October, '12] safro: llme sulphur wash 385 



LIME-SULPHUR WASH AN INEFFICIENT OVICIDE FOR 

 CODLING MOTH 



By V. I. Safro, Oregon Agricultural College, Corvallis, Oregon 



Reports have occasionally been published showing a decrease in 

 codling moth infestation following applications of a lime-sulphur 

 wash. Until within the past few years a coating of lime-sulphur 

 upon insect eggs has generally been considered fatal. Only recently 

 have experiments shown a surprising lack of insecticidal power in 

 spraying aphid and red spider eggs with lime-sulphur mixtures. 



The Oregon Station, and doubtless other stations, has received 

 letters from growers claiming a reduction in codling moth infestation 

 due to applications of lime-sulphur. One grower even stated that 

 summer applications alone of lime-sulphur had kept the crop prac- 

 tically free from codling moth. 



This is a report of a short preliminary series of experiments con- 

 ducted during the fall of 1911, in order to obtain data on the possible 

 efficiency of lime-sulphur in killing the eggs of the codling moth. 

 From an infested orchard, more than two hundred apples were col- 

 lected upon which codling moth eggs had been deposited.^ These 

 were examined and only the apparently healthy eggs were used in 

 the experiment. 



Method of Facilitating Daily Observations. The small size of the 

 eggs and their inconspicuous color rendered their necessarily frequent 

 location and examination a rather slow process. A simple method was 

 devised that resulted in but a minimum loss of time in locating eggs. 



The side of the apple opposite the egg was cut to form a flat base. 

 Each apple, then, rested on this base with the egg (where but one was 

 present) on top. To still further facilitate location of the eggs and 

 provide for the ready location of several eggs on one apple, an arrow 

 was cut in the epidermis pointing to and but about one-fourth of an 

 inch from the egg. The arrow, upon exposure to the air, turned brown 

 and became quite prominent. It is interesting to note that the arrow 

 was a very convenient place for the recently hatched larva to begin 

 feeding. In fact, in almost every case, the young larva was found 

 feeding in the arrow. Each apple was placed upon a slip of paper 

 which bore the number of the apple and other data. 



Conditions of the Experiment. The experiments were carried on 



1 Of the 221 apples collected, 19S had one egg each, 20 had two eggs each, one had 

 three, and two had four eggs. In four cases the two eggs present on an apple were 

 partly superimposed, indicating two successive eggs from the same moth. 



