Answer: A. Unwanted plant in a field. A weed is a plant growing where it is unwanted or interferes with the intended crop or land use.
What is a central goal of weed management?
A Replace crop rotation
B Eradicate every plant species
C Reduce competition and seedbank growth
D Increase weed seed production
Answer: C. Reduce competition and seedbank growth. Weed management aims to limit harmful competition and prevent further buildup of weed populations and seed banks.
Which resources do weeds commonly compete for?
A Harvest bags and machinery
B Pollen and fruit color
C Seed tags and farm records
D Light, water, nutrients, space
Answer: D. Light, water, nutrients, space. Weeds can compete with crops for light, water, nutrients, and growing space.
When can weed competition be especially harmful to crops?
A Only after crop harvest
B During sensitive crop growth stages
C Only during seed storage
D After weeds stop growing
Answer: B. During sensitive crop growth stages. The crop’s critical period for weed control varies, but competition during sensitive growth stages can reduce yield.
What does the critical period for weed control describe?
A The time after final harvest
B When control prevents yield loss
C The weed’s entire lifespan
D The crop’s storage period
Answer: B. When control prevents yield loss. It is the crop-specific period when weeds must be controlled to prevent unacceptable yield loss.
What is a soil weed seed bank?
A Viable seeds and propagules underground
B A seed-testing laboratory
C Only seeds on plant leaves
D Stored fertilizer in a shed
Answer: A. Viable seeds and propagules underground. The weed seed bank is the reserve of viable weed seeds and vegetative propagules in or on soil.
How can farmers reduce new additions to the weed seed bank?
A Delay harvest indefinitely
B Prevent weeds from setting seed
C Increase bare soil exposure
D Scatter mature weed seed
Answer: B. Prevent weeds from setting seed. Preventing surviving weeds from producing seed reduces future seed-bank inputs.
Which practice helps prevent weeds spreading with planting material?
A Store seed outdoors
B Mix seed with field soil
C Harvest after weeds mature
D Use clean, weed-free seed
Answer: D. Use clean, weed-free seed. Clean planting seed reduces the chance of introducing weed seeds into a field.
Why should farm machinery be cleaned between infested fields?
A Improve seed germination
B Raise fertilizer grade
C Limit weed seed movement
D Increase soil moisture
Answer: C. Limit weed seed movement. Soil and seed carried on machinery can spread weeds to uninfested fields.
Which description fits an annual weed?
A Lives and regrows across years
B Completes one life cycle yearly
C Needs two growing seasons
D Never produces seed
Answer: B. Completes one life cycle yearly. Annual weeds complete their life cycle within one growing season or year.
How do perennial weeds differ from annual weeds?
A They grow only in water
B They cannot reproduce
C They live only one season
D Persist and regrow across years
Answer: D. Persist and regrow across years. Perennial weeds survive for multiple years and may regrow from roots or other vegetative structures.
Which life-cycle group typically needs two seasons to complete growth and reproduction?
A Biennial weeds
B Perennial weeds
C Ephemeral weeds
D Annual weeds
Answer: A. Biennial weeds. Biennial plants generally complete their life cycle over two growing seasons.
Which stem feature often helps identify sedges?
A Hollow round stems always
B Woody trunks
C Flattened leaf blades
D Often triangular stems
Answer: D. Often triangular stems. Many sedges have solid, triangular stems, unlike the often round stems of grasses.
Which structures allow some perennial weeds to spread vegetatively?
A Leaf veins and stomata
B Pollen and petals
C Rhizomes and tubers
D Seeds and flowers only
Answer: C. Rhizomes and tubers. Some perennial weeds regenerate from rhizomes, tubers, or other vegetative propagules.
What is the purpose of field sanitation in weed prevention?
A Keep weed seeds from spreading
B Encourage seedling emergence
C Replace crop scouting
D Increase weed seed production
Answer: A. Keep weed seeds from spreading. Sanitation measures such as cleaning tools and machinery help prevent weed seeds and propagules from moving between fields.
How can crop rotation help suppress weeds?
A Guarantee weed eradication
B Break weed life cycles
C Increase one weed species
D Stop crop competition
Answer: B. Break weed life cycles. Changing crops and planting seasons can disrupt weeds adapted to one crop sequence.
Why can a vigorous cover crop suppress weeds?
A It increases bare soil
B Shades and competes with weeds
C It removes all soil nutrients
D It prevents crop rotation
Answer: B. Shades and competes with weeds. Cover crops compete for light and resources and can reduce opportunities for weeds to establish.
