My advice is to slow down a little and understand what you’re doing and set a strategy that will get the weeds under control. Which realistically will need to be a multi year strategy. There is no quick fix for a water hemp infestation.
Water hemp reproduces by setting seed heads on the mature plant. These seed heads contain millions of tiny seeds. The key to long-term water hemp control is to STOP the water hemp plants from maturing and producing seeds while you also focus on killing the new water hemp plants as they emerge from the seed that is in your soil already.
First off, let’s understand your herbicide options. Water hemp is resistant to Roundup (brand name for generic glyphosate), so spraying more glyphosate will NOT fix your problems.
Also, you need to understand that glyphosate, 2-4-D and other common herbicides are POST-EMERGENT. This means they only kill plants that are green and actively growing, they do NOT kill seeds in the soil. Spraying post-emergent chemicals on bare dirt just wastes chemicals, it will have NO effect on the seed that is lying dormant in the soil waiting to germinate.
2-4-D (2,4,D) – This is a BROADLEAF killer. It kills most things that are NOT relatives of the grass/grain family. 2-4-D will kill water hemp, but here is the issue–it can’t be used in any broadleaf crop like brassicas, soybeans, and clover/alfalfa because these are broadleaf plants.
2-4-D DOES NOT kill members of the grass/grain family including corn, wheat, rye, oats, etc.
Last thing to understand is your brassicas (radish, turnip, rapeseed, beets, are all members of the brassicas family() plot is dead. These plants are all killed by the frost, they do not re-emerge in the spring.
Strategy for this year:
– Soybeans are going to be the most difficult crop to grow in terms of water hemp control because you cannot mow them or spray them with 2-4-D, which is your only effective (reasonably available) chemical control. I would ditch the soybean idea for this year.
– I really would encourage you to look hard at the cover crop strategy of planting a clover blend. Why?
1. This option allows you to take your time in the spring and let the water hemp germinate, you can then control some plants by spraying 2-4-D and roundup (for other weeds) before you plant the clover.
2. As long as you can mow the clover plot before the water hemp sets seed heads, you will essentially grow the water hemp out of existence. Mowing i, IMO, a lot more desirable of a way to control weeds than is constant spraying. Just do NOT let it mature to set more seed heads. Also, clover makes it difficult for the water hemp to compete in that plot.
3. Clover is just an awesome food plot crop. There is never a time when deer will not eat clover. This is a staple deer food and very few crops can top clover’s tonnage per acre on a full-year basis. Corn isn’t even close to the tonnage of clover.
BTW, clover should always be planted with a nurse crop in the northern tier. Reply if you don’t know what this means or what to do.
For your brassicas plot (turnips/radish), I would cover crop this plot with oats. Control the water hemp by spraying 2-4-D as plants emerge.
Then in late June, spray gly to terminate the oats. Spray 2-4-D also if there is active water hemp growth. Then thoroughly disc the plot and plant a quality brassicas blend (like Midwest Monster’s Brassicas Bender! Hey, I had to…) and get it in no later than July 4.
This cover crop and summer tillage combined with weed control will do 2 things. It will kill germinated plants before you plant the crop and it will also provide a good crop, but even though you won’t be able to spray the brassicas, the water hemp that does germinate will be generally too late to form seed heads in most cases.
But take no chances! Carefully watch for water hemp and hand pull all plants before they form seed heads. Dispose of plants in a fire.
Now somebody’s probably going to come in with ideas about pre-emergents like atrazine or applications of (mostly licensed) over-the-top controls. This is fine if you know what you are doing AND can legally and safely get and use the chemicals. Most food plotters do not have this ability and should not be messing with licensed or restricted use chemicals that they don’t understand.
OVERALL GOAL: Do NOT allow ANY water hemp plants ANYWHERE in your plots to mature to the seed head stage! Walk the plots and pull them by hand. The few hours spent doing this will pay you back way more than hours and hours spent trying to solve the problem after the seeds have spread.
