Unit 2: Weed Control for Corn, SB, & Sorghum. Unit 2 Objectives: Awareness of safety, proper use, and label warnings of pesticides Understanding of herbicide

Unit 2: Weed Control for Corn, SB, & Sorghum

Unit 2 Objectives: Awareness of safety, proper use, and label warnings of pesticides Understanding of herbicide application methods Preemergence application Postemergence application Discussion of the effect of various tillage methods and its relationship to chemical efficacy

Unit 2: Weed Control for Corn, SB, & Sorghum Precautions Risks and benefits must be evaluated Crops, people, & environment Use should be restricted to minimize exposure Current Label Herbicides classified as Restricted Use Pesticides must be applied by a certified applicator Chemical may be toxic or pose environmental concerns

Unit 2: Weed Control for Corn, SB, & Sorghum Degree of toxicity indicated on the label by a Signal Word Danger-Poison and Danger high toxicity hazard Warning moderate toxicity Always use personal protective equipment as recommended on the label for safety Be aware of drift potential, especially near residential areas Environmental Hazards Groundwater advisories must be observed Toxicity of fish/wildlife will be listed on the label

Unit 2: Weed Control for Corn, SB, & Sorghum Proper Herbicide Use Apply only to approved crops Use proper rates Apply at the proper time Proper use will decrease risk of illegal residual, and environmental pollution Be aware of proper harvesting or grazing withholdings

Unit 2: Weed Control for Corn, SB, & Sorghum Proper Equipment Use Spray tanks should be clean and free of other residues Especially critical when spraying postemergence herbicides Sprayer should be correctly calibrated and adjusted before adding herbicide to the tank Follow recommendations on the label

Unit 2: Weed Control for Corn, SB, & Sorghum Drift Precautions Apply on calm or light wind days only Be aware of wind direction and residential areas, ornamental crops, etc. Some chemicals are very mobile, and effects can be observed far from the application site Protecting the Crop Do not apply to stressed crops

Unit 2: Weed Control for Corn, SB, & Sorghum Understand crop sensitivities Crop size Climatic conditions Previous injury from diseases, insects, or other chemicals Proper Recropping Interval Understand chemical carryover and how it can affect the next crop Soil texture, organic matter, soil pH all may affect persistence

Unit 2: Weed Control for Corn, SB, & Sorghum Proper Storage of Herbicides Store in original, labeled containers in a secure place Keep away from kids, livestock, etc. Proper Disposal Pressure wash, or triple rinse containers Properly cleaned containers may be recycled, or be acceptable in some landfills Mini-bulk returnable containers are desirable Use caution if you are going to burn

Unit 2: Weed Control for Corn, SB, & Sorghum Cultural and Mechanical Weed Control Practices that aid in weed control Adequate seedbed preparation Adequate fertilization Crop rotation Proper planting date Optimal row width Optimal seeding rate

Unit 2: Weed Control for Corn, SB, & Sorghum Planting in relatively warm soil helps the seed emerge quickly and compete with emerging weeds 1 st 3-5 wks. are critical for good weed control in corn and soybeans Crops tend to compete very well after this point Narrow rows can help Squeezes out weeds Puts more pressure on herbicides for weed control If control is inadequate it is better to leave room for cultivation

Unit 2: Weed Control for Corn, SB, & Sorghum Row cultivation Can control when weeds are small Smothers weeds Careful adjustment to minimize crop injury May not be necessary if herbicide controls weeds adequately, and no aeration is needed

Unit 2: Weed Control for Corn, SB, & Sorghum Herbicide Incorporation Reasons for incorporation Minimizes depending on rainfall May improve control of some weeds Minimize surface losses Distribute herbicide uniformly in the top 1-2 of soil Suggested depth of operation for proper incorporation is 3-4

Unit 2: Weed Control for Corn, SB, & Sorghum May require two passes for best operation Second pass should be at angle and no deeper than first pass Proper application and incorporation minimizes crop injury and carryover problems Uniform distribution depends on type of equipment, depth of operation, speed of operation, soil texture, soil moisture Placement deeper than 1-2 may dilute the herbicide and reduce effectiveness

Unit 2: Weed Control for Corn, SB, & Sorghum Field Cultivators At least 3 rows w/ sweeps 7 or less spacing between sweeps Level and operate at 3-4 depth Minimum 5 mph ground speed Tandem Disks Blade diameter of 20 or less 7-9 blade spacing 3-4 operating depth

Unit 2: Weed Control for Corn, SB, & Sorghum 4-6 mph ground speed Want to move soil full width of the blade space Slower speed or lack of leveling device can cause streaking of herbicide Combination Tools Advantage is they can handle more surface residue More uniform one-pass incorporation than disk or field cultivator No better than two passes w/ one of the other tools

Unit 2: Weed Control for Corn, SB, & Sorghum Chemical Weed Control Several factors to consider when planning weed control: Soil Tillage program Crops Weed problems Management operations

