.=

_____________________________________________________________________
| |
Treatment | Composition of leaves | Mg (percent)
________________|__________________________________| Ratio ____________
| | K (percent)
| Ash N P K Ca Mg |
________________|__________________________________|
| % % % % % % |
1. Nitrogen | 6.68 2.52 .129 .945 1.30 .143| .151
2. Phosphorus | 8.56 2.29 .160 .885 1.60 .186| .210
3. Potassium | 9.39 2.31 .150 1.650 1.93 .155| .094
4. Complete | 7.18 2.43 .133 1.175 1.63 .132| .112
5. Nitrogen and | |
potassium | 7.62 2.49 .119 1.480 1.33 .110| .073
6. Check | 7.38 2.32 .188 .890 1.70 .149| .167

Potassium applications produced the greatest effect on leaf composition, as they increased the concentration of that element in the leaves by 0.285 to 0.760 percentage unit over that in the leaves from the check trees. In addition, it seems likely that this great increase in the potassium content of the leaves was accompanied by a decrease in their magnesium content, since this usually has been found to result. When the ratios of the percentage of magnesium to the percentage of potassium in the leaves were calculated, it was found that they were rather low for the trees that had been fertilized with potassium. The magnesium-potassium ratio was highest in the leaves from the trees fertilized with phosphorus only, followed in order by the check and nitrogen treatments.

Relation of Magnesium Deficiency to Leaf Scorch, Winter Injury, and Fungus Infection

On August 15, 1950, at the time the leaf samples were taken, each tree in the experiment was scored as to the degree of leaf scorch present. In the winter of 1950-51 soil samples were taken from each plot receiving potassium alone and the lime requirement was determined by the Division of Soil and Management and Irrigation, of this Bureau. The lime requirement was found to vary greatly, ranging from 1500 to 6700 pounds per acre. In early spring of 1951, high-magnesium dolomitic lime was applied uniformly at the rate of 1500 pounds per acre and in addition each tree received 5 pounds of Epsom salt.

Each tree in the experiment was scored for degree of winter injury on May 10, 1951. By August 3, leaf scorch was evident on trees in certain treatments and the trees were scored for leaf scorch. At this time it was found in certain treatments that the trees that had not shown any appreciable amount of scorch heretofore had some severely necrotic leaves on them. Careful examination revealed many fruiting bodies of one or more fungi in these necrotic areas. Each tree was, therefore, scored for the presence of this disease, which has been tentatively identified by Paul L. Lentz, of this Bureau, as being caused by _Labrella coryli_. The data on leaf scorch, winter injury, and the fungus disease are given in table 2.

Table 2. Relation of magnesium deficiency in filbert leaves to leaf scorch, winter injury, and disease caused by _Labrella coryli_

______________________________________________________________________

Ratio Scorch[1] Winter[2] Scorch[1] Disease[1]
Treatment Mg (percent) score injury score score score
K (percent) (1950) (spring, 1951) (1951) (1951)
______________________________________________________________________
1. Nitrogen .151 1 4 7 9
2. Phosphorus .210 1 3 1 11
3. Potassium .094 21 22 24 3
4. Complete .112 2 5 8 11
5. Nitrogen
and potassium .073 13 19 9 5
6. Check .167 14 6 6 8

Note 1: Total plot score for 12 trees; highest possible score 36.
The scale for scoring was 0, none; 1, light; 3, severe.

Note 2: Total plot score for 12 trees; highest possible score 48.
The scale for scoring winter injury was 0, full leaf, no injury; 1,
few dead twigs; 2, half of buds not growing; 3, very large amount
of dead twigs; 4, only a few buds growing.

Trees that had received potassium alone had the most severely scorched leaves and more of them on August 15, 1950, followed by those that had received nitrogen plus potassium. The trees that had received nitrogen or phosphorus alone showed practically no scorch, each having a total score of 1; and the complete fertilizer trees a total score of only 2, while those in the check had a total score of 6. These scores indicate that scorch is related to magnesium deficiency or unbalance. There was a close relation between the amount of leaf scorch in August, 1950, and the amount of winter injury, the coefficient of correlation being 0.97, which is very highly significant. This coefficient means that 94 percent of the winter injury sustained could be accounted for by the leaf scorch present the preceding summer and early fall.