What is one way surface mulch suppresses weeds?
A Blocks light at soil surface
B Raises weed seed production
C Removes crop roots
D Adds weed seeds to soil
Answer: A. Blocks light at soil surface. Mulch can reduce light reaching the soil surface and inhibit some weed emergence.
How does a stale seedbed technique work?
A Plant weeds with the crop
B Allow weeds to set seed
C Kill weeds before crop sowing
D Harvest only weed seed
Answer: C. Kill weeds before crop sowing. A stale seedbed allows a flush of weeds to emerge after seedbed preparation, then controls them before planting the crop.
What is a practical benefit of inter-row cultivation?
A Replace all crop management
B Increase seed dormancy
C Improve weed seed spread
D Control weeds between crop rows
Answer: D. Control weeds between crop rows. Mechanical cultivation between rows can control emerged weeds when timed to avoid crop injury.
When is hand removal most practical?
A For small or scattered patches
B After weeds have seeded
C During crop storage
D Across very large fields only
Answer: A. For small or scattered patches. Hand removal can be useful for small patches or escaped weeds before they reproduce.
Why mow weeds before seed production?
A Increase vegetative spread
B Prevent seed formation
C Improve weed seed viability
D Delay crop emergence
Answer: B. Prevent seed formation. Mowing at an appropriate stage can prevent or reduce seed production by some weeds.
How can tillage affect weed populations?
A It replaces crop rotation
B It removes every seed permanently
C It prevents all emergence
D Buries or exposes weed seeds
Answer: D. Buries or exposes weed seeds. Tillage can change weed seed placement and stimulate or suppress emergence depending on timing and system.
What is biological weed control?
A Remove crops mechanically
B Increase herbicide dose
C Use natural enemies or pathogens
D Apply only mineral fertilizers
Answer: C. Use natural enemies or pathogens. Biological control uses natural enemies or pathogens to suppress particular weed species.
What defines integrated weed management?
A Repeat one tactic every season
B Use herbicides alone
C Combine complementary control methods
D Ignore local weed species
Answer: C. Combine complementary control methods. Integrated weed management combines suitable cultural, mechanical, biological, and chemical methods over time.
When is a pre-emergence herbicide generally applied relative to weeds?
A Before weeds emerge
B Once weeds are mature
C After weeds set seed
D After crop harvest only
Answer: A. Before weeds emerge. Pre-emergence describes application before target weeds emerge; product labels specify crop and timing requirements.
When is a post-emergence herbicide applied?
A Only after harvest
B After weeds emerge
C Before soil preparation
D Before seeds are planted
Answer: B. After weeds emerge. Post-emergence herbicides are applied after target weeds have emerged, following the product label.
What is a selective herbicide designed to do?
A Kill every plant equally
B Improve soil structure
C Increase crop seed size
D Control weeds without harming crop
Answer: D. Control weeds without harming crop. A selective herbicide controls certain weeds while causing acceptable injury to a specified crop when used as labeled.
How does a nonselective herbicide generally act?
A Improves soil aeration
B Targets one weed only
C Supplies crop nutrients
D Kills many plant species
Answer: D. Kills many plant species. Nonselective herbicides can injure or kill many plant species they contact or affect.
What does a contact herbicide mainly damage?
A Tissue it reaches
B The entire plant automatically
C Soil nutrients only
D Only seed-bank seeds
Answer: A. Tissue it reaches. Contact herbicides injure plant tissues they reach; coverage and the product label matter.
How does a systemic herbicide move?
A Only along soil surface
B Through seed coats only
C Translocated through the plant
D Into rain clouds
Answer: C. Translocated through the plant. Systemic herbicides are absorbed and moved within the plant to varying degrees.
What is herbicide resistance in a weed population?
A A change in soil texture
B Inherited ability to survive treatment
C Temporary leaf wilting
D A crop’s natural tolerance
Answer: B. Inherited ability to survive treatment. Herbicide resistance is an inherited ability of a weed population to survive a herbicide dose that previously controlled it.
How can repeated use of one mode of action select resistant weeds?
A Herbicides lose nutrient content
B Survivors reproduce and spread
C Crop seeds change variety
D All weeds become harmless
Answer: B. Survivors reproduce and spread. Repeated selection allows resistant survivors to reproduce and increase their share of the population.
Which approach helps delay herbicide resistance?
