Rich Braman
14 KiB
GTBOP Moodle Quiz
Weed Control in Turf — A Review of the Basics and Recent Updates
Webinar Date: November 17, 2017 Speaker: Dr. Patrick McCullough, Weed Scientist, University of Georgia Series: Green & Commercial Course Context: Weed Science Certificate Course Source: Corrected SRT (Stage 1) + Archive Package (Stage 2)
Question 1
Timestamp Reference: 0:46 – 1:53 Difficulty: Recall
Which two weed identification books does McCullough specifically recommend for turfgrass managers?
a) Weeds of the Northeast and Southern Weed Science Society Field Guide b) Color Atlas of Turfgrass Weeds and Weeds of Southern Turfgrass c) Weed Identification Guide for Georgia and Color Atlas of Turfgrass Weeds d) Weeds of Southern Turfgrass and Crop Weed Identification Manual
Correct Answer: b Explanation: McCullough recommends the Color Atlas of Turfgrass Weeds (published by GCSAA) and Weeds of Southern Turfgrass (a UGA publication available through the Athens bookstore). Source in transcript: Blocks 10–14
Question 2
Timestamp Reference: 2:43 – 3:56 Difficulty: Recall
According to McCullough, what is typically the first and best characteristic he looks for when trying to identify a grassy weed species?
a) Ligule structure b) Leaf color c) Seed head d) Root system
Correct Answer: c Explanation: McCullough states that the seed head is usually the first characteristic he looks for on a weed sample and is typically the best characteristic to quickly key out a weed species. Source in transcript: Blocks 27–36
Question 3
Timestamp Reference: 3:57 – 5:11 Difficulty: Application
A turfgrass manager finds a warm-season perennial grassy weed with a V-shaped seed head where the two spikes join at the base. Which species is this most likely, and what herbicide does McCullough suggest for its control?
a) Dallisgrass; metsulfuron b) Bahiagrass; metsulfuron c) Dallisgrass; specific application programs depending on turfgrass species d) Goosegrass; prodiamine
Correct Answer: b Explanation: McCullough describes bahiagrass as having a V-shaped (or B-shaped) seed head where the spikes join at the base, distinguishing it from dallisgrass which has alternating spikes. Bahiagrass responds well to metsulfuron, while dallisgrass requires more specific application programs. Source in transcript: Blocks 37–48
Question 4
Timestamp Reference: 5:34 – 6:47 Difficulty: Application
During the growing season, a lawn care operator finds an unfamiliar summer grassy weed with no visible seed head. On closer inspection, the plant has no ligule at the base of the leaf blade. Based on McCullough's identification guidance, which weed species should they suspect?
a) Large crabgrass b) Smooth crabgrass c) Barnyardgrass d) Goosegrass
Correct Answer: c Explanation: McCullough explains that barnyardgrass does not have a distinct ligule — that structure is absent from the plant. Crabgrass species, by contrast, have a fleshy ligule often with a fringe of hairs. The absence of a ligule in a summer grassy weed is a strong indicator of barnyardgrass. Source in transcript: Blocks 54–61
Question 5
Timestamp Reference: 10:16 – 12:04 Difficulty: Recall
Which of the following is a true winter annual weed that germinates in the fall and dies out in the summer?
a) Spotted spurge b) Goosegrass c) Henbit d) Doveweed
Correct Answer: c Explanation: McCullough identifies henbit as a winter annual weed that germinates in the fall, grows actively in winter, goes to seed in spring, and then dies in summer. Spotted spurge, goosegrass, and doveweed are all summer annuals that germinate in spring and die in winter. Source in transcript: Blocks 94–107
Question 6
Timestamp Reference: 12:05 – 15:06 Difficulty: Analysis
Why are complex perennial weeds like bermudagrass and purple nutsedge more difficult to control than annual weeds, according to McCullough?