The scorch scores of August, 1951, show that there had been no consistent improvement from the magnesium-deficiency condition as a result of the dolomite and Epsom salt applications. The scores for the disease caused by _Labrella_ show that applications of phosphorus alone increased the incidence of the disease and those of potassium alone or potassium plus nitrogen decreased it.

In all cases, the incidence of leaf scorch, winter injury, and disease were strikingly different on the Reed and Potomac varieties. In the summer of 1950, the total scorch score of the Reed variety was 26 and that of the Potomac 18, and in August, 1951, the scores were 36 and 19, respectively. The total winter injury scores were 46 for the Reed variety and 21 for the Potomac. Thus, it is clearly evident that under the conditions of this experiment the Reed variety was much more susceptible to leaf scorch and to the winter injury resulting from magnesium deficiency or unbalance between magnesium and calcium plus potassium than was the variety Potomac. Furthermore, the total score for the incidence of the disease caused by _Labrella coryli_ on the variety Reed was 38 as compared with 9 for the Potomac variety. It would, therefore, seem that the Reed is about four times as susceptible to infection by this fungus as is the Potomac. Its less vigorous tree growth, susceptibility to leaf scorch, winter injury, and infection by _L. coryli_ may be due to the differences between its nutritional requirements and those of the Potomac variety.

Conclusions and Summary

The preliminary results of the experiment described show that there is a great difference in vigor, growth, flowering habit, susceptibility to leaf scorch, winter injury, and infection with a fungus disease tentatively believed to be caused by _L. coryli_ between trees of the Reed and Potomac filbert varieties. In all cases the Potomac variety has been the superior.

It would appear that much of the leaf scorch on filberts experienced in the past has been due to a magnesium deficiency or to an unbalanced condition between magnesium and calcium plus potassium in their nutrition. The symptoms of magnesium deficiency (scorch), which in general are similar to those on apple and tung, are described. The data presented show that liberal applications of potassium alone, or in combination with nitrogen, resulted in a highly significant increase in the incidence of leaf scorch due to magnesium deficiency. This in turn resulted in susceptibility to winter injury, the coefficient of correlation being 0.97, which means that the severity of the leaf scorch in August, 1950, would account for 94 percent of the winter injury sustained.

Applications of 1500 pounds per acre of high-magnesium dolomite, together with five pounds of Epsom salt per tree in early spring of 1951, did not produce consistent improvement in leaf scorch. It seems that recovery from magnesium deficiency in filberts is slow after treatment, just as has been found to be the case in fruit trees (2, 4).

Literature Cited

1. Boynton, Damon, Cain, Carlton J., and Van Geluwe, John
Incipient Magnesium Deficiency in Some New York Apple Orchards.
Proc. Amer. Soc. Hort. Sci. 42:95-100. 1943.
2.----
Magnesium Nutrition of Apple Trees. Soil Sci. 63:53-58. 1947.
3. Drosdoff, Matthew, and Kenworthy, Alvin L.
Magnesium Deficiency of Tung Trees. Proc. Amer. Soc. Hort.
Sci. 44:1-7 1944.
4.----, and Lagasse, Felix S.
The Effect of Some Magnesium and Calcium Fertilizers in a
Magnesium Deficiency Bearing Tung Orchard. Proc. Amer. Soc.
Hort. Sci. 56:5-11. 1950.
5. Southwick, Lawrence
Magnesium Deficiency in Massachusetts Apple Orchards. Proc.
Amer. Soc. Hort. Sci. 42:85-94. 1943.
6. Wallace, T.
Magnesium Deficiency of Fruit Trees. Jour. Pom. and Hort. Sci.
17:150-166. 1939.

FOOTNOTES:

[Footnote 10: Principal Horticulturist and Horticulturist, respectively, U. S. Department of Agriculture, Bureau Plant Industry, Soils, and Agricultural Engineering, Beltsville, Md.]

