Weed Science and Weed Management MCQs 2026

In weed science, the critical period of crop-weed competition means the period during which:

1. A Only herbicides can be applied safely ✓
2. B The crop must be kept weed-free to avoid major yield loss ✓
3. C The crop is ready for harvest ✓
4. D Weeds cannot produce seed ✓

A herbicide tank mix is used mainly to:

1. A Increase drift deliberately ✓
2. B Broaden weed control spectrum or manage resistance when products are compatible ✓
3. C Remove the need for label instructions ✓
4. D Convert a contact herbicide into seed ✓

Weed index expresses:

1. A Yield loss percentage due to weeds compared with a weed-free crop ✓
2. B Soil pH of a weedy field ✓
3. C Number of sprayer nozzles only ✓
4. D Crop price at market ✓

A crop can be made more competitive against weeds by:

1. A Reducing plant population below recommendation ✓
2. B Delaying sowing without reason ✓
3. C Allowing weed seed set before control ✓
4. D Using optimum seed rate, timely sowing and proper fertilizer placement ✓

Sorghum halepense, known as Johnson grass, spreads mainly by:

1. A Spores only ✓
2. B Leaf cuttings only ✓
3. C Rhizomes and seeds ✓
4. D Aerial tubers only ✓

Flooding helps suppress many weeds in transplanted rice mainly by:

1. A Increasing weed seed dispersal by wind ✓
2. B Maintaining a water layer that limits oxygen and emergence ✓
3. C Making soil permanently dry ✓
4. D Changing rice into a legume ✓

Amaranthus viridis is commonly known as:

1. A Pigweed ✓
2. B Wild oat ✓
3. C Barnyard grass ✓
4. D Water hyacinth ✓

Herbicide drift means movement of spray or vapor:

1. A Into the seed embryo naturally ✓
2. B Only through crop roots ✓
3. C From grain to flour ✓
4. D Away from the intended target area ✓

Integrated weed management is best described as:

1. A Using only one herbicide every year ✓
2. B Leaving all weeds until harvest ✓
3. C Combining cultural, mechanical, biological and chemical methods ✓
4. D Replacing crop seed with weed seed ✓

Repeated use of herbicides with the same mode of action increases the risk of:

1. A Improved crop pollination only ✓
2. B Selection of resistant weed biotypes ✓
3. C Permanent soil sterilization at label rate ✓
4. D Elimination of all future weed seeds ✓

For control of perennial weeds, herbicide translocation is important because it allows movement of the chemical to:

1. A Underground growing points and storage organs ✓
2. B Only the spray tank lid ✓
3. C The harvested grain surface only ✓
4. D The farm record book ✓

A pre-plant incorporated herbicide is one that is:

1. A Sprayed only on mature grain ✓
2. B Applied to harvested seed bags ✓
3. C Used only in irrigation canals ✓
4. D Mixed into the soil before planting ✓

Orobanche is an important example of a:

1. A Aquatic algae ✓
2. B Beneficial legume cover crop ✓
3. C Parasitic weed ✓
4. D Storage mold ✓

A post-emergence herbicide is applied:

1. A Only before sowing the crop ✓
2. B After the crop or weeds have emerged ✓
3. C Only during grain storage ✓
4. D Only to dry seed in bags ✓

Weed seed rain refers to:

1. A The addition of newly shed weed seeds to the soil ✓
2. B Rainfall during herbicide spraying only ✓
3. C Irrigation water stored in seed bags ✓
4. D Seed treatment with fungicide ✓

The risk of herbicide leaching is generally greater in soils that are:

1. A Heavy clay with high humus always ✓
2. B Covered by plastic mulch always ✓
3. C Sandy and low in organic matter ✓
4. D Frozen throughout the season ✓

The nozzle on a sprayer mainly influences:

1. A The botanical name of weeds ✓
2. B Droplet size, spray pattern and distribution ✓
3. C Soil pH buffering capacity ✓
4. D Seed germination temperature ✓

Annual weeds are plants that generally complete their life cycle in:

1. A One growing season or less ✓
2. B Ten years only ✓
3. C A woody perennial phase only ✓
4. D Dormant tubers only ✓

The economic weed threshold is the weed density at which:

1. A All weeds become beneficial ✓
2. B The crop no longer needs water ✓
3. C The field must be abandoned permanently ✓
4. D The expected loss justifies the cost of control ✓

Rogueing in weed management means:

1. A Adding weeds to seed lots ✓
2. B Spraying at double recommended dose ✓
3. C Removing isolated objectionable weeds by hand before seed set ✓
4. D Burning all crop residues every season ✓

Persistence of soil-applied herbicides is strongly affected by:

1. A Only the color of the spray tank ✓
2. B Soil organic matter, clay content, moisture and microbes ✓
3. C The size of the grain market ✓
4. D Number of farm laborers only ✓

Sedges are commonly distinguished from grasses by their:

1. A Triangular stems ✓
2. B Woody trunks ✓
3. C Needle-like leaves only ✓
4. D Taproot nodules ✓

An adjuvant in a herbicide formulation or spray mixture is added to:

1. A Increase soil clay content ✓
2. B Change crop genetics ✓
3. C Replace all irrigation water ✓
4. D Improve herbicide handling or performance ✓

Herbicide selectivity may occur because the crop and weed differ in:

1. A Color of harvested grain only ✓
2. B Name of the variety only ✓
3. C Absorption, translocation or metabolism of the herbicide ✓
4. D Farm boundary length only ✓

