BUREAU OF ENTOMOLOGY AXD PLANT QUARANTINE 67 
PINK BOLLWORM 
In the pink bollworm investigations special attention was given to the estab- 
lishment of introduced parasites, the studies of varietal resistance, the factors 
influencing survival under field conditions, and control by cultural methods and 
insecticides. 
Microbracon Mrkpatricki appears to be the most promising of the parasites 
studied, and 122,000 of this species were liberated in Texas. Mexico, and Puerto 
Rico. Recoveries have been made in the fields where liberated, but establish- 
ment is still uncertain. Thirty-two thousand Chelonus blackbumi Cameron, the 
egg parasite introduced from Hawaii, were reared on the Mediterranean flour 
moth and the Angoumois grain moth and released in the Presidio Valley of 
Texas and in Puerto Rico. The Hawaiian pink bollworm strain of M. mellitar 
was not reared in sufficient quantities for field release, but in hibernation tests a 
winter survival of 80 percent was recorded, and this species seems promising. 
In the Egyptian strain of Exeristes roborator F. the sexes were about equally 
divided, whereas the European corn borer strain produced a much greater num- 
ber of males than females when reared on pink bollworm larvae. 
Although no varietal resistance was found in the nine varieties of cotton 
tested, the tests indicated the importance of early maturity in reducing pink 
bollworm damage. Further experiments are being conducted along this line in 
connection with spacing tests and withdrawal of irrigation water early in the 
season to hasten maturity. Examination for overwintering larvae in soil under 
plants that had been stripped of all fruit at various intervals during the fail 
corroborated the reduction in the overwintering soil population from the early 
maturity and destruction of the cotton stalks. The number of worms found in 
the fields with heavy soil and rank growth of cotton was much greater than on 
the lighter soils. Survival and spring emergence of moths were again much less 
where the bolls and trash had been buried and irrigated early in the winter than 
they were where any other treatment had been applied. 
Further improvements were made in the push-type tractor-operated stalk 
shaver and rake for cleaning fields. 
From the more promising of the insecticides previously used, barium lluosiU- 
cate, cube, annd cube-sulphur mixtures were selected for additional field-plot 
tests. All of these gave some control, as indicated by a reduction of the number 
of worms per boll, but none was very effective or satisfactory- 
HEMIPTEROUS INSECTS 
Investigations were continued in Arizona on the seasonal abundance and im- 
portance of the hemipterous insects attacking cotton, their host-plant relation- 
ships, and the methods for their control. At least 15 species were found to affect 
cotton. The most important of the boll-feeding group are the pentatomid bugs 
Euschistus impictiventris Stal, Chlorochroa sayi Stal, and Thyanta custator P., 
while the mirids Lygus hesperus Knight and Psallus striatum Reut. were the 
most injurious to squares. The fact that cotton is not the favorite food plant of 
any of the species studied complicates the problem. All of these insects migrate 
from other cultivated and wild host plants to cotton when these plants become 
unsuitable for food. Considerable variation in the amount of damage by the 
boll-feeding group was found in different districts of the State, ranging from 8 
percent of the bolls punctured in Pima County to 43 percent in Yuma County, 
the average for the State being 27 percent. Cotton from punctured bolls is 
stained and discolored, and as a result the entire crop of cotton in the Buckeye 
Valley in 1985 was reduced at least a full grade in value. Studies to differ- 
entiate the damage caused by the various species were made by confining each 
species separately in cages with growing plants. Good gains in yields were 
secured in plots dusted with a number of insecticides, and further tots are 
needed to determine the most efficient insecticide and details of methods of 
application. Thirty percent of the bolls confined with C. sayi and 20 percent of 
those confined with field-collected E. impictiventris developed boll rot, while tests 
with the western cotton stainer (Dysdercus mimulus Hussey) have all resulted 
negatively. 
ANIMAL FAUNA OF THE SOIL 
In cooperation with the Bureau of Plant Industry, studies were continued on 
the effect on the soil fauna of heavy applications of green and barnyard ma- 
nures applied for the control of cotton root rot. Periodic samplings from plots 
