
- 19 - 
per cent in the case of stems containing one infested joint, 31.6 per cent 
for those containing two infested joints, and42.l per cent for those con- 
taining three infested joints. According to these findings, the reduction 
in yield for the whole field, taking into consideration the relative numb— 
ers of each kind of infested stem in the field, was 21.1 per cent." 
COTTON INSECTS 
In general the infestation by the cotton leaf perforator (Buc- 
cultatrix thurberiella Busck) is much lighter this year than last, accord- 
ing to T. C. Barber, Calexico, Calif., who says: "This is mainly due to 
the -improved methods which have been adopted this year, including plowing 
of the land, the use of imported high-class seed, thorough early cultiva— 
tion, etc. However, the excessive heat also appears to have had a certain 
restraining effect upon the infestation. * * * During the last few days 
of July, there were indications of an increase in general infestation 
corresponding to a drop in temperatures to normal conditions." 
Mr. Barber also reports: "For the second month the results at- 
tained in the use of a sticky flight screen eregpted (at Calexico) for the 
purpose of attempting to capture perforator moths in flight were entirely 
negative, not a single moth of this species having been caught to date. 
As the screen is located on the corner of a cotton field in which perfora- 
tor infestation has been observed all spring, it is evident that the 
method is valueless for the purpose for which the screen was erected," 
Studies on the parasitism of the cotton bollworm (Heliothis ob- 
soleta Fab.), as reported by E. W. Dunnam, College Station, Tex., revealed 
that the natural parasitism of Heliothis eggs by Trichogramma minutum 
Riley was practically nothing on either corn or cotton. Mr. Dunnam says: 
"The highest egg count per 100 silks never ran above 749 eggs in any sur— 
vey. This lack of concentration was probably responsible for the lack of 
egg parasitism. * * * Several releases of parasites were made in various 
cornfields. Weekly records were kept around points of releases and at 
varicus distances. Thus far, there is no evidence in favor of artificial 
‘parasite releases. This was probably due to the lack of eggs to be para— 
sitized, and natural parasitism and predators. It was found that if the 
release capsules were not placed in fields until the day before the para- 
sites began to emerge, the capsules would not collapse." Collapse of the 
capsules seems to come after their exposure to the weather for 3 or 4 
days. 
W. S. Cook, Tallulah, La., has been continuing work on the arti-~ 
ficial inoculation of cotton plants with substances in the heads of vari- 
‘ous plant~sucking: insects,.including the cotton flea hopper (Fsallus 
seriatus Reut.,)} and the tarnished plant bug (Lygus pratensisL.) to see 
whether lesions could be produced similar to those characterized by 
"hopper damage" as occurring on cotton in the field. He has made some 
attempts to extract the salivary juice from the insects, but so far the 
