36 ANNUAL REPORTS 01 DEPARTMENT OF AGRICULTURE, 1951 
Insecticidal Residues in Milk of Sprayed Dairj Cattle Determined 
Application of an emulsion spray containing 0.5 percent of dieldrin 
(«> ;i dairy cow resulted in excretion of a maximum of B.3 p. p. m. of 
dieldrin in milk, as determined by bio-assa^ bests by the manuiact urer 
<■! ilit- insecticide. A similar treatment of a cow, u-iiiL r a wettable- 
powder spray, resulted in a maximum of L2 p. p. m. Determinations 
of organic chloride in milk at the Kerrville, Tex., laboratory gave 
results comparable with those obtained by bio assay. 
The application of 0.03-percent lindane sprays to four dairy cows 
ni intervals of 10 days resulted in about (, .."» p. p. m. of Lindane in milk 
the day following treatment. The lindane content of milk by the 
third day was so low the data were of questionable significance. There 
was no indication that repeated treatments at LO-day intervals resulted 
in progressive increase in the amount of lindane in milk following 
each t reat ment. 
Treat incut of four dairy cow- with a 0.5-percent methoxychlor 
spray, as used for fly control, resulted in an average of about 0.15 
]). p. m. of methoxychlor the first week after treatment. During the 
second and third weeks the average in the milk was less than 0.05 
p. p. in. 
FRUIT AND NUT INSECTS 
Oriental Fruit Fly Investigated 
\\ ide variety of control measures found available 
The diversified activities in which the Bureau, the University of 
California, the California Department of Agriculture, the Hawaiian 
Agricultural Experiment Station, the Territorial Hoard of Com- 
missioners of Agriculture and Forestry, the Pineapple Research In- 
stitute, and thi' Hawaiian Sugar Planter-" Association have cooperated 
have developed a variety of control measures, some of which have. 
already been of direct benefit to Hawaiian farmer.-. Other measures, 
though >till being developed, have shown exceptional promise. The 
information being developed and that now available on method- for 
controlling the oriental fruit fly are important resources in readiness 
Bhould this fly evade the rigid controls set up to prevent its introduction 
into t he United State- mainland. 
Foreign parasites vigorously attack oriental fruit fly in Hawaii 
Control of the oriental fruit fly in Hawaii by introduced natural 
enemies has caused spectacular drop- in fly numbers in some areas 
and a definite decline in ot her-. 
More than 20 Species of parasites and 1 Species of predator have 
hcci i imported and released on the islands, t M" these, 011I3 three species 
of parasites are important thus far, one species predominantly so, 
( 'heck- .ni the effectiveness of the parasites show that it is now possible 
to find w dd lt 1 1 : 1 \ : i - that are entirelj free from the oriental fruit fly. 
The drop in guava infestation appears to be associated with a some- 
what general decline in il\ numbers. There is enough evidence, how- 
ever, to assume that reduction to the present infestation of guavas is 
!.!!:■■ I\ due i" parasite activity. A similar result cannot be fore-ecu 
ni tin time in the fly's other host fruits. Ii 1- not anticipated that 
