30 BULLETIjST 959, U. S. DEPARTMENT OF AGRICULTURE. 



Season of 1918. 



In 1918 in a plat sprayed six times with arsenate of lead and fish- 

 oil soap at the usual strengths 77.36 per cent of the fruit was free from 

 worms, this being the highest percentage of worm-free fruit obtained 

 during the season. In two untreated plats, 8.43 and 24.08 per cent 

 of fruit were free from worm infestation. The use of fish-oil soap in 

 combination with arsenate of lead gave somewhat variable results. 

 The codling-moth trap was of little value as a supplemental control 

 measure. Arsenate of lead powder, one-half pound to 50 gallons, was 

 about as effective as when used at twice this strength. 



SUGGESTIONS FOR THE CONTROL OF THE CODLING MOTH IN THE 

 GRAND VALLEY OF COLORADO. 



The experience of the writers and others who are acquainted with 

 Grand Valley conditions indicates that the codling moth presents a 

 very difficult problem. As previously stated, there are two full 

 broods of larvae per annum and a partial third brood. The moth is 

 extremely prolific because of the warm dry climate, and, as a result, 

 the apples are exposed to large numbers of newly hatching larvae 

 practically every day during the development of the fruit. 



The primary object of spraying is to cover the fruit and foliage 

 with poison, and when this is properly distributed good protection 

 is obtained for a time. It is, however, quite impossible in commercial 

 spraying to coat completely all parts of the fruit, and further, as the 

 apple develops in size it gradually outgrows the spray residue. The 

 result is, that with numerous larvae seeking a place of entrance, some 

 will start feeding where there is no poison, gain entrance, and thus 

 produce wormy apples. It is not commercially profitable to spray 

 too many times during the season, but a sufficient number of applica- 

 tions should be made at such intervals as constantly to provide a pro- 

 tective coating of poison on the fruit, particularly when the larvae 

 are hatching in large numbers. 



As a result of the life-history investigations in the Grand Valley 

 and other places, it has been found that the development of the cod- 

 ling moth from the time of hatching of the first eggs of the season 

 does not as a rule vary to any great extent and that an average can 

 be struck which, over a series of years, would usually represent the 

 approximate development of the insect with sufficient accuracy for 

 spraying purposes. 



Some growers of the Grand Valley have attempted to ascertain 

 the time to spray by making observations in the orchard, such as 

 inspection of the leaves for eggs and of the fruit for newly entered 

 larvae. The writers are inclined to believe that this particular method 

 as practiced by the fruit grower is unreliable and frequently mislead- 

 ing, although regular and systematic inspections over a considerable 



