BOLL WEEVIL CONTROL BY USE OF POISON. 2 
afforded between the poisoned and unpoisoned plats. Throughout 
this work the gains have varied from nothing to over 1,000 pounds 
of seed cotton per acre. 
The most that can be expected of poisoning is the elimination of 
weevil injury. Soil fertility is very important and really becomes the 
determining factor in the amount of gain which can be secured from 
the poisoning. One interesting feature of the work which has been 
conducted so far is the large number of tests on fields which had a 
fairly low degree of weevil infestation and which have shown abso- 
lutely no gain from the operation. In many cases comparable plats 
have been selected and started with an infestation of 10 or 15 per cent, 
one plat being poisoned and the other left unpoisoned as a check. In 
such cases, the infestation of the check plat, instead of increasing as 
would normally be the case, has been held in check by some climatic 
condition so that there was only a gradual increase to a maximum of 
from 35 to 50 per cent of the squares punctured at the end of the sea- 
son. Usually, under such conditions, no gain in yield is shown in spite 
of the fact that imfestation of the poisoned plat was practically 
wiped out. In other words, the degree of infestation in the check 
plat was not sufficient to overtake the normal shed of squares and 
thus there was no reduction in crop yield. This, of course, illustrates 
the needlessness of poisoning unless the weevils are sufficiently — 
abundant to injure the crop. 
There are many fields where weevil infestation becomes so complete 
by the middle or latter part of the summer that it would seem ad- 
visable to start poisoning, but the plants in these fields may have 
reached the limit of their production on that soil, thus being unable 
to take advantage of any protection from weevil attack. This is 
particularly true of many of the sandy soils upon which the plant 
produces a very quick crop of cotton and then matures and stops 
fruiting at an early date. This point is further complicated by vari- 
ations in the habits of the different cottons. For example, certain 
varieties of cotton have what is ordinarily termed a “determinate ” 
growth. They make their crop early and then stop fruiting alto- 
gether. Consequently, any poisoning under such conditions, regard- 
less of the degree of weevil control secured, is a useless expense unless 
undertaken for the protection of the young bolls already set on the 
plants. 
In still other cases there are soils of such low potential productivity 
that even if the entire crop were saved from destruction by the 
weevil its value would still not justify the expense of poisoning. 
To summarize the results of the experiments which can be tonsid- 
ered of real value in this connection, it may be said that the actual 
gains in seed cotton per acre have ranged from about 200 to 1,000 
