1. Introduction to Weed Management Principles
Topic #2044
Aaron Gearhart

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

3. Why care? Food costs Aquatic nuisance Allergies
Hosts for diseases and insects
Dandelion

4. Why care? Increased soil erosion
Decreased amount of food we can produce
Decreased grazing area
Barnyard Grass

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

6. So difficult. Effective dispersal habits Allelopathy Deep root system
Waxy or pubescent leaves
Milkweed

7. Weed germination Stratification Vegetative reproduction Scarification
Johnsongrass Seedling
Stratification
Vegetative reproduction
Scarification

8. Classification
Grasses
Broadleafs
Sedges
Annual
Biennial
Perennial

9. Grass Weeds Hollow rounded stems Parallel veins
Longer than they are wide
Johnsongrass, foxtails, crabgrass
Witchgrass

10. Broadleaf weeds Highly variable Have showy flowers
Ladysthumb
Highly variable
Have showy flowers
Have different growth habits
Velvetleaf, ladysthumb, dandelion.

11. Sedges “grass like” but not true grasses.
Yellow Nut Sedge
“grass like” but not true grasses.
Solid traingular – shaped stems

12. Annual Weeds Complete their life cycle in one year
Can be grasses, broadleaves or sedges.
Can be summer or winter annuals
Not many winter annuals in Michigan

13. Biennial Weeds 2 year life cycle First year vegetative growth
White campion
2 year life cycle
First year vegetative growth
Second year flower and seed production
Onions are a good example.

14. Perennial Weeds Live more than two years Reproduce by vegetative parts
Tubers, bulbs, rhizomes, stolons
During winter most survive in a dormant state.

15. Seed Characteristics
Redroot Pigweed
Redroot pigweed can produce 100,000 seeds in one plant.
Dormancy ensures weed survival
4%broadleaf and 9%grass seeds germinate in a given year

16. Methods of Control Prevention Chemical Biological Mechanical
Controlled burning
Grazing
Revegetation
Crop competition
Crop rotation

17. Prevention Weed seed may be distributed in a number of ways
Crop seed, wind, water, animals, machinery and other ways
Neglected fence rows and ditches
Proactive thinking

18. Chemical Use of chemicals to control or retard growth of weeds
Bull Thistle
Use of chemicals to control or retard growth of weeds
Allowed us to become an agricultural powerhouse
Very useful if application is well thought out

19. 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

20. Area of application
Broadcast
Band
Directed
Spot treatments

21. Types of Herbicide
Contact herbicide: sprayed on foliage and only affects area it comes into contact with
Systemic herbicide: sprayed on soil or foliage then translocated through plant
Selective
Non-selective

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

23. Biological Control
Using beneficial creatures such as insects or fungi that damage the weeds
Not very common

24. Mechanical
Burial
Cultivation
Tillage
Mowing

25. Controlled Burning Not very common
Sometimes used when corn 1-2” tall and growing point is still under the soil

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

27. Revegetation Reseeding a distubed site to block or choke out weeds
Hairy Vetch
Reseeding a distubed site to block or choke out weeds
Cover crops are a good example

28. Crop competition
Planning your planting so that crops have the competitive advantage over weeds.
Factors such as planting date, row spacing, seeding rate, planting depth, soil moisture, fertility, and soil pH have an influence on competitive advantage of the crop.

29. 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.

30. Are weeds all bad? Quickly fill in unsightly spots
Lambsquarters
Quickly fill in unsightly spots
Shelter for beneficial insects
Beneficial properties for humans
Provide food for wildlife

31. Integrated Weed Management
An integrated approach means assembling a weed management plan that incorporates a number of tools consistent with farm goals.
Field Bindweed

32. Questions?