BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 13 
than 28 days at 45°. Complete kill of the melon fly was obtained 
after 7 days at 30° and 10 days at 37°. The low temperature storage 
thresholds for most Hawaiian fruits and vegetables are above 45°. 
This would prevent the use of a cold storage treatment except for 
snap beans, bell pepper, and possibly some varieties of avocado. How- 
ever, cold storage might be useful for many mainland fruits such as 
citrus, grapes, apples, and pears, which withstand long storage periods 
at the experimental temperatures. 
Mexican Fruit Fly Control 
Although practically all of the citrus trees in Texas were severely 
damaged and many of them were killed outright during the freeze of 
January 1951, those which remained made rapid progress toward 
recovery. There was a small fruit crop produced in the Mexican- 
fruit-fly-regulated area. This light fruit production made it possible 
to reduce field activities considerably. It was necessary to continue 
those activities that are essential to control the Mexican fruit fly and 
prevent its spread. Accordingly, traps were operated and inspections 
were made in Texas where warranted. Fruit was moved from the 
regulated area under the same type of supervision as during former 
seasons. 
During the season 1,400 groves were inspected for larval infesta- 
tions. About 2,000 traps were operated continuously throughout the 
regulated area. More than 62,000 fly trap inspections were made. 
Ordinarily, several hundred larval infestations are found each year 
and thousands of fruit flies trapped. During this period, however, 
due to the scarcity of the fruit and an early harvest, no larval infes- 
tations were found. Only a few fruit flies were trapped. 
Particular emphasis was placed on inspection of fruit being shipped 
to other fruit-producing areas, such as Arizona and California. Fruit 
designated for shipment to these States was inspected tree by tree 
before harvesting. Fly traps were operated in the vicinity of each 
grove to make doubly certain that no infested fruit was being moved 
which might cause an infestation in another fruit-producing State. 
The short citrus crop in Texas allowed the assignment of personnel 
to operate fruit fly traps in the small but important Louisiana citrus 
area. Men were also available to conduct some needed exploratory 
work along the Mexican border in the States of Tamaulipas, Sonora, 
and Baja California. These surveys were in localities adjacent to 
the citrus plantings in Texas, Arizona, and California, 
Along with their other duties, Mexican fruit fly inspectors were able 
to inspect 1,945 citrus plantings in the lower Rio Grande Valley for 
possible infestations of the citrus blackfly. No such infestations were 
found there. 
Parasites Survive DDT Sprays 
Further field studies were made of the effectiveness of the preda- 
ceous coccinellid beetle Stethorus punctum following DDT spray ap- 
plications in apple orchards at Yakima, "Wash. These studies con- 
firmed the observation, first made in 1950, that this species can survive 
two applications of DDT and still recover sufficiently to prevent late 
season economic damage by host mites. 
