Planning Sugarcane Weed Control Programs for Cost and Value

January 23, 2005

By Jim Griffin                                                          Printer friendly version

Weeds reduce sugarcane yield or quality and can interfere with harvesting.  Herbicides are used to reduce or eliminate the negative effects of weeds on the crop.  Herbicides used in sugarcane are expensive and represent a major cost in the sugarcane production program.  Consequently in planning weed control programs in sugarcane there should be a return on investment for the herbicide expense.  Otherwise, your money was wasted.  The intent of this article is to provide a starting point for you to assess the weed problems in your operation and to plan weed control programs based on the herbicide cost and the value received.  This article will address only winter and spring weed control programs.  Cost effective weed control programs at layby will be addressed at a later date.

Before you can start planning your herbicide program you must first address the following questions.

• What herbicide program are you currently using and what is the cost of that program? 

• What value are you receiving from the herbicides being used and is the value of economic significance? i.e. does use of herbicides have value in increasing sugar yield, quality, and/or harvest efficiency

• Could herbicides be eliminated without an economic loss?

• How much are you willing to spend?

• What weed problems do you have and which weeds are most problematic?

Some herbicides to include Gramoxone Max, Weedmaster, Kambamaster, Brash, and 2,4-D have only foliar activity.  Other herbicides have only soil activity and they must be moved into the soil either by mechanical incorporation or by rainfall.  Soil active herbicides to include various trifluralin (Treflan) formulations, Prowl, and Pendimax are picked up by roots or shoots of seedling weeds.  Many herbicides to include atrazine, Direx/Karmex, DuPont K-4, Sencor, Spartan, and Valor have both foliar and soil activity.  In sugarcane it is common for two or more herbicides to be applied in combination to control both weeds that are present at application and also those that will come up after the application.  It is important to know that herbicide rates recommended by the LSU AgCenter and USDA are based on research and reducing herbicide rates can greatly affect the weed control obtained.

Weed Problems in Fields Right Now

Winter Weeds.  Weed pressure in sugarcane fields right now in January ranges from nothing to a mat of green vegetation completely covering the rows.  Winter weeds must be controlled to eliminate competition with sugarcane, to promote drying and warming of seedbeds, and to facilitate tillage operations.  Generally the winter weeds present in fields will include some combination of the winter broadleaf weeds buttercups, chickweeds, clovers, medics, vetch, common dandelion, cressleaf groundsel (yellow top), curly dock, cutleaf eveningprimrose, Carolina geranium, henbit, marestail, purslane speedwell, shepherdspurse, smallflower bittercress, sowthistle, swine cress, and Virginia pepperweed; and the winter grasses annual bluegrass, ryegrass, rescuegrass, and timothygrass. 

In general winter broadleaf weeds are easier to control than grasses.  Some broadleaf weeds, however, are more difficult to control than others.  Our research shows that if clovers, medics, vetch, or dock is present in sufficient quantity to justify treatment then Weedmaster, Brash, or Kambamaster should be used.  2,4-D, Gramoxone Max, atrazine, Direx/Karmex, DuPont K-4, Sencor, Spartan, and Valor are not as effective on clovers, medics, vetch, or dock, but have good activity on most of the other broadleaf weeds listed above.  A significant presence of ryegrass, rescuegrass, or timothygrass will require that Gramoxone Max be applied.   Remember that winter weeds are controlled to free emerging sugarcane from early season weed competition.  In some cases 100% weed control with herbicides may not be obtained, but control may be sufficient to maximize the yield potential of the crop.  As the temperatures increase in the spring winter weeds begin to flower and senesce.  Even partial control of winter weeds with herbicide will often speed up this maturation (dying) process.

Bermudagrass.  Consideration also should be given right now to bermudagrass.  Although not a winter weed, bermudagrass can be an aggressive competitor as sugarcane is emerging in the spring.  In the sugarcane weed control guide provided through the LSU AgCenter we are careful in using the word “control” with any herbicide for bermudagrass.  Suppression is a better term although we have seen excellent suppression/control in some cases.  Only DuPont K-4 and Command + Direx/Karmex are effective on bermudagrass and both are active only when applied prior to emergence of bermudagrass from the winter dormant period.  It is very important that herbicide be applied early (January-early February) if you expect to reduce bermudagrass competition.

Other Weed Control Considerations.  Winter weeds can be controlled in March at the same time that herbicides are applied to control of summer weeds.  For example, a combination of Prowl + atrazine + Weedmaster could be used in March.  Weedmaster will control winter broadleaf weeds and the Prowl and atrazine will control summer grass and broadleaf weeds that germinate as the soil temperature increases.  It is important that you question the value of herbicides being used.  Prowl would be needed to control seedling johnsongrass, itchgrass, and other grasses but what is the value of atrazine.  If tie-vines are the answer then you should ask yourself when tie-vines are a problem in your operation.  If tie-vines are more of a problem after layby then it might be better to wait and use atrazine or another herbicide after layby cultivation.

Herbicide Cost Comparisons and Winter/Spring Weed Control Scenarios

To help in planning your winter and spring weed control programs I have included a table with the costs of various herbicides used in sugarcane at the recommended rates.  These costs may not be exact but they will allow you a starting point to make cost comparisons.  Also provided are several winter/spring weed control scenarios for weed problems that you might have along with specific herbicide programs and costs.  In reviewing the winter/spring weed control scenarios consider the following important points:

• If clovers, medics, vetch, or dock is present at a level to justify control Weedmaster, Brash, or Kambamaster should be used.
• If ryegrass, rescuegrass, or timothygrass is present at a level to justify control Gramoxone Max should be used.
• If bermudagrass is expected to be a problem DuPont K-4 or Command + Direx/Karmex should be applied in January or early February prior to emergence of bermudagrass from the winter dormant period.
• If itchgrass (Raoulgrass) is expected to be a problem Prowl/Pendimax at the high rate should be used either alone or in combination with other herbicides.
• If frosted sugarcane regrowth is present such that herbicide contact with the soil surface would be prevented then remove standing residue by mowing and apply herbicide.  The crop residue should not interfere with herbicide activity.  In many cases winter weeds in the drill will be sparse which will reduce the herbicide inputs needed.  Plan your weed control program based on expected weed problems.

Herbicide costs for recommended rates of herbicides applied broadcast or on a band.  2005

Weed Control Scenarios for Banded Herbicide Application in Winter/Spring

Scenario #1 - Weed problems

Winter weeds: clovers, medic, or vetch and other winter broadleaf weeds

Summer weeds: itchgrass (Raoulgrass) and seedling johnsongrass

Scenario #2 – Weed problems

Winter weeds: clovers, medic, or vetch and other winter broadleaf weeds

Summer weeds: itchgrass (Raoulgrass) and seedling johnsongrass

Scenario #3- Weed problems

Winter weeds: clovers, medic, or vetch and other winter broadleaf weeds

Summer weeds: bermudagrass and other summer grasses

Scenario #4- Weed problems

Winter weeds: clovers, medic, or vetch and other winter broadleaf weeds; ryegrass, rescuegrass, timothygrass, and other winter grasses

Summer weeds: bermudagrass and other summer grasses