Pesticides and Pest Control

DDT (Dichloro-diphenyl-trichloroethane) is an organochlorine insecticide that was widely used but later banned due to environmental concerns. The name reflects its chemical structure: two phenyl rings connected to a trichloroethane group with two chlorine atoms. Options B, C, and D incorrectly substitute parts of the chemical name.

Agent Orange was a herbicide used by the U.S. military during the Vietnam War to defoliate forests and destroy crops. It contained dioxin contaminants and caused serious health and environmental damage. The other options are common agricultural herbicides not associated with military use.

Freon is a chlorofluorocarbon (CFC) used as a refrigerant, not as a pesticide. BHC (benzene hexachloride), Malathion, and DDT are all well-known pesticides used in agriculture and public health.

Herbicides are most effectively applied after the first irrigation (Option D) because this timing allows for weed germination and emergence, ensuring the herbicide targets young weed seedlings when they're most vulnerable. Applying at germination (Option A), tillering (Option B), or ear emergence (Option C) is less effective as weeds may have already established or the crop is too developed.

Linuron is a phenylurea herbicide with a long soil half-life of 3-6 months, persisting longer than the other options. Chlorpropham and Propachlor break down within weeks, while Simazine, though persistent, generally degrades faster than Linuron in most soil conditions.

DDT (Dichlorodiphenyltrichloroethane) was first synthesized in 1874 but its insecticidal properties were discovered in 1939. It became widely used as an insecticide during World War II to control malaria and typhus, and later in agriculture. It was never used as a de-humidifier, fertilizer, or weedicide.

Pests raised for invalid or unsubstantiated defects are marked as Deferred Pests in this system's terminology. This differs from Invalidated Pests which may indicate a different status. On Hold and Resolved are active states for valid defects.

This is the correct option. Insecticide spray pumps work on this principle. When the pump is pumped, the air comes out of it at a very high speed. This, in turn, reduces the pressure over the small tube, which is dipped in the insecticide. This causes the liquid insecticide to rise up and is blown out in the form of fine spray.

Fumigation and addition of plant products are the control measures against pests attacking stored grains. In chemical control method, insecticides can be applied by spraying over the gunny bags that contain grains.

Mechanical, cultural, chemical and biological methods are used to control weeds.

Atrazine is a herbicide of the triazine class. Atrazine is used to prevent pre- and postemergence broadleaf weeds in crops such as maize (corn) and sugarcane and on turf, such as golf courses and residential lawns.

Both neem leaves and turmeric are used as bio-pesticides.

BHC (Benzene hexachloride) was indeed one of the most extensively used pesticides in India during the mid-to-late 20th century, particularly in agriculture. DDT was also widely used but BHC (also known as HCH or Lindane) had significant usage due to its effectiveness against a broad spectrum of pests. However, both have been banned or severely restricted due to environmental persistence and health hazards.