CCA - Certified Crop Advisor Weed Identification and Control Questions and Answers 1 — Questions and Answers
Question 1: A CCA is scouting a field and finds a pigweed species with smooth, hairless stems and petioles that are consistently longer than the leaf blades. Some leaves exhibit a faint, V-shaped watermark. Which of the following weeds has been identified?
- Redroot pigweed (Amaranthus retroflexus)
- Common waterhemp (Amaranthus tuberculatus)
- Palmer amaranth (Amaranthus palmeri) (Correct answer)
- Common lambsquarters (Chenopodium album)
Correct answer: Palmer amaranth (Amaranthus palmeri)
The key identifying characteristic for Palmer amaranth, which distinguishes it from similar species like waterhemp, is a petiole that is longer than the leaf blade itself. Both Palmer amaranth and waterhemp have smooth, hairless stems, whereas redroot pigweed has a hairy stem.
Question 2: A post-emergence herbicide application results in severe twisting, cupping, and epinasty (downward bending of petioles) on susceptible broadleaf weeds. These symptoms are characteristic of which herbicide mode of action group?
- ALS inhibitors (Group 2)
- Synthetic auxins (Group 4) (Correct answer)
- PPO inhibitors (Group 14)
- EPSP synthase inhibitors (Group 9)
Correct answer: Synthetic auxins (Group 4)
Synthetic auxin herbicides (Group 4), such as 2,4-D and dicamba, mimic the plant growth hormone auxin, causing uncontrolled and abnormal growth in susceptible broadleaf plants. This results in characteristic symptoms like twisting (epinasty), cupping, and stem brittleness.
Question 3: A producer has confirmed glyphosate-resistant (Group 9) common waterhemp in a no-till soybean field. Which of the following represents the MOST effective and sustainable management strategy?
- Increase the application rate of glyphosate and add a surfactant.
- Rely solely on a post-emergence application of a PPO inhibitor (Group 14) herbicide.
- Implement a program using a pre-emergence residual herbicide with a different effective mode of action, followed by a timely post-emergence application of another effective mode of action. (Correct answer)
- Switch to intensive tillage to bury the weed seeds before planting.
Correct answer: Implement a program using a pre-emergence residual herbicide with a different effective mode of action, followed by a timely post-emergence application of another effective mode of action.
The most effective strategy for managing herbicide-resistant weeds like waterhemp is an integrated approach that does not rely on a single mode of action. A program that starts with a pre-emergence herbicide with residual activity prevents early-season competition and reduces the number of weeds that need to be controlled post-emergence. Following up with a timely post-emergence herbicide with a different effective mode of action provides a second layer of control and helps prevent the selection of further resistance.
Question 4: What is the primary function of a non-ionic surfactant (NIS) when added to a post-emergence herbicide spray mixture?
- To increase the pH of the water to prevent herbicide degradation.
- To reduce the surface tension of spray droplets, allowing for better spreading and coverage on the leaf surface. (Correct answer)
- To bind with hard water ions, increasing herbicide activity.
- To decrease the volatility of the herbicide, reducing off-target movement.
Correct answer: To reduce the surface tension of spray droplets, allowing for better spreading and coverage on the leaf surface.
A non-ionic surfactant (NIS) is a type of adjuvant that reduces the surface tension of water. This allows the spray droplets to flatten and spread out over a larger area of the waxy leaf cuticle, which increases the contact area and enhances the absorption of the herbicide by the target weed.
Question 5: A grower is dealing with a heavy infestation of giant foxtail, a grass weed known for a prolonged germination window, in their cornfield. Which strategy provides the most effective, season-long control?
- A single post-emergence application of a grass herbicide when the foxtail is 6 inches tall.
- A layered program using a full rate of a pre-emergence residual herbicide at planting, followed by a timely post-emergence application as needed. (Correct answer)
- A burndown application of a non-selective herbicide one month before planting.
- In-season cultivation with a row-crop cultivator two times during the season.
Correct answer: A layered program using a full rate of a pre-emergence residual herbicide at planting, followed by a timely post-emergence application as needed.
Giant foxtail has a long emergence period, meaning new plants can germinate and emerge throughout the early growing season. A single post-emergence application will miss later-emerging weeds. The most robust strategy is to use a pre-emergence herbicide with residual activity to control the initial flushes, followed by a post-emergence application to control any escapes or later-emerging weeds, ensuring season-long protection.
Question 6: Which weed life cycle is generally the most difficult to control and eradicate from a field, primarily due to its ability to reproduce vegetatively from extensive underground structures?
- Summer annuals
- Winter annuals
- Biennials
- Creeping perennials (Correct answer)
Correct answer: Creeping perennials
Creeping perennials are the most difficult to control because they reproduce by both seed and vegetative structures like rhizomes, stolons, and tubers. Tillage can break up these structures and spread them, creating new plants. A single herbicide application may kill the top growth but often fails to translocate sufficiently to kill the entire extensive root and rhizome system, allowing the weed to regrow.
CCA - Certified Crop Advisor Weed Identification and Control Questions and Answers 1
A CCA is scouting a field and finds a pigweed species with smooth, hairless stems and petioles that are consistently longer than the leaf blades.
Some leaves exhibit a faint, V-shaped watermark.
Which of the following weeds has been identified?