qn.r>% Properly of the United States DEPOSITORY U.S. DEPARTMENT OF AGRICULTURE, i;i READ OF PLANT [NDUSTRY— Circular N T o. 9. B. T, Q U.l.i >\\ A.Y, Chief of Bureau. TEXAS ROOT-ROT OF COTTON FIELD EXPERIMENTS IN L90T. By C. L. SHEAR, Pathologist, \NI> GE( )i;».l' F. MILKS. Scientifk Assistant. i ■!•■ !l— 08 WASHINGTON : GOVERNMENT PRINTING OFFICE : 1008. BUREAU OF PLANT INDUSTRY. Physiologist and Pathologist, and Clue) o) Bureau, Beverlj T. Gallov Physiologist and Pathologist, and Assistant Chief of Bureau, Albert 1' Woods. atory of Plant Pathology, Erwin I". Smith. Pathologist in Ch Investigations of Diseases of Fruits, Merton 1'.. Waite, Pathologist in Charge. Laboratory of Forest Pathology, Haven Metcalf, Pathologist in Charge. Cotton and Truck Diseases < ml Plant />/-.< » r v < Survey, William A. Orton, Pathologist in Charge. Plant Life History Investigations, Walter T. Swingle, Physiologist in Charge. Cotton Breeding Investigations, Archibald I». Shamel and Daniel X. Shoemaker, n gists in Charge. Tobacco Investigations, Archibald 1 >. Shamel, Wightman W. Garner, ami Ernest II. Mathewson, in Charge. Com Investigations, Charles I'. Hartley. Physiologist in Charge. Alkali mill Drought Resistant Plant Breeding Investigations, Thomas n. Kearney, Physi oio^is! in Charge. Soil Bacteriology and Water Purification Investigations, Kail I'. Kellerman, Physiologist in Charge Bionomic Im^cstigations of Tropical and Subtropical Plants, Orator 1'. Cook, Bionomist in Charge. Drug mill Poisonous Plant Investigations and Tea Cultun Investigations, Rodney II. True, Physiologist in Charge Physical Laboratory, Lyman .1. Briggs, Physicist in Charge. Crop Technology and Fiber Plant Investigations, Nathan A. Cobb, i rop Technologist in Charge. Taxonomic ami Range Investigations, Frederick V. Coville, Botanist in Charge. Farm Management Investigations, William J. Spillman, Agriculturist in Charge. Grain Investigations, Mark Alfred Carleton, Cerealist in Charge. Arlington Experimental Farm, Lee C. Corbett, Horticulturist in Cha Vegetabh Testing Gardens, William W. Tracy, sr., Superintendent. Sugar-Beet Investigations, Charles <>. Townsend, Pathologisl in Charge Western Agricultural Extension Investigations, Carl S. Scofleld, Agriculturist in Charge. Dry I. mni Ail.- imiliii, i Investigations, E. Channing Chilcott, Agriculturist in Charge. Pomoloi/irni colli i lions, Cnstavns P.. [Srackett, Pomologist in Charge. Field Investigations in Pomology, William A. Taylor and G. Harold Powell, Pomologists in Charge. Experimental Gardens and Grounds, Edward M. Byrnes, Superintendent. Foreign Seed ami Plant Introduction, David Fairchjld, Agricultural Explorer in Charge. Forage Crop Investigations, Charles V. riper. Agrostologist in Charge. Seed Laboratory, Edgar Brown, Botanist in Ch Grain Standardisation, John D. Shanahan, Crop Technologist in Charge. Subtropical Laboratory and Garden, Miami, Fla., Ernst A. Bessey, Pathologist in I Plant Introduction Garden, Chico, Cal., August Mayer, Expert in Charge. South Texas Garden, Broivnsville, Tex., Edward C. Green, Pomologist in Charge, Farmers' Cooperative Demonstration Work, Seaman A. Knapp, Special Agent in Charge. Seed Distribution (Directed by Chief of Bureau), Lisle Morrison. Assistant in General Charge. Edit oi . J. E. Rockwell. cl,ii f < 7i / /.-, James E. Jones. [Cir. 9] II I' I 37S TEXAS ROOT-ROT OF COTTON FIELD EXPERIMENTS IN L907. INTRODUCTION. [nvestigations have been carried oh for a number of years hy the Bureau of Plant [ndustry in determine the cause and the best methods nf controlling the cotton root-rot. A brief account of the field work of 1906, announcing the very promising results which were obtained by i Ice 1 1 fall plowing and rotation of crops, has been published. 6 Dur- ing the past season ii I periments were continued along the same line in order to verify, if possible, the previous results. The results of the past two seasons have been so satisfactory that it is believed thai the method is practicable and worthy of general adoption in combating the root-rot of cotton and also that of other annual or short-lived perennial crop- which are attacked by this disease. CAUSE OF ROOT-ROT. The cause of this disease, a- has been pointed out in previous publi- cations, i- a fungus, < >:<>ii'hiiii omnii'orum Shear.' which infests the >oil and destroys the roots of the plant. REPRODUCTION AND DISTRIBUTION OF THE FUNGUS. The fungus can he readily reproduced from -mall hit- of the mycelium or vegetative portion of the plant. Such pieces of the This reporl of the