Weed Science PDF

MAJOR GROUP OF PEST WEEDS Topics 1. Weeds: The Beginning 2. Weed Identification and Classification 3. Weed Reproduction and Dispersal 4. Crop-Weed Competition 5. Weed Management Topic 1 Weeds: The Beginning Learning Objectives 1. Define weeds and weed science as a disciplin...

MAJOR GROUP OF PEST WEEDS Topics 1. Weeds: The Beginning 2. Weed Identification and Classification 3. Weed Reproduction and Dispersal 4. Crop-Weed Competition 5. Weed Management Topic 1 Weeds: The Beginning Learning Objectives 1. Define weeds and weed science as a discipline 2. Know the characteristics of weeds 3. Understand how weeds cause harm 4. Know some of the uses of weeds Weed Science Study of vegetation management in agricultural production systems, natural areas, and managed properties in residential and urban areas. (USDA NIFA) The study of vegetation management in agriculture, aquatics, horticulture, right-of-way, essentially anywhere plants need to be managed. (Purdue University Weed Science) Main goal is the formulation of most effective, economical and satisfactory methods of WEED SCIENCE  The study of weeds and their control  an offshoot of plant physiology, having evolved from the study of auxins and plant growth regulators  came about after the discovery of 2,4-D in the 1940’s  GOAL : formulation of the most satisfactory, economical and environment-friendly control program  covers the fields of weed biology, weed control, herbicide biochemistry, herbicide physiology and herbicide resistance  it used to be equated with the use of herbicides HISTORICAL OVERVIEW  Archeological artifacts proved that weed control was practiced since men started settled cultivation of the land. Though somewhat obscure, evidence point back around 15,000 B. C to 12, 000 BC  Around 1, 000 BC men used animals to drag hoe. A farmer could produce enough for two. The Development of Weed Science as a discipline does not coincide with the presence of weeds in agriculture, rather with the birth of modern day agriculture and is estimated to be a little less than a hundred years old. Jetro-Tull, who is more popularly known for his Horse Houng Husbandry, ia among the first to used the word weed around 1731 A.D  HISTORICAL OVERVIEW  In 1987, Bonnet of France Schultz of Germany and Dolley of United States, each working independently, found that a solution of copper and salts would selectively kill broadleaf weed in cereals.  Bolley of the United States reports successful weed control in wheat using common table salts, iron sulfate, copper sulfate and sodium arsenite in 1908. Pokorny (USA) in 1941 reported the chemical synthesis for 2-4 D (2, 4-dichlorophenoxy acetic acid.) This was later tried as fungicides and insecticide which turned out to be ineffective. P. Zimmerman and A. Hitchcock (US) reported that 2-4D is a growth substance in 1942. In 1944, P. Marth and J. Mitchel (USA) established the selectivity of 2-4 D, that is the removal of dandelion, and other broadleaf weeds from bluegrass lawn. In addition, C. Hammer and H. Tukey successfully used 2-4 D in field control.  HISTORICAL OVERVIEW  It was W. Templeman, an Englishman, who established the premergence principle of soil treatment for selective weed control in 1945. In the Philippines, Capinpin and Ocfemia initially tested 2-4, D in 1948 to eradicate weeds in lawns, vacant lots and pastures. In 1955, other new herbicides and growth inhibitors were studied. The International Weed Science Society was established by weed scientist in 1975 which aimed to enhance wider interchange of ideas and developments in weed control. CAREER OPPORTUNITIES  Researcher Educator Consultant Marketing Agent or Sales Representatives Agribusiness Extension Worker  Can you distinguish where is the rice? Definition of Weeds..  Other definition of weeds  Unwanted, undesirable, useless plants  A plant or plant part interfering with the objectives of man  A plant interfering with the utilization of land and water resources or adversely intrudes upon human welfare.  A plant that colonizes disturbed habitats (agricultural lands) and has evolved as an interfering associate of crops, locally abundant, with little or no value and are costly to control THE IMPACT OF WEEDS ON HUMAN HEALTH Weeds can also cause human health problems. Many common weeds such as Parthenium Weed, Ragweed, Rye Grass and Privet cause asthma and other respiratory problems, especially in children. Some weeds can also cause skin irritation and some are poisonous. People are plagued year after year with hay fever and asthma aggravated by pollen of weeds. 4. Based on HABITAT… UPLAND / TERRESTRIAL Grow and complete their life cycle under dry or wet, but not flooded soils LOWLAND / AQUATIC Grow and complete their life cycles in flooded areas o FLOATING o EMERGED o SUBMERGED 5. Based on GROSS MORPHOLOGY… GRASSES Graminae or Poaceae Narrow leaves with parallel veins ; rounded stems with distinct nodes & internodes ; fibrous root system;presence of ligule/or auricle SEDGES Cyperaceae Narrow leaves with parallel veins ; triangular stems ; fibrous root system ; absence of ligule BROADLEAVES Monocotyledonae Wide/broad leaves ; stems and Dicotyledonae. woody or succulent ; usually with tap root system 6. Based on STEM STRUCTURE… HERBACEOUS Stem is succulent, does not undergo secondary growth; common in annuals WOODY Stem is hard and with a bark. Common in perennials 7. Based on GROWTH HABIT… ERECT Stem grows vertically upward without the aid of any support TWINING Stem needs support in order to grow vertically PROSTRATE Stems grows horizontally along the ground o PROCUMBENT o DECUMBENT CREEPING Spread horizontally rather than verticaly Based on Photosynthetic Activity 1. C3 weeds Weeds that employ a photosynthetic pathway where a 3-carbon compound is the first stable product. Weeds belonging to this group prefer environments where temperature and sunlight intensity are moderate, and water supply is plenty. (ex. sensitive plant, three lobe morning glory, water hyacinth) 2. C4 weeds Weeds that employ a more efficient photosynthetic pathway in which a 4-carbon compound is the first stable product. (ex. Barnyard grass, Bermuda grass, cgon grass, crabgrass, itchgrass, goosegrass, purple nutsedge, common purslane, garden spurge)  End of Presentation  END OF PRESENTATION Reference: Power point presentation of Dr. Nina Grace Dimaano Institute of Weed Science, Entomology and Plant Pathology College of Agriculture and Food Science University of the Philippines Los Banos