Doug from Southern Ontario writes
I have a single red delicious tree and was advised to use Sevin as a post-bloom insecticide to assist in the thinning process particularly in the difficult to reach upper branches. Although Sevin was the brand name suggested, I was actually told to use carbaryl.
Sevin Concentrate used to contain the active ingredient carbaryl, which is sometimes used for chemical thinning of apple trees. However, the new formulation with zeta-cypermethrin does not have that labeling and will not affect thinning. We do carry PROKOz Sevin SL Carbarly Insecticide, which is labeled to be used for apple thinning. We recommend consulting with an arborist before doing this treatment if you have done it before. This article from the Penn State Extension has great information about chemical apple thinning.
Answer last updated on: 04/10/2018
