Burndown Herbicide Programs and Weed Potential of Cover Crops

Rich HoormannEC Region Agronomist

Cover Crops and Weed Potential

• Rye• Wheat • Oats• Red clover• White clover• Lespedeza• Medics• Crimson clover• Other legumes

• Hairy vetch• Rape• Radish• Turnips• Winter peas• Brassica• Annual ryegrass• Summer annual grasses• Barley

Burndown Recommendations

No-Tillage burndown

HerbicideAnnual

ryewinter wheat Alfalfa

Crimson Clover

Red Clover

Hairy Vetch

Cover Crops

2,4-D 0 0 7 8 8 9

Aim 1 0 - - - -

Aatrex 6 6 4 3 5 7

Balance Pro - - - - - -

Bavnvel/Clarity 0 0 9 8 9 9

Basis - 5 5 5 5 5

Canopy EX - 1 4 5 5 -

Distinct/Status 1 1 8 8 8 8

Glyphosate 9 9 4 3 6 6

Gromoxone Max 7 6 4 9 4 8

Sencor 9 9 4 3 5 5

Septer 4 4 3 2 5 3

Spartan - - - - - -

Valor - - - - - -

Valor XLT - 6 4 4 4 -

Purdue University: Keith D. Johnson Forage Specialist

Annual Ryegrass Control• Tillage very effective• Mowing after

bloom/before complete seed development– Variable success– Some seed may be produced

• Plastic mulch smothered– Smaller easier to control

• Michael Plumer Natural Resources Management

Annual Ryegrass• Annual ryegrass volunteers are particularly undesirable in small grains,

so special care must be taken if they are part of your rotation. It can be controlled with tillage and/or herbicides. When tilling, plow under and disk as soon as conditions permit.

• The timing of herbicide applications is important to control ryegrass. Apply glyphosate at 3 pt/ac when the grass is 6-9 inches tall, day temperatures are > 50 F and the weather is sunny.

• A second or third application may be necessary to burn down ryegrass. • Simazine can be added to the tank mix but requires rain to activate, • Atrazine should not be tank mixed with other herbicides. Apply 14-21

days after the glyphosate. Atrazine also needs rain to activate. Cornell

Annual Ryegrass Control as Influenced by Rate and Application Timing

(graph adapted from Lins et al. 2005)

A. Ryegrass Application Timing

Glyphosate Rate (lb ae/A)

Roundup PowerMax

Rate (fl ozs/A)A. Ryegrass Control (%)*

Late Tiller 0.375 11 400.75 22 591.5 44 75

Second Node 0.375 11 29

0.75 22 461.5 44 66

Boot 0.375 11 430.75 22 671.5 44 86

Early Flower 0.375 11 580.75 22 791.5 44 88

*Results summarized across 6 locations in 3 states

More Thoughts on Annual Ryegrass (Lolium multiflorum) as a Cover Crop

• For control prior to corn, I would prefer to see a burndown herbicide like glyphosate or Gramoxone applied in combination with a photosynthetic inhibitor like Atrazine or Princep

• Annual ryegrass is one of the worst weeds of wheat production in the southeastern and mid-Atlantic states.

• Glyphosate-resistant biotypes of annual ryegrass occur in Mississippi and Oregon (and other countries as well).

Competition of Ryegrass

Michael Plumer Natural Resources Management

Determine Growing Point

Timing of Burndown & Adjuvant

Purdue University: Keith D. Johnson Forage Specialist

Hairy Vetch• WORDS OF CAUTION: Hairy vetch contains many hard

seeds with 15 to 30 percent common. These hard seeds can remain in the soil for several years, then germinate to develop into unwanted plants. Vetch is an especially serious weed plant in wheat. Thus it should never be permitted to mature and set seed.

• Glyphosate alone was relatively ineffective at controlling hairy vetch in corn;

• (1) Paraquat, (2) Paraquat + 2,4-D, (3) Paraquat + dicamba, (4) Glyphosate, (5) Glyphosate + 2,4-D, (6) Glyphosate + dicamba, (7) 2,4-D, (8) Dicamba.

• California Data

Hairy Vetch control

• 2,4-D, Banvel or their mixtures should be used • Note - if hormone sensitive crops are following

the cover crop, apply hormone sprays in the fall to avoid injury. OMAFRA

Rye

• Control on time. Incorporate before seed set. May regrow if tilled before boot stage, typically early May.

• Mow in the spring after all the tillers are past the boot stage but before the plants have headed out.

• For no-till planting, roll at heading.

Wet warm spring weather can cause quick growth and make incorporation difficult. Apply glyphosate at 1 lb/ac ai. for effective control of rye. Cornell

Balance is difficult

Thanks for your time