12 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR 
It will be obvious that if poor soil aeration is a factor of importance in the 
production of wilt, the types which will be affected most are deep-rooting types 
like (b), (c), (d) and (e) while (a) will be least affected. In 1917, a comparison 
was made between the growth and wilt resistance of Type 11, an early type 
with a vertical habit whose laterals pot downwards (Fig. 2) and Type 15, an 
early bush type with laterals near the surface (Fig. 1). The former proved 
to be much more wilt lable than the latter. In 1918, this point received 
further confirmation. It was found that after the first cut, all the plants 
which did not shoot and which were attacked by wilt could not be uprooted 
by hand as the laterals ran deep into the soil. On the other hand, the plants 
which formed healthy new growth could be pulled up with comparative ease 
as the laterals were much nearer the surface. In 1919, every case of wilt 
examined in detail during the monsoon was found to be associated with deep- 
rooting while the healthy plants examined for comparison were all found to be 
surface-rooted. 
The occurrence of wilt under monsoon conditions. The amount of wilt 
during the rainy season and the general vigour of the indigo crop under 
estate conditions, have been found to depend on two factors—the rainfall 
and the rise of the ground water. If the rainfall is heavy, particularly 
during July and August, and if the ground water rises rapidly and remains 
at a high level during this period, the second crop is a failure and wilt 
is widespread. Although unfavourable years are common, they are not 
universal. In 1919, the monsoon rainfall was about 12 inches below the 
average, there were no floods and the rise of the ground water was not con 
siderable. The details relating to the rainfall and to the movements of the river 
and well levels at Pusa, in 1919, are given in Plate IV. Wilt was negli- 
gible and only made its appearance on two occasions—between July 23rd 
and August 7th—and again during the first three weeks of September. Both 
these attacks were associated with an increased rainfall and a rise in the well 
levels. They were, however, not severe and had little influence on the yield. 
Three good cuts of indigo were obtained at Pusa and for many years the 
indigo crop has never been so healthy after the rains. 
Although wilt is often universal during the late rains, it is not uncommon 
in Bihar to find young self-sown indigo plants in September and October, 
growing vigorously in fields practically destroyed by disease. In 1912, at 
Pusa, this occurred on the large scale in a wilted field in which the blank spaces 
in the lines had been filled by resowing during the first week in August. The 
late sown plants without exception were not affected by wilt but grew 
well and gave heavy crops of well-ripened seed. Here, healthy and wilted 
