Northeast Region Certified Crop Adviser (NRCCA) Study Resources

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In This Section

• PO 10 Weed life cycles
• PO 11 Weed survival mechanisms
• PO 12 Common weed identification
• PO 13 Dichotomous key
• PO 14 Timing of control
• PO 15 Mechanical weed control
• PO 16 Cultural weed control
• PO 17 Biological weed control
• PO 18 Chemical weed control
• PO 19 Herbicide site of action
• PO 20 Environmental affects herbicides performance
• PO 21 Problems associated with herbicide use

Competency Area 2: Weed Management

PO 11. Understand the survival mechanisms of weeds, i.e. how they reprodue, spread, and the role seed dormance plays in survival.

Reproductive capacity:
Sexual reproduction - weeds are prolific seed producers and average about 20,000 seeds/plant (250 from wild oat and 6 million from tumble pigweed).
Asexual reproduction - vegetative means of reproduction, i.e. bulbs, tubers, stolons, rhizomes, rootstocks.

Dissemination of propagules is by wind, water, and animal, especially humans

Dormancy or extended viability is the inability of propagules (seeds or vegetative reproductive structures) to germinate when provided with proper conditions:
Innate dormancy - inherent in mature seed, i.e. mechanically restricted seed coats, impermeable seed coats, germination inhibitors, immature embryos, etc.
Induced dormancy – seeds become dormant after exposure to environment
Enforced dormancy - limitations of the environment prevent seed germination