22 BUIXETIN 1225, U. S. DEPARTMENT OF AGRICULTURE. 
The camphor thrips can be readily killed with a solution consisting 
of | pound of 40 per cent nicotine sulphate, 2 quarts of potash- 
fishoil soap, and 2 quarts of lime-sulphur solution to 50 gallons of 
water. This spray will kill all thrips which are hit by it. If it is 
applied when the insects are present on the foliage in the greatest 
abundance, it will reduce their numbers to a large extent. The 
addition of the lime-sulphur solution and soap gives the spray com- 
bination a greater penetrating power than the tobacco extract alone 
and this seems to be an essential quality. 
On August 15, 1921, a row of camphor trees was sprayed with 
this spray combination. The spray was most thoroughly applied 
at 200 pounds pressure and the trees were drenched both inside and 
out. The sun was shining brightly at the time and the temperature 
was about 90° F. A large number of thrips were in the buds and 
on the foliage, but of course many of them were also in the bark 
lesions. On the following day, August 16, an examination showed 
only 1 dead larva and no living thrips, either adults or larvae, on the 
buds or new growth. On August 19, four days after the spraying 
had been done, a very careful examination was made. No live 
thrips were found on the leaves or buds, but 1 living adult and 2 
living larvae were cut out of the limbs. Several dead adults were 
also seen, some in cracks and lesions and others on the limbs. There 
is no doubt that the spray killed all the adults and larvae that it 
hit, but of course some of the insects were so thoroughly protected 
in the bark lesions that they could not be reached. On August 
22 a further examination showed that practically all of the thrips 
in the buds had been killed. The examination showed only 1 live 
adult and 1 first-stage larva. It should be stated, however, that a 
heavy rain took place on August 21 which may have washed some 
of the insects away. On unsp rayed trees in adjoining rows not 
more than 10 feet away many times more living thrips were present 
than on the sprayed row. Prof. J. R. Watson (3) also has had 
satisfactory results in killing the insects with this spray. 
Although it is generally admitted that the nicotine in the fore- 
going combination spray is the killing agent, it appears that the 
addition of lime-sulphur solution produces a much higher mortality. 
On June 17 a row of camphor trees abundantly infested with camphor 
thrips was thoroughly wet, both inside and outside, with a spray 
containing 2 pounds of potash-fishoil soap and 1 pound of 40 per 
cent nicotine sulphate to 50 gallons of water. The morning was 
bright and the temperature high, and many thrips were feeding on 
the buds and crawling over the branches. On examination, within 
10 minutes after the spray had been applied, several of the thrips 
seemed to be paralyzed. They were on their backs and kicking but 
were still alive. The limbs were still wet and the thrips were held 
in the liquid. At the expiration of an hour, when the spray had 
dried, 7 dead adults were found, besides 5 living adults, 5 dead 
larvae, and 10 living larvae. Some of the live ones were kicking 
and it was doubtful if they would recover. After three hours, 
however, many living adults and larvae were present on the trees. 
At 1.30 in the afternoon, or five hours after the spraying, many liv- 
ing adults and larvae w^ere also found. There were not so many 
adults as in the morning, but some of them may have crawled back 
into the lesions in the bark. On the following day there appeared 
