lllatvreNotes

102

Photo by Willard G . Van Name, courtesy of Emergency Conservation Committee.

Mature sugar pines in Yosemite National Park . Size of trees indicated by man on left.

Cover Photo : Bridalveil Fall and Cathedral Rocks, thunderstorm, Yosemite Valley . By AnselAdams from " Yosemite and the Sierra Nevada," text by John Muir, 64 photographs by AnselAdams . Reproduction by kind permission of Houghton Mifflin Company .

Yosemite Nature NotesTHE MONTHLY PUBLICATION OF

THE YOSEMITE NATURALIST DIVISION AND

THE YOSEMITE NATURAL HISTORY ASSQ]BBl'1N Imo.

C. P . Russell, Superintendent

D. E . McHenry, Park Naturalist

H . C . Parker, Assoc . Park Naturalist

N . B . Herkenham, Asst. Park Naturalist

VOL. XXIX

NOVEMBER . 1950

NO. 11

THE WHITE PINE BLISTER RUST

By Thomas H. Harris, Forester'

"What is the purpose of those ease, are highly susceptible to itsstrings I see running everywhere attacks . Though an unwanted alienthrough the woods? " That 's a ques- in worse disrepute than a Commun-tion asked of the park rangers a hun- ist, blister rust is 'fast becoming nat-dred times a day during the sum- uralized. It is generally distributedmer (we 're conservative[) . "They are in white pine districts in northernused to guide crews controlling the California, but has not yet beenwhite pine blister rust" is the correct found in Yosemite . Control work inthough perhaps meaningless an- the park is in this respect preventive.swer. "What in thunder is that--- The blister rust fungus belongs tosome kind of bug?" comes next . a group of highly specialized para-Well, let 's get down to business— sitic fungi that require two hosts forwhat is this blister rust? What does their existence. For the white pineit do? Why are we controlling it? blister rust these hosts are the white

First, let's set down a few facts, pines on one hand and the currantThe white pine blister rust is a bark and gooseberry bushes on the other.disease of white pines. It is caused Currants and gooseberries areby a fungus, one of a group of prim- classed by botanists in the genusitive plants which include the molds, Ribes, and hence have come to beblights, mildews, mushrooms, and called "rites" (pronounced ry-bees)the like. This fact dispels any con- collectively by blister rust workersnection with the insect world . Sci- everywhere. In Yosemite, as indeedentists have a name for it : Cronart- throughout California generally, theium ribicola Fischer. White pines are white pine hosts include that largestthose pines that bear their needles and noblest of all pines, the sugarfive in a bundle and have fine-tex- pine (Pious lambertiana Douglas) ; thetured, easily worked wood . No other western white pine (P . monticolaforest trees are attacked by this dis- Douglas) ; and the whitebark pineease. Another important fact is that (P . albicaulis Engelmann) . Sugar pinethe blister rust, having been un- grows in our mixed coniferous forestwittingly introduced into this coup- _ at elevations between 4,000 andtry from Europe, is not native here ; 7,000 feet; the other two species areconsequently, our white pines, hav- essentially' high-mountain trees grow-ing no natural immunity to the dis- ing above 7,000 feet. In Sequoia and

1 . Bureau of Entomology and Plant Quarantine, United States Department of Agriculture,Berkeley, California. Photos in this article by courtesy of Division of Plant Disease Control.

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YOSEMITE NATURE NOTES

Kings Canyon National Parks the ably thirsty (we. hope!) for more factsfoxtail pine (P . balfouriana Murray) on the domestic life of white pineand the limber pine (P . f lexilis James) blister rust . In what sort of relation-are also white pine hosts . The ship does it live with its hosts? Howbristlecone pine (P . aristata Engel- does it travel from one host to an-mann), which grows on the desert other? And so on. Let 's start withranges east of the Sierra Nevada, the rust on a sugar pine . The fungusis the only other white pine in is definitely parasitic . The micro-California.

