80 ANNUAL H Kl'OKT- UK DKl'AK TM KNT UK AGKIC l/LT URE, 1940 
( (ITTON KLKA HOTPKR 
There was a light infestation of the cotton flea hopper in Texas 
in r.KV.) and con-e<jtient ly the gains from control experiments were 
low. In the 1-acre field* plot - at Port Lavaca tin 1 highest gain was 
100 pounds of -eed cotton per acre a> compared with a maximum 
gain of 680 pounds in 1938 when a heavy flea-hopper infe-tation 
existed. In the Waco, Tex., experiments the highest gain was 189 
pounds of seed cotton per acre from dusting with a 1 to 2 mixture 
of calcium arsenate and micronized sulfur applied at the rate of 
T'j pounds per acre per application during the middle of the day 
while the cotton was dry. In that section, where high winds and 
light dews make dusting conditions unfavorable, micronized sulfur 
was more effective than the ordinary 325 -mesh ground sulfur when 
used alone or in mixtures with calcium arsenate. Wettahle micro- 
nized sulfur applied as a spray at the rate of 15 pounds per acre 
also »';ive promising results although the infestation was too light for 
definite conclusions to be drawn from this method of application. 
Four varieties of cotton with different plant and growth charac- 
teristics were planted in Latin squares at Port Lavaca and at Waco 
for a study of resistance to the flea hopper. The average seasonal 
infestation at both locations was more than twice as high in the 
most susceptible as in the most resistant variety. There was also a 
marked varietal difference in the injury by flea hopper- in untreated 
cotton and some indication that insecticides were more effective 
against the flea hopper on some varieties than on other-. 
HEMIPTEROUS INSECTS 
The investigations on the control of hemipterous insects attack- 
ing cotton have caused the grower- of Arizona to become very insect 
conscious and aroused a great demand for information on dusting on 
a large scale applicable to their conditions. Although power-driven 
ground dusters would probably be more economical to operate, the 
irrigation schedules interfere seriously with their use, as on some soils 
ground machines cannot be used for several day- on account of muddy 
conditions. When cotton reaches ii^ maximum growth during the 
latter part of the season the insect population is usually at i 1 .- peak 
and material damage, to the plants IS caused by the machine. Al-o 
sudden migrations of insects from other crops to cotton require quick 
applications of insecticides oyer large acreages. The use of airplane 
dusters promises to meet these requirements. During 1939 a large* 
scale airplane experiment was conducted cooperatively with growers, 
whereby they were to furnish the airplane and insecticide and the 
Bureau the entomological Supervision, to obtain information on the 
efficiency, practicability, cost, and minimum populat ion- of insects that 
would justify airplane dusting. 
The species present were the same as those reported last year. How- 
ever, Uysdercus minvulus Hussey was very scarce and Oreontuutes 
femoralis Van 1). was much more abundant than in the past, greatly 
outnumbering the two species of Lyqtu w hich were formerly the most 
abundant and destructive mirids, Light fields of 40 or 80 acres were 
selected repre-ei 1 1 a 1 1 ve of area- that were lightly and heavily in- 
fested in previous years. Half of each field was dusted with 7'- per- 
cent of pari- green and 92^ 2 percent of -ul fur and half left untreated. 
