1. What is a Weed? Any plant can be a weed under the right circumstances
It all depends on what type of production you are trying to accomplish

2. Why care? Food costs Aquatic nuisance Allergies
Hosts for diseases and insects
Increased soil erosion
Dandelionالهندباء

3. Why are they so difficult to control?!
Can sprout in many environments
Long – lived seed
Variable seed dormancy
Rapid growth
High seed production
Burdockنبات الارقطيون

4. So difficult.
Allelopathy
Deep root system
Milkweedالصقلاب

5. Classification
Grasses
Sedges نبات السعد
Annual سنوي
Perennialمعمرة

6. Methods of Control Prevention Chemical Biological Mechanical
Controlled burning
Grazing
Crop rotation

8. Prevention Weed seed may be distributed in a number of ways
Crop seed, wind, water, animals, machinery and other ways

9. Chemical Use of chemicals to control or retard growth of weeds
Bull Thistle الثور الشوك
Use of chemicals to control or retard growth of weeds

10. Time of Application
Preplant: made before crop is planted and is incorporated into the soil
Preemergence: Made directly to soil and requries rainfall in order to move into the soil
Postemergence: Applied after weed or crop emergence

11. Types of Herbicide
Contact herbicide: sprayed on foliage and only affects area it comes into contact with
Systemic herbicide: sprayed on soil

12. Factors Affecting Herbicide Effectiveness
Annual or perennial
Tolerance
Type of soil
Temperature
wax on leaves
Shape/orientation of leaf

13. Biological Control
Using beneficial creatures such as insects, bacteria and fungi that damage the weeds
Not very common

14. Mechanical
Burial دفن
Tillage
Mowing

15. Controlled Burning
Not very common

16. Grazing
Use of animals such as sheep or goats that will eat weeds and weed seeds.

17. Crop rotation
Rotating your crops from year to year and season to season to take away competitive advantage from weeds of the previous years crop.

18. Are weeds all bad? Shelter for beneficial insects
Lambsquarters
Shelter for beneficial insects
Beneficial properties for humans
Provide food for wildlife

19. The word allelopathy derives from two separate words.
What is Allelopathy?
The word allelopathy derives from two separate words.
They are allelon which means "of each other", and pathos which means "to suffer".
Allelopathy refers to the chemical inhibition of one species by another. The "inhibitory" chemical is released into the environment where it affects the development and growth of neighboring plants.

20. Allelopathic chemicals can be present in any part of the plant.
They can be found in leaves, flowers, roots, fruits, or stems. They can also be found in the surrounding soil.

21. Allelopathy has been defined as the direct or indirect harmful or beneficial effects of one plant on another through the production of chemical compounds that escape into the environment
Numerous allelochemicals have been idendified as
Phenolic acids,
Coumarins,
Terpenoids,
Flavonoids,
Alkaloids,
Glycosides,
Isothiocyanate,

22. Target species are affected by these toxins in many different ways
Target species are affected by these toxins in many different ways. The toxic chemicals may inhibit shoot/root growth, they may inhibit nutrient uptake, or they may attack a naturally occurring symbiotic relationship thereby destroying the plant's usable source of a nutrient.

23. Chemical Warfare in the Plant Kingdom
Black Walnutالجوز الاسود - The chemical responsible for the toxicity in Black Walnut is Juglone and is a respiration inhibitor.
Tree-Of-Heavenشجرة الجنة - Ailanthone, an allelotoxin.
Sorghum الذرة - Sorgolene is found in the root and disrupts mitochondrial functions and inhibits photosynthesis.