218 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



given to every tree in the dusted blocks on June 19 just after worm 

 entrance began. This application experienced only three rainfalls 

 until July 1st. The first of these three rainfalls was about .25 of an 

 inch, the second was about .51 of an inch and the third was .4 of an inch. 

 Furthermore this application of dust was made the day following a 

 rainfall of .75 and this may have something to do with causing the 

 dust to stick to the foliage more effectively than if applied during a 

 dr>^ period . Furthermore, it is probable that the period of entry being 

 bunched because of the lateness of the season had largely occurred by 

 July 1st, when a rain of 2^ inches fell completely removing the dust from 

 the trees. Under these conditions, the control obtained with the dust 

 was as good as that obtained with the spray. 



On July 9th the trees in the dusted block received an average of two 

 pounds each and those in the sprayed block 7.5 gallons each. This 

 spray was applied according to schedule and as can be seen from consult- 

 ing the chart occurred much earlier than it should have. As a matter 

 of fact, application 6 A should have been given about July 24th. Fol- 

 lowing this application of July 9th there were seven rains preceding 

 August 6th when a rain of 1 . 1 inches fell followed at very frequent intervals 

 by rains of considerable size, one of which amounted to 3.1 inches. 

 The entrance of side worms began about July 25th and 26th and from 

 that date on to August 6th, a matter of 1 1 days, it is fair to assume that 

 the dust was still on the trees in sufficient quantities to be an effective 

 factor in control. 



From August 6th on to near the end of the month, a period of about 

 25 days, it is fair to assume, in view of the rainfall, that the dusted 

 trees were practically unprotected. As a matter of fact, the dust 

 exerted less than one-half as much control of the codling moth of the 

 second brood as did the spray. 



Thus there appears a definite relation between the effects of the dust 

 and the distribution of the rainfall. It is also evident that the only way 

 in which the effect of rainfall can be evaluated is to know not only the 

 daily distribution of rainfall, but its daily distribution in relation to the 

 period covered by entry of the codling moth worms of the first and sec- 

 ond broods. 



No data with which the writer is familiar has shown decidedly as 

 satisfactory a control of the plum curculio on apple as has the liquid 

 spray, but the amount of data available on control of this insect by dust 

 applications on apple, taking the country as a whole, is decidedly limited. 

 There is no reason, known to the writer, to indicate that the effect of 

 rainfall on dust applications for codling moth will not apply with equal 

 force to dust applications for curculio. This relative ineffectiveness 



