fOHCK^ 



ESSENTIAL 



to control persistent apple pest 



By ARTHUR I. BOURNE^ 



The Plum Curculio (greaf// 



THE PLUM CURCULIO is no 

 new pest to apple growers, 

 neither are recommendations to 

 combat it a novelty. Massachusetts 

 growers have been fighting the pest 

 for many years with different de- 

 grees of success. Nevertheless, this 

 species is still persistent, pernicious, 

 and resourceful enough to take 

 quick advantage of any loophole in 

 the control program or carelessness 

 on the part of the grower. 



From the results of research and 

 demonstrations by growers, it is evi- 

 dent that thorough and timely 

 spraying with proper materials of- 

 fers an effective and practical means 

 of control. The matter of timing is 

 one of the most decisive factors, 

 especially in regard to the early 

 growth of the fruit. 



Experiments carried on by Pro- 

 fessor Whitcomb of the Department 

 of Entomology have indicated that 

 fruits less than -\y^ of an inch in 



Left: Egg-laying and feeding scars on matur- 

 ing apple. Right: Young apple showing fresh 

 egg. laying scars. 



diameter are seldom attacked by the 

 Curculio and that injury does not 

 usually occur until apples reach that 

 size. 



No Universal Spray 



Growers who have mixed varieties 

 in their orchards discover not only 

 the above fact to be true but also 

 that different varieties have different 

 rates of growth. Thus, the young 

 fruit of some varieties become sus- 

 ceptible to Curculio injury earlier 

 than others, and a spray application 

 that gives excellent protection to one 

 variety may be only partially effec- 

 tive on another whose fruits increase 

 in size more rapidly. 



Tests of different spray materials 

 for Curculio control were made in 

 one of the University orchards. 

 Since the main variety in all the 

 plots was Rhode Lsland Greening, 

 the schedule of applications was 

 based on that variety following the 

 standard recommendations on tim- 

 ing based on temperature conditions 

 and rate of growth. A few trees of 

 Gravenstein, however, were present 

 in each plot and were sprayed at 

 the same time. 



Control Schedule 

 Recommended 



In the first collection of June 

 drops, counts indicated, in general, 

 that more Gravenstein apples were 

 damaged and more scars per fruit 



* Head, Department of Entomology 



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