Sevin carbaryl insecticide is NOT A BLOSSOM THINNER AND SHOULD NOT BE 
USED ANY TIME THERE ARE BLOSSOMS PRESENT.
Typical thinning applications ,should begin when the fruit as about 3-5 
mm in diameter or approximately 10 days AFTER bloom. Sprays should be no 
more concentrated than 2 X as the fruit must be covered for proper 
thinning. For Hard to thin varieties may may growers add a half rate of 
Natphalenic acetic acid.

Sevin will thin certain varieties such as red delicious very readily ~ 
1/2 pound active in 100 gallons  (1 part active in 1666 parts of water 
by weight?)
while golden delicious will take twice that amount for only fair to 
little thinning. Sevin ONLY thins apples, a kind of unique property.
Dan V in the NC Mountains USA

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