68 ANNUAL REPORTS OF DEPARTMENT OP AGRICULTURE, 1936 
that bad been treated with manure for 10 years showed an Increase In the 
Dumber of b< ii animals, both of the root-feeding and saprophytic types, due to 
jiii increase in food supply and Improvement in soil structure. The data indi- 
cate thai the control of the root-rot fungus by manuring was brought about 
Independently <>i' the soil animals present 
THURBBRIA WEEVIL 
The droughts in Arizona during recent years have tended to reduce the cum- 
bers of the Thurberia weevil. Studies of this Insect removed from Thu 
.•Mid bred exclusively on cotton for the last :> years indicate that it Is not likely 
to become a serious cotton pest under Arizona conditions. The danger of Its 
spread Into cotton-growing areas may be greatly reduced by the destructi 
wild Thurberia plants In the areas adjacent to and draining into the cotton- 
growing districts. 
WORK IN PUERTO RICO 
The production of sea island cotton in Puerto Rico, once an Important indus- 
try, has been discontinued in recent years, partly because of the damage caused 
by the pink bollworm. Studies of the causes of the heavy damage by this pest 
were begun in September 1935 to assist in the rehabilitation of cotton growing 
on the island, special attention has been given to the host plants of the pink 
bollworm, to the formation of the long-cycle or resting-stage larvae, produced 
and continuing through the season when cotton is not available for breeding; and 
to the duration of this long-cycle stage. The wild cotton (plants escaped from 
cultivation) that grew abundantly in waste places and was the most Important 
reservoir for the carry-over of larvae of the pink bollworm has now been almost 
completely eradicated by the Puerto Rico Emergency Relief Administration. 
The seed pods of the trees Montezuma speciosissitna and Thespesia populnen, 
commonly used for ornamentals and roadside plantings, were found to he the 
most Important alternate hosts, although other plants are attacked. The forma- 
tion of resting-stage larvae which continue for several months was definitely 
established. A study of the climatic conditions and agronomic practices in the 
main cotton sections on the north and south coasts shows the feasibility of 
having uniform planting and closed-season dates for cotton in both areas. Col- 
onies of the pink bollworm parasites Exeristes roborator, Microbracon kirk- 
patricki, and ChelOflUS Wackbumi were furnished by the Presidio, Tex., labora- 
tory for liberation. Recoveries have been made in the held, although it is not 
definitely known if these parasites have become established. 
Considerable information has been obtained on a number of other Insect 
pests <»f cotton, some of which do not occur on the mainland. 
PINK BOLLWORM CONTROL 
The most outstanding development in the pink bollworm situation is the 
fact that no new infestations were found during the Inspection oi the 1088 
CTOp; furthermore, there was no recurrence of the pest in several areas still 
under regulation. These areas Include all ^^\' Georgia and Florida and that 
p. mi of Texas ami New Mexico is known us the Western extension. As two CTOP 
seasons have elapsed since the original infestation was found in southern 
Georgia in the 1933 crop, tins area has been released from quarantine restric- 
tions. The area actually found to be Infested in 1935 Is -mailer than at any 
lime sime the 1926 crop and is limited to the Rio Grande and Pecos Valleys 
of Texas and New .Mexico and the Safford area of Arizona. 
INSPECTIONS within REGULATED AREAS 
Intensive gin-trash Inspections were carried on in the regulated areas of 
southern Georgia and northern Florida. Machines were operated from about 
the middle of August until the end of October, at which time ginning was 
largelj Completed. All trash from the glnS in these areas Was inspected. Hot. 
drj weather caused the cotton to open rapidly, so that by the middle i)\' August 
most of the l.oiis were open. Before very much picking was done, however. 
rains Bet In and continued for several weeks. Picking was thus delayed, and 
in many cases cotton was stored or remained open In the fields several weeks 
before being ginned In many cases the tra8fa at the gins was rained on before 