a) They are resistant to all available herbicides b) They reproduce through stolons, rhizomes, and tubers in addition to seed, and pre-emergent herbicides do not control plants emerging from vegetative structures c) They only germinate during a narrow window that is difficult to predict d) They require non-selective herbicides that also damage the desired turfgrass
Correct Answer: b Explanation: McCullough explains that complex perennials survive multiple years and primarily reproduce through asexual means — stolons, rhizomes, and tubers. Pre-emergent herbicides, which target seedling establishment, do not control plants emerging from below-ground vegetative structures. This makes control unpredictable and difficult compared to annual weeds with predictable germination windows. Source in transcript: Blocks 109–132
Question 7
Timestamp Reference: 17:08 – 19:15 Difficulty: Recall
In the North Carolina mowing height study McCullough presents, what happened to crabgrass cover when tall fescue mowing height was raised from one inch to four inches?
a) Crabgrass was reduced by approximately 50% b) Crabgrass was reduced from 95% cover to essentially 0% c) Crabgrass was unaffected by mowing height d) Crabgrass was reduced from 60% cover to 20%
Correct Answer: b Explanation: McCullough presents the North Carolina study showing that raising tall fescue from a one-inch to a four-inch mowing height cut crabgrass population from 95% cover to basically 0%. The taller fescue was able to shade out crabgrass and prevent its emergence. Source in transcript: Blocks 159–165
Question 8
Timestamp Reference: 24:07 – 26:09 Difficulty: Analysis
A homeowner asks whether a pre-emergent herbicide will stop weeds from sprouting in the first place. Based on McCullough's explanation, what is the correct response?
a) Yes, pre-emergent herbicides prevent seeds from germinating in the soil b) No, seeds still germinate, but the herbicide inhibits cell division in the seedling roots and shoots so they fail to establish c) Yes, pre-emergent herbicides create a chemical barrier that seeds cannot penetrate d) No, pre-emergent herbicides only work on established weeds
Correct Answer: b Explanation: McCullough specifically states that pre-emergent herbicides do not prevent weed seed germination. Seeds must first germinate and the young roots and shoots absorb the herbicide from the soil water solution. Most pre-emergent herbicides then tie up cell division, so the seedling fails to establish a healthy root system and dies. Source in transcript: Blocks 226–227
Question 9
Timestamp Reference: 29:38 – 31:06 Difficulty: Application
A golf course superintendent needs to apply a pre-emergent herbicide but has no irrigation available and no rain is expected for two weeks. Based on McCullough's guidance, which formulation should they choose and why?
a) Sprayable formulation, because it provides more uniform coverage b) Granular formulation, because it can reach the soil more readily without irrigation and has less potential for loss c) Either formulation, since irrigation timing does not affect pre-emergent efficacy d) Sprayable formulation applied at double the rate to compensate for losses
Correct Answer: b Explanation: McCullough explains that sprayable formulations can lose efficacy through photodegradation, volatilization, and clipping collection when they cannot be watered in promptly. Dry granular formulations get to the soil much better and have less potential for losses compared to sprayable products when irrigation is unavailable. Source in transcript: Blocks 266–282
Question 10
Timestamp Reference: 35:11 – 36:20 Difficulty: Application
Instead of applying prodiamine (Barricade) at one pound of active ingredient per acre in a single March application, a lawn care operator splits it into two applications. What is the recommended split program McCullough describes?
a) One-quarter pound in February and three-quarters pound in April b) Half a pound in March and half a pound in late May or June c) One pound in March and one pound in September d) Half a pound in January and half a pound in March
Correct Answer: b Explanation: McCullough recommends splitting the application into half a pound active per acre in March and another half pound active per acre in late May or June. This provides a fresh supply of herbicide to the soil and extends residual control beyond a single full-rate application, improving control of late-season crabgrass flushes. Source in transcript: Blocks 319–324
Question 11
Timestamp Reference: 37:31 – 40:11 Difficulty: Analysis
McCullough explains that herbicide resistance is not caused by the herbicide changing the weed. What is actually happening when a weed population becomes resistant?
a) The herbicide breaks down in the soil faster over time, reducing its effectiveness b) Repeated applications select for naturally occurring biotypes with altered target sites that do not respond to the herbicide, allowing them to reproduce and spread c) Weeds develop immunity after repeated exposure, similar to antibiotic resistance in bacteria d) Resistant weeds are introduced from other regions through contaminated seed or equipment
Correct Answer: b Explanation: McCullough emphasizes that resistance is a naturally occurring trait — not a change caused by the herbicide. A resistant biotype (perhaps one in a million) has a mutated target site where the herbicide cannot bind properly. Using the same herbicide repeatedly kills susceptible plants while the resistant biotype survives, reproduces, and eventually dominates the population through selection pressure. Source in transcript: Blocks 345–363
Question 12
Timestamp Reference: 46:05 – 48:06 Difficulty: Recall
In McCullough's golf course field trials testing resistance management programs, what combination provided complete Poa annua control at all three test locations, including those with resistance issues?
