2-4D preplant for corn already planted
Question: I finished planting corn late last week. First planted corn is germinated. I'm going to put down a pre-emerge application of acetochlor and atrazine. I also have some Dandelions in my strip-tilled/planted fields that I'd like to knock down or out at the same time.
Would I be safe to include a pint of 2-4D right now before emergence? Should I wait until after emergence but while the corn is still real small? Should I use glyphosate instead? I read conflicting reports on the use of 2-4D in this case. On the one hand, I believe, the label says you can burn down with it and plant soybeans 7-14 days later, but it would appear for corn the same recommendation would apply which doesn't make sense since 2-4D isn't a grass herbicide. I understand potential injury from a growth regulator herbicide, but is that mitigated as long as the actual spray doesn't hit the plant? Will it leach through the soil and harm the seedling? If so, how is 7-14 days enough?
Re: 2-4D preplant for corn already planted
2,4-D Ester...is an oil based type of dichlorophenoxyacetic acid. 2,4-D Amine..is a water based type. If you apply Ester...the chances of it being mobile enough in the soil to move into the germination/sprouting zone of the soil profile..is directly related to the amount of rain you get. If you get 2 inches of rain..you "might" see some germination problems from Ester...but the label says it is probably OK..and the crop will grow out of it quickly. If you apply Amine..and you have corn just planted and germinating and sprouting..you better hope you don't get 2 inches of rain..because it will curl the sprout up..and cause real problems. There is no completely safe way to use it. If you wait till the corn is spiking/sprouting...I would go with Dicamba. It's probably just a little gentler on sprouting corn than 2,4-D is. There is even a label for pre-emergent use for Dicamba on heavier soils..but it isn't any different than 2,4-D on sandy soils..it will, if rained in with "enough" rain..cause germination/sprouting problems. At any rate...a pint of 2,4-D..or a half pint of Dicamba..will not control your dandelions...but neither will a quart of generic Glyphosate. It will curl them up..and they'll look like they're dying...but the next spring they'll still be there (I'm talking about established dandelions..seedling dandelions are much easier to control). If you want to control them with the older types of products like 2,4-D and Dicamba or Glyphosate...the best way is a late fall application..right about after first frost..when they're moving sugars to the root.
If it were me..and I was trying to do what you want to do...(Which I have and probably will do again) I'd put a pint of 2,4-D Ester in the pre-emerge...hope it doesn't rain for 4 days..and by then..the amount volatilized would cut the amount available to be rained in to the seed. I don't think I'd let it worry me.