[Footnote 11: Numbers in parenthesis refer to Literature cited, p. 55.]

[Footnote 12: The authors take this opportunity to thank Dr. Harald E. Hammar for making the chemical analyses of the leaf samples.]

Bunch Disease of Black Walnut

[Paper expanded from a talk given at the 41st annual meeting of NNGA in 1950.]

JOHN W. MCKAY, _horticulturist_, and HARLEY L. CRANE, _principal horticulturist, United States Department of Agriculture, Agricultural Research Administration, Bureau of Plant Industry, Soils, and Agricultural Engineering, Division of Fruit & Vegetable Crops and Diseases, Plant Industry Station, Beltsville, Maryland_

Introduction

For the past several years observations have been made on the development and spread of the bunch (brooming)[13] disease on _Juglans nigra_ and on other species of walnut growing in the orchards at Plant Industry Station at Beltsville, Maryland. Because of the widespread interest in growing walnuts a brief survey of these observations will be given in this paper together with a summary of the history of the disease and a discussion of its possible effect on walnut production.

History of the Disease

The bunch disease of walnut has been known for years. Waite[14] in 1932 said, "It turned up in Delaware several years ago, where quite a variety of walnuts, including the Persian, the Japanese Group, and the American Black Walnut, were found to be affected. At Arlington Farm, Virginia, during the past 15 years it has boldly riddled the collection of nut trees assembled in the grounds for study and ornamental purposes." Photographs made in 1914 of Japanese walnut trees growing in Georgia and thought to be affected by rosette (now known to be caused by zinc deficiency) have been found in the files of the U. S. Department of Agriculture. Now that the symptoms of the two different disorders are known, it seems clear that the bunch disease was present in those two states at that early date.

Becker,[15] of Climax, Michigan in 1940 reported on his observation of this disease in that area. He reports that he observed several cases of it on Persian walnut, Japanese walnut, and butternut, in addition to many diseased eastern black walnuts. He says, "My conclusions are that in witches'-broom (bunch disease) we have a very bad disease that threatens the black walnut trees everywhere".

In 1939, the late Howard E. Parsons, pathologist of the U. S. Department of Agriculture, made an inspection trip to Climax and other areas in Michigan where he studied and photographed diseased trees. Parsons at that time was working on a similar disease of pecan and water hickory and was of the opinion that the disease found on the various species of walnuts in Michigan was similar to the one he was studying.

For the past 20 years the bunch disease of walnuts has been under observation by the writers and it seems clear that its incidence has increased greatly during that time. In 1935 scions and buds were taken from diseased eastern black walnut and butternut trees growing at Arlington Farm and grafted or budded on eastern black walnut stock growing in the original nut tree nursery at the Plant Industry Station at Beltsville, Maryland. This was done in an attempt to determine whether the disease was caused by a mineral deficiency or by a virus. All buds and scions died, but the following year two of the seedling rootstocks showed characteristic symptoms of the bunch disease. Since this disease was already present on the station farm it was not definitely known that it was transmitted to the stocks by budding or grafting the diseased material on them.

In December of 1946 Hutchins and Wester[16] presented a paper before the American Phytopathology Society giving the results of their studies on the bunch disease. In this paper they reported that the disease was transmitted by patch bark grafts performed in 1944 and 1945 and that the incubation period varied from several months to two years. It was concluded that since the disease was transmitted by grafting, and in the absence of a visible pathogen, a virus causal agent was indicated.

Symptoms

The characteristic symptoms of the bunch disease are mainly the production of brooms or sucker shoot growth on the tree trunk and main branches and the tufting of terminals, profusion of small branches from axillary buds, the dwarfing and narrowing of the leaflets, and the dying back of the trees resulting sometimes in the death of the trees. The principal symptom is the production during summer of bushy, wiry growth caused by the breaking into growth of lateral buds that normally would remain dormant over the winter. These buds produce shoots that again branch from lateral buds and the process may be repeated for three or four times, resulting in a tightly packed mass or bunch of small, wiry twigs and undersized leaves. Another characteristic symptom is that this growth proliferation continues unabated until the first frost, and, since the wood of these shoots is thus not properly matured, killing back of the diseased portions of the tree usually occurs with the first hard freezes of winter.

