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MICROCOPY RESOLUTION TEST CHART

MICROCOPY RESOLUTiON TEST CHART

NATIONAL BUREAU Of STANOARDS-196l-A

NATIONAL RUR£AU OF SlI,NOAIlDS I9GJ·A

Aeration and Other Soil Factors

Affecting Southern Pines as

Related to Littleleaf Disease

by Bratislav Zak, Southeastern Forest ExperiInent Station, Forest

Service

TECHNICAL BULLETIN NO. l248 u.S. DEPAHT)IENT OF AGIUCULTUHE

ISSUED SEPTEMBER 1961 FOREST SERVICE

ACK!.~OWLEDG~IIENT

The subject matter of this bulletin was submitted to Duke Univer­ sity in partial fulfillment of the requirements for the degree of Doctor of Forestry. The writer wishes to express his appreciation to 'V. A. Campbell, G. H. Hepting, O. L. Copeland, Jr., 'r. C. Evans, J. F. Smith, and E. R. Roth of the ·U.S. Forest Service, and to J. Giddens of the University of Georgia for aid and suggestions dUl'ing the course of the study. The COUIlSel of Professors P. J. Kramer, F. A. 'VolC, and F. X. Schumacher, Duke University, is gratefully acknowledged. The author is on the staff of the Athens Research Center, maintained at Athens, Ga., by the Forest Service's Southeastern Forest E:l'. -periment Station in cooperil.tion with the University of Georgia. This work was sponsored by the Division of Forest Pathology, Bureau of Plant Industry, Soils and Agricultural Engineering, now th", Division of Forest Disease Research, Forest Service, U.S. Depart­ ment of Agriculture. Greenhouse and laboratory facilities were furnished by the School of Forestry, University of Georgia, Athens, Ga. II

CONTENTS Introduction_______ __________________ ___________________________

Page

1

Previous work_____________________________________________________ Plal1 of study _______ -_ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Geneml tcchniques_ _ _ _ _ _ __ _ _______ . __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

2

4

4

Experiment L Effects of soil aeration and Phylophlhoro cinnamomi on root

developmcnt and seedling growth_________ ___ _____________________ ~Iethod of Study______ _ _____________________________________ Results t''1d discussion _______________ •• ________________________

5

6

9

Experiment 2. Effects of soil texture, Ph1l1ophthora cinnamomi, and soil

moisture on root devclopmen t ancl seedling growth ___ • _ _ __ • __ . _ _ _ _ _ _ ~:lethod of study- ___________________________ .____________

12

13

Results and discussion _ _ _ _ _ _ .

General discussion _ _ _ _ _ __ _ _ _ _. _. _ _ .

Summary and conclusions _____ • _ _ __ _.. _. Literature cited _____________________ . _. _____________________ _

For sale hy the Superintendent of l1ocuments. e.S. Government Prtntlng Ornce WashIngton 2.5. D.C. - Price 21) cents HI

14

20 27 2!)

INTRODUCTION

Shortlcaf (Pi1J,US echinata, :Mill.) tl.nel loblolly {line (P, taeda L,), both principltl components of upland sites in the Piedmont region of the Southeast, are I.l.fllicted with littlclea[-a disease associatea with soil erosion. Originnlly, the deep, friable, rich soils of the Piedmont bore climax forests of oll.k, hickory, lWei othel' hn.rdwooc\s, with scaUered pine. Although l1'ltl.hy sitcs were underlain with helwy tlond POOI']Y dmined subsoils, tr{'c growth was good when dct'p and rich surfl~ce soils were prescnt. As these stands wcre removed and the soils cultivn.ted tl.ud pln.nted to row crops, sh('ct (,I'osion began n.ne! eontinuccl. Rn.thel' gl'n('mll,\-, when row-crop fields /11'e abandolled in the Picdmont, the hUH.! sc-c(\s in Imtul'I1l1y to shorU('!~£ and loblolly pincs. This hus happencd on millions of acres of fOl'lI1cl' ('ottonfic-Ids, On Illany such fields the tI'CC-S lllwe h~t('r I>('('n hal'\~eslI"I.tiol1 wns rC'sponsibll' for root injury Iwd

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:3.--(:(>n('r:11 compari'''JI1 of "hr-rtl1'af (til and loblolly ([., phil' in E'qIPri­ mpnt I: A, Upip;ht in cpntimptpr,,: n, top wpiedl!' in gmlll": (', root 1I'('ight in grnrn,;; D, total wpight in grnll1": I:', root-top ratio; P, rr'lati"p ahllndan("f­

FWl'HS

of mycorrlti7.lw. Each ntlllP i~ til!' nW:lIl of 80 ;;(·prlling;,;. Diff('rf'Ilc!' ]"!'qllin-d betwt'f'11 twu \-alup:{ for ~i[!nificallC(> at 5 and 1 IW("C!'rlt II-no],.; i,; indicatf'd (~D\.

9

LITTLELEAF DISEASE FACTORS AFFECTING SOUTHERN PINES

The 4 gas treatments were each replicated 20 times in split-plot (1 shortleaf and 1 loblolly pine seedling were planted in each pot) randomized blocks. The soil in one-half of each gas series was in­ oculated with Phytophthora cinnamomi and the other half treated as control.

Results and Discussion Based on an average of all treatments, the total height of loblolly was considerably greater than that of shortleaf (fig. 3). The two species differed very little in top weight, but shortleaf produced a significantly heavier and more fibrous root system than did loblolly.

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abundancr of mycorrhizll(' of shortlt'nf (8) and loblolly (1.) pine seedlingR grown in variouR ~oil" of Exprrilllent 2. J;;ach \'!L!lI(' is the mrlln of 2·1 tree". Difference req uirpd bet \\'c('n two \·alll(·s for Rignificancr at 5 !lnd I pC'rcrnt Icvels is indicated (SD).

19

LITTLELEAF DISEASE FACTORS AFFECTING SOUTHERN PINES

This same relationship was also e)..-pressed by height, top weight, and total weight data which are not shown. Best mycorrhizal development for both species occurred in the sand, loam and silt soils and poorest in the clays (fig. 11). This indicates, in part, the beneficial effects of adequate soil oxygen in the formation of mycorrhizae, as was shown in Experiment l. The presence of Phytophthom cinnarnomi in the soil caused a sig­ nificallt drop in root weight and root-top ratio of shortleaf pille tfig. 12). As in E:\-periment I, loblolly pille grew somewhat; better in the inoculated thiln in the noninocl1l!Lted soils. The weakened root SYS­ tem of shortleaf in the inoculn,ted crock caused a reduction in compe­ tition by this species and probably allowed the loblolly seedling in the same container to improve its growth. Evidently, loblolly pine roots are much less susceptible to attack anci injury by P. cinnamomi than are those of shortleaf pine. Root systems of the two species grown in the inoculated and control series of the IfA" group of soils (Sand A, Loam A, Silt A, ilnd Clay A), each at two le\-els of wetness, are depicted in figures 1:3 through 16. Shortlen,f roots exhibit considerable c1nmnge in soils infected with Phyfophthora cinnammni, while those of loblolly appear uninjured. 5%

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