Program Approach to Weed Control

Dr. Becky Grubbs and Dr. Chrissie Segars Texas A&M AgriLife Extension Assistant Prof & Turfgrass Extension Specialists [email protected] [email protected] Outline

Proper Identification is Key Design an Integrated Approach ◉ Use Indicator Weeds to Your ◉ Advantage ◉ What are some of your biggest culprits? Start with Proper Identification Start with Proper Identification

bioninja.com Stem Characteristics

Hollow Milky

Square Modified or Specialized Stems Absent or Present Venation Leaf Shape Leaf Arrangement Types of Roots Inflorescences Unique to Grasses

Vernation Resources

AgriLife Extension Service

◉ County Programs Research and Specialist ◉ Programs ◉ AggieTurf Website

◉ aggieturf.tamu.edu Weed ID General Management ◉ Publications ◉ ◉ Integrated Weed Management (IWM)

“Integrated weed management (IWM) means integrating multiple methods to manage weeds, using the combination of practices that is most effective for solving the specific weed issue at hand.” integratedweedmanagement.org 1. Preventative Control

A conscientious effort to prevent the unnecessary introduction of weeds and weed seeds into a turfgrass area

Efforts made to prevent conditions which may lead to weed infestations in a turfgrass area 1. Preventative Control

Use caution when acquiring Grass seed Sod ◉ Compost ◉ Top Soil ◉ Other organic and soil duda-sod.com ◉ amendments which may ◉ contain seeds

planetnatural.com 1. Preventative Control

Avoid mulching clippings when weed pressure is ◉ significant, particularly when seed heads are present Clean mower between cuttings, and prior to moving ◉ from an infested to a non- infested area Mow at the highest ◉ recommended height of cut to crowd weeds for most grass species 1. Preventative Control Other preventative practices Annual irrigation audit Annual or semi-annual soil ◉ testing ◉

soiltesting.tamu.edu 2. Biological Control

The use of biological organisms to help manage turfgrass weeds 2. Biological Control Use of Various Organisms ◉ Nematodes Bacteria ◉ Fungi ◉ Livestock (backyard chickens) ◉ Least common approach ◉ ◉ May help improve other system properties that indirectly ◉ help with weed control 3. Mechanical Control

The use of mechanical tools used to disrupt weed growth ◉ Regular Mowing Hoeing ◉ Hand-pulling ◉ www.fiskars.com ◉

Emerging technology Weeding robots www.linak.com ◉ ◉

www.franklinrobotics.com 4. Cultural Control

Management practices that optimize turfgrass health and allow turfgrass to be more competitive against weeds

Management practices that improve efficacy of chemical control including pre- and post-emergent herbicides 4. Cultural Control

Adjusting mowing practices Raising or lowering mowing height, as needed ◉ Changing mowing frequency ◉ 1/3 Rule ◉ ◉ Improving irrigation efficiency Coverage ◉ Timing ◉ Frequency ◉ Infiltration ◉ ◉ 4. Cultural Control

Cultivation, as needed Thatch removal ◉ Core aeration ◉ Balanced fertility program in ◉ response to soil test results ◉ Soil amendments, as needed to alter soil pH, structure, and ◉ organic matter 4. Cultural Control

Control of other pests that may compromise turfgrass health Diseases

◉ Insects ◉ Wildlife ◉ 4. Cultural Control

Precision Turfgrass Management (PTM) Site-specific management: targeting specific areas for all of the practices mentioned ◉ Irrigation ◉ Cultivation ◉ Fertilization ◉ Pesticide Applications ◉ 5. Chemical Control

The use of pre- and post-emergent herbicides to control weeds

In IWM, particular emphasis is put on using multiple modes of action (MOAs) to prevent resistance that can occur overtime with repeat applications of products with the same MOA Pre- vs. Post-Emergence Herbicides

What is the difference? Pre-Emergence Timing

These products are most effective when applied BEFORE seedling germination.

Application timings vary based on environmental and annual conditions.

Typical Spring Application: Soil Temps around 50-55F (February/March)

Typical Fall Application: mid-Aug through mid/late September Pre-Emergence Herbicides Pre-Emergence Herbicides Post-Emergence Timing

Many different post-emergence herbicide products Systemic vs. Contact ◉ Most products will be more efficacious when applied EARLY◉ to IMMATURE plants ◉ Mature, established plants will be harder to control Sequential Applications ◉ Tank Mixing ◉ ◉ Common POST Herbicides General Warnings

Atrazine can damage bermudagrass 2,4-D and Dicamba can damage St. Augustinegrass ◉ Glyphosate will injure most plants and should be used with ◉ great caution ◉ Will not work on clover or sedge Always be mindful of nearby plants Be◉ mindful of drift and off-target movement ◉ Be mindful of appropriate timing when using Weed-n-Feed ◉ products ◉

ALWAY FOLLOW THE LABEL Balance is Key…

Healthy Turfgrass System

Appropriate Balanced, Optimum Good Soil Optimum Optimum Good Soil Mowing Available Water and Water Soil pH Sunlight Structure Height & Nutrients Availability Quality Frequency What is an ‘Indicator Weed’?

Any weed that may reveal something about the overall health of our turfgrass system ◉

Weeds that flourish under specific conditions: out-competing desired turfgrass ◉

Spotted Spurge https://aggieturf.tamu.edu/turfgrass-weeds/ Why does it matter?