results of the pasl season's field experiments in the pre vention of cotton rool rot bj Doctor Shear ami .Mr. Miles corroborates in greal pari I he very satisfactory results of the previous season and justifies a thorough trial "I' the s| ifled plan by planters who are suffering less from this disease. As [minted em here, climatic conditions and ether factors are always likelj to cause degree of variation in the results nf this treatment. Further efforts are being made in determine, it' possible, what modifications nf this method, if any. may increase iis efficiency. A. I'. \V< s. Physiologist and Pathologist, and icting Chief of Bureau. I'll.' Control "i' Texas Rool Rot "i Cotton, by <'. 1.. Shear and George 1'. Miles. Bui. 102, pt. •">. Bureau of Plant Industry, 1JK)7. ■' Bui. Torrey Botanical Club, vol. 34, p. 305, 1JK)7. [Clr 3 4 TEXAS ROOT-ROT OF COTTON. fungus are probably distributed by the wind when soil containing the organism is blown from one place to another. The fungus may also undoubtedly be distributed by infected soil adhering to tools and to the feet of animals. Since the disease may be carried in the soil, the practice which we arc informed has been recommended in Texas of distributing the nitrogen-gathering organisms of alfalfa roots by the use of soil from old alfalfa fields is exceedingly dangerous and almost certain to lead to the further dissemination of this serious disease, which so far a> known at present is restricted to southern Oklahoma, Texas. New Mexico, and Arizona. Since alfalfa is affected by the same root-rot as cotton and many alfalfa fields in Texas are known to be badly infected with the fungus causing the disease, every effort should be made to prevent the distribution of soil from alfalfa fields in that region, and no person should purchase or use such soil, particularly in localities or States where the root-rot fungus does not already occur. The root-rot is also suspected on strong circumstantial evidence of having one or two spore forms by which it may be reproduced and distributed. These spores may be easily transported long distances by the wind, and perhaps by water also. More work bearing on the spore production of this fungus is necessary, however, in order to prove the connection between the forms suspected and the root-rot organism. METHODS OF CONTROL. ROTATION OF CROPS. In order to determine experimentally the efficiency of rotation of crops in controlling this disease, an area of aboul 20 acres >>f very badly infected black waxy land was selected at Terrell. Tex. This land had been planted to cotton for several seasons and in 1903 about 95 per cent of the cotton died from root-rot. In the fall of 1 DOT this field was planted to winter wheat. A good stand was obtained and the wheat grew about 4 inches during the fall. The winter being very severe, however, the wheat was mostly killed, and in the spring of L905 the land was plowed -hallow and planted with corn. Fol- lowing the corn the land was plowed 2 to -I inches deep and drilled to wheat. In 1906, after the wheat was harvested, a portion of 'he field was plowed and planted to sorghum and the remainder of the held plowed, hut lefi without a crop for the remainder of the season. In the winter of L906-7 this field was bedded and in the spring of L907 it was planted in cotton, producing one of the besl crops in the vicinity. There were only a very lew small spot- in the held upon which the cotton was affected by the disease, whereas at the begin mini: of the rotation about !)."> per cent of the crop was killed by root-rot. I fii-. :>\ I I \ \> ROOT ROT OJ ' M ON. \ri:\un\ hi I ill: SOIL r.1 DEEP FALL PLOWING. A- \v;i- pointed out in our previous report, one of the inosl im- portant factors in the development of this disease is the condition of the soil in regard to its aeration. The heavy black clay soils, being very poorh aerated, furnish favorable conditions fur the develop- ment of the root-rot fungus and at the same time are very unfavor- able for the most healthy development of the rool system of the cot- ton plant, and any practice which will loosen this soil and improve its physical condition so that more air will reach the roots of the plants appears greath to Lessen the injury from tin-, disease. On November 12, 1906, a field at Petty, Tex., upon which most of the cotton for sev- eral years had died with mot -ml. was plowed 7 to 9 inches deep with •I LO-inch plow. In the spring of L907 the land was bedded and planted to cotton. Owing to unfavorable weather conditions the cotton had to be replanted twice, the final planting being done on May L8. A portion of the same held was also plowed .