scopic, filamentous threads forming

The two principal ribes hosts in its body (comparable to the roots,

Yosemite are the Sierra gooseberry stem, and leaves of cm ordinary(Ribes reezli Regel) and the Sierra cur- plant) pervade the cells of the grow

rant (R. nevadense Kell .) . These grow mg- layer—or cambium, which lies

in the coniferous forests of the mid lust beneath the bark—of the pine.dle elevations in company with These threads feed upon the sapsugar pine. Other hosts of less fin and cells of the cambium layer,portance growing at the higher ele slowly destroying the life of the tree;

vations in Yosemite are the sticky After spending about three yearscurrant (R. viscosissimum Pursh), the beneath the bark, the fungus, like

wax currant (R. cereum Dough), the all other living things, begins to pre-

whitestem gooseberry (R. inerme pare for multiplying its kind . The

Ryab.), the gooseberry currant filaments multiply and concentrate

(R. montigenum McCl.), and the wool a certain point, the branch or stem

lyflower gooseberry (R. lasiantb urn thickens, the bark swells, and we

Greene) .

have an abnormal growth called a

Is the white pine blister rust an en canker . From April to June fine

tirely new kind of thing to our Amer cracks, within which are whiteicon flora? No

. We have its counter walled sacs, appear on the surface

part right here in Yosemite. A rela of the canker . The sacs grow largerpLively harmless native rust, the pin- until on some warm day they burstyon blister rust (Cronartium occidentale

and release into the air myriads ofHedgcock, Bethel & Hunt), is so sun- minute, orange-colored spores, each

liar to the white pine rust that it, too, capable under the proper conditions

lives part of its life on gooseberries of starting a new fungus plant . These

and currants. Indeed the stage on sacs, full of brilliantly colored spores,

ribes can be distinguished from resemble blisters when they burst;

white pine blister rust only by micro hence the name blister rust . Thescopic means, and then not always spores, which in mass look like rust

for certain. The principal host is that colored powder, sufficiently account

interesting tree, the singleleaf pinyon for the rust part of the name . From

(Pinus monophyllaTorrey and Fre 18 to 36 months may elapse between

mont), which . played so prominent the first outward sign of a canker ' sa part in the economic life of the formation and the production of theYosemite and other California In first aeciospores, for such they are

diems. But it is not necessary to pro called ; a canker may produce spores

teat pinyon against the pinyon for several years . The limb or stem of

blister rust because the pine is not the pine beyond or above the cankergreatly damaged by the rust's eventually dies and the needles turnattacks.

a reddish brown, forming what isBy this time the reader is prole- called a "flag . " Death is due to the

YOSEMITE NATURE NOTES

105

Blister rust canker on trunk of white pine.Note white spore sacs breaking through bark.

destruction of the cambium layer atthe point where the canker forms;the flow of sap is cut off . This actionis commonly called ""girdling . " Theflags and the cankers are outwardsigns of the presence of the fungusin a white pine, which may havemany cankers on both limbs andstem depending on the intensity ofthe infection . Cankers may be froma few inches to two or three feet inlength and sometimes encircle thestem or limb.

The thick-walled aeciospores pro-duced on the pine can travel longdistances in the air, sometimesseveral hundred miles, and remainalive. They are wind-borne, andbeing generated in e n o r m o u snumbers, they soon permeate theair currents . One significant factabout them—the key to the controlof the disease's spread —_is thatthese aeciospores cannot infect

white pines they have the powerto infect only currant and goose-berry plants . When a spore iscarried by the wind to the under-surface of a ribes leaf, and whenample moisture is present and thetemperature is right, the spore maygerminate and enter the leaf tissue.On ribes the fungus lives only inthe leaves and has no more than adefoliating effect on the shrub . Afterabout two weeks small orange-yel-low pustules appear on the under-surface of infected leaves . These re-lease a second kind of spore, calledthe urediospoFe, which may infectribes leaves on the same and near-by shrubs . Its purpose is to intens-ify the rust on the currant and goose-berry hosts during the summer . Inthe fall the fungus develops brown-ish, hairlike columns on the under-side of the leaves composed of athird kind of spore, the teliospore. Theteliospores germinate and producea fourth (I) kind of spore, called thesporidium, capable of infecting onlywhite pines . Since these last stagestake place only in the presence ofplenty of moisture, the disease ' sspread to white pines depends uponfall rains . The thin-walled sporidiaare delicate and short-lived. They,too, are wind-borne, but because oftheir frailty they usually cannot sur-vive an air voyage of more than afew hundred feet from their sourceon a ribes.

