FRUIT THINNING WITH CHEMICAL SPRAYS 



of the Northwest. Where DN No. 1 was used in central Washington 

 in 1948 (a cool, humid bloom season) it resulted in rather seriously 

 malformed and russeted fruit. This type of injury with this material 

 had not been observed before or since the 1948 season. Southwick 

 and Weeks (4-0), working in Massachusetts, have also reported fruit 

 russeting with DN No. 1. 



The greatest amount of experimental work to date has been per- 

 formed with Elgetol, and at present (1950) this material is being used 

 commercially more than any other form of dinitro chemical for fruit 

 thinning. Further work may prove other forms of dinitro chemicals 

 preferable to those now being used. Limited work with the triethanol- 

 amine salt of dinitro-ortho-sec-butylphenol (DN No. 289) has shown 

 promise as an agent for thinning fruit, but at present this material does 

 not seem to have any advantage over those mentioned above. 



Time of Application and Mechanism of Action 



MacDaniels and Hildebrand (28) found that Elgetol at 0.25 percent 

 (1 quart per 100 gallons) concentration completely prevented pollen 



Table 2. — Effectiveness of Elgetol thinning sprays applied at 

 different stages of bloom development on several varieties of apples 

 in specified areas 



Variety 



Amount 



of 

 Elgetol 

 per 100 

 gallons 



Date sprayed 



Bloom stage 



Fruits 

 per 100 



blos- 

 soming 



spurs 



Reduc- 

 tion 

 in 



fruit 

 set 



State and 

 literature 

 reference 





Pint» 



fo 



11.6 

 1.6 



1.6 







1,6 



1.6 







1.2 



1.2 







1.2 



1-2 







1.2 



1.2 







1.2 



1.2 



1.5 

 1.5 







1.4 



1.4 







1.0 



1.0 







1.33 

 [1.33 







Number 



48 

 47 

 44 

 27 

 52 

 42 

 30 

 26 

 13 

 10 

 23 

 5 

 5 

 56 

 34 

 37 

 49 

 22 

 33 

 107 

 81 

 87 

 73 

 49 

 56 

 42 

 24 

 26 

 42 

 33 

 25 



Percent 



2~ 



8 

 43 



~~19~ 



42 



""56" 



62 



""78" 

 78 



""39" 

 34 



""55" 

 33 



"""24" 

 19 



"""33" 

 23 



""43" 



38 



" _ 2l" 

 40 





Wealthy .... 



April 29, 1941 

 April 30, 1941 _ 

 May 1,1941_ 



35 percent open _ 

 75 percent open- 

 Full bloom 



Hudson Val- 

 > ley, New 

 York (20). 



Do 



May 11,1941. 

 May 14, 1941 _ 



75 percent open- 

 Full bloom 



1 Western New 

 York (#6>) . 



Y ork Im- 

 perial. 



May 4,1943. 

 May 6, 1943_ 



Full bloom 



Early petal fall. _ 



1 West Vir- 

 j ginia (4) . 



Do 



Yellow 



May 1,1943_ 

 May 4,1943- 



Full bloom 



Early petal fall. _ 



[ Do. 



Trans- 

 parent. 



April29,1943_ 

 May 2, 1943_ 



Full bloom 



Early petal fall. _ 



1 Do. 



Grimes 

 Golden. 



May 2, 1944_ 

 May 4, 1944_ 



Full bloom 



Early petal fall. _ 



t Do. 



[Washington 



J (5). 



Golden 

 Delicious. 



May 3, 1945_ 

 May 5,1945. 



Full bloom 



Early petal fall.. 



Winesap 



April 30, 1945_ 

 May 2, 1945. 



Full bloom 



Early petal fall _ _ 



Do. 



< 



Do 



May 3,1945. 

 May 5, 1945_ 



Full bloom 



Early petal fall. . 



Do. 



< 



Do 



May 2, 1945_ 

 May 4,1945. 



Full bloom 



Early petal fall. _ 



Do. 



