50 



James R. Holbert 



fields this results in a fifteen to twenty percent 

 reduction in stand during the first two or three 

 weeks. 



The next slide shows again a strong, vigor- 

 ous corn plant grown from disease-free seed. 

 These others (indicating) grew from ' slightly 

 infected seed. 



Q. How long will they live? 

 Prof. HOLBERT: They would probably 

 live throughout the season. The difference be- 

 tween these plants so noticeable now may 

 disappear somewhat in a few weeks, perhaps by 

 the middle of July, so that these may look 

 apparently equal. But we find that plants 

 stunted in their early stages of growth never 

 recover sufficiently to produce a normal yield 

 of corn. They are usually nubbin bearers or 

 barren, or in case they do produce an ear, it 

 is frequently of poor quality. 



This slide (indicating) shows the same 

 thing from a different standpoint. In this 

 case we have taken two seedlings from the 

 germinator, one a clean healthy, vigorous seed- 

 ling, which is represented by the solid line, 

 and the other a badly diseased seedling, repre- 

 sented by the broken line. They were the same 

 height when they were transplanted. From the 

 graph you will note that the diseased plant spent about a week or ten days in 

 sending out a new set of roots so that it could gather nutrient from the soil. 

 After that time it grew at a parallel rate with the disease-free, and finally 

 obtained the same circumference at the base but was not quite as high. The 

 difference in yield is well illustrated by the photograph of the good-sized ear 

 from the healthy plant and the nubbin from the plant grown from infected 

 seed. 



Here (indicating) we have the same thing again in the field. These 

 two were planted in adjacent hills, one from badly infected seed and the 

 other from clean healthy seed. Note the difference in vigor. The next slide 

 will show the same plants at harvest time. The plants are practically equal 

 in height. The one has two nubbins, the other has three good sized ears. 



The next slide shows the same thing carried over to larger plats. Poorly 

 selected seed usually contains a large amount of infected seed. Fields of 

 corn grown from such seed have many missing hills, a poor field stand, and 

 many weak plants. These two plats were planted with the same man's corn 

 at the same time, no difference in the soil treatment. Note the irregularity 

 in growth, some plants waist high, other shoulder high, and some only knee 

 high. The difference in total yield was not so marked. However, the plat 

 planted with nearly disease-free seed gave an increase of twenty-five bushels 

 of sound, marketable corn. 



During the past two years we have been studying the influence of time 

 of planting, soil temperature, soil moisture, and other factors with relation 

 to the development of the different corn root and stalk rot diseases. This 

 graph represents the data secured from just one of these experiments. The 

 solid line indicates the portion of the corn planted that produced strong, 

 healthy plants in the case of nearly disease-free seed. This is the first plant- 

 ing (indicating) May 7th; the second, May 14th; the third, May 21st; and 

 the fourth, May 30th. Time of planting had little effect on the stand and 

 vigor of corn grown from good seed. But in the case of the diseased seed 

 the percentage of strong plants dropped in the first planting. But in the 

 last planting when all conditions were very favorable the diseased seed 

 produced a large percentage of strong plants. However, those strong plants 



