SOLUBLE POISONS IN THE POISONED BAIT SPRAY. 1 57 



soluble poison was used in one or more applications of the spray 

 and an insoluble arsenical in the other treatments, only such 

 details of the work of 1914, worthy of mention will be taken 

 up in the following discussion of the season's work of 19 15. 



Experimental area. As the poisoned bait has been found 

 to be more effective in the control of other species of Trype- 

 tidae in a well isolated orchard or in a large isolated area com- 

 posed of many non-isolated orchards, a description of the loca- 

 tion of our experimental area is necessary. A glance at the map 

 thaws that all of the apple trees indicated by dots were isolated 

 on one side by the Penobscot river, and a bay of this river, but 

 on the other sides apple trees were sometimes found at short 

 distances from the margin of the experimental area. A more 

 careful examination of the map shows that there are six or- 

 chards indicated by the following figures which represent the 

 number of trees in each orchard: 84, 31, 40, 57, 47 and 38. 

 The principal part of each orchard is situated above the figures. 

 A series of dashes indicates the boundary between two orchards 

 or separates an orchard from trees present in adjacent door- 

 yards. The residential district contained 274 apple trees scat- 

 tered in the different yards. The entire area covered about 

 cne square mile and contained a total of 571 apple trees. 



Since we bred the apple fruit fly from haws gathered near 

 Orono, Maine it was decided to spray all of the hawthorns 

 near the orchards, and also those located on a hillside along the 

 bay of the Penobscot river. Seedlings and crabapple trees near 

 the orchards were also baited. 



Care of orchards. The orchard which contained 84 trees 

 was sprayed on May 4, 19 14, with Scalecide to control the 

 oyster-shell scale. Seventy-five gallons of spray containing 

 4 \-2 gallons of scalecide were used. On May 23-25, a com- 

 bination spray consisting of dry powdered arsenate oi lead and 

 lime-sulphur was applied to control the tent-caterpillar, codling 

 moth and fungous diseases. On July 8, the combination spray 

 was again applied. Seventy-five gallons of the following for- 

 mula were used with each application of the spray : 



Dry powdered arsenate of lead. . 1 1-2 lb. 



Lime-sulphur 1 gal. 



Water 50 gal. 