As the disease progresses, the wood in the main branches becomes very brittle and is easily broken by wind or ice. This condition is followed by the dying back of branches and finally the death of the tree. Trees even moderately affected soon become worthless for nut production, as few nuts are set and those that mature are usually poorly filled.

Susceptibility of Species

Extended observations show that of the walnut species now grown in eastern United States, the Japanese walnuts, i.e., the Siebold and the heartnut, are by far the most subject to attack by this disease. These walnuts are so susceptible that in localities where this disease is present the planting of young trees is inadvisable, as they are almost certain to be short lived. Once infected, will endanger other walnut trees in the area.

Observations at Beltsville show that the butternut is almost as susceptible to attack as is the Japanese walnut. Some workers are inclined to believe that the rather serious decrease in numbers of butternut trees in some areas is due to the bunch disease. The Persian (English) walnut is also quite susceptible, although probably not so much so as the butternut or the Japanese walnut. The eastern black walnut seems to be the most resistant of all, although some evidence indicates that at least certain trees of this species may have the disease but not show symptoms of it. Gravatt and Stout[17] report that walnut trees may be affected for a considerable length of time without showing recognizable symptoms. Out of a lot of 300 healthy-appearing trees, 37 per cent showed bunch disease symptoms following pruning. Only four percent of the unpruned check trees developed similar symptoms during the same period of time.

Distribution

At the present time bunch disease is quite widespread in eastern United States, occurring in Maryland, District of Columbia, Delaware, New Jersey, New York, Michigan, Ohio, Indiana, Illinois, Pennsylvania, West Virginia, Virginia, North and South Carolina, Georgia, Tennessee, Alabama, and probably other States. No special surveys have been made for bunch disease, and all distribution information has been obtained from observations of U. S. Department of Agriculture or State workers or from specimens submitted.

Damage Caused

Trees with bunch disease may live for several years in a stag-horned or tufted condition. Affected trees generally set few nuts and the nuts that mature are usually poorly filled and hence low in oil content. It is likely that a part of the unsatisfactory growth and fruiting performance of certain eastern black walnut trees may be due to the disease, even though they do not show the symptoms as they are now known. Severely affected trees are subject to cold injury, and in addition the wood becomes very brittle and is easily broken by storms. Although this disease has been known for several years, it is believed that its seriousness has not been fully appreciated, as it does not cause death as soon as symptoms appear. Several years must elapse before the tree succumbs. In the nut tree plantings made at the Plant Industry Station at Beltsville, Maryland, large numbers of butternut, Japanese walnut, and Persian walnut trees were planted. During the following years, although no records have been kept, several hundred of these trees have become affected and have been removed. Consequently at the present time we do not have any butternut or Japanese walnut trees, and only a few Persian (English) walnut trees left in the plantings. So far, not a single eastern black walnut tree has been removed from the orchards because of the bunch disease. Some trees have shown characteristic symptoms of the disease, but following the removal of the entire diseased limbs the symptoms have not reappeared.

Possible Effects of Bunch Disease on the Walnut Industry

This disease is known to spread to nearby healthy walnut trees, but the means by which it is spread or how infection occurs is not known. No survey has been made to determine whether the disease is present in the various regions in which walnut trees are grown, and hence it is not known how widely it is distributed at present. Its spread is probably associated with an insect vector, and the presence of the vector would determine whether or not local spread would occur. Much more must be learned about this disease before its importance and destructive nature can be fully determined. It seems certain that in localities where the disease is already present there is little use in planting young trees of the most susceptible species unless trees in the vicinity that are already diseased are destroyed. Nurserymen growing trees of the Japanese walnut, butternut, and Persian walnut should be sure that no diseased trees which might infect the nursery trees are close to their nurseries. It is not known how far the inoculum may be carried, but at this time it would seem that in order to be reasonably safe no diseased tree should be allowed to grow within a mile radius of a nursery. Infected nursery trees (or scions) probably constitute the most important means of long-distance spread for a disease of this type.