A Repeat one herbicide alone
B Treat only mature weeds
C Use varied methods and modes
D Ignore surviving patches
Answer: C. Use varied methods and modes. Diversifying control methods and herbicide modes of action reduces reliance on one repeated selection pressure.
Why follow the herbicide label directions?
A Ensure safe, approved use
B Replace protective equipment
C Guarantee weed eradication
D Avoid identifying weeds
Answer: A. Ensure safe, approved use. The label provides approved crop uses, rates, timing, safety, and environmental precautions.
What should be identified before choosing a weed-control method?
A Only the crop’s color
B The machinery brand
C The field’s marketing slogan
D Weed species and growth stage
Answer: D. Weed species and growth stage. Weed identity, growth stage, density, and crop context help determine suitable control options.
How can regular field scouting improve weed control?
A Eliminate the need for records
B Change herbicide chemistry
C Reveal patches and new flushes
D Prevent every seed from germinating
Answer: C. Reveal patches and new flushes. Scouting identifies weed species, density, patches, and new emergence that guide timely management.
How can a competitive crop canopy suppress weeds?
A Raise weed seed production
B Shade emerging weeds
C Increase bare soil
D Stop all crop roots
Answer: B. Shade emerging weeds. A vigorous crop canopy reduces light available to many emerging weeds.
Why establish a uniform crop stand?
A Delay crop competition
B Encourage weed seed set
C Increase open soil space
D Reduce gaps for weed growth
Answer: D. Reduce gaps for weed growth. Uniform crop establishment can reduce open spaces where weeds might establish.
When a parasitic weed attaches to a host plant, what does it obtain?
A Resources from the host
B Only sunlight from stones
C Fertilizer from machinery
D Water from stored seed
Answer: A. Resources from the host. Parasitic weeds obtain water or nutrients from host plants through specialized connections.
What is allelopathy in weed ecology?
A Chemical suppression by released compounds
B Nutrient uptake by roots
C Mechanical removal of roots
D Movement of seeds by wind
Answer: A. Chemical suppression by released compounds. Allelopathy describes chemical effects released by one plant on the germination or growth of another.
Why can weeds growing near crops require attention beyond competition?
A They prevent all disease
B They stop irrigation losses
C They can host crop pests
D They increase crop seed purity
Answer: C. They can host crop pests. Some weeds can serve as hosts or refuges for pests or pathogens, depending on species and setting.
How should weed-control decisions account for local conditions?
A Use one method everywhere
B Choose species-specific control
C Ignore soil and climate
D Apply the same timing always
Answer: B. Choose species-specific control. Effective strategies depend on the weed species, crop, soil, climate, and available methods.
What can strong wind do during herbicide spraying?
A Prevent droplets from moving
B Increase crop root depth
C Improve spray targeting
D Cause off-target drift
Answer: D. Cause off-target drift. Wind can carry spray droplets away from the target, so label and weather restrictions matter.
Why time control when weeds are small and actively growing?
A Large weeds cannot absorb water
B Treatment may work more effectively
C Timing has no effect
D Small weeds have mature seeds
Answer: B. Treatment may work more effectively. Many control methods work best on susceptible stages, but the correct timing depends on species and treatment.
Why remove escaped weeds before harvest?
A Small weeds have mature seeds
B Create more weed patches
C Delay crop maturity
D Reduce reproduction and seedbank
Answer: D. Reduce reproduction and seedbank. Removing escaped weeds before seed production can reduce future seed-bank additions.
What is a risk of relying only on herbicides?
A Resistance and control failures
B Crop rotation becomes unnecessary
C Weeds stop evolving
D Seed banks disappear instantly
Answer: A. Resistance and control failures. Repeated reliance on limited herbicide strategies can select resistance and leave other management gaps.
Why record weed species and control results each season?
A Replace field scouting
B Prevent rainfall
C Improve future management choices
D Change crop genetics
Answer: C. Improve future management choices. Records help track troublesome species, treatment outcomes, and resistance concerns over time.
Why are weed-control programs planned across multiple seasons?
A Make one spray permanent
B Stop all crop rotation
C Reduce populations and seedbank
D Eliminate the need for scouting
Answer: C. Reduce populations and seedbank. Long-term integrated strategies aim to reduce weed populations and prevent seed-bank buildup, not rely on one rescue treatment.
Why can dormant weed seeds remain in soil for long periods?
A Germination waits for suitable cues
B They are already harvested
C They have no viable embryo
D They cannot absorb water
Answer: A. Germination waits for suitable cues. Dormancy delays germination until appropriate environmental cues or treatments occur.