ANM AL KKroliTS OF DKl'A KTMI:NT (JF AGRICULTURE, 1937 
:M('xican fruillly is more rcsi-staiiL to low tempera lures than are the other fruit- 
Hies so fur studied. 
The resistiiiiee of adults to low*- temi>eratures was studied with au instrument 
designed hy W. E. Stone which permits the reproduction of a continuous tem- 
jierature record taken in any locality. The exposure covered G days of cold 
weather during which the temperature ranged as low as liG.U° F. Only 30 i)er- 
tent of the young Hies used were killed and the remainder subsequently infested 
fruit in a normal manner. 
Spraying experiments with 4 pounds of tartar emetic and 20 i)Ounds of 
granulated sugar in lOU gallons of water gave promising results in reducing 
the populations of the ^lexican fruitlly, as high as UO percent reduction being 
obtained in one instance. Sprayed grapefruit trees held their croi) well on 
into June, whereas the entire crop fell from the unsprayed trees early in the 
season. 
In Hawaii low-temperature sterilization experiments with fruits infested by 
the Mediterranean fruitfly were continued. At 33° F. no larvae were able 
to mature to adults alter 10 days of exposnn'. At a tenipfraTure of SG.ri" no 
adults were obtained after an exposure of 12 days. The early stages of the 
meh.i.Ily appeared more susceptible to low temperatures, since no adults were 
obtaL^^d 30.5° after an exposure of 10 days. In the treating room there was 
a fluctuation of 1", so that for short periods the larvae were held at slightly 
below 30°. 
Studies were conducted with papayas to determine their susceptibility to 
nttack by the melonfly. Both ripe and commercially picked pajiayas proved to 
be definitely susceptible. 
Studies with screen barriers against the drift of melonflies into cucumber 
plots have shown a definite reduction in infestation. The barrier cost, however, 
has not been offset by the returns. More promising results from the monetary 
viewpoint were obtained with a nicotine spray. 
Studies on holding fruits infested by the Mediterranean fruitfly in sealed 
containers showed that 100 percent mortality of the early staiies of the insect 
can be obtained in this way, but effects of such treatment on sound fruits have 
not as yet been obtained. 
In Puerto Rico studies on low-temperature sterilization of fruit infested by 
the two .species of fruitflies Aiia.strepha su.spoisn Loew and .1. acidiisa "Walk, 
have been continued. Work at 32° F. has shown that 11 days of exposure at 
this temperature will prevent the early stages from maturing to adults. Later 
studies at 34° F. gave complete mortality of the early stages after exposure of 
33 days at this temperature. Studies at 36° F. were inaugurated and show 
that larvae exposed to this temperature for a period of 1." days are still able to 
form puparia. No adults, however, have so far been obtained after an exposure 
of 12 days. 
Sterilization studies with fhe vapor-heat process, exposing fruits to 110° F. 
for 8 hours with an approach period of 8 hours before the temiKn-ature of 110° 
is readied, sliowed that the Puerto Rican species of fruitllies require a .^lightly 
longer period for a complete kill to be obtained by this method than does the 
Mediterranean fruitfly, since there were a few survivals after 8 hours. 
MEXICAN FRUITFLY CONTROL 
INFESTATIONS 
Traps were used extcMisively on this project in Texas to determine the extcMit 
of the adult i)opulatiou of tlu^ Mexican fruitfly {Awistrcplin ludcns Loew). Few 
flies were taken before the first (»f the year. In January, however, it became 
ai)i)arent that theie were many more flies in the area than during any iirevious 
season, and that if conditions remained favorable, larval infestations might 
become general. The number of flies recov<M-ed from traps continued to mount 
throughout February, l)ut no infesl(Ml fruit was found until tt>ward the closr of 
the month. Eai'ly in March the condition changed radically. Relatively few 
flies were trapixMi. but larval infestations were found in all districts. In April 
the fly population again mounted, and the numbtM* of larval infestations 
decn^ased. In M:\y only a small amount of infested fruit was found during the 
tree-to-tree insix'cfion work, and none was discovered in June. Throughout 
these 2 months the fly cati'h contiinied to decline to a point where oidy four fli<*s 
were trai)p(Ml the latter half of June. 