Control

The only known method of control of the bunch disease is to prevent healthy trees from becoming infected. This can be done only by destroying completely all diseased trees. In the early stage of the disease, sometimes only one branch on a tree may show symptoms; and complete removal of this branch may result in the tree's not showing additional symptoms for a year or more. Except in the case of black walnut, the disease breaks out again; hence cutting out diseased limbs cannot be considered a satisfactory control measure, except possibly on the eastern black walnut.

Case Histories at Beltsville

As a part of walnut breeding work carried on during the past 14 years, approximately 20 large _nigra_ trees of named horticultural varieties have been topworked to seedlings of natural first-generation hybrids between _J. regia_ and _J. nigra_ for the purpose of forcing the seedling scions into early fruiting. Of these 20 trees, 3 have shown such unusual behavior as to merit a description of each in the form of a case history.

_Tree Number 838._ This tree was cut back severely in the spring of 1942, and on August 26, 1943 vigorous new shoots were budded to 47.11-P17, a second-generation seedling of the O'Conner natural hybrid. The buds grew vigorously in 1944 and early in the season developed symptoms of the bunch disease. By the end of the growing season of 1944 the scion limbs were heavy with the typical proliferated shoots characteristic of the disease. Also, a few vigorous sucker limbs of the stock tree that grew out from below the point of union of the scions showed typical symptoms of the disease, although these limbs were later outgrown by normal shoots and are not now to be seen. In the early spring of 1945 the diseased limbs were all removed from the tree to prevent the further spread of the disease in the area.

At the same time that the above seedling was budded in the top of this tree, a large lateral limb of the stock tree was budded to seedling number 40.70-P1. This seedling originated from a nut of the Ohio variety of black walnut that was only about 1/4 the size of nuts typical of the variety. At the time it was thought that this nut resulted from a cross of Ohio with pollen of the Persian walnut, as it was produced under bag and following hand-pollination. Later growth of the seedling indicated, however, that the pistillate flower was probably pollinated by _J. nigra_ before the bagging occurred, since only _J. nigra_ characteristics have shown up in the seedling. In 1950, one bud of the _nigra_ seedling 40.70-P1 has almost completely regenerated the top of the tree and no symptom of the disease is evident. By contrast in 1944, almost all of the top of the tree was occupied by diseased limbs, five in number, of the O'Conner seedling.

_Tree Number 854._ This tree has shown behavior almost identical with that of Number 838, but three seedlings were topworked instead of one. All three originated from the Coye hybrid and all were budded on July 27, 1944. Less than one month later all buds had produced a foot or more of growth, and one to two scions of each seedling reached sufficient size and vigor to survive the following winter without damage. None of the scions branched in 1944, and all failed to show symptoms of the disease. Early in 1945 profuse branching occurred on the one surviving scion of seedling number 39.03-P2, and by midsummer excessive proliferation of the buds of primary shoots had resulted in the formation of a mistletoe-like growth characteristic of the disease. Scions of the two other seedlings, 39.03-P8 and 39.03-P11, were lost by wind damage in midsummer, but at the time they showed no signs of the disease. Most of the shoots of 39.03-P2 were killed during the following winter, and in April, 1946, the remaining live portions were removed by the Division of Forest Pathology for use in transmission studies.

On August 18, 1944, four patch buds of the O'Conner natural hybrid were placed on one of the main limbs of this tree. One of these buds grew, and in 1950 has come to occupy more than half the top of the tree. The remainder of the top is made up of the original stock tree. There is no evidence of bunching in the tree at present.

_Tree Number 411._ This tree was budded to six seedlings of the Fox natural hybrid on April 28, 1943. Only one of these lived, 40.45-P4, and one scion of this seedling in 1950 comprises the entire crown. No symptom of the disease has appeared in this scion, and the tree is healthy at present.

On April 8, 1944, small lateral limbs of the tree were splice-grafted to two Coye seedlings, 39.03-P8 and 41.26-P10. One scions of each grew vigorously during the summer, and 41.26-P10 first became chlorotic, then diseased. Seedling 39.03-P8 became chlorotic but at the end of the season had not shown symptoms of the disease. Both were removed from the tree early in 1945 and the living shoots used for scionwood in transmission studies by the Division of Forest Pathology.

