Managing Weeds in Herbaceous Ornamentals: Introduction

Excerpt from 2008 Chapter 16, Publication 75, Guide to Weed Control, Order this publication

Introduction

• Cultural Weed Control - See notes on Cultural Weed Control in Fruit Crops section.
• Site Preparation Before Planting - see Chapter 6, Special Methods of Weed Control
• To convert kg/ha or L/ha to g/ha or mL/100 m² - Multiply by 10 and change units to 100 m².
  Example: 11 kg/ha becomes 110 g/100 m²: 28.4 L/ha becomes 284 mL/100 m².
• All treatments should be applied in 150-300 L/ha (60-120 L/ac) water.
• Recommended rates /ha or /ac refer to area actually treated with herbicide.
• The best weed management system for herbaceous ornamentals uses a combination of chemical weed control with cultivation and other techniques. See Chapter 1, Principles of Integrated Weed Management.
• Herbicide Application Timings:
  • Soil Applied Treatments include:
    • Preplant (PP) - Also see Chapter 6, Special Methods of Weed Control for details of products, rates and remarks.
    • Preplant Incorporated (PPI) - Two incorporations at right angles operating at a depth of 10 cm using a double disk (7-10 km/hr) or vibrating shank S-tine cultivator (10-13 km/hr) are required unless otherwise stated. Cultivation-type equipment used for herbicide incorporation is known to spread perennial weeds to previously uninfested areas. Special attention should be directed toward machinery cleanliness, and/or treating fields with perennial weeds last.
    • Preemergence (PRE) - Rainfall of 15-20 mm within 7-10 days after application is necessary to activate preemergence treatments. Shallow cultivation, rotary hoeing or harrowing will control weed escapes and improve herbicide activity in the absence of rainfall.
  • Postemergence (POST) - Leaf stage of the weeds is critical for good weed control. Smaller weeds are generally easier to kill but there needs to be enough leaf surface to intercept the herbicide. Apply according to recommended leaf stages. Crop stage is important to optimize crop safety. Adjuvants will frequently improve the weed control when used as directed. Weather or other conditions may influence the optimum rate of adjuvant, see the product label for more details. Always use appropriate drift management technology.
• WARNING - Certain species may be injured by the following herbicides. Check manufacturer's directions for labeled species before use.

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Related Links

• Weeds in Ontario
• Nursery and Landscape Plants in Ontario
• Problem Weed Control in Field Crops
• Integrated Pest Management (IPM)
• Pesticide Application and Safety
• Pesticide Companies and Agents
• OMAFRA Sprayer Calibration Calculator
• Search the PMRA website
• OMAFRA Publication 505: Ontario Weeds
• OMAFRA Publication 75: Guide To Weed Control

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