Weed Control Test - 1

The correct answer is Boerhavia erecta.

• Weeds that live only for a season or a year and complete their life cycle in that season or year are called annual weeds.
• These are small herbs with shallow roots and weak stems.
• Produces seeds in profusion and the mode of propagation is commonly through seeds.
• After seeding, the annuals die away and the seeds germinate and start the next generation in the next season or year following.
• The most common field weeds are annuals.

• The examples are:

1. Monsoon annual:

• Commelina benghalensis and Boerhavia erecta

2. Winter annual:

• Chenopodium album

The correct answer is Gram.

• In India, yield losses due to weeds are more than those from pest and diseases.
• Every crop is exposed to severe competition from weeds.
• Most of these weeds are self-sown and they provide competition caused by their faster rate of growth in the initial stages of crop growth.
• In some crops, the yields are reduced by > 50% due to weed infestation.

• Loss in crop yields due to weeds:

The correct answer is All of the above.

• Herbicides are usually applied to soil surface to form a uniform herbicide layer.
• The applied herbicides, due to their low solubility may penetrate only few centimeters into the soil.
• Weeds germinating in the top layers are killed due to incidental absorption of herbicides.
• Examples: triazines, ureas and anilide

The correct answer is Statement I is true and Statement II is false. 

Key Points

• According to FAO (Food and Agriculture Organization), IWM is a method whereby all economically, ecologically and toxicologically justifiable methods are employed to keep the harmful organisms below the threshold level of economic damage, keeping in the foreground the conscious employment of natural limiting factors.
• Integrated Weed Management (IWM) involves the utilization of a combination of mechanical, chemical, and cultural practices of weed management.​

The correct answer is  All are the options are wrong

Key Points

• IWM is the combination of two or more weed-control methods at low input levels.
• It shifts the crop-weed competition in favor of crops by reducing weed competition.
• It is suitable for high cropping intensity fields
• IWM approach gives a high net return.

The correct answer is 1-A, 2-B, 3-C, 4-D

Key Points

• The duration between early growth during which weeds can grow without affecting crop yield and the point after which weed growth does not affect the yield is called the critical period.
• Weeding in the critical period will result in the highest economic returns. 
• The critical period is approximately 1/3rd of the duration of the crop.
• The critical period of weed control for rice starts from 15 days after sowing (DAS) to 45 DAS.
• The critical period of weed control for wheat starts from 30 DAS to 45 DAS.
• The critical period of weed control for groundnut starts from 30 DAS to 50 DAS.
• The critical period of weed control for sugarcane starts from 30 DAS to 120 DAS

The correct answer is Both Statement I and Statement II are true.

Key Points The narrow spade is called kodali and the broad spade is called Phawara.
The difference is that instead of a wide thin cutting blade, a narrow long pointed thicker section blade is attached to the handle in kodali.
Kodali is most popularly used for cultivating and weeding very close growing plants.

A Rotary paddy weeder is a tool used to remove weeds either manually or mechanically.
It is best suited for uprooting the weeds and burying them in soil and helpful to farmers who use minimal to zero amounts of herbicides.

Striga spp. is a parasitic weed on pearl millet

Key Points

1. Striga spp. or Witch weed is a semi root parasite.

2. Host plants of Striga are Pearlmillet, Sorghum, Maize, Sugarcane, Sunflower.

Additional InformationSpecies of weeds that usually parasitized the host plants.

The correct answer is Before flowering & seed formation.

Key Points

• Weeding is the process of removing unwanted plants from an area of ground.
• It is best done during the vegetative growth of weeds before flowering and seed formation.
• They grow with the main crops and compete for nutrients, sunlight, fertilizer, space, and water with the main crop.
• They are very harmful and there are three types of weeds they are grassy-type, grass-like, and broadleaf.
• It is done either manually or by using khurpi or a mechanical mechanism.
• Some examples of weed are Orange Hawkweed, Deer Tongue, Smooth Brome, Spotted Knapweed, and Dodder.
• It must be done two to three times whenever weeds start to grow again.
• There are five worst weeds such as Yellow nutsedge, Ground ivy, Crabgrass, and White Clover.
• The pulling of weed is a more effective method of preventing main crops from weed damages rather than cutting.

Image of weeds:

Key Points

• Aquatic weeds are unwanted and undesirable vegetation that reproduce and grow in water. If left unchecked may choke the water body posing a serious menace to pisciculture.
  • They provide breeding grounds and harbour predatory insects. 
  • Limit living space for fish  
  • Reduce water movement, thereby limiting oxygen circulation in water.
  • Some weeds release toxic gases that cause fish death and add foul smell to the water.
• Many shallow, nutrient-rich ponds, domestic sewage, lakes, and drainage ditches provide ideal conditions for abundant aquatic weed growth.
• Nutrient-rich water like domestic sewage contains excessive phosphorus and nitrogen that can cause aquatic weeds and algae to grow excessively.
• In nutrient-rich water, weeds and algae can become out of balance with other plants and animals. They quickly absorb nutrient-rich water and use it to produce more weeds and algae. 
• Water hyacinth is a free-floating and flowering invasive aquatic weed that blocks waterways and limits boat traffic, recreation, flood control and wildlife use
• Salvinia is a floating aquatic fern/weed that thrives in slow-moving, nutrient-rich, warm, freshwater.
• Duckweeds are tiny, free-floating, aquatic green weeds commonly found in lentic or slowly moving water bodies.

So from the above explanation, we can say that Both Statement I and Statement II are true.