When a sporidium (the 'pine-in-fecting spore) falls upon the needleof a white pine, it may germinatein the presence of moisture, and itsgerm tube may enter the needle tis-sue by way of a stoma—one of thebreathing pores of a leaf. The fila-mentous threads grow down throughthe needle and enter the limb, thereto establish the fungus in the vitalcambium layer beneath the bark.This is the point where we started

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YOSEMITE NATURE NOTES

on our trip through the life cycle ofwhite pine blister rust.

On pines the fungus may live formany years, or until the tree iskilled. In contrast to this, the parasiteis confined to the leaves of ribes,and disappears each autumn withthe falling of the diseased leaves.

How, then, is blister rust con-trolled? Control rests upon two sim-ple, well-founded, but none-too-ob-vious facts . (I) The fungus cannotspread directly from one white pineto another . Aeciospores producedon a diseased white pine can infectcurrant and gooseberry plants only.The fungus must spend an inter-mediate stage on these hosts beforespreading to white pines . (2) Theshort-lived pine-infecting spores pro-duced in the fall on rites can carrythe rust to pines only over veryshort distances. These distances areusually a matter of only a few hun-dred feet or yards . Removal of ribesfrom the vicinity of white pines willinterrupt the cycle and prevent thespread of the disease back to pines.By this action control is achieved.

Control consists, then, in the de-struction of currant and gooseberrybushes within and near white pinestands chosen for protection . It isaccomplished by crews of men whogrub out the ribes by the roots withspecial forked pick-mattocks . Thisis called "hand eradication" andmay be done either by government-employed crews or by private in-dividuals under contract. Since near-ly all ribes must be removed to givethe degree of protection desired, thestand of timber to be protected issystematically laid out with guide-line strings to ensure complete cov-erage. Hence the presence of thosebaffling string lines in the woodsthat awaken the curiosity of manypark visitors.

Where - ribes are numerous or are

Ribes eradication crew working betweenstring guide Iines.

difficult to dig out, chemicals areoften used . The plant-hormone weedkillers, 2,4-D and 2,4,5-T, are sprayedon the plants with power equipmentor are applied by hand to individ-ual recalcitrant bushes.

Because some plants are missedby control crews and because newplants grow from seed lying dorm-ant on the forest floor, several work-ings or "eradications" at periodicintervals may be needed.

How destructive is blister rust towhite pines? Naturally one wantsto know the magnitude of the dangerfrom which protection is sought.Blister rust spreads back and forthbetween white pines and rites eachyear, causing an accumulation ofcankers on the pines. The funguskills by girdling the trunks andbranches, and sometimes in severeinfections by killing all the twigs . Itkills small trees quickly, largely be-cause, their crowns being nearer theground, theyare closer to ribes; andbecause, being smaller, they areeasier to kill . A few cankers on asmall tree will do what it wouldtake hundreds to do on a large tree.Since blister rust is particularly dam-aging to small trees (those up to30 years old or 15 to 20 feet high,

107YOSEMITE NATURE NOTES

known in the forest as "reproduc- is to preserve the existing stand forton"), it prevents the natural restock- its manifold intangible values, henceing of white pine forests. Infections salvage would be meaningless.are heavy where the ribes hosts are

In this little sketch we have tried

abundant; they are less heavy to set down some of the main facts

where the hosts are more scattered . about white pine blister rust : That itUnfortunately, the disease is decep- is caused by a fungus ; that its rathertive, for infections on pines cannot complicated life history can be re-easily be noticed until damage is duced to simple terms ; that it can be

severe .

controlled; and that uncontrolled it

Large trees are killed slowly ; in is severely damaging to youngcommercial stands they can normal- white pines. The next time you see

ly be salvaged without complete those strings in the woods you will

loss. In national parks the objective know the why of them!

SOME NOTES ON FLIGHT

By Allen Waldo, Senior Ranger Naturalist

While watching a particularly Having made the observation ofbeautiful sunset during the musical the two distinct groups, I began toportion of the Camp 14 naturalist notice how different was the flightprogram this summer, I noticed of these mammals from that of mostabout a dozen bats in flight . With birds . A bat ' s wings flap in constant

some surprise I saw that the bats motion . At no time do bats glide, as

were in two very distinct layers . most birds occasionally do . With one

One group was flying around Cutup wing flap a bat is able to make very

14 at elevations of from 10 to about sudden changes of 90° or more in150 feet from the ground . The sec- direction, never maneuvering byand group was flying, over a larg- swooping curves up, down, or side-er range, at elevations of approxi- ward, as birds so typically do . Atmately 300 to 400 feet above the times they come to a sudden, al-

Valley floor .

most complete stop in the air.

