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WEED MANAGEMENT

WEED MANAGEMENT. Economic Importance of weeds (Contd.). Competition Nutrients, water and light Impede harvesting Clog drainage ditches Reduce yield (handout #1) 20-25 % total production costs. Economic Importance of weeds. Soil and air temp-higher in bare ground

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WEED MANAGEMENT

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  1. WEED MANAGEMENT

  2. Economic Importance of weeds (Contd.) • Competition • Nutrients, water and light • Impede harvesting • Clog drainage ditches • Reduce yield (handout #1) • 20-25 % total production costs

  3. Economic Importance of weeds • Soil and air temp-higher in bare ground • Efficacy of the soil applied pesticides can be reduced • Interfere with the operation of low volume irrigation

  4. Weeds in Citrus Orchard • Grasses • Sedges • Compositae • Gourds • Morning Glory • Nightshades • Milk Weed

  5. Common weeds • Guinea grass- Panicum maximum • Brown top millet- Panicum fasciculatum • Verbanasp • Johnsongrass- Sorghum halapense • Bemudagrass- Cynodon dactylon • Ragweed- Parthenium hysterophorus • Sowthistle- Socnhus sp. • Climbing Hempweed - Mikania scandens Contd.

  6. Common weeds • Texas virgin bower - Clematis drummondi • Ipomea amnicola • Morning Glory- Ipomea hederacea • Ipomea spp. • Purple nightshade • Silverleaf nightshade • Black nightshade- Solanum nigrum • Milkvine- Cynachum unifarium contd.

  7. Common weeds • Amaranthus palmeri • White poppy (Prickly poppy)- Argemone albifloria • Henbit- Lamium amplexicanle • Old’s man beard • Phacelia • Climbing milk weed

  8. How to Control Weeds? • Tillage • Managed Cover crop • Chemical Weed Control • Biological Methods

  9. Tillage • Cultivation-no longer used • Problems • Difficult to remove weeds from tree row • Will spread perennials: nutsedge • Water erosion on slopes • Compaction of soil

  10. Managed cover crops • Benefit: Low growing weeds predominate. • Problems: • conversion of annuals to perennials • Fert and water use by cover crops • Rodents have a place to live

  11. Chemical Weed Control (Contd.) Benefits • Clean orchard to work • Fewer host plants for fungi • Roots return to upper layer of the soil • Soil O.M. increases • Increased yield • Fewer snails and aphids

  12. Chemical Weed Control (Contd.) History • First materials (Handout # 2) • Development of Chemical Weed Control for Texas Citrus orchards (Handout #3)

  13. Chemical Weed Control (Contd.) Federal and State Regulations • Label • properties, advantages, limitations, and precautions • Application: • select rate of application based on the soil type • Calibration of the equipment

  14. Chemical Weed Control (Contd.) • Herbicide • Toxicity-Handout # 4 • Safety- Handout # 5

  15. Classification-Herbicide (Contd.) • Chemical affinity • Timing of application (Handout #6) • preemergence • postemergence • Persistence • residual • non residual

  16. Classification-Herbicide • Formulation (handout # 6) • Wettable Powder (WP) • Dry Flowable (DF) • Emulsifiable Concentrates (EC) • Water Soluble (WS) • Granular (G)

  17. Requirements for an effective preemergence herbicide • Safe for trees • Long lasting weed control • Broad spectrum of weeds controlled • Low cost (handout # 8)

  18. Requirements for an effective postemergence herbicide • Safe for trees • Broad spectrum of weeds controlled • Must be translocated (systemic) to control perennial weeds • Low cost (handout # 9)

  19. Techniques of herbicide applications • Spray from the boom • Spot spray • Injection into irrigation water • Impregnated on fertilizers

  20. Problems-Herbicides • More phytophagous mites • More dust-fewer predators-more mites • Vegetation shifts from annual toward perennials • Resistant plants become established • Injury to trees (http://hammock.ifas.ufl.edu/txt/fairs/27825) • Water penetration may become a problem

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