22 BULLETIN 256, U. S. DEPARTMENT OE AGRICULTURE. 
Plats 1, 2, 4, and 5 received two applications containing lime-sulphur 
and arsenicals and one application of lime-sulphur alone ; plats 3 and 6 
received one application containing both lime-sulphur and arsenicals 
and two applications of lime-sulphur alone; plats 7, 8, and 9 received 
only two applications of arsenicals alone. The chief purpose of adding 
lime-sulphur to the sprays was to make them effective against the 
citrus thrips. The third application was directed solely against this 
insect, only two applications of arsenicals being made in any case. 
The applications were timed, also, partly with a view to controlling 
thrips as well as katydids, and the dates of beginning were May 22, 
June 3, and June 24, respectively. 
Results. 
The efficiency of the sprays in killing katydids was determined by 
a comparison of the number of living insects, occurring in the sprayed 
and unsprayed blocks some days after spraying was completed. 
Arsenite of zinc at the rate of 2 pounds per 100 gallons killed 93.1 
per cent of the fork-tailed katydids and 100 per cent of the angular- 
winged katydids. Arsenate of lead at the rate of 4 pounds per 100 
gallons killed 100 per cent of the insects in each case. 
The results of the season's spraying work were principally mani- 
fested in three ways: (1) By preventing a complete loss of a certain 
amount of fruit by dropping; (2) by almost complete prevention of 
katydid injury to the mature fruit and the leaves and reduction in 
the amoimt and severity of thrips injury; and (3) by improvement 
in the amount and vigor of growth of the sprayed over the unsprayed 
trees. 
PREVENTION OF DROPPING. 
During July, fruits injured by both katydids and thrips were very 
conspicuous on the unsprayed trees, at once attracting the attention 
when one entered the orchard. While in the orchard on August 9 
the senior writer noted that badly injured outside fruit was decid- 
edly less hi evidence on unsprayed trees than had been previously 
the case. The cause of this disappearance of fruit was soon found; 
it had fallen to the ground. By counting all the fruit on and under 
10 unsprayed trees it was found that 18.7 per cent of the crop had 
fallen from these trees. Examination of the fruit which had fallen, for 
the location of the insect injury, disclosed 62.8 per cent of it full of 
holes, while 83.3 per cent were severely marked by thrips. Many of 
these fruits had been eaten into near the point of attachment to the 
stems. However, much of the dropped fruit dining this period was 
caused by thrips injury, the most severe dropping due to katydids 
coming earlier in the season when very small fruits were chewed to 
pieces by these insects. At all e rents, the 18.7 per cent of dropped 