Little Brown Bat (Myotis Iuoifugus) . From Mammals of Lake Tahoe by Robert T. Orr . Courtesyof the publisher, California Academy of Sciences . -

YOSEMITE NATURE NOTES

Another interesting difference be- It was interesting to observe thetween birds and bats, which may methods employed in this glidingaccount in part for the difference in "flight, " and the way the squirrelthe flight habits of the two, is in the prepared for it. The glide is possiblebody outline. Bats have round, because of a thin fold of skin whichstubby looking tail structures con- extends along each side of the bodylisting mainly of a membrane of between the fore and hind limbs ofskin stretched between the hind the squirrel . If the four legs of thelegs, whereas birds have more or animal are spread out as far as pos-less elongate, feathered tails which sible, this flap of skin is stretchedthey spread in flight and use to help broad and flat around the body,guide themselves . Perhaps this lack thus nearly tripling the planing sur-of a comparable tail in the bai face exposed, and at the same timemakes possible its sudden reversals making a flat—instead of the normal-of direction, while the elongate tail ly rounded—body outline.of the bird causes it to perform a

For gliding, a high "take-off" pointsweeping turn .

is, of course, essential . Thus theAn additional flight note was squirrel would scamper up the trunk

made during the middle of a bright of a tree until he was nearly at theafternoon in the naturalist living top . Here he would make a big leap.area at Camp 19 . While several of After he had been in the air a secondus were seated, talking, a flying or so and was well clear of the treesquirrel (Glaucomys sabrinus lascivus) branches, he would spread his legsappeared. This was unusual, since out, stretching his skin fold . Immedi-these animals are normally noc- ately his downward fall was check-turnal . It made several "flights " be- ed and a slanting glide was startedfore it finally escaped our view. Its which he was able to control veryflight, of course, is not truly a flight completely . He did it in such a wayat all, but merely a glide .

as to plane directly toward the lower,

Flying Squirrel . From Mammals of Lake Tahoe by Robert T . Orr. Courtesy of the publisher,California Academv of Sciences

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YOSEMITE NATURE .NOTES

109

branchless part of a tree trunk . Upon bawls of protest, and he started upapproaching the trunk he raised his a tree. Since there was no desire toforefeet and the front part of the flap . have him noisily hanging aroundThis brought his head end up sud- camp for several hours, attack wasdenly, and at exactly the right time, stopped . He soon came. down andso that his body was vertical and started on his way, with loud urg-parallel to the tree trunk at just the ing on our part.instant at which he struck it . So he It was then that the other twohit the tree head-up and practically cubs and their mother were ob-scampering . No time, thus, was lost served . It was clear then that wein starting for the top of the tree to had best be careful how we han-make his next glide . He did this four died the cubs and that we shouldtimes. At the end of the last "flight" not get between the mother and anyhe ran high up the tree and disap- of the three . It was also apparentpeared from view.

that if we were to have safe foodThe final "flight " noted was -that we would first have to get all three

of the bear, or I should say four cubs around the mother, and thenbears. It is true that bears all-too- get her moving on her way.seldom flee . These four bears were

Five of us, therefore, started aa mother and her triplet cubs who herding process from three direc-were invading our campground for tions . We soon drove the scatteredthe purpose of helping us all get rid cubs to their mother. Then with muchof our groceries .

shouting, and several very poorlyThe first bear to be discovered placed rocks, all of which missed

was one of the cubs, and we thought her, we got the mother movingthat it was the only one present . away, closely followed by her threeTwo well-placed small rocks on the small progeny. Thus is recorded theposterior of the cub elicited loud "flight " of the bear.