-hallow in the ordinary manner in the spring of L907 and used as a check plat to compare with the plat which was deep fall plowed. The cotton on both plats was given ordinary cultivation during the season. < )n November 11. L907, all the living and dead plants on both plats were counted. On the plat which had received the deep fall plowing only 26.79 per cent of the plants were death and most of these plant- had matured their crop before dying. On the adjoining plat which had received ordinary spring tillage 69.5J per cent of the plant- were dead from the disease, and most of these plants had died SO early that they produced but little cotton. The accompanying reproduction of a photograph of these plats .-hows their appearance al the lime the count- were made. (Fig. 1.) At the same time another Held in the same vicinity, also very badly infected with root-rot, was plowed 7 to 9 inches deep with a 1 1-inch riding plow. The plat was planted in the spring, and at the same time an adjoining plat was given ordinary tillage and planted as a check. Both plats received the same cultivation during the season. On November 11. L907, the plat which received the deep fall plow- ing showed by adnal count of all the plant- only 1 l. s 7 per cent dead. and on these most of the crop had matured before their death. On the check plat which received ordinary spring tillage .">7. v 7 per cent of the plants were killed by the disease, and these plant- died so early that they did not mature nearly so mam bolls a- those on the deep-plowed plat. These results are not quite so satisfactory as those obtained in L906, but are quite sufficient to justify and make profitable this method of treatment. The benefit derived from thi- treatment necessarily de- pend- in -nine extent upon various factors which arc more or less [Clr. '.'I 6 TEXAS ROOT-ROT OF COTTON. uncontrollable. The most important of these are the condition of the soil at the time the plowing is done and the climatic condition- which prevail during the succeeding winter, as these factors will greatly affeel the amount of disintegration and aeration which will take place in the soil during the winter. The plowing, of course, should be done only when the soil is in proper condition — neither too wet nor too dry. SUMMARY. Rotation with immune crops at Terrell. Tex., resulted as follow-: 1904. planted to cotton, about 95 per cent of which was killed by root-rot. Fig. 1. — Experimental plats of cotton at Petty, Tex., showing the results of (loop fall plow- ing. Plat A, at the left, was plowed 7 to inches deep "ti November 12, 1906. Only 26.79 per cent of these plants were dead on November 11, 1907, and most of these had matured their crop. Plat B, at the right, received ordinary spring plowing. Of these plants, 69.54 per cent were dead on November 11, 1907, and these had died so early that they matured bu1 a small part of their crop. L905, planted to coin. 1900. planted to wheat, followed by sorghum the same season. 1907. cotton again planted, with the result that as nearly as could be estimated less than 5 per cent of the cotton was dead at the close of the season. Land badly infected with root-rot was plowed 7 to !• inches deep November 11. 1906, at Petty. Tex. In experiment No. 1 the deep- plowed plat showed 1:2.75 per cent Less dead plant- than the adjoining check plat which received the customary tillage. In experiment No. ■2 the deep-plowed plat showed 43 per cent le>s dead plants than the [Cir. !)J TEX V.S Ri '< ' i R( 1 1' OF COT rON. , adjoining check plat, and in both cases a much larger amounl of cotton was produced on the dead plants on the treated plats, because these plants did not die until later than those on the untreated plats. and therefore had greater opportunity to mature their liolls. CONCLUSIONS. A combination of rotation of crops and deep fall plowing will probabl}' be found the most satisfactory, efficient, and practicable means of controlling the root rot of cotton. In combination with a short rotation the deep fall plowing would perhaps be needed only i \ i i ■ \ ot her year. Experience indicates that better tillage and rotation of crops in any case must be more generally practiced in the future by cotton planters i I' profitable crops are to be produced, even in localities where the root -rot is not present. Approved : J \ siES Wilson, v i n tin ij of . Agriculture. Washington, i>. c. May u, wos. 9] O /cr^oii t ur rLunuft 3 1262 08929 0018