Angela R. Post Aug 20, 2015

Transcription

1 1 Angela R. Post Aug 0, 015 Banded application - treating narrow strips with herbicides. The strip centered on the crop row A Band is usually 10 to 1 inches wide. This is an efficient way to manage weeds by applying herbicides close to plants. Cotton and corn plants are common crops where band application is used. Broadcast application -treating the entire field. Broadcast application is used with pastures, lawns, and grain crops that are not in rows. This application is used in places where cultivation cannot be used to destroy weeds. Herbicides can be classified by their mode of action. The biochemical method by which a herbicide kills plants depends on how the plant translocates and metabolizes the chemical.

2 Contact photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) Contact herbicides do not move in the plant Xylem mobile herbicides move up in the plant Phloem mobile herbicides move up and down in the plant,-d, dicamba, Quelex Highly systemic in susceptible plants Primarily broadleaf activity but may affect grasses Broadleaf plant stem twisting and curling Leaves on broadleaf plants exhibit cupping, crinkling, strapping, or drawstring affect Symptoms on grass plants include leaf rolling, crinkling, brace root fusion and malformation. Also, flower sterility and missing grain in crops. Twisting of stems and leaf cupping are typical symptoms of the growth regulator herbicides.,-d dicamba Leaf strapping is another typical symptom of these herbicides.

3 3 Vanquish (dicamba) untreated Upward cupping of leaves on azalea. Common symptom with dicamba exposure. Upward cupping of leaves from,-d exposure. photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) We have many wheat herbicides in this class: Finesse, Harmony Extra, Osprey, Peak, Powerflex, Beyond These block production of 3 essential branchchain amino acids Cause bottle-brush roots and darkened veins yellow growing point on susceptible plants and shortening internodes Takes up to 3 weeks to kill plants Plateau or Escort Injury Symptoms Chlorosis of youngest tissue Stunting

4 19 days after exposure 5 days after exposure 1 days after exposure 7 days after exposure 1 days after exposure 7 days after exposure Seedlings exposed to soil residual blackberry sweetgum 3 Compact growth Untreated boxwood

5 5 Bunched, compact growth on dogwood and sassafrass Treatment Soybeans Grain sorghum 5 Sunflowers Sesame Axiom DF Buctril Axial XL Ally * -- Finesse * Maverick 3* / Olympus * / Olympus Flex Osprey PowerFlex Beyond** Treatment Wheat Canola atrazine varies with rate 9 Dual, Cinch.5 1 Harness, Surpass, others Bicep, Cinch ATZ -- following year following year Buctril 1 1 Callisto 18 Accent (corn) 10 Permit 15 glyphosate 0 0 photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) 5,6,7 5,6,7 There are only wheat herbicides in this class: metribuzin and Axiom These herbicides interrupt photosynthesis the process by which green plants convert light energy into food. Symptoms appear in older leaves that are exporting sugars Interveinal or veinal yellowing followed by death of plant tissue from leaf margins inward Symptoms often appear on the margins of the oldest leaves (pear).

6 6 Karmex (diuron) on oak. Symptoms often appear on the margins of the oldest leaves. With photosynthesis inhibitors, symptoms start on the margins of the older leaves and move inward. 1 photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) 13 7 With photosynthesis inhibitors, symptoms start on the margins of the older leaves and move inward Pigment inhibitors cause white leaves in susceptible plants new leaves White growth may be observed within veins (primarily with Zorial) and between veins (primarily with Command)

7 photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) 8,15 3 Plant death generally occurs before emergence Roots on susceptible plants will be stubby and thick, especially lateral roots The root inhibitors interrupt cell division (mitosis) stopping root growth in seedling plants. 8,15 8,15

8 8 8,15 1 photosynthesis (food) respiration (energy) amino acids (proteins/growth) lipids (cell membranes) pigments (energy/light capture) mitosis (cell division) 1 These herbicides act by disrupting lipid biosynthesis in grass plants. Plant cells and cellular organelles all contain lipid membranes. Therefore, these herbicides affect cell membrane integrity in the meristems. The affected area will become rotten and will easily separate from rest of plant 1 Grass herbicides symptoms on johnsongrass

9 9 1 Grass herbicides symptoms on wheat Glyphosate in wheat Paraquat in wheat 51 5 Describe how we classify herbicides based on time of application. Describe how we classify herbicides based on application placement. Describe how we classify herbicides based on mode of action. What are the major plant pathways interrupted by each mode of action?