Unit 2: Weed Control for Corn, SB, & Sorghum Herbicide performance depends on: Weather Proper selection Application Minimize crop injury by using proper timing, application rates, uniform spraying Damaged crops are more prone to disease

Unit 2: Weed Control for Corn, SB, & Sorghum Unfavorable conditions Cool, wet weather Delayed crop emergence Deep planting Seedling disease Poor physical condition of soil Poor quality seed

Unit 2: Weed Control for Corn, SB, & Sorghum Next seasons plans must also be considered when selecting a herbicide program Corn/SB herbicides may have restrictive recropping intervals Check label for restrictions Can vary depending on the number of applications, timing, weather, soil, pH, etc. Ex. Atrazine restricts planting wheat after corn

Unit 2: Weed Control for Corn, SB, & Sorghum Persistent corn herbicides of concern for SB Atrazine Clopyralid (Stinger) Prosulfuron Persistent SB herbicides of concern for corn Imazaquin (Scepter) Chlorimuron (Classic)

Unit 2: Weed Control for Corn, SB, & Sorghum Weed Resistance to Herbicides Like insects, weeds have the ability to become resistant Weeds that have become resistant to different chemicals Pigweed, waterhemp, lambquarters, ragweed, cocklebur, and many others Management recommendations to help prevent herbicide resistance: Scout fields regularly & identify resistant weeds, keep records of weed populations to monitor/restrict their spread

Unit 2: Weed Control for Corn, SB, & Sorghum Rotate herbicides w/ different sites of action No more than two applications of the same herbicide in the same or successive years on the same weed w/ same site of action Use other strategies for weed control Especially critical when using herbicide tolerant crops Use multiple sites of action Tank mix Premix Sequential applications

Unit 2: Weed Control for Corn, SB, & Sorghum If practical use rotary hoeing and cultivation to control resistant weeds Hand weeding may be needed Herbicide resistant weeds can spread from nearby highways, railroads, utility areas etc. where total vegetation control may be used Herbicide Combinations In tank mixes, premixes, or sequential applications Can control more weed, reduce carryover, reduce crop injury

Unit 2: Weed Control for Corn, SB, & Sorghum May be able to split apply (same herbicide, two apps.) or sequential apply (two apps., different herbicides) Many combinations sold as premixes Harness Xtra Lightning Canopy XL Alleviates some compatibility problems associated w/ tank mixing Some are tank-mixed Allows adjustment for local problems Weed pressures Soil conditions

Unit 2: Weed Control for Corn, SB, & Sorghum Read and follow all restrictions when tank mixing Problems may occur when mixing emulsifiable concentrates w/ suspendible herbicides (liquid- flowable, dry-flowable) Proper mixing can minimize the difficulties (agitation, carriers, etc.) Must be cautious of accumulations in tank thoroughly clean after application

Unit 2: Weed Control for Corn, SB, & Sorghum Herbicide Rates Rates vary Time & method of application Soil conditions Tillage system Weed pressure Rates of herbicides in combination often are lower than the same chemical used alone

Unit 2: Weed Control for Corn, SB, & Sorghum Soil-applied herbicides Texture of the soil Amount of organic matter Specific recommendations for sandy soils Postemergence rates Size of the weed Species of weed Rates listed are broadcast rates Adjustment will be needed if a different method is used Formulations w/ different combinations may vary amount of active ingredient

Unit 2: Weed Control for Corn, SB, & Sorghum Postemergence Herbicide Principles Efficacy relies on foliar activity more than soil action Some may have both modes of action Rates and timing based on: Weed size The smaller the weed, the lower the rate Weather Penetration & action is higher in warmer weather and higher humidity Rainfall within 30 min to 6 hrs. can reduce effect

Unit 2: Weed Control for Corn, SB, & Sorghum Contact herbicides require more complete coverage Coverage increases as water volume and spray pressure are increased Nozzles that produce small droplets also increase coverage Usually 10-40g of water/ac. for ground application 30-60 psi suggested Flat-fan Hollow-cone nozzles May be more drift risk

Unit 2: Weed Control for Corn, SB, & Sorghum Crop size limitations often indicated on the label Minimize crop injury Maximize weed control Weeds smaller than the crop Basal-directed sprays may help minimize crop injury Place more herbicide on the weed Weeds taller than the crop Rope-wick Sponge app. Place herbicide on weed instead of crop

Unit 2: Weed Control for Corn, SB, & Sorghum Herbicide Adjuvants Crop-oil concentrate (COC) Spread herbicide across foliar surface Keep surface moist longer Aid penetration to the cuticle Increases mixing ability w/ water Petroleum or vegetable origin 1-3 pints/ac, or 1% by volume Better effect on postemergence app. compared to surfactants (both on weed and crop)

Unit 2: Weed Control for Corn, SB, & Sorghum Nonionic Surfactants (NIS) Cause spreading & wetting action by decreasing surface tension of water Mixes and spreads over waxy/hairy surfaces rather than form droplets Increase herbicide absorption into the weed .25 1 pint/ac., or 1/8 to % volume Should contain 75-85% active ingredient Ammonium Fertilizers Increase herbicide activity on weeds like velvetleaf Usually ammonium sulfate or Urea-ammonium nitrate (28%)