An additional case is _Tree Number 795_. This is a grafted tree of the Graham variety of black walnut that was planted in 1932 within 100 feet of trees of the Bates and Faust varieties of heartnuts. By 1940 the latter trees were heavily infected with bunch disease, but it was not until 1943 or 1944 that symptoms were discovered in the Graham tree. At this time the heartnuts were removed from the orchard. The Graham tree has shown only a few small diseased limbs during the past six or seven years, and in 1950 a fair crop of nuts is in prospect.

Discussion

The following observations should be mentioned briefly before discussing the questions raised by the case histories:

1. Out of more than one hundred seedling scions from 13 hybrids
topworked on large _nigra_ trees, three have become diseased the
first or second year after the scions began to grow on black walnut
stock.

2. The three susceptible seedlings have all been grafted on
different _nigra_ stock trees, and the three stock trees have since
regenerated only healthy limbs, after removal of the diseased
shoots.

3. Seedlings from a total of 13 natural hybrids between _J. nigra_
and _J. regia_ have been used, and only two of these hybrids have
yielded susceptible seedlings. However, only a few seedlings were
available from certain hybrids.

4. A total of 156 trees of approximately 36 horticultural varieties
has been grown at Beltsville, and only one tree of the variety
Graham has shown well developed symptoms of the bunch disease. Two
other Graham trees have shown slight or questionable symptoms of
the disease.

It should be pointed out that a considerable number of heartnut and butternut trees were planted at random in the same orchards with the black walnut trees used in these experiments and at the same time (1932). In many cases black walnut trees grew within 50 or 100 feet of the heartnut trees. The bunch disease first appeared on heartnut trees, the most susceptible walnut species, and spread quickly to butternut, which is also very susceptible. By 1940 most of the diseased heartnuts had been removed from the orchards, but it was not until after the top-working experiments described above were completed that the orchards were cleared of all diseased trees. It is therefore possible that insect vectors or other agencies may have spread the disease to the scions of the topworked seedlings from the infected heartnut and butternut trees.

Number 795 is the only _J. nigra_ tree on the station farm that has consistently shown symptoms of the disease during the past eight years, and in 1950 only a few limbs are affected. On the basis of the admittedly meager information reported here, it can be stated that the black walnut varieties used in these experiments are more resistant to the bunch disease than are varieties and seedlings of heartnut and butternut. That this is generally true is also borne out by the fact that in the vicinity of Beltsville, Maryland, and the District of Columbia, practically all dooryard trees of the Japanese walnut are infected with bunch disease, many of them having already been killed, whereas relatively few black walnut trees in the area show symptoms of the disease.

The suggestion has been made that most varieties and seedlings of black walnut are symptomless carriers of the disease, and only under certain adverse conditions of environment would symptoms appear. This would explain why trees that are cut back severely, as was the case with tree Number 838 described above, show symptoms on the excessively vigorous shoots of the next year's growth.

Little can be said at the present time about the relative resistance of black walnut varieties to the bunch disease because nothing is known about how it is spread from one individual tree to another. The case histories of trees described in the present paper are considered to be worth recording because they show that black walnut trees may support diseased scions and later regenerate apparently healthy tops. In these cases the trees showed a type of resistance to the disease. However, there are many cases known, the majority of which are seedlings, in which black walnut trees became so badly infected with the disease that nut production ceased and the trees later died. Whether the type of resistance described in this paper is widely prevalent in the black walnut as a species will be impossible to determine until more is known about how the disease is spread.

FOOTNOTES:

[Footnote 13: Several common names have been applied to this disease, among which "bunch" and "brooming" have most frequently been used. The authors strongly feel that the accepted common name should be "bunch" for the following reasons: (1). The term is very descriptive of the symptoms of the disorder. (2). It is the accepted name of a disease of pecan and hickory species that is very similar if not identical to the one occurring on walnut species. (3). The names "brooming" and "witches'-broom" have already been applied to diseases caused by fungi.]