I would let them be for now, you will know for sure next spring. If they leaf out next spring they will likely pull through fine. Repeated exposure definitely weakens the tree and can definitely kill them. My farming neighbor has had drift hit my ornamental pear in my front yard almost yearly and somehow it hasnt died, though it certainly doesnt look well.
Let me preface what I am about to say by this, I come from a farm family, my family has farmed since 1870. My family still farms. I understand the value of agriculture and that in some states, like mine, Ag makes up a huge portion of income for a lot of families. Now...... I am freaking fed up with the lack of interest and concern shown by today's farmers towards anyone who doesnt farm exactly like them and grow the same crops as they do. Herbicide drift has cost me money and will likely cost me money in the future (working towards reducing that odds). Around here you will be pretty much black balled if you complain about a farmer. Yet they damage other folk's property with drift and think nothing of it. They have created a nightmare with weed control as they have created a few different weeds that are now resistant to the more user "friendly" herbicides, because of improper usage in the past. The only option is to genetically modify crops so that they can spray harsher and harsher herbicides and yet not kill their crop. Sadly the rest of us pay the cost as these harsher herbicides drift affecting our crops, trees and plantings more and more. I filed a complaint against one of my neighboring farmers this year as he has repeatedly sprayed when wind conditions are not favorable for me. I am listed on the DriftWatch Program so if he had done his due diligence he would know not to spray when conditions are likely to cause drift towards me. Our state Ag inspectors told me when I filed my complaint that last year they had 2 inspectors for the entire frickin state of Nebraska, and they were back logged a solid 6 months. Not sure if the crop growing associations such as corn and soybeans have lobbied to reduce funding for those inspection programs. Since those inspectors probably have a negative impact on their members.
I know my attitude towards using herbicides has definitely changed over the last few years. I try and rely less and less on post emergence applications and more on pre-emergent as it has a lot less negative effects on other things.
Rant over.