Identifying a larger Addressing the issue Weeds are often a issue allows for and optimizing symptom of a larger more turfgrass health can turfgrass issue comprehensive prevent future weed control weeds What might be indicated?

High pH/Low pH

◉ Fertility imbalances ◉ Water Issues (too much or too little) ◉ Soil Compaction ◉ Improper Mowing Height ◉ Excess Shade ◉ High Salinity ◉ Common Texas Indicator Weeds Condition 1: Low Fertility

Possible Causes: pH imbalance affecting availability Low cation exchange capacity (CEC) ◉ Sandier soils ◉ ◉Leaching Physical removal or displacement of nutrient-rich soil ◉ horizons: ◉ Urban construction practices and topsoil removal

◉ Surface runoff ◉ Erosion ◉Inadequate fertility practices over time

◉ Common Texas Indicator Weeds Condition 1: Low Fertility

Legumes (Fabaceae or Leguminosae Family) Form symbiotic relationships with bacteria to produce their own nitrogen ◉ Able to thrive in low-nitrogen soils

◉ Plants adapted to low-fertility environments (sandy soils) Common Texas Indicator Weeds Condition 1: Low Fertility

Common Texas Legume Weeds

Powderpuff Sweet Clover (Mimosa strigillosa Torr. & A. (Melilotus officinalis (L.) Lam.) Gray)

Arrowleaf Clover Black Medic (Trifolium vesiculosum Savi) (Medicago lupulina L.)

Reversed Clover (Trifolium resupinatum L.) Burclover (Medicago polymorpha L.)

White Clover (Trifolium repens) Vetch (Vicia spp.) Common Texas Indicator Weeds Condition 1: Low Fertility Texas Thistle

Sand Adapted or Common Weeds with Low Fertility Requirement

Thistle Large Crabgrass Sandbur ◉ Dandelion Field Sandbur ◉ Crabgrass ◉ Bahiagrass ◉ ◉ Common Texas Indicator Weeds Condition 2: Too Little Water

Possible Causes: Faulty or malfunctioning irrigation equipment ◉ Poor irrigation practices Poor infiltration (Compaction, ◉ Thatch, Hydrophobicity, Texture) ◉ Poor water-holding capacity (Sandy/Coarse-textured Soils) ◉ High evapotranspiration rates Living in Texas ◉ ◉ Common Texas Indicator Weeds Condition 2: Too Little Water

Drought Survival Mechanisms 1. Drought Avoidance (deep roots + storage structures) 2. Drought Escape (rapid life cycle) 3. Drought Tolerance (CAM plants) 4. Drought Recovery Common Texas Indicator Weeds Condition 2: Too Little Water

Deep-Rooting Plant Species ● Arid-adapted Grasses ● Tap-root Species

CAM Plants (succulents)

Other drought-responsive plant species Common Texas Indicator Weeds Condition 2: Too Little Water

Common Texas Indicators of Too Little Water Common Texas Indicator Weeds Condition 3: Too Much Water

Possible Causes: Faulty or malfunctioning irrigation equipment ◉ Poor irrigation practices Poor drainage (Compaction, ◉ Texture, Low Spots) ◉ High water-holding capacity (clay/fine-textured soils) ◉ Common Texas Indicator Weeds Condition 3: Too Much Water

Hydrophyllic (water-loving) Species

Species adapted to low oxygen soils (poor drainage) Common Texas Indicator Weeds Condition 3: Too Much Water Common Texas Indicators of Too Much Water Common Texas Indicator Weeds Condition 4: Soil Compaction

Possible Causes: Poor irrigation practices Traffic (pedestrian, vehicle, ◉ equipment) ◉ Soil texture (shrinking & swelling clays) ◉ Topography

◉ Common Texas Indicator Weeds Condition 4: Soil Compaction Taproot Plant Species ● Take advantage of soil cracks ● Can penetrate compacted soil when fibrous roots cannot Vining or Creeping Plant Species ● Shallow-rooted, but lateral growth with multiple points of entry Common Texas Indicator Weeds Condition 4: Soil Compaction

Common Texas Indicators of Soil Compaction Common Texas Indicator Weeds Condition 5: Excess Shade

Possible Causes: Surrounding vegetation (trees and other perennials) ◉ Adjacent buildings and other structures ◉ Common Texas Indicator Weeds Condition 5: Excess Shade

Common Texas Indicators of Excess Shade Common Texas Indicator Weeds Condition 5: Salinity

Possible Causes: High evapotranspiration rates Poor fertility practices (excess fertility) ◉ Poor water quality ◉ Historically high soil salinity ◉ ◉ Halophytic Plants Excrete ◉ Exclude ◉ Accumulate ◉ ◉ Common Texas Indicator Weeds Condition 5: Salinity Common Texas Indicators of Excess Shade Inland Saltgrass

Inland Saltgrass Kochia Kochia ◉ Curley Dock ◉ Some ◉ bluegrasses ◉ Common Texas Indicator Weeds Condition 5: Low Mowing Height Short or lateral growth habits

◉ Able to withstand low mowing ◉ Conclusion

A dense, healthy stand of turfgrass is the best defense against weeds!