Unit 2: Weed Control for Corn, SB, & Sorghum 28 2-4 quarts/ac. Care should be used to reduce drift Drift-reduction agents/retardants Make sure you read the labels Conservation Tillage & Weed Control Minimum/ reduced till = any tillage system intentionally leaving crop residue on the soil surface Mulch tillage = leave at least 30% of the soil covered w/ crop residue

Unit 2: Weed Control for Corn, SB, & Sorghum Ridge & Zero tillage = no major tillage prior to planting Ridge till ideal for banding preemergence herbicides because cultivation is part of the plan No-Till Conserves soil moisture Conserves soil Saves fuel Increase timeliness of planting

Unit 2: Weed Control for Corn, SB, & Sorghum If tillage eliminated before planting, must control existing weeds either before, at, or after planting Greater reliance on chemical control of weeds Preplant or postplant soil-applied not incorporated Contact herbicides Soil-residual herbicides may eliminate need for knockdown at planting Early Preplant application may lead to more applications later in the season, or cultivation

Unit 2: Weed Control for Corn, SB, & Sorghum Todays equipment much better suited for reduced-till systems If done properly, crop residue should not effect herbicide distribution Early preplant app. or postemergence herbicides often provide adequate control Existing vegetation in corn and SB stubble is often annual weeds If small, easily controlled w/ contact herbicide that has some soil-residual activity

Unit 2: Weed Control for Corn, SB, & Sorghum Broadleaves 2,4-D or dicamba (Clarity) may be used prior to corn or no-till SB Observe planting delay recommendations Using Cover Crops What are people in IL using? What is the advantage of a cover crop? Hairy vetch Controlled w/ 2,4-D or dicamba before planting

Unit 2: Weed Control for Corn, SB, & Sorghum Winter rye or wheat Controlled by glyphosate(ex. Touchdown) prior to planting corn or SB How early should you spray? Varies depending on the season Dry late control can dry out soil too much for the crop Wet late control can help to dry out the soil Too much decomposing residue can inhibit the emergence/viability of the corn seedling

Unit 2: Weed Control for Corn, SB, & Sorghum Control of Perennial Sods Pasture land or CRP returning to production Perennial Grass Sods Glyphosate is most effective Fall application is best Mow in late summer Allow 6-8 growth before application Springtime application Must wait for 6-10 new growth Paraquat + atrazine (Gramoxone Max) also very effective

Unit 2: Weed Control for Corn, SB, & Sorghum Perennial Legume Sods Need 6-8 growth Do not take a spring cutting (will delay corn planting too much) When planting corn can follow with: 2,4-D Dicamba Glyphosate May apply glyphosate in the fall after the last cutting taken

Unit 2: Weed Control for Corn, SB, & Sorghum Fall Herbicide Applications Increasing in popularity in IL Two approaches: First approach Use soil-applied grass control herbicide to control annual grasses the following season Usually in very northern IL Helps to reduce workload in the spring Disadvantage Higher application rates

Unit 2: Weed Control for Corn, SB, & Sorghum Grass control may not last throughout following season Second approach Control winter annuals and perennials in no-till corn & SB Used by those who have problems w/ control in the spring Problem weeds Marestail, chickweed, purple deadnettle Form dense mat that makes burndown control difficult

Unit 2: Weed Control for Corn, SB, & Sorghum Insufficient spray coverage Fluctuation in spring temperature Timeliness of application Potential benefits: Prevent those mats that can interfere w/ planting and tillage Reduce vegetation where insects may harbor May allow earlier planting as soil may warm & dry sooner Prevents these weeds from producing seed, reduces future weed problems

Unit 2: Weed Control for Corn, SB, & Sorghum Fall application of chemical takes the chemical w/ the food to roots, so you get complete root control as well Can use higher application rates, if needed (some herbicides) Three approaches to controlling winter annuals with fall herbicide app. 1. Apply a herbicide w/ residual soil activity before most winter annual weeds germinate 2. Use a nonresidual (glyphosate, 2,4-D, paraquat) to emerged while they are small 3. Combination of these two strategies

Unit 2: Weed Control for Corn, SB, & Sorghum Goal is to reduce the detrimental vegetation pressuring the crop at planting Possibly eliminate need for spring burndown control May or may not be effective Herbicide selection App. Rate Weather Time of planting

Unit 2: Weed Control for Corn, SB, & Sorghum How should you decide if this is a good tool for your operation? If youve had a control problem in the past Things to remember: May not need fall application, if spring app. Provide satisfactory control Spring burndown may still be needed even if you spray in the fall

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Unit 2: Weed Control for Corn, SB, & Sorghum. Unit 2 Objectives: Awareness of safety, proper use, and label warnings of pesticides Understanding of herbicide