a) Barricade applied at double rate b) Specticle alone at standard timing c) A sulfonylurea herbicide combined with simazine d) Dismiss NXT at the fall timing
Correct Answer: c Explanation: McCullough found that combining a sulfonylurea with simazine — two different modes of action — gave complete control of Poa at all three golf courses, even where individual products like Revolver or simazine alone had resistance failures. The combination addressed different resistance profiles at each location. Source in transcript: Blocks 438–445
Question 13
Timestamp Reference: 55:01 – 59:05 Difficulty: Recall
What is the new active ingredient from Dow that McCullough discusses, and what is its primary characteristic?
a) Pyrimisulfan; long residual soil activity b) Mesosulfuron; excellent sedge control c) Halauxifen; very rapid broadleaf weed activity within five to seven days d) Carfentrazone; controls both grassy and broadleaf weeds
Correct Answer: c Explanation: Halauxifen is a new synthetic auxin (Group 4) herbicide from Dow. McCullough highlights its very rapid activity — susceptible broadleaf weeds typically show browning and necrosis within five to seven days. It is the active ingredient in RELZAR, Game On, and Switchblade. Source in transcript: Blocks 505–513
Question 14
Timestamp Reference: 1:06:27 – 1:08:17 Difficulty: Application
A lawn care company wants the fastest possible visual response when treating kyllinga for a demanding client. Based on McCullough's research, which product should they consider, and what is its limitation?
a) SedgeHammer, but it requires a surfactant to be effective b) Dismiss NXT, but it does not provide significantly better long-term control than standard Dismiss c) Vexis, but it requires dew to be present on the plant d) Solero, but it is only labeled for cool-season grasses
Correct Answer: b Explanation: McCullough reports that Dismiss NXT (sulfentrazone + carfentrazone) provides rapid control of kyllinga within seven days — a very fast takedown. However, his research did not show a significant difference in long-term control compared to straight Dismiss. The speed of response is the main advantage, which can satisfy clients who want to see quick results. Source in transcript: Blocks 612–627
Question 15
Timestamp Reference: 1:08:19 – 1:09:53 Difficulty: Analysis
Why does McCullough view Coastal (simazine + imazaquin + prodiamine) as representing a significant trend in turfgrass herbicide development?
a) It is the first herbicide specifically developed for centipedegrass b) It combines pre-emergent and post-emergent activity with multiple modes of action in a single product, addressing both weed control and resistance management c) It provides season-long control with a single application d) It is the first product safe for use on all warm- and cool-season turfgrass species
Correct Answer: b Explanation: McCullough describes Coastal as having both post-emergent activity (simazine and imazaquin controlling broadleaf weeds, sedges, and Poa annua with two different modes of action) and pre-emergent residual control (prodiamine). He sees it as the first of many combination products that will combine multiple chemistries for both weed control and resistance management in the turfgrass industry. Source in transcript: Blocks 628–644
Quiz Summary
Total Questions: 15 Difficulty Distribution:
- Recall: 6 questions (40%) — Questions 1, 2, 5, 7, 12, 13
- Application: 5 questions (33%) — Questions 3, 4, 9, 10, 14
- Analysis: 4 questions (27%) — Questions 6, 8, 11, 15
Coverage Distribution:
- Weed Identification (0:00–10:15): Questions 1, 2, 3, 4
- Lifecycles and Cultural Practices (10:16–24:06): Questions 5, 6, 7
- Pre-Emergent Science (24:07–36:20): Questions 8, 9, 10
- Herbicide Resistance (37:31–55:00): Questions 11, 12
- New Products (55:01–1:09:53): Questions 13, 14, 15
Generated for UGA Center for Urban Agriculture / GTBOP Moodle Certificate Course — Weed Science Source: Corrected SRT (Stage 1) — GTBOP_Transcript_2017-11-17_WeedControlTurf.srt (649 blocks)