TRACKING THE CAT FAMILY IN LOWER TENAYA CANYON

By C. Dewey Youngblood, Field School, 1950

During the first two weeks of July The wildcat is not a gentle animalseveral careful observations were It is typically a cat and is difficultmade of animal tracks around and to tame . I have observed wildcat kit-above Mirror Lake in the lower tens in captivity and they appear toTenaya Canyon. The tracks found be independent and resourceful evenand studied were those of wildcat, when very young. When they growmountain lion, fox, bear, coyote, and to adulthood in captivity, they dosquirrel . Casts were made of the not become domesticated as doeswildcat, mountain lion, and the bear the house cat.tracks. This article deals only with

The wildcat tracks observedthe wildcat or bobcat (Felis rufa tali- around Mirror Lake were about 2fornica) 1 and the mountain lion or inches in diameter and were num-cougar (Felis concolor californica) .

erous in the muddy and loose sand

1 . Simpson, G. G . (1945) The Principles of Classification and a Classification of Mammals . Bull. Am.Mus . Nat . I-tist. B5 . Lynx rufus californicus of most authors .--Ed .

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YOSEMITE NATURE NOTES

near and away from the lake. Observation disclosed the tracks nearthe nesting places of the robinswhich nest in considerable numbersjust above the lake . It was evidentthat the cat was making early morn-ing and late evening forays into therobin nesting territory and many afeast probably resulted when ayoung robin became careless orwhen a nest of young was found tobe . accessible. Scattered featherswere found which point to this tact.Observations made during the firsttwo weeks of August did not revealas many tracks as were found inearly July . The conclusion can bedrawn that the wildcat had beentaking the fullest advantage of theplentiful source of food earlier in thesummer.

It is interesting to note that thewildcat was a frequent visitor to anarea used by so many people as isMirror Lake in the middle of thesummer . Even though it fears man,it does not hesitate to hunt in suchareas if it can find its food supplythere.

The food habits of the wildcat orbobcat are diversified. Its food con-sists of all the birds it is able to kill,including chickens and turkeys,rodents of all kinds, rabbits, lambs,fawns, turtles and other reptiles, fish,insects, and carrion . The wildcat isuseful to man at least in keepingdown the rodent and rabbit popu-lation.

Casts were made of a mountainlion or cougar track found nearMirror Lake . This measured about4½ inches in length. Evidently thecougar had been making one of itsfar-ranging hunting circuits becauseits track was not again found duringseveral subsequent observations.The animal apparently was run-ning almost at full speed because itwas slipping in the soft mud, using

California Mountain Lion

its claws for surer footing . It mighthave been after a deer at the timesince many deer frequent the areaabove Mirror Lake.

Cougars forage over a large area,the distance covered depending onthe abundance of their food supply.Where deer are plentiful the cougarwill live principally on deer meat.They tend to remove the weak orsickly deer from a given herd andin this way actually improve thelocal deer population.

The cougar is difficult to observesince it seldom allows itself to beseen by man . I have seen only onemountain lion in all of my trail andmountain hiking of many years . Afew years ago I saw one race acrossan open meadow in the CuyamacaMountains 50 miles east of SanDiego. It was fascinating to see thebig cat running for several hundredyards in plain sight . Often on coldwinter days with the ground cov-ered by a light snow I have observedthe signs of a race between a deerand a pursuing mountain lion, and Ihave tracked their course to thepoint where the deer had outdis-tanced- the hungry feline . Evidentlythe big cat had chosen a healthydeer for his meal that day but was

111YOSEMITE NATURE NOTES

forced finally to seek a weaker ani- been eliminated from deer range inmal. Most of the dead deer I have other parts of the country, the deerfound which I was convinced were have suffered heavily from starva-killed by a mountain lion were small tion and disease brought about by

deer .

overpopulation and the resultant

Harry C. Parker, Associate Park overuse of their natural food supply.Naturalist of Yosemite National Park : One large area in Arizona had tohas told me that he is of the opinion import the mountain lion in order tothat this park area does not have a improve the deer of the region . Ap-

sufficient number of mountain lions parently the mountain lion has itsto kill off the surplus, unhealthy role to play in the great balancingdeer. Where the mountain lion has program of Nature .

Photo by Ralph ,4, 1c, ,,,;

California Wildcat

CORRECTION

Our readers probably were mystified by the missing name of the newmouse reported for the park by Ranger O . L. Wallis in his article on page 97of the October 1950 issue of Yosemite Nature Notes. A printer 's error thatcaused the omission requires correction to clarify the article . The eighth lineas it is printed is out of place, so that the second sentence should read:"Stopping to examine the animal, I discovered it tc be a California pocketmouse (Perognaihus callforrnicus) , a mammal which had not previously beencollected within the boundary of Yosemite National Park . "--Ed .

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