24 BULLETIN" 256, U. S. DEPARTMENT OF AGRICULTURE. 
As shown in Table III, two applications of arsenite of zinc, at the 
rate of 2 pounds per 100 gallons plain water (plat 7) or dilute lime- 
sulphur solution (plat 1), gave practically the same results as one 
application at the rate of 4 pounds per 100 gallons (plat 3), being 
sufficient in each case to kill the katydids and insure approximately 
100 per cent sound fruit. Two applications of arsenate of lead, at 
the rate of 4 pounds per 100 gallons plain water (plat 9) or dilute 
lime-sulphur solution (plat 4), were practically as effective as the 
arsenite of zinc and gave just as good results as when used at the 
rate of 8 pounds per 100 gallons with but one application (plat 6). 
The addition of lime-sulphur to the arsenicals, besides being abso- 
lutely essential where it is desired to control both katydids and the 
citrus thrips, increased the adhesive quality of the arsenicals and 
facilitated their even distribution over the leaves and fruit. This 
was especially noted after a slight rain, occurring May 25, when the 
combination sprays appeared to be very little affected. Lime- 
sulphur solution itself without the addition of arsenicals proved 
deterrent to the katydids and measurably reduced the amount of 
injury to the fruit. It also, therefore, appears to have some insec- 
ticidal value against these insects. 
RECOMMENDATIONS. 
On the basis of the foregoing results the writers make the following 
recommendations for the control of katydids on oranges in the San 
Joaquin Valley: 
1. Two applications of arsenite of zinc at the rate of 2 pounds per 
100 gallons of water; or, 
2. Two applications of arsenate of lead at the rate of 4 pounds per 
100 gallons of water. 
The first application should be made, at the latest, immediately 
after most of the petals have fallen; the second application, from 10 
days to 2 weeks after the first. If it seems desirable to spray for 
the citrus thrips also, lime-sulphur should be added to the above at 
the rate of 2 gallons per hundred, and a third application of lime- 
sulphur only, at the same dilution, should be made about two or 
three weeks after the second. 
The cost of spraying will vary somewhat according to size of 
trees, cost of labor, team hire, insecticides, etc., but with ordinarily 
good management will not exceed $5 per acre. 
WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915- 