Crop rotation contributes to weed management by:

1. A Making all weed seeds nonviable instantly ✓
2. B Disrupting weed life cycles and control escape patterns ✓
3. C Replacing the need for clean seed ✓
4. D Increasing weed seed production ✓

The most direct way weeds reduce crop yield is by competing for:

1. A Light, nutrients, water and space ✓
2. B Packaging material ✓
3. C Tractor fuel ✓
4. D Market commission ✓

Perennial weeds are often harder to control than annual weeds because many have:

1. A No roots at all ✓
2. B Only one leaf per plant ✓
3. C Seeds that never germinate ✓
4. D Underground vegetative storage organs ✓

The stale seedbed technique controls weeds by:

1. A Harvesting the crop early ✓
2. B Mixing seed with fertilizer ✓
3. C Allowing weeds to emerge before sowing and then destroying them ✓
4. D Flooding mature grain ✓

Atrazine is commonly associated with weed control in:

1. A Chickpea only ✓
2. B Maize ✓
3. C Mango orchards only ✓
4. D Mushroom houses ✓

Calibration of a sprayer is done mainly to determine:

1. A The spray volume and chemical dose applied per unit area ✓
2. B The market price of herbicide ✓
3. C The maturity date of the crop ✓
4. D The seed moisture content ✓

Herbicide resistance in weeds is the inherited ability of a weed biotype to:

1. A Absorb all fertilizers faster than crops ✓
2. B Produce only sterile seeds ✓
3. C Grow only in waterlogged soil ✓
4. D Survive a herbicide dose that normally controls the species ✓

Echinochloa crus-galli, a common weed of rice fields, is known as:

1. A Bermuda grass ✓
2. B Horse purslane ✓
3. C Barnyard grass ✓
4. D Wild oat ✓

A weed shift is a change in weed flora caused by repeated use of particular:

1. A Seed labels only ✓
2. B Crops, herbicides or management practices ✓
3. C Rain gauges only ✓
4. D Threshing machines only ✓

Hand hoeing usually gives the best weed control when weeds are:

1. A Young and actively growing ✓
2. B Fully mature and shedding seed ✓
3. C Dormant underground only ✓
4. D Completely dry after harvest ✓

Biological weed control involves the use of:

1. A Only synthetic fertilizers ✓
2. B Deep tube wells ✓
3. C Combine harvesters ✓
4. D Natural enemies of weeds ✓

Narrow row spacing suppresses weeds primarily by:

1. A Increasing weed seed dormancy ✓
2. B Sterilizing the soil surface ✓
3. C Faster canopy closure and shading ✓
4. D Reducing crop plant population ✓

Paraquat is mainly known as a:

1. A Slow systemic nematicide ✓
2. B Fast-acting contact herbicide ✓
3. C Selective cereal fungicide ✓
4. D Soil-applied biofertilizer ✓

Glyphosate is generally classified as a:

1. A Non-selective systemic herbicide ✓
2. B Selective contact insecticide ✓
3. C Seed dressing fungicide ✓
4. D Plant growth regulator for tillering ✓

The main purpose of adding a surfactant to a herbicide spray solution is to:

1. A Increase seed viability ✓
2. B Neutralize soil salinity ✓
3. C Raise grain protein directly ✓
4. D Improve wetting and spreading of spray droplets ✓

Pendimethalin is best described as a herbicide commonly used as:

1. A A post-harvest grain protectant ✓
2. B A systemic fungicide ✓
3. C A pre-emergence soil-applied herbicide ✓
4. D A foliar micronutrient ✓

Weed seed dormancy is important because it helps weeds to:

1. A Absorb nitrogen directly from air ✓
2. B Survive unfavorable periods in the soil seed bank ✓
3. C Avoid all herbicide contact permanently ✓
4. D Convert into crop plants ✓

Allelopathy refers to the effect of one plant on another through:

1. A Biochemical compounds released into the environment ✓
2. B Mechanical harvesting ✓
3. C Artificial pollination ✓
4. D Soil compaction only ✓

Cyperus rotundus is difficult to control mainly because it reproduces through:

1. A Aerial roots only ✓
2. B Bulbils on leaves ✓
3. C Spores ✓
4. D Underground tubers ✓

The first line of defense in integrated weed management is usually to:

1. A Increase irrigation frequency ✓
2. B Apply fertilizer before sowing ✓
3. C Prevent introduction and spread of weeds ✓
4. D Delay harvesting ✓

A pre-emergence herbicide is generally applied:

1. A Only after flowering of the crop ✓
2. B After sowing but before crop or weed emergence ✓
3. C At physiological maturity ✓
4. D Only after harvest ✓

2,4-D is most commonly used in cereal crops for the control of:

1. A Broadleaf weeds ✓
2. B Nematodes ✓
3. C Fungal diseases ✓
4. D Storage insects ✓

A herbicide that kills certain weed species without seriously injuring the crop at the recommended dose is called:

1. A Non-residual herbicide ✓
2. B Soil sterilant ✓
3. C Fumigant ✓
4. D Selective herbicide ✓

Parthenium hysterophorus is commonly known in South Asia as:

1. A Johnson grass ✓
2. B Water hyacinth ✓
3. C Congress grass ✓
4. D Barnyard grass ✓

An unwanted plant growing where it is not desired and competing with a crop is called a:

1. A Weed ✓
2. B Pathogen ✓
3. C Predator ✓
4. D Biofertilizer ✓